What are ultrasonic and infrasonic sound waves? - CBSE Class 8

Difference between ultrasonic and infrasonic sound Infrasonic sound waves Infrasonic sound: A frequency of less than 20Hz is considered to be an infrasonic sound. Infrasonic sounds have a frequency that is below the range of human hearing ability.

For example, earthquakes, thunder, and volcanic eruptions can all produce infrasonic sound waves. While the human ear is incapable of hearing this sound, elephants and whales are able to detect it. Elephants, whales, Rhinos, pigeons communicate using infrasonic sounds

Ultrasonic sound waves Ultrasonic sound: Ultrasonics are sounds that have a frequency greater than 20,000 hertz (cycles per second). Ultrasonic noises have a frequency that is higher than the range of human hearing ability to distinguish.

Dogs, cats, bat, and mice, for example, have a hearing range that extends into the ultrasonic frequency range. They have the ability to detect wavelengths that humans do not.

Ultrasonic sound and Infrasonic sound

Characteristics of sound waves Below are the characteristics of sound waves: 1. Amplitude (A) – The most significant movement of medium particles in either direction from their equilibrium (rest) location is the amplitude of a wave. The meter (m) is its SI unit. The image depicts the transverse equivalent of a longitudinal sound wave.

Amplitude (A)

Such that PQ = RS (amplitude)

2. Loudness and Intensity – The terms loudness and intensity are frequently used interchangeably in the same sentence. These two phrases are diametrically opposed to one another. A sound’s intensity is defined as the amount of energy conveyed per unit area per unit time, whereas loudness is defined as the amount of reaction a human ear has to a sound.

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3. Wavelength (λ): The wavelength is the distance between two successive compressions or rarefactions. The meter (m) is its SI unit.

Wavelength (λ)

Such that BF = DH (Wavelength)

4. Frequency (ν): The frequency is the number of complete oscillations per second. The frequency gets expressed in hertz (Hz).

5. Pitch: Pitch refers to the proportionate highness or lowness of its frequency. It’s a sound that’s shrill.

6.Time period (T) The time period is the amount of time it takes for one complete oscillation or cycle to be completed. The interval is defined as the amount of time that elapses between two successive wave crests or troughs. It is the reciprocal of the frequency of the wave. Such that

Applications of Ultrasounds 1. Ultrasound is also used to track the growth of a baby within the womb at various stages.

2. Plastic surfaces are welded using ultrasound.

3. The use of ultrasound to investigate the anatomy and motion of the heart is known as echocardiography. The data is utilized to determine if the patient’s heart has a defect.

FAQs (Frequently Asked Questions) 1.

Define echo.

It is a repeated sound because the original sound gets reflected off a hard surface. When you clap in a large room, you first hear the original sound, followed by the reflected sound. The original sound gets echoed in this reflected sound.

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2. Why aren’t we able to hear the echo that gets created in our classroom?

An echo can get heard when the time difference between the original and the reflected sound is more significant than 0.1 seconds. The distance between the sound source and the wall must be at least 17.2 meters to hear the echo. We cannot hear the echo since such a situation does not occur in our classroom.

3.

Explain the human ear’s auditory aspects.

The ear is the most vital organ for a human being to perceive sound. It converts sound impulses from the hearing range into electrical signals via the auditory nerve to the brain. The ear has three major parts, i.e., outer, middle, and inner ear. The pinna, the outer portion, gathers sound that gets transported to the eardrums via the auditory canal. The cochlea subsequently turns the vibrations into electrical impulses sent to the brain through auditory nerves and heard.

4.

What do you mean by ‘Reverberation’?

Reverberation is the persistence of sound after the source has stopped creating it owing to recurrent reflection. As soon as the source makes a sound, it spreads out in all directions. It gets partially reflected off a room’s wall once it reaches it.

This reflected sound comes from the opposite wall and gets partially reflected.

As a result, sound can get heard even after the source has stopped producing it.

Sound must be absorbed when it reaches the room’s walls and ceiling to prevent repercussions. Sound-absorbing materials such as fibreboard, rough plastic, thick drapes, and cushioned chairs can be employed to lessen resonance.

5.

Which kind of waves are sound waves?

A sound wave is a longitudinal mechanical wave that must propagate across a material medium.

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