Textbook Illustrations: Physics of Hi-Fi: Analog to Digital (1995)

Contents 1 Introduction to Hi-Fi

1

2 Waves

14

3 Decibels

63

4 Loudspeakers

67

5 Electricity

112

6 Ampli ers

138

7 Electromagnetism

153

8 Electromagnetic Waves and Tuners

173

9 Analog Recording and Playback

202

10 Digital Optical Recording & Playback

226

11 Digital Magnetic Recording & Playback

247

12 Heat

260

13 Mechanics

273

i

List of Figures 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10 1.11 1.12 1.13

Stereo process in recording and playback. : : : : : : : : : : : Surround sound reproduction of audio information. : : : : : : Storage or transmission of sound in stereo. : : : : : : : : : : : Playback process in stereo. : : : : : : : : : : : : : : : : : : : Elements of a receiver. : : : : : : : : : : : : : : : : : : : : : : Example of basic connections to a receiver. : : : : : : : : : : Elements of an integrated ampli er. : : : : : : : : : : : : : : Connections to an integrated ampli er. : : : : : : : : : : : : : All separate approach. : : : : : : : : : : : : : : : : : : : : : : Connections in all-separate approach. : : : : : : : : : : : : : Basic A/V System. : : : : : : : : : : : : : : : : : : : : : : : : A/V receiver driving a surround-sound system. : : : : : : : : Details of the tape monitor switch when listening to a sound source with available tape recording. : : : : : : : : : : : : : : 1.14 Listening to a tape; tape switch in. : : : : : : : : : : : : : : : 1.15 A/V receiver with Dolby Pro Logic processor. : : : : : : : : : 1.16 Various wave forms. : : : : : : : : : : : : : : : : : : : : : : : 2.1 Phono record and an enlarged groove showing engraved wave representing sound. : : : : : : : : : : : : : : : : : : : : : : : : 2.2 Simpli ed picture of a water wave; displaced water as a function of position. : : : : : : : : : : : : : : : : : : : : : : : : : : 2.3 Details of one wave as a function of position. : : : : : : : : : 2.4 Large and small amplitude waves. : : : : : : : : : : : : : : : : 2.5 Time dependence of displacement of a point on a water wave.

2.6 Displacement as a function of time; time required to complete one wave. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2.7 Transverse wave on a string. : : : : : : : : : : : : : : : : : : : 2.8 Longitudinal waves along a solid bar. : : : : : : : : : : : : : : ii

2 3 3 4 4 5 5 6 6 7 8 9 10 11 12 13 15 15 16 16 17 17 18 18

2.9 Addition of two waves. : : : : : : : : : : : : : : : : : : : : : : 2.10 Sound requires a medium in which to propagate; in a vacuum there is no sound propagation. : : : : : : : : : : : : : : : : : 2.11 Direct radiator speaker can move air like a drumhead. : : : : 2.12 Generation of sound by loudspeaker. : : : : : : : : : : : : : : 2.13 Disturbances created by loudspeaker; pressure changes cause sound. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2.14 Representation of sound created by a loudspeaker. : : : : : : 2.15 Wave Y has 4 times the power of wave X, but their amplitudes di er only by a factor of 2. : : : : : : : : : : : : : : : : 2.16 Re ection of a wave by an obstacle or a di erent medium. : : 2.17 Speaker producing a pulse of sound in a hall. : : : : : : : : : 2.18 Paths of direct and re ected sound in a hall. : : : : : : : : : : 2.19 Direct and reverberant sound in a hall. : : : : : : : : : : : : : 2.20 Direct and reverberant sound contributions to sound in a hall.

2.21 Sound radiated by a speaker; as one moves away the intensity decreases. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2.22 Sound intensity through surface 2 is di erent from that of 1. : 2.23 Observer and source at rest and in relative motion. : : : : : : 2.24 Doppler E ect produced by speaker producing simultaneously 100 Hz and 1,000 Hz sound waves. : : : : : : : : : : : : 2.25 Sound wave in cold air entering hot air. : : : : : : : : : : : : 2.26 Refraction of a sound wave. : : : : : : : : : : : : : : : : : : : 2.27 Above a critical angle of incidence there is only re ection. : : 2.28 Sound travels in a curved hollow plastic tube by multiple re ections. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2.29 Sound wave produced by a musical group; a complex wave. : 2.30 Simple sine waveform. : : : : : : : : : : : : : : : : : : : : : : 2.31 Comparison between one full wave and one rotation of a circle.

2.32 Addition of two waves. : : : : : : : : : : : : : : : : : : : : : : 2.33 Addition of two waves out of phase by 180 degrees. : : : : : : 2.34 Constructive interference. : : : : : : : : : : : : : : : : : : : : 2.35 Destructive interference. : : : : : : : : : : : : : : : : : : : : : 2.36 Obstacle with aperture receiving high frequency waves. : : : : 2.37 Low frequency behavior of obstacle and aperture. : : : : : : : 2.38 Comparison of di raction behavior of a room with opening and a loudspeaker. : : : : : : : : : : : : : : : : : : : : : : : : 2.39 Dispersion characteristics of a speaker. : : : : : : : : : : : : : 2.40 Standing wave produced by incident and re ected waves. : : : iii

18 19 19 20 21 21 22 22 23 24 25 26 27 28 29 30 31 31 32 33 34 34 35 35 35 36 37 38 39 40 41 41

2.41 Simplest possible standing wave on a string. : : : : : : : : : : 2.42 Simplest standing wave on a string during one cycle. : : : : : 2.43 Second harmonic on a string showing position of nodes and antinodes. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2.44 Third harmonic on a string clamped at both ends. : : : : : : 2.45 Setting up a standing wave in a tube. : : : : : : : : : : : : : 2.46 Simplest standing wave in a tube open at both ends. : : : : : 2.47 Second harmonic in tube open at both ends. : : : : : : : : : : 2.48 Fundamental in a tube. : : : : : : : : : : : : : : : : : : : : : 2.49 Tube open at one end excited by a tuning fork. : : : : : : : : 2.50 Fundamental in tube open at one end. : : : : : : : : : : : : : 2.51 Next more complicated standing wave; the third harmonic. : 2.52 Fifth harmonic. : : : : : : : : : : : : : : : : : : : : : : : : : : 2.53 Standing wave in a tube 1 meter long; fundamental. : : : : : 2.54 Tube closed at both ends. : : : : : : : : : : : : : : : : : : : : 2.55 Fundamental of a tube closed at both ends. : : : : : : : : : : 2.56 Room where independent standing waves can be set up in the x, y, and z directions. : : : : : : : : : : : : : : : : : : : : : : 2.57 A drumhead xed at its edges and its fundamental mode of vibration. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2.58 Overtone on a drumhead. : : : : : : : : : : : : : : : : : : : : 2.59 Standing wave pattern on a Chladni plate. : : : : : : : : : : : 2.60 Complex wave created by the superposition of a 100 Hz fundamental and its fourth harmonic. : : : : : : : : : : : : : : : 2.61 Violin string plucked by a nger and producing all sorts of harmonics. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2.62 Complex wave generated by plucking string. : : : : : : : : : : 2.63 Square wave; it is made up of many harmonics. : : : : : : : : 2.64 Spectrum of a square wave. : : : : : : : : : : : : : : : : : : : 2.65 Sawtooth wave and its harmonic content. : : : : : : : : : : : 2.66 Spectrum of a sawtooth wave. : : : : : : : : : : : : : : : : : : 2.67 A string bowed at its middle and harmonics which are excited.

2.68 String on a piano struck by hammer at a distance 1/10 the string length from one end. : : : : : : : : : : : : : : : : : : : 2.69 Vibrations of an object at di erent excitation frequencies. : : 2.70 Oscillations of a mass on a spring, undamped and damped when submersed in oil. : : : : : : : : : : : : : : : : : : : : : : 2.71 Resonance of wine glass excited by sound. : : : : : : : : : : : iv

42 43 43 43 44 45 45 45 46 46 47 47 47 48 48 49 50 51 51 52 53 54 55 56 57 58 59 60 60 61 61

2.72 Beats caused by the combination of two waves with slightly di erent frequencies. : : : : : : : : : : : : : : : : : : : : : : : 62 3.1 3.2 3.3 3.4

Decibel meter. : : : : : : : : : : : : : : : : : : : : : : : : : : Receiver with volume control marked in dB. : : : : : : : : : : Response of human ears at the threshold of hearing. : : : : : Response of human ears for various sound levels: FletcherMunson curves. : : : : : : : : : : : : : : : : : : : : : : : : : : 3.5 Outer ear approximated by a tube closed at one end. : : : : : 3.6 Measuring the frequency response of a speaker. : : : : : : : : 3.7 Frequency response of a speaker. : : : : : : : : : : : : : : : : 4.1 Role of loudspeaker. : : : : : : : : : : : : : : : : : : : : : : : 4.2 Distortion of spectrum of original waveform by non- at frequency response of speaker. : : : : : : : : : : : : : : : : : : : 4.3 Dispersion properties of speakers. : : : : : : : : : : : : : : : : 4.4 Two low frequency waves from speaker arriving at O. : : : : : 4.5 Two high frequency waves from speaker arriving at O. : : : : 4.6 Details of waves 2 and 1 at high frequencies. : : : : : : : : : : 4.7 Sound dispersion of a driver as the frequency is increased. : : 4.8 Division of audio spectrum for a three-way loudspeaker. : : : 4.9 Net e ect of subdividing the whole audio range into three sections. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 4.10 Subdivision of audio spectrum in a two-way system. : : : : : 4.11 Amount of sound produced depends on volume displacement.

A is louder than B. : : : : : : : : : : : : : : : : : : : : : : : : 4.12 To produce same amount of sound by both drivers at the same frequency, the small one has to move through a larger distance than the big one. : : : : : : : : : : : : : : : : : : : : 4.13 Volume of air moved by loudspeaker as a function of frequency to produce same loudness of sound. : : : : : : : : : : : : : : : 4.14 Low frequency and high frequency simple pendulums doing di erent amounts of work per second for same amplitude of displacement. : : : : : : : : : : : : : : : : : : : : : : : : : : : 4.15 Balance between electrical power going to driver and the production of sound power and heat dissipation by driver. : : : : 4.16 Example of a loudspeaker whose e ciency is less than 100%.

4.17 Basic cone speaker. : : : : : : : : : : : : : : : : : : : : : : : :

v

64 64 64 65 65 66 66 68 69 70 71 72 73 74 75 76 76 77 78 79 80 80 81 82

4.18 Comparison of cone-shape over at shape for mechanical strength when thin material is used. : : : : : : : : : : : : : : : : : : : 83 4.19 Modeling of diaphragm action by mass-spring oscillating system. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 84 4.20 Standing wave on diaphragm of driver. : : : : : : : : : : : : : 85 4.21 Standing wave around rim of diaphragm. : : : : : : : : : : : 85 4.22 Typical frequency response of a cone speaker. : : : : : : : : : 86 4.23 Ba e problem in cone driver. : : : : : : : : : : : : : : : : : : 86 4.24 Front and rear of cone speakers are 180 out of phase. : : : : 87 4.25 Ba e action. : : : : : : : : : : : : : : : : : : : : : : : : : : : 88 4.26 Two possible approaches for trapping rear sound in a speaker by means of an enclosure. : : : : : : : : : : : : : : : : : : : : 88 4.27 E ect of enclosure on frequency response of speaker. : : : : : 89 4.28 Reducing standing waves inside speaker enclosure. : : : : : : 90 4.29 Basic bass-re ex enclosure. : : : : : : : : : : : : : : : : : : : 91 4.30 Oscillating components of bass-re ex speaker. : : : : : : : : : 92 4.31 Splitting of original resonance into two new resonances in bass-re ex system. : : : : : : : : : : : : : : : : : : : : : : : : 93 4.32 Resonant behavior, in-phase and out-of-phase, motion of strongly coupled components of bass-re ex system. : : : : : : : : : : : 94 4.33 Coupled components of a bass-re ex speaker. : : : : : : : : : 95 4.34 Bass-re ex speaker using a passive radiator over the port. : : 96 4.35 Helmholtz resonator behaves like mass-spring system. : : : : 97 4.36 Bass-re ex speaker using a port or a duct. : : : : : : : : : : : 98 4.37 Acoustic labyrinth enclosure. : : : : : : : : : : : : : : : : : : 99 4.38 Change of frequency response of speaker when a small enclosure is used. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 100 4.39 E ect of small enclosure on frequency response of driver. : : : 101 4.40 Transfer of energy from a bob to one of equal mass, and to one of di erent mass. : : : : : : : : : : : : : : : : : : : : : : : 102 4.41 A horn for matching vibrations of a light diaphragm to a large volume of air. : : : : : : : : : : : : : : : : : : : : : : : : : : : 103 4.42 Low frequency response of a horn. : : : : : : : : : : : : : : : 103 4.43 Some common horn shapes. : : : : : : : : : : : : : : : : : : : 104 4.44 Folded horn. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 105 4.45 Two-way horn loudspeaker with bass-re ex enclosure. : : : : 106 4.46 Standing wave set up in a room with maxima and minima in sound pressure. : : : : : : : : : : : : : : : : : : : : : : : : : : 107 vi

4.47 Re ected waves by a wall appear to come from behind the wall since it acts like a mirror. : : : : : : : : : : : : : : : : : 4.48 Stereo coverage in a room. : : : : : : : : : : : : : : : : : : : : 4.49 Speaker phasing: speakers are in phase. : : : : : : : : : : : : 4.50 Speaker phasing: speakers are out of phase. : : : : : : : : : : 4.51 Geometry of a Bose 901 speaker. : : : : : : : : : : : : : : : : 4.52 E ect of equalizer on frequency response of Bose speakers. : : 4.53 Bass horn in Klipsch horn speaker. : : : : : : : : : : : : : : : 4.54 Graphic equalizer. : : : : : : : : : : : : : : : : : : : : : : : :

107 108 108 109 109 110 111 111

5.1 Example of an atom: a Helium atom. : : : : : : : : : : : : : 113 5.2 Forces between charged objects; like charges repel and unlike charges attract. : : : : : : : : : : : : : : : : : : : : : : : : : : 114 5.3 Charged ping-pong balls repelling each other. : : : : : : : : : 115 5.4 Electric eld produced by a charged object. : : : : : : : : : : 115 5.5 Electric eld between two charged plates. : : : : : : : : : : : 116 5.6 Examples of voltage sources: a battery, the output of a receiver.116 5.7 Electrostatic speaker: basic principle and actual speaker. : : : 117 5.8 Simpli ed version of an electrostatic speaker at equilibrium. : 117 5.9 Push-pull action by two plates on charged sheet. : : : : : : : 118 5.10 An electrostatic speaker. : : : : : : : : : : : : : : : : : : : : : 118 5.11 Some crystals under pressure produce positive and negative charges on surface. : : : : : : : : : : : : : : : : : : : : : : : : 119 5.12 Dimensional changes of a piezoelectric ceramic when a voltage is applied. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 119 5.13 Bending action of a double piezoelectric driver. : : : : : : : : 120 5.14 Pumping action of cone caused by bending of bimorph. : : : 120 5.15 Typical piezo horn. : : : : : : : : : : : : : : : : : : : : : : : : 121 5.16 Wire connected between two charged objects allows charges to be transferred. : : : : : : : : : : : : : : : : : : : : : : : : : 121 5.17 Flow of electric current from ampli er to speaker. : : : : : : : 122 5.18 Solid with atoms where electrons are tightly bound and which does not conduct electricity under normal circumstances. : : 122 5.19 Motion of one electron in a conductor in the presence of an electric eld. Changes of direction are due to scattering. : : : 123 5.20 Temperature dependence of the electrical resistance in a conductor. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 124 5.21 Superconductivity at Tc below which the resistance is zero. : 124 vii

5.22 The resistance to current or to water ow increases as the length of a conductor or pipe increases. Resistance of 2 is double that of 1. : : : : : : : : : : : : : : : : : : : : : : : : : 5.23 By increasing the cross-sectional area of a conductor, resistance to current or water ow decreases. : : : : : : : : : : : : 5.24 Resistor with colored bands to specify its resistance value. : : 5.25 Pure silicon, silicon doped with arsenic, and silicon doped with gallium. : : : : : : : : : : : : : : : : : : : : : : : : : : : 5.26 Example of simple circuit. : : : : : : : : : : : : : : : : : : : : 5.27 Model using water for electric circuit. : : : : : : : : : : : : : 5.28 Comparison between DC and AC current. : : : : : : : : : : : 5.29 Representation of a sound wave by an AC electrical signal. : 5.30 Variable resistance between X and Y. : : : : : : : : : : : : : 5.31 Fuse to protect speaker. : : : : : : : : : : : : : : : : : : : : : 5.32 Two speakers connected in series to one channel of ampli er.

5.33 Model of series circuit. : : : : : : : : : : : : : : : : : : : : : : 5.34 Parallel connection of two speakers to an ampli er. : : : : : : 5.35 Model of parallel connections. : : : : : : : : : : : : : : : : : : 5.36 Parallel connections of hi- components to house electrical outlet. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 5.37 Response of cone speaker to a force. : : : : : : : : : : : : : : 5.38 Coil used to produce a magnetic eld when a current ows through it. It has inductance. : : : : : : : : : : : : : : : : : : 5.39 Frequency dependence of impedance associated with inductance. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 5.40 Charging of a capacitor. : : : : : : : : : : : : : : : : : : : : : 5.41 Charging of a capacitor when polarity of voltage source is reversed. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 5.42 Frequency dependence of impedance due to capacitance. : : : 5.43 Inductance in series with woofer prevents high frequencies from reaching it. : : : : : : : : : : : : : : : : : : : : : : : : : 5.44 Capacitance in series with tweeter. It prevents low frequencies from reaching it. : : : : : : : : : : : : : : : : : : : : : : : : : 5.45 Capacitance and inductance in series with mid-range speaker to prevent the high and low frequencies from reaching it. : : : 5.46 Impedance curve of driver. : : : : : : : : : : : : : : : : : : : : 6.1 Importance of ampli er in hi- system. : 6.2 Basic ampli er. : : : : : : : : : : : : : : viii

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125 125 126 126 126 127 128 128 129 129 129 130 130 131 131 132 133 134 134 135 135 136 136 137 137 139 139

6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 6.11 6.12 6.13 6.14 6.15 6.16 6.17 6.18 6.19 6.20 6.21 6.22 6.23 6.24 6.25 6.26 6.27 6.28 6.29

Ampli er command for more current. : : : : : : : : : : : : : 140 Ampli er command for less current. : : : : : : : : : : : : : : 140 Semiconductor junction. : : : : : : : : : : : : : : : : : : : : : 141 Reverse-biased semiconductor junction. : : : : : : : : : : : : 141 Forward-biased semiconductor junction. : : : : : : : : : : : : 142 Symbol for diodes and its characteristics. : : : : : : : : : : : 142 Recti er action of a diode when an AC voltage is applied. : : 142 Diagram of transistor and its circuit symbol for two possibilities.143 Ampli er action of transistor in a circuit compared to control of water ow. : : : : : : : : : : : : : : : : : : : : : : : : : : : 143 Function of an ampli er. : : : : : : : : : : : : : : : : : : : : : 144 Ampli er integrated on a chip. : : : : : : : : : : : : : : : : : 144 Operational ampli er with negative feedback. : : : : : : : : : 144 Negative feedback corrects uctuations in gain. : : : : : : : : 145 Positive feedback in large hall with a mike and a loudspeaker system driven by mike. : : : : : : : : : : : : : : : : : : : : : : 145 Volume control. : : : : : : : : : : : : : : : : : : : : : : : : : : 146 Comparison of potentiometer action with energy of a ball on a ladder. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 146 Bass and Treble controls. : : : : : : : : : : : : : : : : : : : : 147 E ect on signal spectrum of Bass and Treble controls. : : : : 148 Action of LOW and HIGH lters with 6 dB/octave attenuation, and also with 18 db/octave attenuation. : : : : : : : : : 148 Harmonic distortion by ampli er. : : : : : : : : : : : : : : : : 149 Non-linear gain of ampli er. : : : : : : : : : : : : : : : : : : : 149 IM distortion in ampli er. : : : : : : : : : : : : : : : : : : : : 150 Distortion increases sharply about power rating of ampli er. : 150 Clipping of waveform by ampli er at high output levels beyond the rated value. : : : : : : : : : : : : : : : : : : : : : : : 151 E ect of noise from ampli er. : : : : : : : : : : : : : : : : : : 151 Comparing 2 ampli ers with the same specs. Even though their specs are the same, the ampli ers will sound di erent. : 152 A-weighted method of measuring noise. : : : : : : : : : : : : 152

7.1 E ect of current in a wire on compasses around it. : : : : : : 7.2 Bar magnet has a north pole and a south pole. : : : : : : : : 7.3 Cutting a bar magnet produces shorter magnets each with its own respective north and south poles. : : : : : : : : : : : : : 7.4 Magnetic dipole is the basic unit of magnetism. : : : : : : : : ix

154 154 154 155

7.5 Unmagnetized piece of iron. : : : : : : : : : : : : : : : : : : : 155 7.6 Alignment of domains in a piece of iron by a bar magnet. Iron becomes magnetized. : : : : : : : : : : : : : : : : : : : : : : : 156 7.7 Magnetic eld around a bar magnet and a wire carrying a current. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 156 7.8 Increasing the magnetic eld produced by a current in a wire: by forming a loop, and by using many loops. : : : : : : : : : 157 7.9 An electromagnet. : : : : : : : : : : : : : : : : : : : : : : : : 157 7.10 Determination of direction of magnetic eld using rst lefthand rule. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 158 7.11 Rule for determining direction of magnetic eld in an electromagnet. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 158 7.12 First left-hand rule and how a cone speaker works. : : : : : : 159 7.13 Force on wire carrying a current in a magnetic eld. : : : : : 159 7.14 The second left-hand rule showing direction of force on wire carrying a current in a magnetic eld. : : : : : : : : : : : : : 160 7.15 Direction of force depends on orientation of current with respect to magnetic eld. : : : : : : : : : : : : : : : : : : : : : 161 7.16 A Heil Speaker. : : : : : : : : : : : : : : : : : : : : : : : : : : 162 7.17 One set of folds in Heil speaker. : : : : : : : : : : : : : : : : : 163 7.18 Magnetic Planar Speaker. : : : : : : : : : : : : : : : : : : : : 164 7.19 Forces on diaphragm when current direction is as indicated. : 165 7.20 A bar magnet moving into a coil induces an electric current in that coil. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 165 7.21 Induced current in coil by moving magnet. : : : : : : : : : : : 166 7.22 Signi cance of relative motion between magnet and coil. : : : 167 7.23 Direction of induced current (wrong). : : : : : : : : : : : : : 167 7.24 Direction of induced current (correct). : : : : : : : : : : : : : 168 7.25 Schematic of a transformer and its circuit symbol. : : : : : : 169 7.26 Step-up transformer. : : : : : : : : : : : : : : : : : : : : : : : 170 7.27 Step-down transformer. : : : : : : : : : : : : : : : : : : : : : 170 7.28 Schematic of microphone based on Faraday's law of induction. 171 7.29 Exercise 7.14. : : : : : : : : : : : : : : : : : : : : : : : : : : : 171 7.30 Exercise 7.15. : : : : : : : : : : : : : : : : : : : : : : : : : : : 172 7.31 Exercise 7.18. : : : : : : : : : : : : : : : : : : : : : : : : : : : 172 8.1 Electric Field around charged ping-pong ball.

8.2 Oscillating charged ball. : : : : : : : : : : : : x

: : : : : : : : : : : : : : : : : :

174 174

8.3 Generation of electromagnetic waves at two di erent frequencies. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 175 8.4 Spectrum of electromagnetic waves. : : : : : : : : : : : : : : : 175 8.5 Electromagnetic waves are transverse waves with oscillating electric and magnetic elds. : : : : : : : : : : : : : : : : : : : 176 8.6 Production of electromagnetic waves by oscillating electrons in antenna. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 176 8.7 Generation of electric and magnetic elds by antenna. : : : : 177 8.8 Production of electromagnetic waves by antenna. : : : : : : : 177 8.9 Some examples of modulation. : : : : : : : : : : : : : : : : : 178 8.10 Amplitude modulation. : : : : : : : : : : : : : : : : : : : : : 178 8.11 Carrier and audio signals broadcast by two stations. : : : : : 179 8.12 Spectrum of an AM carrier at frequency f when modulated by audio signal. : : : : : : : : : : : : : : : : : : : : : : : : : : 179 8.13 Audio frequencies modulating carrier. : : : : : : : : : : : : : 180 8.14 Spectrum of frequencies on carrier for audio frequencies up to 5 kHz. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 180 8.15 Spectrum of frequencies due to modulation of carrier. : : : : 181 8.16 Frequency modulation (FM). : : : : : : : : : : : : : : : : : : 181 8.17 A low frequency and a high frequency audio signal frequency modulating a carrier. : : : : : : : : : : : : : : : : : : : : : : : 182 8.18 A loud and a quiet audio signal frequency modulating a carrier.183 8.19 Action of limiter in FM. : : : : : : : : : : : : : : : : : : : : : 184 8.20 Pre-emphasis in FM broadcasting. : : : : : : : : : : : : : : : 184 8.21 Information brought to tuner on carrier. : : : : : : : : : : : : 185 8.22 De-emphasis of audio information to reduce high frequency noise. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 185 8.23 Elements of radio communications. : : : : : : : : : : : : : : : 186 8.24 Superheterodyne receiver. : : : : : : : : : : : : : : : : : : : : 186 8.25 Processing part of AM signal with a simple diode and lters. 186 8.26 Audio information which will modulate carrier in stereo broadcasting. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 187 8.27 Alternating current in antenna produces electromagnetic wave.188 8.28 Electric eld around charged antenna wires is similar to that between charged capacitor plates. : : : : : : : : : : : : : : : : 189 8.29 Magnetic elds around a wire and antenna with current. : : : 189 8.30 Development of a standing wave on antenna. : : : : : : : : : 190 8.31 Comparison of standing wave on antenna to that of a string. 191 xi

8.32 Radiation pattern of electric eld around half-wave dipole antenna. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 8.33 Polar graph representation of radiation pattern around halfwave dipolar antenna. : : : : : : : : : : : : : : : : : : : : : : 8.34 Basic elements of a grounded vertical antenna. : : : : : : : : 8.35 Quarter-wave antenna. : : : : : : : : : : : : : : : : : : : : : : 8.36 Total antenna length is made shorter by inserting a coil in series. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 8.37 When the electric eld of radio wave is vertical, the receiving antenna should also be vertical. : : : : : : : : : : : : : : : : : 8.38 Loop antenna detects the magnetic eld part of radio wave. : 8.39 Two common loop antennas. : : : : : : : : : : : : : : : : : : 8.40 Vertically polarized radio wave. : : : : : : : : : : : : : : : : : 8.41 Horizontally polarized radio wave. : : : : : : : : : : : : : : : 8.42 Broadcasting with circular polarization. : : : : : : : : : : : : 8.43 Low frequency ground wave follows curvature of earth. : : : : 8.44 Direct (line-of-sight) mode of propagation. : : : : : : : : : : : 8.45 Earth's ionosphere layers. : : : : : : : : : : : : : : : : : : : : 8.46 Sky wave world communications. : : : : : : : : : : : : : : : : 8.47 Two-hop transmission of radio wave using ionosphere. : : : : 8.48 Communication using a satellite. : : : : : : : : : : : : : : : : 8.49 Selectivity relates to how well alternate channels are rejected.

8.50 Direct and re ected waves from a broadcasting station. : : : 8.51 Capture ratio in tuner. : : : : : : : : : : : : : : : : : : : : : : 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 9.9 9.10 9.11 9.12

192 192 193 193 194 195 195 196 196 197 197 198 198 199 199 200 200 201 201 201

Record with grooves representing mechanically engraved waves.203 Phono playback systems. : : : : : : : : : : : : : : : : : : : : : 204 Stereo with only one stylus. : : : : : : : : : : : : : : : : : : : 205 A stereo moving magnet phono cartridge. : : : : : : : : : : : 206 Unmagnetized and magnetized magnetic material. : : : : : : 206 Magnetic eld produced by a coil when current ows through it. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 207 Alignment of domains in a magnetic material. : : : : : : : : : 208 Behavior of magnetic material in a coil whose current is increased and decreased to zero. : : : : : : : : : : : : : : : : : : 209 Memory is destroyed by reversed current in coil. : : : : : : : 210 Hysteresis curve of magnetic material. : : : : : : : : : : : : : 211 Groups of magnetic materials. : : : : : : : : : : : : : : : : : : 212 Side and top views of magnetic tape. : : : : : : : : : : : : : : 213 xii

9.13 9.14 9.15 9.16 9.17 9.18 9.19 9.20 9.21 9.22 9.23 9.24 9.25 9.26 9.27 9.28 9.29 9.30 9.31 9.32

Magnetic particle of gamma { Iron (III) Oxide as used on tapes.213 Recording head aligning magnetic domains on tape. : : : : : 214 Analog recording on a magnetic tape. : : : : : : : : : : : : : 215 Recorded information on magnetic tape. : : : : : : : : : : : : 216 Playback head for reading information on a tape. : : : : : : : 216 Playback head reading signals. : : : : : : : : : : : : : : : : : 216 Order of heads on a tape deck. : : : : : : : : : : : : : : : : : 217 Recording on material with magnetic hysteresis. : : : : : : : 217 Recording a signal on a tape. : : : : : : : : : : : : : : : : : : 218 Ideal magnetic characteristics for tape | linear behavior. : : 219 Useful region on hysteresis curve for magnetic recording. : : : 220 Recording on magnetic tape with bias. : : : : : : : : : : : : : 221 Details of heads for magnetic recording. : : : : : : : : : : : : 222 Frequency dependence of output from playback head. : : : : 222 Output from playback head as a function of frequency for various gap sizes and tape speeds. : : : : : : : : : : : : : : : 223 Equalization in playback. : : : : : : : : : : : : : : : : : : : : 223 Equalization in recording. : : : : : : : : : : : : : : : : : : : : 224 Typical musical spectrum. : : : : : : : : : : : : : : : : : : : : 224 Frequency response at di erent recording levels. : : : : : : : : 225 Exercise 9.4. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 225

10.1 Sound wave and its analog representation as a voltage. : : : : 227 10.2 Grooves on a record representing analog signals. : : : : : : : 228 10.3 Distortion of analog signal by dirt stuck between playback head and tape. : : : : : : : : : : : : : : : : : : : : : : : : : : 229 10.4 Original number 2 and worn out number 2; basic information is not lost when number is worn out. : : : : : : : : : : : : : : 229 10.5 (a) Analog signal, decimal scale (b) Analog signal, binary scale.230 10.6 20 Hz wave will get more samples per wave than a 200 Hz wave.230 10.7 Aliasing due to inadequate sampling rate. : : : : : : : : : : : 231 10.8 Audio spectrum and sideband frequencies due to sampling. : 232 10.9 Sample and hold of a signal for digitizing. : : : : : : : : : : : 233 10.10 Multiplexing of left and right channels. : : : : : : : : : : : : 233 10.11 Digitizing a signal. : : : : : : : : : : : : : : : : : : : : : : : : 234 10.12 Output of D-A converter. : : : : : : : : : : : : : : : : : : : : 234 10.13 Output of low-pass lter. : : : : : : : : : : : : : : : : : : : : 235 10.14 Main features of playback of digital signal. : : : : : : : : : : 235 10.15 Details of information on a CD. : : : : : : : : : : : : : : : : 236 xiii

10.16 Interference between light beam re ected from pit and from at. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 10.17 Focusing action of a laser beam by lens. : : : : : : : : : : : : 10.18 Reduced e ect of surface defect on CD. : : : : : : : : : : : : 10.19 Laser spot focused on disc data. : : : : : : : : : : : : : : : : 10.20 Three-beam detection; one for read-out and two beams for tracking. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 10.21 Randomly polarized beam and plane-polarized beam. : : : : 10.22 Path of laser beam and role of its polarization. : : : : : : : : 10.23 Coherent and incoherent beams of light. : : : : : : : : : : : : 10.24 Semiconductor laser. : : : : : : : : : : : : : : : : : : : : : : : 10.25 E ect of 2-times and 4-times oversampling. : : : : : : : : : : 10.26 Shock-proof memory in mini-disc. : : : : : : : : : : : : : : :

237 237 238 239 240 241 242 243 244 245 246

11.1 Magnetic digital signals recorded vertically on a mini disc. : : 248 11.2 Recording digital signals on a mini disc. : : : : : : : : : : : : 248 11.3 Kerr e ect: plane of polarization of light beam rotates upon re ection from a magnetized surface. : : : : : : : : : : : : : : 249 11.4 Read-out of digital information using Kerr e ect. Magnetic

eld direction a ects plane of polarization of re ected laser beam. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 249 11.5 Di erence in read-out between pre-recorded and recordable mini-discs. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 250 11.6 Section of a recordable mini disc. : : : : : : : : : : : : : : : : 251 11.7 Layered structure of recordable mini disc. : : : : : : : : : : : 251 11.8 Track pattern in DCC tape. : : : : : : : : : : : : : : : : : : : 252 11.9 The playback head reads only a portion of the recorded track. 252 11.10 Threshold of hearing curve. : : : : : : : : : : : : : : : : : : : 252 11.11 Sounds which will be recorded by PASC and masking of quiet passages. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 253 11.12 Representation of digital signal on magnetic tape. : : : : : : 253 11.13 Helical recording with rotating heads. : : : : : : : : : : : : : 254 11.14 Tape contact to rotating head. : : : : : : : : : : : : : : : : : 255 11.15 Time compression to reduce wrap angle. : : : : : : : : : : : 256 11.16 Guard band between tracks on analog tape reduces cross-talk.257 11.17 Azimuthal recording. : : : : : : : : : : : : : : : : : : : : : : 257 11.18 Digital information on magnetic tape recorded longitudinally. 258 11.19 Arrangement of signals on a tape. : : : : : : : : : : : : : : : 259 11.20 Exercise 11.7. : : : : : : : : : : : : : : : : : : : : : : : : : : 259 xiv

12.1 Sources of heating in hi- due to mechanical friction and electrical \friction". : : : : : : : : : : : : : : : : : : : : : : : : : : 12.2 Electrical \friction" causes heating in ampli er components and voice coil. : : : : : : : : : : : : : : : : : : : : : : : : : : : 12.3 Two types of thermometers: alcohol expansion thermometer and gas thermometer. : : : : : : : : : : : : : : : : : : : : : : 12.4 Temperature dependence of electric resistance of a semiconductor. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 12.5 Basic circuit for resistance thermometer. : : : : : : : : : : : : 12.6 Heating of spot on mini-disc for recording. : : : : : : : : : : : 12.7 Heat conduction along a bar between a hot body and a cold one. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 12.8 Thermal resistance depends on length of heat conductor. : : : 12.9 Thermal resistance depends inversely on cross-sectional area of heat conductor. : : : : : : : : : : : : : : : : : : : : : : : : 12.10 Transfer of heat in air by convection. : : : : : : : : : : : : : 12.11 Object at temperature T emits electromagnetic waves. : : : 12.12 Thermal expansion of an object when heated. : : : : : : : : 12.13 Bimetallic strip and its behavior when heated or cooled. : : : 12.14 Mounting of transistor and diode on heat sink to transfer heat away from devices by heat conduction. : : : : : : : : : : 12.15 Heat removal by convection and radiation. : : : : : : : : : : 12.16 Action of circuit-breaker when too hot. : : : : : : : : : : : : 12.17 Thermo-magnetic recording on mini-Disc. : : : : : : : : : : : 13.1 Speed of tape past recording head. : : : : : : : : : : : : : : : 13.2 Time for a radio wave to go around the Earth at the equator.

13.3 Speed of a recorded signal is the same at X and at Y; their velocities are di erent. : : : : : : : : : : : : : : : : : : : : : : 13.4 Force on voice coil giving it a push or a pull depending on direction of current in voice coil. : : : : : : : : : : : : : : : : 13.5 Force on tape by capstan-pinch roller. : : : : : : : : : : : : : 13.6 Static friction-force pulling on tape. : : : : : : : : : : : : : : 13.7 Releasing a CD from its case by applying a pressure on the clips with a nger. : : : : : : : : : : : : : : : : : : : : : : : : 13.8 Inertia of a tweeter is less than that of a woofer. : : : : : : : 13.9 Outer ear; ear drum's inertia limits response at frequencies above 20 kHz. : : : : : : : : : : : : : : : : : : : : : : : : : : : xv

261 262 263 264 264 265 265 266 267 268 268 269 269 270 271 271 272 274 274 275 276 277 277 278 279 280

13.10 Adjusted weight in cartridge for helping the stylus to track the groove in phono record. : : : : : : : : : : : : : : : : : : : 280 13.11 Force of clamped magnet on a voice coil accelerates diaphragm in loudspeaker. Force of clamped magnet on focus coil accelerates focus lens in CD player. : : : : : : : : : : : : : : : : : 281 13.12 Re ection of a pulse on a string clamped at wall and its inversion. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 282 13.13 Force on voice coil and force on magnet. : : : : : : : : : : : 283 13.14 Waves recorded on a phono record and a CD. : : : : : : : : : 284 13.15 Distances covered along outer track and inner track on a phono record. : : : : : : : : : : : : : : : : : : : : : : : : : : : 285 13.16 Frequency of rotation of a CD is made higher near the inner edge and lower near the outer edge to maintain constant linear speed on a tracks. : : : : : : : : : : : : : : : : : : : : : : : : 286 13.17 Rotation of drum head relative to magnetic tape in DAT. : : 286 13.18 When same force is applied to the CD case lid, it is easier to open the lid near the edge because torque is larger there. : : 287 13.19 For the same force exerted on lid, the torque is larger in B than in A. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 288 13.20 Moment of inertia of a CD is larger than that of a mini-Disc. 288

xvi

Chapter 1

Introduction to Hi-Fi

1

CHAPTER 1. INTRODUCTION TO HI-FI

2

Microphone

R

Record

L R Microphone

Playback

Speakers

L

Figure 1.1: Stereo process in recording and playback.

CHAPTER 1. INTRODUCTION TO HI-FI

3

Stereo Right Surround Right

Center Speaker

Surround Left Stereo Left

Figure 1.2: Surround sound reproduction of audio information.

Left Left Sources of Sound

Stereo

Store (Record) or Transmit

Stereo

Right

Figure 1.3: Storage or transmission of sound in stereo.

Right

CHAPTER 1. INTRODUCTION TO HI-FI

4

Right Right Sources of Sound

Playback Left Left

Figure 1.4: Playback process in stereo.

Tuner

+ Pre-Amplifier

=

Receiver

+ Power Amplifier

Figure 1.5: Elements of a receiver.

CHAPTER 1. INTRODUCTION TO HI-FI

5

Antenna

Phono

Receiver

Tape Deck

CD

DAT

Figure 1.6: Example of basic connections to a receiver.

Pre-Amplifier

+

=

Integrated Amplifier

Power Amplifier

Figure 1.7: Elements of an integrated ampli er.

CHAPTER 1. INTRODUCTION TO HI-FI

6

Antenna

Tuner

CD

Integrated Amplifier

Phono

Tape Deck

DAT

Figure 1.8: Connections to an integrated ampli er.

Pre-Amp

+

Power Amplifier

Separate components

Figure 1.9: All separate approach.

CHAPTER 1. INTRODUCTION TO HI-FI

7

Antenna

Tuner

CD

Phono

Pre-Amp

Power Amplifier

Tape Deck

DAT

Figure 1.10: Connections in all-separate approach.

CHAPTER 1. INTRODUCTION TO HI-FI

8

Audio Input Audio Output

A/V Receiver

Stereo Speaker L Output

VCR VCR

R

Video Monitor

Figure 1.11: Basic A/V System.

Video

CHAPTER 1. INTRODUCTION TO HI-FI

L

9

R

Surround Speaker Output Audio Input Audio Output

A/V Receiver

Stereo Speaker L Output

VCR VCR

Video

R

Video Monitor

Figure 1.12: A/V receiver driving a surround-sound system.

CHAPTER 1. INTRODUCTION TO HI-FI

10

Tape Deck In

Out

Out for Recording

In from Tape Deck

Inputs Out

In Out

Selector Switch

Tape Monitor Switch

Tone Controls

Figure 1.13: Details of the tape monitor switch when listening to a sound source with available tape recording.

CHAPTER 1. INTRODUCTION TO HI-FI

11

Tape Deck In

Out

Out for Recording

In from Tape Deck

Inputs In Out Selector Switch

Out

Tape Monitor Switch

Tone Controls

Figure 1.14: Listening to a tape; tape switch in.

CHAPTER 1. INTRODUCTION TO HI-FI

12

Center Channel Speaker

R Left Front Speaker

Right Front Speaker

TV

Video

A/V Receiver

Video

Audio

VCR

Left Surround Speaker

Right Surround Speaker

Figure 1.15: A/V receiver with Dolby Pro Logic processor.

CHAPTER 1. INTRODUCTION TO HI-FI

A

13

B

C

Amplitude of Signal

Time

D

Time

E

Time

F

Amplitude of Signal

Time

Time

G Amplitude of Signal

Time

Figure 1.16: Various wave forms.

Time

Chapter 2

Waves

14

CHAPTER 2. WAVES

15

Figure 2.1: Phono record and an enlarged groove showing engraved wave representing sound.

Displacement up

Equilibrium Position Distance No Waves

Waves

Displacement down

Figure 2.2: Simpli ed picture of a water wave; displaced water as a function of position.

CHAPTER 2. WAVES

16

Displacement up

Distance

1 Wave Displacement down

Figure 2.3: Details of one wave as a function of position.

Displacement

Distance

Large Amplitude

Small Amplitude

Figure 2.4: Large and small amplitude waves.

CHAPTER 2. WAVES

17

+

Displacement from Equilibrium

Time

Figure 2.5: Time dependence of displacement of a point on a water wave.

+

Displacement

Time

1 Period

Figure 2.6: Displacement as a function of time; time required to complete one wave.

CHAPTER 2. WAVES

18

String

Clamp

Clamp

Figure 2.7: Transverse wave on a string.

Figure 2.8: Longitudinal waves along a solid bar.

Wave 1

Position

Wave 2

+

Position

Result

=

Figure 2.9: Addition of two waves.

Position

CHAPTER 2. WAVES

19

Sound

No Sound

Air

Vacuum Bell Jar

Figure 2.10: Sound requires a medium in which to propagate; in a vacuum there is no sound propagation.

Diaphragm Diaphragm

Direct Radiator Speaker

Drum

Figure 2.11: Direct radiator speaker can move air like a drumhead.

CHAPTER 2. WAVES

20

Air at Atmospheric Pressure

Speaker

≈ 14.7 lbs./sq.in.

Increase in Pressure = Condensation

Speaker

Motion

Figure 2.12: Generation of sound by loudspeaker.

CHAPTER 2. WAVES

21

Rarefaction

Condensation

Motion

Motion

Speaker

Pressure Change Equilibrium Pressure at ≈ 14.7 lbs./sq.in.

1 Wave

Figure 2.13: Disturbances created by loudspeaker; pressure changes cause sound.

Air Pressure Increase

Equilibrium Air Pressure

Vibrating Speaker

Air Pressure Decrease

Distance

Louder Sound

Figure 2.14: Representation of sound created by a loudspeaker.

CHAPTER 2. WAVES

22

Amplitude 2

Amplitude Wave Y

Wave X

2

1

1

0 -1

0 Distance

-2

Distance

-1 -2

Figure 2.15: Wave Y has 4 times the power of wave X, but their amplitudes di er only by a factor of 2.

al m r o N Obstacle Incoming Wave Angle of Incidence

Angle of Reflection

Reflected Wave

Figure 2.16: Re ection of a wave by an obstacle or a di erent medium.

CHAPTER 2. WAVES

23

Sound Produced Sound Power

Time 0

Speaker produces a Pulse of Sound

Figure 2.17: Speaker producing a pulse of sound in a hall.

CHAPTER 2. WAVES

24

Reflected

Direct

Sound Produced Direct

Amount of Sound

Reflected

Time 0

Reverberant Sound

Figure 2.18: Paths of direct and re ected sound in a hall.

CHAPTER 2. WAVES

25

Reflected Sound (Reverberant)

Direct Sound

Figure 2.19: Direct and reverberant sound in a hall.

CHAPTER 2. WAVES

26

Amount of Sound

Reverberant

Direct Source

Distance from Source

About 6 meters from Stage

Figure 2.20: Direct and reverberant sound contributions to sound in a hall.

CHAPTER 2. WAVES

27

1

2

3

4

Figure 2.21: Sound radiated by a speaker; as one moves away the intensity decreases.

CHAPTER 2. WAVES

28

1

2

Figure 2.22: Sound intensity through surface 2 is di erent from that of 1.

CHAPTER 2. WAVES

29

At Rest

Relative Motion

Figure 2.23: Observer and source at rest and in relative motion.

CHAPTER 2. WAVES

Speaker moving toward Listener

30

Speaker moving away from Listener

100 Hz Signal

1000 Hz Signal

Increase in Frequency heard by Listener

Decrease in Frequency heard by Listener

Figure 2.24: Doppler E ect produced by speaker producing simultaneously 100 Hz and 1,000 Hz sound waves.

CHAPTER 2. WAVES

31

Hot Air

Incoming Sound Wave

Cold Air

Figure 2.25: Sound wave in cold air entering hot air.

Hot Air

Normal

Cold Air

Figure 2.26: Refraction of a sound wave.

CHAPTER 2. WAVES

32

Hot Air

Normal

Critical Angle Cold Air

Figure 2.27: Above a critical angle of incidence there is only re ection.

CHAPTER 2. WAVES

33

Plastic

Sound Waves

Air

Figure 2.28: Sound travels in a curved hollow plastic tube by multiple re ections.

CHAPTER 2. WAVES

34

Displacement

Time

Figure 2.29: Sound wave produced by a musical group; a complex wave.

Displacement

Time

0

Figure 2.30: Simple sine waveform.

CHAPTER 2. WAVES

35

90˚ 90˚ 360˚ 180˚

Time or Position

180˚

360˚

270˚ 270˚

Figure 2.31: Comparison between one full wave and one rotation of a circle.

Disturbance

Disturbance

0 Time or Position

+

Disturbance

0 Time or Position

=

0 Time or Position

Figure 2.32: Addition of two waves.

Displacement

Displacement

0 Position

+

Displacement

0 Position

=

0 Position

Figure 2.33: Addition of two waves out of phase by 180 degrees.

CHAPTER 2. WAVES

36

In Phase

Figure 2.34: Constructive interference.

CHAPTER 2. WAVES

Out of Phase

Figure 2.35: Destructive interference.

37

CHAPTER 2. WAVES

Figure 2.36: Obstacle with aperture receiving high frequency waves.

38

CHAPTER 2. WAVES

Figure 2.37: Low frequency behavior of obstacle and aperture.

39

CHAPTER 2. WAVES

40

Figure 2.38: Comparison of di raction behavior of a room with opening and a loudspeaker.

CHAPTER 2. WAVES

41

High Frequencies

Low Frequencies

Figure 2.39: Dispersion characteristics of a speaker.

Incident Wave

Reflected Wave

Result

Figure 2.40: Standing wave produced by incident and re ected waves.

CHAPTER 2. WAVES

Figure 2.41: Simplest possible standing wave on a string.

42

CHAPTER 2. WAVES

43

1/2 Wave

Figure 2.42: Simplest standing wave on a string during one cycle.

Displacement:

Node

Antinode

Node

Antinode

Node

Figure 2.43: Second harmonic on a string showing position of nodes and antinodes.

Third Harmonic

Figure 2.44: Third harmonic on a string clamped at both ends.

CHAPTER 2. WAVES

Or

Figure 2.45: Setting up a standing wave in a tube.

44

CHAPTER 2. WAVES

45

1/2 Wave

Displacement Antinode

Node

Displacement Antinode

Figure 2.46: Simplest standing wave in a tube open at both ends.

Second Harmonic

Figure 2.47: Second harmonic in tube open at both ends.

1/2 Wave

1 Meter

Figure 2.48: Fundamental in a tube.

CHAPTER 2. WAVES

46

Figure 2.49: Tube open at one end excited by a tuning fork.

1/4 Wave

Displacement Antinode

Displacement Node

Figure 2.50: Fundamental in tube open at one end.

CHAPTER 2. WAVES

47

3/4 Wave

1/4 Wave

1/4 Wave

1/4 Wave

Figure 2.51: Next more complicated standing wave; the third harmonic.

Fifth Harmonic

Figure 2.52: Fifth harmonic.

1/4 Wave

1 Meter

Figure 2.53: Standing wave in a tube 1 meter long; fundamental.

CHAPTER 2. WAVES

48

Figure 2.54: Tube closed at both ends.

1/2 Wave

Displacement Node

Antinode

Displacement Node

Figure 2.55: Fundamental of a tube closed at both ends.

CHAPTER 2. WAVES

49

z

2 1/

e av W

1/2 Wave y 1/2 Wave x

Figure 2.56: Room where independent standing waves can be set up in the x, y, and z directions.

CHAPTER 2. WAVES

50

Figure 2.57: A drumhead xed at its edges and its fundamental mode of vibration.

CHAPTER 2. WAVES

Figure 2.58: Overtone on a drumhead.

Figure 2.59: Standing wave pattern on a Chladni plate.

51

CHAPTER 2. WAVES

52

Complex Wave

=

+ 100 Hz

400 Hz

Figure 2.60: Complex wave created by the superposition of a 100 Hz fundamental and its fourth harmonic.

CHAPTER 2. WAVES

53

Figure 2.61: Violin string plucked by a nger and producing all sorts of harmonics.

CHAPTER 2. WAVES

Displacement

Figure 2.62: Complex wave generated by plucking string.

54

Time

CHAPTER 2. WAVES

55

Amplitude Time

Frequency

Relative Amplitude

f

1

3f

1/3

5f

1/5

...

...

...

nf

1/n

n = odd integer

Figure 2.63: Square wave; it is made up of many harmonics.

CHAPTER 2. WAVES

56

1.0 Relative Amplitude 0.5

0

Harmonics

1

2

3

4

5

6

7

Figure 2.64: Spectrum of a square wave.

CHAPTER 2. WAVES

57

Amplitude Time

Frequency

Relative Amplitude

f

1

2f

1/2

3f

1/3

4f

1/4

5f

1/5

...

...

...

nf

1/n

n = integer

Figure 2.65: Sawtooth wave and its harmonic content.

CHAPTER 2. WAVES

58

1.0 Relative Amplitude 0.5

0

Harmonics 1

2

3

4

5

6

7

8

Figure 2.66: Spectrum of a sawtooth wave.

CHAPTER 2. WAVES

59

Figure 2.67: A string bowed at its middle and harmonics which are excited.

CHAPTER 2. WAVES

60

Hammer

Figure 2.68: String on a piano struck by hammer at a distance 1/10 the string length from one end.

Amplitude

Frequency

Natural Frequency

Figure 2.69: Vibrations of an object at di erent excitation frequencies.

CHAPTER 2. WAVES

61

Oil

Undamped

Damped

Figure 2.70: Oscillations of a mass on a spring, undamped and damped when submersed in oil.

Ping Pong Ball

Figure 2.71: Resonance of wine glass excited by sound.

CHAPTER 2. WAVES

62

F1

Time

F2

Time

Time

Resultant

Figure 2.72: Beats caused by the combination of two waves with slightly di erent frequencies.

Chapter 3

Decibels

63

CHAPTER 3. DECIBELS dB

64

Figure 3.1: Decibel meter.

0 dB

-70 dB Volume

Receiver

Sound Pressure Level (dB)

Figure 3.2: Receiver with volume control marked in dB.

140

Threshold of Pain

120 100 80

Range of Human Hearing

60 40 20 0

Threshold of Hearing

20

100

1,000

10,000

Frequency (Hz)

Figure 3.3: Response of human ears at the threshold of hearing.

Sound Pressure Level (dB)

CHAPTER 3. DECIBELS

65

140 130 dB

120

120 dB

100

100 dB

110 dB 90 dB

80

80 dB 70 dB

60

60 dB 50 dB

40

40 dB

20

20 dB

0

30 dB 10 dB

Threshold of Hearing 20 31.5

63

125

250

500

1000

2000

4000

8000 16000 20000

Frequency (Hz)

Figure 3.4: Response of human ears for various sound levels: FletcherMunson curves.

Outer Ear

Tube closed at one End

Figure 3.5: Outer ear approximated by a tube closed at one end.

CHAPTER 3. DECIBELS

Aux

dB

Audio Signal

66

Receiver

Generator Sound Level Meter (dB Meter)

Speaker

Figure 3.6: Measuring the frequency response of a speaker.

Sound Level (dB)

Ideal

90

70

Real

Frequency 20 Hz

1,000 Hz

20,000 Hz

Figure 3.7: Frequency response of a speaker.

Chapter 4

Loudspeakers

67

CHAPTER 4. LOUDSPEAKERS

Electrical Signal Input

68

Sound Output

Loudspeaker

Figure 4.1: Role of loudspeaker.

CHAPTER 4. LOUDSPEAKERS

69

Spectrum of an Input Tone

Amplitude

Frequency

+

1

2

3

4

5

6

7

Harmonics

Frequency Response of Speaker

Amplitude

Frequency

Resultant Amplitude

Sound from Speaker

Frequency 1

2

3

4

5

6

7

Harmonics

Figure 4.2: Distortion of spectrum of original waveform by non- at frequency response of speaker.

CHAPTER 4. LOUDSPEAKERS

70

High Frequencies

Low Frequencies

Figure 4.3: Dispersion properties of speakers.

CHAPTER 4. LOUDSPEAKERS

71

2

O 1

Figure 4.4: Two low frequency waves from speaker arriving at O.

CHAPTER 4. LOUDSPEAKERS

72

2

O

1

Figure 4.5: Two high frequency waves from speaker arriving at O.

CHAPTER 4. LOUDSPEAKERS

73

2 1/2 W aves

2

O

1

Figure 4.6: Details of waves 2 and 1 at high frequencies.

CHAPTER 4. LOUDSPEAKERS

74

"On Axis" All Frequencies are heard.

Highs

Speaker

Middles

Lows

"Off Axis" High Frequencies are almost not heard.

Figure 4.7: Sound dispersion of a driver as the frequency is increased.

CHAPTER 4. LOUDSPEAKERS

Total Sound Output

75

Woofer

Frequency

Total Sound Output

Midrange

Frequency

Total Sound Output

Tweeter

Frequency Cross-over Frequencies

Figure 4.8: Division of audio spectrum for a three-way loudspeaker.

CHAPTER 4. LOUDSPEAKERS

76

3-Way Speaker Woofer

Midrange

Tweeter

Total Sound Output

500 Hz

5000 Hz

Frequency

Figure 4.9: Net e ect of subdividing the whole audio range into three sections.

Woofer

Tweeter

Sound Output

Frequency Cross-over Frequency

Figure 4.10: Subdivision of audio spectrum in a two-way system.

CHAPTER 4. LOUDSPEAKERS

77

Displacement

A

Displacement

B

Figure 4.11: Amount of sound produced depends on volume displacement.

A is louder than B.

CHAPTER 4. LOUDSPEAKERS

78

Displacement

Displacement

Figure 4.12: To produce same amount of sound by both drivers at the same frequency, the small one has to move through a larger distance than the big one.

CHAPTER 4. LOUDSPEAKERS

79

Volume of Air moved (cm 3) 500

0.5

0.0005

Frequency 20

200

2000

20,000

Figure 4.13: Volume of air moved by loudspeaker as a function of frequency to produce same loudness of sound.

CHAPTER 4. LOUDSPEAKERS

80

High Frequency

Low Frequency

Figure 4.14: Low frequency and high frequency simple pendulums doing di erent amounts of work per second for same amplitude of displacement.

Electrical Power In

Sound Power and Heat Dissipation

IN

OUT

Figure 4.15: Balance between electrical power going to driver and the production of sound power and heat dissipation by driver.

CHAPTER 4. LOUDSPEAKERS

Electrical Power Input from Receiver (80 Watts)

81

Sound Output (2 Watts)

Loudspeaker

Figure 4.16: Example of a loudspeaker whose e ciency is less than 100%.

CHAPTER 4. LOUDSPEAKERS

Basket

82

Suspension

Spider

Magnet Cone

Voice Coil

Figure 4.17: Basic cone speaker.

CHAPTER 4. LOUDSPEAKERS

Cone-shaped Diaphragm

83

Flat Diaphragm

Figure 4.18: Comparison of cone-shape over at shape for mechanical strength when thin material is used.

CHAPTER 4. LOUDSPEAKERS

84

Flexible Edge

Diaphragm

Figure 4.19: Modeling of diaphragm action by mass-spring oscillating system.

CHAPTER 4. LOUDSPEAKERS

85

1

1

2

2

3 3

Side View

Front View

Figure 4.20: Standing wave on diaphragm of driver.

N

N

A

A

A Up

Down N

N

N Up

Up

A

Down

A

A N

Up

Down

N Down

A

N = Node A = Antinode

A N

Figure 4.21: Standing wave around rim of diaphragm.

CHAPTER 4. LOUDSPEAKERS

86

Main Resonance

Standing Wave Resonances Sound Pressure (dB)

Frequency

Figure 4.22: Typical frequency response of a cone speaker.

Rear Sound (Out of Phase)

Front Sound (In Phase)

Rear Sound (Out of Phase)

Figure 4.23: Ba e problem in cone driver.

CHAPTER 4. LOUDSPEAKERS

Figure 4.24: Front and rear of cone speakers are 180 out of phase.

87

CHAPTER 4. LOUDSPEAKERS

88

Path = 1/2 Wave

Baffle

Figure 4.25: Ba e action.

Figure 4.26: Two possible approaches for trapping rear sound in a speaker by means of an enclosure.

CHAPTER 4. LOUDSPEAKERS

89

Without Enclosure

With Enclosure Amplitude

Frequency

Resonant Frequency of Driver + Enclosure Resonant Frequency of Driver OR Without Enclosure With Enclosure Amplitude

Frequency

Resonant Frequency of Driver + Enclosure Resonant Frequency of Driver

Figure 4.27: E ect of enclosure on frequency response of speaker.

CHAPTER 4. LOUDSPEAKERS

Cotton Wool

Figure 4.28: Reducing standing waves inside speaker enclosure.

90

CHAPTER 4. LOUDSPEAKERS

91

Driver

Port

Figure 4.29: Basic bass-re ex enclosure.

CHAPTER 4. LOUDSPEAKERS

Figure 4.30: Oscillating components of bass-re ex speaker.

92

CHAPTER 4. LOUDSPEAKERS

Amplitude

93

Driver

+ Amplitude

Frequency

Enclosure

Frequency

Resultant Amplitude

Result

Frequency

Figure 4.31: Splitting of original resonance into two new resonances in bassre ex system.

CHAPTER 4. LOUDSPEAKERS

Air in Enclosure

94

Driver

Air in Enclosure In-Phase Motion Air in Enclosure

Air in Enclosure Out-of-Phase Motion Air in Enclosure

Figure 4.32: Resonant behavior, in-phase and out-of-phase, motion of strongly coupled components of bass-re ex system.

CHAPTER 4. LOUDSPEAKERS

95

Driver

Air in Enclosure

Port

Figure 4.33: Coupled components of a bass-re ex speaker.

CHAPTER 4. LOUDSPEAKERS

96

Driver

Passive Radiator

Figure 4.34: Bass-re ex speaker using a passive radiator over the port.

CHAPTER 4. LOUDSPEAKERS

97

Mass

Spring

Figure 4.35: Helmholtz resonator behaves like mass-spring system.

CHAPTER 4. LOUDSPEAKERS

Port

98

Duct

Figure 4.36: Bass-re ex speaker using a port or a duct.

CHAPTER 4. LOUDSPEAKERS

Figure 4.37: Acoustic labyrinth enclosure.

99

CHAPTER 4. LOUDSPEAKERS

100

Driver alone Driver + Small Enclosure

Amplitude

Frequency

Very Low Resonant Frequency

Figure 4.38: Change of frequency response of speaker when a small enclosure is used.

CHAPTER 4. LOUDSPEAKERS

101

Driver alone

Amplitude

Frequency 15 Hz Large Compliance

+

= Small Enlosure

Driver + Small Enclosure Amplitude

Frequency 30 Hz

Figure 4.39: E ect of small enclosure on frequency response of driver.

CHAPTER 4. LOUDSPEAKERS

102

Figure 4.40: Transfer of energy from a bob to one of equal mass, and to one of di erent mass.

CHAPTER 4. LOUDSPEAKERS

103

Diaphragm

Air Chamber

Mouth

Throat

Figure 4.41: A horn for matching vibrations of a light diaphragm to a large volume of air.

Amplitude

Frequency Cut-off Frequency

Figure 4.42: Low frequency response of a horn.

CHAPTER 4. LOUDSPEAKERS

104

Conical Parabolic

Exponential

Hyperbolic

Figure 4.43: Some common horn shapes.

CHAPTER 4. LOUDSPEAKERS

105

Diaphragm

Figure 4.44: Folded horn.

CHAPTER 4. LOUDSPEAKERS

Figure 4.45: Two-way horn loudspeaker with bass-re ex enclosure.

106

CHAPTER 4. LOUDSPEAKERS

107

1/2 Wavelength

Loudspeaker

Figure 4.46: Standing wave set up in a room with maxima and minima in sound pressure.

Loudspeaker Direct

Figure 4.47: Re ected waves by a wall appear to come from behind the wall since it acts like a mirror.

CHAPTER 4. LOUDSPEAKERS

108

Lows Middles

Middles

Highs

Highs

Lows

Lows

Figure 4.48: Stereo coverage in a room.

L

+ _

R

+ _

+ _

+ _

Figure 4.49: Speaker phasing: speakers are in phase.

CHAPTER 4. LOUDSPEAKERS

L

+ _

R

+ _

109

+ _

+ _

Figure 4.50: Speaker phasing: speakers are out of phase.

Wall

Reflected

Reflected

Direct

Figure 4.51: Geometry of a Bose 901 speaker.

CHAPTER 4. LOUDSPEAKERS

110

Speaker Amplitude

Frequency

Amplitude

Equalizer

Frequency

Speaker Resultant Amplitude

Frequency

Figure 4.52: E ect of equalizer on frequency response of Bose speakers.

CHAPTER 4. LOUDSPEAKERS

111

Wall

Figure 4.53: Bass horn in Klipsch horn speaker.

Left Channel +12 dB

0 dB

-12 dB

62Hz 250Hz 1kHz 4kHz 8kHz

Figure 4.54: Graphic equalizer.

Chapter 5

Electricity

112

CHAPTER 5. ELECTRICITY

113

Electron

Proton

N N

Neutron

Electron

Figure 5.1: Example of an atom: a Helium atom.

CHAPTER 5. ELECTRICITY

114

Figure 5.2: Forces between charged objects; like charges repel and unlike charges attract.

CHAPTER 5. ELECTRICITY

Figure 5.3: Charged ping-pong balls repelling each other.

Figure 5.4: Electric eld produced by a charged object.

115

CHAPTER 5. ELECTRICITY

116

Figure 5.5: Electric eld between two charged plates.

Output

Left

Battery

Right

Receiver

Figure 5.6: Examples of voltage sources: a battery, the output of a receiver.

CHAPTER 5. ELECTRICITY

117

Plates

Sheet

Figure 5.7: Electrostatic speaker: basic principle and actual speaker.

Plates

Sheet

Figure 5.8: Simpli ed version of an electrostatic speaker at equilibrium.

CHAPTER 5. ELECTRICITY

118

Figure 5.9: Push-pull action by two plates on charged sheet.

Spacers

Diaphragm (Vibrating Sheet)

Plates

Figure 5.10: An electrostatic speaker.

CHAPTER 5. ELECTRICITY

119

Stress

Si Ion

O2 Ion

Quartz Stress

Figure 5.11: Some crystals under pressure produce positive and negative charges on surface.

V=0

V

V

Figure 5.12: Dimensional changes of a piezoelectric ceramic when a voltage is applied.

CHAPTER 5. ELECTRICITY

120

V

V

Figure 5.13: Bending action of a double piezoelectric driver.

Bimorph

Cone

Figure 5.14: Pumping action of cone caused by bending of bimorph.

CHAPTER 5. ELECTRICITY

121

Diaphragm

Figure 5.15: Typical piezo horn.

Wire

Figure 5.16: Wire connected between two charged objects allows charges to be transferred.

CHAPTER 5. ELECTRICITY

122

L

+ _

R

+ _

Figure 5.17: Flow of electric current from ampli er to speaker.

Atom

Bound Electrons

Figure 5.18: Solid with atoms where electrons are tightly bound and which does not conduct electricity under normal circumstances.

CHAPTER 5. ELECTRICITY

123

Electron

Figure 5.19: Motion of one electron in a conductor in the presence of an electric eld. Changes of direction are due to scattering.

CHAPTER 5. ELECTRICITY

124

Metal Electrical Resistance

Temperature (ËšK) 0

100

200

300

Figure 5.20: Temperature dependence of the electrical resistance in a conductor.

Superconductor Electrical Resistance

Temperature (ËšK) 0

100

200

300

Tc

Figure 5.21: Superconductivity at Tc below which the resistance is zero.

CHAPTER 5. ELECTRICITY

125

1 Wire of Conductor 2

1

Water flowing in Pipe

2

Figure 5.22: The resistance to current or to water ow increases as the length of a conductor or pipe increases. Resistance of 2 is double that of 1.

Wire of Conductor

Water flowing in Pipe

Figure 5.23: By increasing the cross-sectional area of a conductor, resistance to current or water ow decreases.

CHAPTER 5. ELECTRICITY

126

Figure 5.24: Resistor with colored bands to specify its resistance value.

Extra Electron

Bonding

Missing Electron = Hole

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

As

Si

Si

Ga

Si

Si

Si

Si

Si

Si

Si

Si

Si

Si

Figure 5.25: Pure silicon, silicon doped with arsenic, and silicon doped with gallium.

+ Voltage Source

Amplifier

Resistance

_ Simple Model

Figure 5.26: Example of simple circuit.

CHAPTER 5. ELECTRICITY

127

Water Flow

Pump

Resistance to Water Flow

Figure 5.27: Model using water for electric circuit.

CHAPTER 5. ELECTRICITY

128

DC Current Time

AC

Current

Time

Figure 5.28: Comparison between DC and AC current.

Pressure

Voltage

Sound

Time

AC Signal

Time

Figure 5.29: Representation of a sound wave by an AC electrical signal.

CHAPTER 5. ELECTRICITY

129

Y

X

Z

Figure 5.30: Variable resistance between X and Y. Fine Wire

Voltage Source

Fuse

Figure 5.31: Fuse to protect speaker.

Speaker 1

L

+ _

R

+ _

Speaker 2

Figure 5.32: Two speakers connected in series to one channel of ampli er.

CHAPTER 5. ELECTRICITY

130

Speaker 1

Speaker 2

Effective Resistor

Voltage Source

Figure 5.33: Model of series circuit.

L

+ _

R

+ _

Figure 5.34: Parallel connection of two speakers to an ampli er.

CHAPTER 5. ELECTRICITY

131

Speaker 1

Speaker 2

Voltage Source

Effective Resistor

Figure 5.35: Model of parallel connections.

House Outlet Receiver 120 V 60 Hz

CD Player

Equalizer

Etc.

Figure 5.36: Parallel connections of hi- components to house electrical outlet.

CHAPTER 5. ELECTRICITY

132

Mass • Mass of Cone

• Compliance of Suspension

• Friction

Suspension

Figure 5.37: Response of cone speaker to a force.

CHAPTER 5. ELECTRICITY

133

Figure 5.38: Coil used to produce a magnetic eld when a current ows through it. It has inductance.

CHAPTER 5. ELECTRICITY

134

Impedance due to Inductance

Frequency 20 Hz

20,000 Hz

Figure 5.39: Frequency dependence of impedance associated with inductance.

Voltage Source

Voltage Source

Figure 5.40: Charging of a capacitor.

CHAPTER 5. ELECTRICITY

Voltage Source

135

Voltage Source

Figure 5.41: Charging of a capacitor when polarity of voltage source is reversed.

Impedance due to Capacitance

Frequency 20 Hz

20,000 Hz

Figure 5.42: Frequency dependence of impedance due to capacitance.

CHAPTER 5. ELECTRICITY

136

Inductance Sound Output In from Amplifier

Woofer Woofer

Frequency

Figure 5.43: Inductance in series with woofer prevents high frequencies from reaching it.

Capacitance Sound Output In from Amplifier

Tweeter Tweeter

Frequency

Figure 5.44: Capacitance in series with tweeter. It prevents low frequencies from reaching it.

CHAPTER 5. ELECTRICITY

137

In from Amplifier

Mid-range

Sound Output Mid-range Frequency

Figure 5.45: Capacitance and inductance in series with mid-range speaker to prevent the high and low frequencies from reaching it.

Impedance

Frequency Resonant Frequency

Figure 5.46: Impedance curve of driver.

Chapter 6

Ampli ers

138

CHAPTER 6. AMPLIFIERS

Sources of Audio Signals (CD, Tape, etc.)

139

Amplifier Weak Signals

Large Signals

Figure 6.1: Importance of ampli er in hi- system.

Source Command from Audio Signals Sound Output

Power Supply

Figure 6.2: Basic ampli er.

CHAPTER 6. AMPLIFIERS

140

Source Command: More Current Sound Output

Power Supply

Figure 6.3: Ampli er command for more current.

Source Command: Less Current Sound Output

Power Supply

Figure 6.4: Ampli er command for less current.

CHAPTER 6. AMPLIFIERS

Holes

p-Type

141

Electrons

n-Type

Figure 6.5: Semiconductor junction.

No Current flow

p-type

n-type

Battery

p-type

n-type

Battery

Figure 6.6: Reverse-biased semiconductor junction.

CHAPTER 6. AMPLIFIERS

142

Current flows

p-type

n-type

p-type

Battery

n-type

Battery

Figure 6.7: Forward-biased semiconductor junction.

Current

-Voltage

+Voltage

Figure 6.8: Symbol for diodes and its characteristics.

Diode

Input Voltage

Voltage across Resistor

Figure 6.9: Recti er action of a diode when an AC voltage is applied.

CHAPTER 6. AMPLIFIERS

n

p

143

n

Emitter

p

Collector

Base

n

p

Emitter

Collector

Base

Figure 6.10: Diagram of transistor and its circuit symbol for two possibilities.

Water Tank Current Flow

Command goes in as Current

Control

(Control) Power Supply

Water Flow

Figure 6.11: Ampli er action of transistor in a circuit compared to control of water ow.

CHAPTER 6. AMPLIFIERS

144

Signal Out Signal In Amplifier

Figure 6.12: Function of an ampli er.

Input

Input

+ Battery

Inverting

Non-Inverting

Output

Amplifier - Battery

Ground

Figure 6.13: Ampli er integrated on a chip.

Rf Input R input

Amplifier

Figure 6.14: Operational ampli er with negative feedback.

Output

CHAPTER 6. AMPLIFIERS

145

Rf Input R input

Output

Amplifier

Figure 6.15: Negative feedback corrects uctuations in gain.

Microphone

Speaker

Amplifier

Figure 6.16: Positive feedback in large hall with a mike and a loudspeaker system driven by mike.

CHAPTER 6. AMPLIFIERS

146

Input

Output

Ground

Figure 6.17: Volume control.

Input Output is Maximum Voltage

Ball at Maximum Energy due to its Position

Ground

Input

Output is Minimum Voltage

Ball at Minimum Energy due to its Position

Ground

Figure 6.18: Comparison of potentiometer action with energy of a ball on a ladder.

CHAPTER 6. AMPLIFIERS

147

Bass

Min

Treble

Max

Min

Max

Figure 6.19: Bass and Treble controls.

CHAPTER 6. AMPLIFIERS

+ 13

Relative Output (dB)

-13

148

Max. bass

Max. Treble Middle Position

20 Hz

1000 Hz

Min. Bass

20,000 Hz

Frequency

Min. Treble

Figure 6.20: E ect on signal spectrum of Bass and Treble controls.

Low, 6 dB/Octave

High, 6 dB/Octave

Relative Amplitude (dB)

Ideal Case with no Filter

Low, 18 dB/Octave 20 Hz

High, 18 dB/Octave Frequency 20,000 Hz

Figure 6.21: Action of LOW and HIGH lters with 6 dB/octave attenuation, and also with 18 db/octave attenuation.

CHAPTER 6. AMPLIFIERS

149

Signal Out Signal In Amplifier f

Extra Harmonics

+ ... =

+

+ 2f

3f Signal Out

f

Figure 6.22: Harmonic distortion by ampli er.

Non-linear Output

Linear Input

Figure 6.23: Non-linear gain of ampli er.

CHAPTER 6. AMPLIFIERS

150

Signal Out Signal In

f1 f2

Frequency f1 Amplifier

Frequency f2

f1- f2 f1+ f2

Figure 6.24: IM distortion in ampli er.

IM Distortion (%)

THD

Power Output Power Rating of Amplifier

Figure 6.25: Distortion increases sharply about power rating of ampli er.

CHAPTER 6. AMPLIFIERS

151

Signal Out

Signal In Amplifier

Large THD due to Clipping

Figure 6.26: Clipping of waveform by ampli er at high output levels beyond the rated value.

Signal Out

Signal In Amplifier

Noise

Figure 6.27: E ect of noise from ampli er.

CHAPTER 6. AMPLIFIERS

152

A Relative Output (dB)

20 Hz

20,000 Hz

Frequency

B Relative Output (dB)

20 Hz

20,000 Hz

Frequency

Figure 6.28: Comparing 2 ampli ers with the same specs. Even though their specs are the same, the ampli ers will sound di erent.

0 dB

Noise Level A - weighted 20 Hz

20,000 Hz

Measured Noise Level Frequency

Figure 6.29: A-weighted method of measuring noise.

Chapter 7

Electromagnetism

153

CHAPTER 7. ELECTROMAGNETISM

154

Current

Figure 7.1: E ect of current in a wire on compasses around it.

North

South

Figure 7.2: Bar magnet has a north pole and a south pole.

North

South

N

S

N

S

Figure 7.3: Cutting a bar magnet produces shorter magnets each with its own respective north and south poles.

CHAPTER 7. ELECTROMAGNETISM

155

Current

N

S

Magnetic Field

N

S

Magnetic Field

Figure 7.4: Magnetic dipole is the basic unit of magnetism.

Magnetic Domain

Figure 7.5: Unmagnetized piece of iron.

Iron Atom

CHAPTER 7. ELECTROMAGNETISM

North

156

South

N

S Magnet

Magnetized Iron

Figure 7.6: Alignment of domains in a piece of iron by a bar magnet. Iron becomes magnetized.

Current

North

South

Figure 7.7: Magnetic eld around a bar magnet and a wire carrying a current.

CHAPTER 7. ELECTROMAGNETISM

157

Battery

Many Loops = Coil Single Loop

Figure 7.8: Increasing the magnetic eld produced by a current in a wire: by forming a loop, and by using many loops.

N

S

-

+

Power Supply

Figure 7.9: An electromagnet.

CHAPTER 7. ELECTROMAGNETISM

158

N

S

-

+

Power Supply

Figure 7.10: Determination of direction of magnetic eld using rst left-hand rule.

Current

S

N

-

North Pole

+ Left Hand

Figure 7.11: Rule for determining direction of magnetic eld in an electromagnet.

CHAPTER 7. ELECTROMAGNETISM

159

Direction of Motion Fixed Magnet

N

S

N

S

Amplifier

Figure 7.12: First left-hand rule and how a cone speaker works.

Force

Current

N

S

Figure 7.13: Force on wire carrying a current in a magnetic eld.

CHAPTER 7. ELECTROMAGNETISM

160

Force Current (Negative to Positive)

Magnetic Field (North to South)

Left Hand

Figure 7.14: The second left-hand rule showing direction of force on wire carrying a current in a magnetic eld.

CHAPTER 7. ELECTROMAGNETISM

161

Current Magnetic Field

Magnetic Field

Current

Maximum Force

Zero Force

Figure 7.15: Direction of force depends on orientation of current with respect to magnetic eld.

CHAPTER 7. ELECTROMAGNETISM

162

Magnet Poles

S

S

S

N

N

N

+

Magnet Poles

Figure 7.16: A Heil Speaker.

CHAPTER 7. ELECTROMAGNETISM

S

Force

163

Magnet Pole

Force

Wire with Current

N Magnet Pole

Figure 7.17: One set of folds in Heil speaker.

CHAPTER 7. ELECTROMAGNETISM

164

Wire

Sheet

Magnet

N

S S

N

S

N

+ N

S

N

S

Figure 7.18: Magnetic Planar Speaker.

CHAPTER 7. ELECTROMAGNETISM

S

N

165

S

N

Wire

S

N

S

N

Figure 7.19: Forces on diaphragm when current direction is as indicated.

N

S

Figure 7.20: A bar magnet moving into a coil induces an electric current in that coil.

CHAPTER 7. ELECTROMAGNETISM

N

S

N

N

S

S

Figure 7.21: Induced current in coil by moving magnet.

166

CHAPTER 7. ELECTROMAGNETISM

N

167

S

N

S

Figure 7.22: Signi cance of relative motion between magnet and coil.

WRONG!!

N

S

Figure 7.23: Direction of induced current (wrong).

CHAPTER 7. ELECTROMAGNETISM

168

CORRECT!!

N

S

Figure 7.24: Direction of induced current (correct).

CHAPTER 7. ELECTROMAGNETISM

169

Primary Coil

Secondary Coil

Core

Figure 7.25: Schematic of a transformer and its circuit symbol.

CHAPTER 7. ELECTROMAGNETISM

170

Secondary Coil

Primary Coil

Figure 7.26: Step-up transformer.

Primary Coil

Secondary Coil

Figure 7.27: Step-down transformer.

CHAPTER 7. ELECTROMAGNETISM

N

171

S

Figure 7.28: Schematic of microphone based on Faraday's law of induction.

S

N

Figure 7.29: Exercise 7.14.

CHAPTER 7. ELECTROMAGNETISM

172

S

N Stationary

+ Figure 7.30: Exercise 7.15.

N S

Figure 7.31: Exercise 7.18.

Chapter 8

Electromagnetic Waves and Tuners

173

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

Figure 8.1: Electric Field around charged ping-pong ball.

Figure 8.2: Oscillating charged ball.

174

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

175

High-frequency Oscillating Electron

Oscillating Charged Comb

Figure 8.3: Generation of electromagnetic waves at two di erent frequencies.

Radio

6

10 Hz

Microwave

10 8 Hz

Infrared Light Ultra-violet

10 12 Hz

10 14 Hz

10 15 Hz

X-rays

Gamma-rays

10 16 Hz

10 18 Hz

Figure 8.4: Spectrum of electromagnetic waves.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

176

Electric Field

Magnetic Field

Direction of Travel

Figure 8.5: Electromagnetic waves are transverse waves with oscillating electric and magnetic elds.

eWaveform

eWaveform

eVoltage Source

eVoltage Source

Antenna

Antenna

Figure 8.6: Production of electromagnetic waves by oscillating electrons in antenna.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

Electric Field

177

Magnetic Field

Figure 8.7: Generation of electric and magnetic elds by antenna.

Antenna

Broadcasted Wave

Figure 8.8: Production of electromagnetic waves by antenna.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

178

Modulation: Pressure Increase Ambient Pressure Test Writing Pressure Decrease Painting a Picture

Sound

Figure 8.9: Some examples of modulation.

Audio Signal

Carrier

Amplitude Modulated Carrier Wave

Figure 8.10: Amplitude modulation.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

179

Station 1,000 kHz Modulated Carrier Wave Carrier

Audio Signal

Station 1,400 kHz Modulated Carrier Wave Carrier

Audio Signal

Figure 8.11: Carrier and audio signals broadcast by two stations.

Carrier

Amplitude

Frequency f - Audio Frequency

f

f + Audio Frequency

Figure 8.12: Spectrum of an AM carrier at frequency f when modulated by audio signal.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

180

AM Waves Amplitude Carrier

Frequency

f

Figure 8.13: Audio frequencies modulating carrier.

Sideband Frequencies Carrier

Relative Amplitude

Frequency f - 5 kHz

f

f + 5 kHz

Figure 8.14: Spectrum of frequencies on carrier for audio frequencies up to 5 kHz.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 1 Station Relative Amplitude

Next Station

Carrier 1

995 kHz

1000 kHz

181

Carrier 2

1005 kHz

Frequency

Figure 8.15: Spectrum of frequencies due to modulation of carrier.

Carrier Signal

Audio Signal

Amplitude does not change

Frequency changes Frequency Modulated Carrier Wave

Figure 8.16: Frequency modulation (FM).

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

182

Low Frequency Audio

High Frequency Audio

Carrier

Carrier

Figure 8.17: A low frequency and a high frequency audio signal frequency modulating a carrier.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

183

Quiet Audio

Carrier

Loud Audio

Carrier

Figure 8.18: A loud and a quiet audio signal frequency modulating a carrier.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

184

Spikes

Limiter

Figure 8.19: Action of limiter in FM.

Audio Information

17 Relative Amplitude (dB) 0 20 Hz

1 kHz

15 kHz

Figure 8.20: Pre-emphasis in FM broadcasting.

Frequency

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

185

Audio Information

17 Relative Amplitude (dB)

Noise picked up in Atmosphere 0 Frequency 20 Hz

1 kHz

15 kHz

Figure 8.21: Information brought to tuner on carrier.

Audio Information 0 Relative Amplitude (dB)

Noise

-17 Frequency 20 Hz

1 kHz

15 kHz

Figure 8.22: De-emphasis of audio information to reduce high frequency noise.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS Antenna

186

Antenna

Transmitter

Amp

Tuner

In

Out

Figure 8.23: Elements of radio communications.

rf Amplifier

Mixer

Rectifier and Filter

IF Amplifier

Out

Local Oscillator

Figure 8.24: Superheterodyne receiver.

I-F Signal

A-F Signal

Rectifier Filter

Figure 8.25: Processing part of AM signal with a simple diode and lters.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

187

Amplitude Pilot Frequency

L+R 50

L-R 15,000 19,000 23,000

L-R 38,000

53,000

Hz

Frequency

Figure 8.26: Audio information which will modulate carrier in stereo broadcasting.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

188

Antenna

Electric Field

At the same time ...

Magnetic Field

Figure 8.27: Alternating current in antenna produces electromagnetic wave.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

189

Electric Field

Electric Field

Capacitor Plates

Antenna Wires

Figure 8.28: Electric eld around charged antenna wires is similar to that between charged capacitor plates.

Current

Current

Magnetic Field

Wire with Current

Current

Antenna with Current

Figure 8.29: Magnetic elds around a wire and antenna with current.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

190

Incident Current Wave

Reflected Current Wave

Resultant Wave Current

Figure 8.30: Development of a standing wave on antenna.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

191

Current

Standing Wave on an Antenna

Displacement

Standing Wave on a String

Figure 8.31: Comparison of standing wave on antenna to that of a string.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

192

Antenna Axis

Figure 8.32: Radiation pattern of electric eld around half-wave dipole antenna.

270˚

0˚

180˚

Antenna Radiation Lobe 90˚

Figure 8.33: Polar graph representation of radiation pattern around halfwave dipolar antenna.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

193

Antenna

1/4 Wave

1/4 Wave Current

Co-axial Cable to Electronics

1/4 Wave

Reflection

Electric Conductor

Earth

Figure 8.34: Basic elements of a grounded vertical antenna.

1/4 Wave

Ground Plane

Figure 8.35: Quarter-wave antenna.

Earth

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

194

Reflected Part

Earth

Figure 8.36: Total antenna length is made shorter by inserting a coil in series.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

Electric Field of Radio Wave

195

Receiving Antenna

Figure 8.37: When the electric eld of radio wave is vertical, the receiving antenna should also be vertical.

Loop Antenna

Magnetic Field of Radio Wave

Tuner

Figure 8.38: Loop antenna detects the magnetic eld part of radio wave.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

196

Magnetic Core (Ferrite)

Loop Antenna with many turns

Loop Antenna with many turns and Ferrite Core

Figure 8.39: Two common loop antennas.

Broadcast Antenna

Vertical Polarization

Electric Field

Earth

Receiving Antenna

Figure 8.40: Vertically polarized radio wave.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

197

Broadcast Antenna

Horizontal Polarization

Earth Receiving Antenna

Electric Field

Figure 8.41: Horizontally polarized radio wave.

2 Mutually Perpendicular Antennas

Circularly Polarized Wave

Figure 8.42: Broadcasting with circular polarization.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

Broadcast Antenna

Ground Wave

Earth

Figure 8.43: Low frequency ground wave follows curvature of earth.

Broadcast Antenna

Straight Line Path

Earth

Figure 8.44: Direct (line-of-sight) mode of propagation.

198

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

199

F1 F2

150 Miles

300 Miles

Ionosphere 70 miles D

30 Miles

50 Miles

Earth

Figure 8.45: Earth's ionosphere layers.

Ionosphere

Broadcast Antenna

Reflected Sky Wave

Earth

Figure 8.46: Sky wave world communications.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

200

Ionosphere

Broadcast Antenna

Earth

Figure 8.47: Two-hop transmission of radio wave using ionosphere.

Earth Geostationary Satellite

Figure 8.48: Communication using a satellite.

CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS

99.6

100

100.4 MHz

99.8

201

Dial on Tuner

100.2

Figure 8.49: Selectivity relates to how well alternate channels are rejected.

Reflected

Broadcast Antenna

Receiver

Direct

Figure 8.50: Direct and re ected waves from a broadcasting station.

100 Mhz 100 Mhz Receiver

Should be suppressed

Figure 8.51: Capture ratio in tuner.

Chapter 9

Analog Recording and Playback

202

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

203

Top View

Left Channel

Right Channel

Side View

Figure 9.1: Record with grooves representing mechanically engraved waves.

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

Output

Piezoelectric Element

Piezoelectric Pick-up

Magnet

SN Moving Magnet Pick-up

Figure 9.2: Phono playback systems.

204

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

Left

Right

90˚

Figure 9.3: Stereo with only one stylus.

205

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

SN Figure 9.4: A stereo moving magnet phono cartridge.

Magnetic Domain

Unmagnetized Magnetic Material Magnetization is Zero

Magnetized Magnetic Material Magnetization is Non-Zero

Figure 9.5: Unmagnetized and magnetized magnetic material.

206

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

207

Magnetic Field

Current

Magnetic Field in Coil

Current in Coil

Figure 9.6: Magnetic eld produced by a coil when current ows through it.

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

208

Total Magnetization

Saturation

Current in Coil

Figure 9.7: Alignment of domains in a magnetic material.

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

209

Total Magnetization

Saturation

Rententivity

Current in Coil

Figure 9.8: Behavior of magnetic material in a coil whose current is increased and decreased to zero.

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

210

Magnetization

Current in Coil

Coercivity

Current in Coil

Figure 9.9: Memory is destroyed by reversed current in coil.

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

211

Magnetization

Magnetic Field of Coil

Magnetic Field of Coil

Magnetization

Figure 9.10: Hysteresis curve of magnetic material.

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

Hard

Soft

Figure 9.11: Groups of magnetic materials.

212

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

213

Side View

Magnetic Particles

Polyester Film Stereo L1

1

R1

2

L2

3

R2

4

Heads

Top View

Figure 9.12: Side and top views of magnetic tape.

Figure 9.13: Magnetic particle of gamma { Iron (III) Oxide as used on tapes.

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

Audio Input

N

S

S

N

N

S

Tape Motion

Figure 9.14: Recording head aligning magnetic domains on tape.

214

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

Audio Signal:

Top View of Tape Domain Alignment N S

Domain Alignment S N

1 Wave

Audio Signal:

Top View of Tape

1 Wave

Figure 9.15: Analog recording on a magnetic tape.

215

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

N

S

S

N

N

S

S

1 Wave

1 Wave

High Frequency

Low Frequency

N

Figure 9.16: Recorded information on magnetic tape.

Output

S

N

N

S Tape Motion

Gap (Exaggerated)

216

Figure 9.17: Playback head for reading information on a tape.

Output

S N N S 1 Wave Tape Motion

Figure 9.18: Playback head reading signals.

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

Erase

Record

217

Playback

Tape

Figure 9.19: Order of heads on a tape deck.

Magnetization

Recording Current in Coil

Recording Current in Coil

Magnetization

Figure 9.20: Recording on material with magnetic hysteresis.

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

218

Magnetization Recorded Information Recording Current in Coil Input Current to Coil

Figure 9.21: Recording a signal on a tape.

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

219

Magnetization Recorded Information

Current in Input Coil

Input Information Linear Characteristic of Tape

Figure 9.22: Ideal magnetic characteristics for tape | linear behavior.

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

220

Magnetization Region to be avoided

Current in Coil Almost Linear Regions

Figure 9.23: Useful region on hysteresis curve for magnetic recording.

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

Audio Output

0

Audio + Bias on Tape

+

A-C Bias Input

Audio Input

Audio + Bias Input

Figure 9.24: Recording on magnetic tape with bias.

221

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

222

Audio Signal

Recording Amplifier

Bias Oscillator

Playback Amplifier

Erase

Record

Playback

Figure 9.25: Details of heads for magnetic recording.

Output from Playback Head

Frequency 20 Hz

20,000 Hz

Figure 9.26: Frequency dependence of output from playback head.

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

223

1 µm Gap

Output from Playback Head

2 µm Gap 4 µm Gap

Frequency 10 kHz

20 Hz

20 kHz

15 i.p.s.

Output from Playback Head

71/2 i.p.s.

1 7/8 i.p.s.

Frequency 10 kHz

20 Hz

20 kHz

Figure 9.27: Output from playback head as a function of frequency for various gap sizes and tape speeds.

70 µ sec Equalization

Output (dB)

120 µ sec Equalization

Frequency 20 Hz

100 Hz

1000 Hz

10 kHz

20 kHz

Figure 9.28: Equalization in playback.

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

224

Output (dB)

Frequency 20 Hz

5000 Hz

20 kHz

Figure 9.29: Equalization in recording.

Transients Amplitude Average Sound Levels

Time

Figure 9.30: Typical musical spectrum.

CHAPTER 9. ANALOG RECORDING AND PLAYBACK

225

Recording Level (dB) 0 -10 -20

Frequency 10 Hz

1 kHz

10 kHz

20 kHz

Figure 9.31: Frequency response at di erent recording levels.

X Y Figure 9.32: Exercise 9.4.

Chapter 10

Digital Optical Recording & Playback

226

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

Pressure

227

Voltage

Time

Time Continuous Representation

Figure 10.1: Sound wave and its analog representation as a voltage.

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK High Frequency Signal

Scratch

Groove

Very Large Amplitude Signal

Figure 10.2: Grooves on a record representing analog signals.

228

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

229

Playback

Tape

Dirt

Recorded Signal

Tape Motion

Played Back Signal

Figure 10.3: Distortion of analog signal by dirt stuck between playback head and tape.

2

Original Number 2

Worn out Number 2

Figure 10.4: Original number 2 and worn out number 2; basic information is not lost when number is worn out.

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

Amplitude (Decimal)

230

Amplitude (Binary)

8

1000

4 2 0

0100 0010 0000 Time

Time

Figure 10.5: (a) Analog signal, decimal scale (b) Analog signal, binary scale.

20 Hz Time

200 Hz Time

Figure 10.6: 20 Hz wave will get more samples per wave than a 200 Hz wave.

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK Aliased Signal

Signal

Samples (not enough!)

Signal No Aliasing

Samples (good!)

Figure 10.7: Aliasing due to inadequate sampling rate.

231

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

232

Sampling Frequency

Signal

Good, No Aliasing, Maximum Signal Frequency F = FS / 2

F = FS / 2

Frequency FS

FS + FS / 2

Poor, Aliasing, Maximum Signal Frequency F > FS / 2

Alias Zone

Frequency F > FS / 2

FS

FS + FS / 2

Figure 10.8: Audio spectrum and sideband frequencies due to sampling.

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

233

Sample and Hold of Analog Signal Amplitude

Holds

Time

Sampling Points

Figure 10.9: Sample and hold of a signal for digitizing.

In

Left Multiplexer

In

Right

2 Channels

1 Channel

Figure 10.10: Multiplexing of left and right channels.

Out

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

0110 0100 0011

1000

0010 0001

Analog Signal

Sampled Analog Signal

0111 0101 0011 0010 0001

Digital Signal

Left Channel Low-Pass Filter

Sample & Hold

A/D Converter First Multiplexer

Right Channel Low-Pass Filter

Sample & Hold

A/D Converter

Figure 10.11: Digitizing a signal.

Output from D/A Converter

Figure 10.12: Output of D-A converter.

234

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

Smoothing by Low-pass Filter

Output from D/A Converter

Figure 10.13: Output of low-pass lter.

Left Channel In

Left Channel Analog Out

D/A Converter Digital

Low-Pass Filter

0100 1000 1101 1001

Figure 10.14: Main features of playback of digital signal.

235

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

236

Disc Travels Slower To keep constant Laser Beam to Disc Speed Disc Travels Faster

Pits and Lands

Figure 10.15: Details of information on a CD.

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

237

Land 1/4 Wave

Pit

Laser Beam

Out of Phase by 1/2 Wave

Figure 10.16: Interference between light beam re ected from pit and from at.

Pits

Label

Protective Layer Metal Film Layer Compact Disc Transparent Substrate

Lens In Out Laser Beam

Figure 10.17: Focusing action of a laser beam by lens.

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

238

Dirt out of Focus

Compact Disc Dirt Lens

Laser Beam

Figure 10.18: Reduced e ect of surface defect on CD.

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

239

Land Length Pit Length

Land

Pit

Track Pitch 1.6 µm

Track Width 0.5 µm

Laser Beam 0.8 µ m

Figure 10.19: Laser spot focused on disc data.

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

240

Laser Beam to Track Disc Direction Laser Beam to Read

Laser Beam to Track Pit

Figure 10.20: Three-beam detection; one for read-out and two beams for tracking.

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

Wave

Wave Randomly Polarized

Plane Polarized

Figure 10.21: Randomly polarized beam and plane-polarized beam.

241

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

242

Compact Disc Objective Lens

Circularly Polarized Light

1/4 Wave Plate

Vertically Polarized Light Beam Splitter

To Detector

Out Cylindrical Lens Converging Lens Horizontally Polarized Light In from Laser

Figure 10.22: Path of laser beam and role of its polarization.

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

Coherent Beam of Light

Incoherent Beam of Light

Figure 10.23: Coherent and incoherent beams of light.

243

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

244

Current Front Mirror Rear Mirror

pn Junction

Laser Beam

Current

Figure 10.24: Semiconductor laser.

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

Sampled Signal

2 × Oversampled

4 × Oversampled

Figure 10.25: E ect of 2-times and 4-times oversampling.

245

CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK

Mini Disc

Optical Readout

In: 1.4 MBit / Second

Memory

Out: 0.3 MBit / Second

Figure 10.26: Shock-proof memory in mini-disc.

246

Chapter 11

Digital Magnetic Recording & Playback

247

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK248 Track

Magnetic Domains

Figure 11.1: Magnetic digital signals recorded vertically on a mini disc.

Recording Magnetic Head

Signal In

Protective Layer

Magnetic Recording Layer Substrate

Mini Disc

Lens

Laser Beam

Figure 11.2: Recording digital signals on a mini disc.

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK249 S

Magnet N Polarization Rotation of Polarization Plane

Laser Beam In

Reflected

Figure 11.3: Kerr e ect: plane of polarization of light beam rotates upon re ection from a magnetized surface.

Record Head

Record Head

In Lens

Out Lens

Polarization Plane

Figure 11.4: Read-out of digital information using Kerr e ect. Magnetic

eld direction a ects plane of polarization of re ected laser beam.

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK250

Prerecorded Disc

In

Out Lens

Lens Interference Effect

Change in Intensity Bright

Less Bright

Recordable Disc

In

Out Lens

Lens

Change in Polarization Plane

Kerr Effect

Figure 11.5: Di erence in read-out between pre-recorded and recordable mini-discs.

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK251

Pre-grooved for Tracking Laser Spot Pre-groove SiN

SiN Reflective Layer Magneto-optic Layer

Figure 11.6: Section of a recordable mini disc.

Lead-in Area

Program Area

Lead-out Area

Figure 11.7: Layered structure of recordable mini disc.

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK252

Upper Sector

Lower Sector

Figure 11.8: Track pattern in DCC tape.

DCC Head

Record

Record

Playback

0 1 2 3 4 5 6 7 8

0 1 2 3 4 5 6 7 8

Upper Sector

Read

Digital Right Left

Analog Playback Only

Figure 11.9: The playback head reads only a portion of the recorded track.

SPL-dB

Treshold of Hearing

Frequency .02 .05 .1

.2

.5

1

2

5

10

20

Figure 11.10: Threshold of hearing curve.

kHz

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK253

SPL-dB Record

New Treshold

Ignore Frequency .02 .05 .1

.2

.5

1

2

5

10

20 kHz

Figure 11.11: Sounds which will be recorded by PASC and masking of quiet passages.

1

1

0 Audio Signal:

Tape

Figure 11.12: Representation of digital signal on magnetic tape.

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK254

Head Drum Tape

Audio Tracks Slanted Tape Path

Record / Play Head

Figure 11.13: Helical recording with rotating heads.

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK255

Record / Play Head A

90˚ Tape Record / Play Head B

Figure 11.14: Tape contact to rotating head.

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK256

Head A Head B 90Ëš Wrap Angle

1/4 Revolution Head A Signal

Head B Signal One Revolution

Figure 11.15: Time compression to reduce wrap angle.

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK257

Analog Cassette Track Pattern

Right Side B

Side A

Left Left

Guard Band

Right

Figure 11.16: Guard band between tracks on analog tape reduces cross-talk.

Guard Band not necessary

Tape Head A

Head B

Figure 11.17: Azimuthal recording.

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK258

B

A

Tape - 20˚ Azimuth

+ 20˚ Azimuth

Figure 11.18: Digital information on magnetic tape recorded longitudinally.

CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK259

B

A

Subcode

Tape Au d

ATF

io

Subcode

ATF

Figure 11.19: Arrangement of signals on a tape.

+

X Y

Figure 11.20: Exercise 11.7.

Chapter 12

Heat

260

CHAPTER 12. HEAT

261

Mechanical Friction Friction causes Heating

Friction causes Heating

Stylus

Groove Motion

Friction causes Heating

Friction causes Heating

Metallic Wire Electrical "Resistance" due to Collisions of Electrons and Vibrating Ions

+ +

+

+ +

Vibrating Ions

+

Moving Electrons

Figure 12.1: Sources of heating in hi- due to mechanical friction and electrical \friction".

CHAPTER 12. HEAT

262

Heat

Heat

Current

Current

Resistor

Diode

Heat Heat

Voice Coil Current

Current

Speaker Transistor

Figure 12.2: Electrical \friction" causes heating in ampli er components and voice coil.

CHAPTER 12. HEAT

263

100 째C Pressure

0 째C

Gas Alcohol

Figure 12.3: Two types of thermometers: alcohol expansion thermometer and gas thermometer.

CHAPTER 12. HEAT

264

Electrical Resistance in arbitrary units

-50 째C

0 째C

50 째C

Cold

100 째C

Temperature

Hot

Figure 12.4: Temperature dependence of electric resistance of a semiconductor.

Battery

Current Meter

Resistance Thermometer Element

Figure 12.5: Basic circuit for resistance thermometer.

CHAPTER 12. HEAT

265

T at Room Temperature Laser Beam

TbFeCo

≈ 1000 Å

Aluminum

Section of Mini-Disc

T above Curie Temperature

Section of Mini-Disc

To Record

Figure 12.6: Heating of spot on mini-disc for recording.

Heat Flow

Hot

Cold

Large Amplitude

Small Amplitude

Figure 12.7: Heat conduction along a bar between a hot body and a cold one.

CHAPTER 12. HEAT

266

Hot

Heat

Cold

Smaller Thermal Resistance

Hot

Heat

Cold

Larger Thermal Resistance

Figure 12.8: Thermal resistance depends on length of heat conductor.

CHAPTER 12. HEAT

267

Heat Smaller Thermal Resistance

Hot

Cold

Cross-sectional Area

Larger Thermal Resistance

Hot

Cold Heat

Figure 12.9: Thermal resistance depends inversely on cross-sectional area of heat conductor.

CHAPTER 12. HEAT

268

Warm Air

Cold Air

Source of Heat

Figure 12.10: Transfer of heat in air by convection.

Object Temperature = T

Vibrating Charges

+

Electromagnetic Wave

+

Figure 12.11: Object at temperature T emits electromagnetic waves.

CHAPTER 12. HEAT

269

Vibration of Atoms

At some Temperature

Vibration of Atoms

When Temperature has Increased

Figure 12.12: Thermal expansion of an object when heated.

Brass Hot Cool

Steel Flame

Ice

Figure 12.13: Bimetallic strip and its behavior when heated or cooled.

CHAPTER 12. HEAT

270

Unmounted

Diode

Transistor

Mounted

Heat Sink with Large Area

Heat Sink with Large Area

Figure 12.14: Mounting of transistor and diode on heat sink to transfer heat away from devices by heat conduction.

CHAPTER 12. HEAT

Hot Air

271

Radiation

Convection Holes

Cold Air

Holes

Figure 12.15: Heat removal by convection and radiation.

Materials with different Expansion Amounts

Reset Button

Too Hot

Current In

Open Circuit Current Out

Figure 12.16: Action of circuit-breaker when too hot.

CHAPTER 12. HEAT

272

Signal In

Signal In Write Head

Write Head

Magnetic Film

Motion Laser Off

Spot Heated above Curie Temperature

Spot Cools in Field of Write Head Heat to Record

Recorded

Figure 12.17: Thermo-magnetic recording on mini-Disc.

Chapter 13

Mechanics

273

CHAPTER 13. MECHANICS

274

Recording Head

Tape

Direction of Travel Distance travelled in Elapsed Time

Figure 13.1: Speed of tape past recording head.

Earth

Figure 13.2: Time for a radio wave to go around the Earth at the equator.

CHAPTER 13. MECHANICS

275

Rotation

X Velocity is 0.4 m/sec, down

Y Velocity is 0.4 m/sec, left

Phono Record

Figure 13.3: Speed of a recorded signal is the same at X and at Y; their velocities are di erent.

CHAPTER 13. MECHANICS

276

Fixed Magnet

S

N Force

+ Fixed Magnet

S

N Force

+ Figure 13.4: Force on voice coil giving it a push or a pull depending on direction of current in voice coil.

CHAPTER 13. MECHANICS

277

Pinch-Roller Tape

Capstan

Tape Direction Force

Figure 13.5: Force on tape by capstan-pinch roller.

Pinch-Roller

Tape

Force of Static Friction Tape Direction Capstan No Motion between Tape and Pinch-Roller and Capstan

Figure 13.6: Static friction-force pulling on tape.

CHAPTER 13. MECHANICS

278

CD

Clips

Figure 13.7: Releasing a CD from its case by applying a pressure on the clips with a nger.

CHAPTER 13. MECHANICS

279

Tweeter has Small Inertia

Woofer has Large Inertia

Figure 13.8: Inertia of a tweeter is less than that of a woofer.

CHAPTER 13. MECHANICS

280

Outer Ear

Eardrum

Sound Figure 13.9: Outer ear; ear drum's inertia limits response at frequencies above 20 kHz. Tone Arm Cartridge

Stylus

Weight of Cartridge for Tracking Groove in Phono Record

Figure 13.10: Adjusted weight in cartridge for helping the stylus to track the groove in phono record.

CHAPTER 13. MECHANICS

281

Speaker Mechanism

Fixed Magnet

S

N

Current (Audio)

Information Tracks on CD

Focus Coil Lens Moving Coil to Focus

S

N

N

S

Laser Beam for CD

Figure 13.11: Force of clamped magnet on a voice coil accelerates diaphragm in loudspeaker. Force of clamped magnet on focus coil accelerates focus lens in CD player.

CHAPTER 13. MECHANICS

282

Wall Pulse on String Pulls on Wall

Wall Pulls on String causing Pulse

Wall

Figure 13.12: Re ection of a pulse on a string clamped at wall and its inversion.

CHAPTER 13. MECHANICS

283

Force on Voice Coil Bar Magnet

N

S

Force on Bar Magnet Current

Because of this, Magnet must be clamped

Figure 13.13: Force on voice coil and force on magnet.

CHAPTER 13. MECHANICS

284

Phono Record

Constant Frequency of Rotation

Both at same Frequency

CD

Variable Frequency of Rotation Both at same Frequency

Figure 13.14: Waves recorded on a phono record and a CD.

CHAPTER 13. MECHANICS

285

Phono Record r inner router

Circumference at r inner 2 π r inner

Circumference at router 2 π router

Figure 13.15: Distances covered along outer track and inner track on a phono record.

CHAPTER 13. MECHANICS

286

CD

Rotation Rate increased to 500 rpm Rotation Rate at 200 rpm

Figure 13.16: Frequency of rotation of a CD is made higher near the inner edge and lower near the outer edge to maintain constant linear speed on a tracks.

2000 rpm

Record / Play Heads

Drum

Tape Guide

Tape

Figure 13.17: Rotation of drum head relative to magnetic tape in DAT.

CHAPTER 13. MECHANICS

287

CD

CD

Ca

se

Li

d

A. Harder to Open

CD

CD

Ca

se

Li

d

B. Easier to Open

Figure 13.18: When same force is applied to the CD case lid, it is easier to open the lid near the edge because torque is larger there.

CHAPTER 13. MECHANICS

288

Large Torque Small Torque Force Force

Distance Distance Lid

Lid

Hinge Point

Hinge Point

B

A

Figure 13.19: For the same force exerted on lid, the torque is larger in B than in A.

CD

MD

Figure 13.20: Moment of inertia of a CD is larger than that of a mini-Disc.