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Module 10 : Noise & Vibration Hazards Theory 1. Noise – unwanted sound originated from vibrations of objects. 2. Can be defined in terms of the frequencies that determine its tone and quality, along with the amplitude that determine its intensity. 3. Frequency (in Hertz, HZ) audible to the human ear range from 20 to 20,000 cycles per second, Hz. 4. The equation of wave propagation is : a. C= f λ b. Where C = sound velocity (1,100 ft/s) i. F = Frequency in Hz ii. λ = wave length in ft 5. Wave length increases if frequency decreases. 6. Noise can be divided into three; a. Wide band noise – noise that is distributed over a wide range of frequencies (most manufacturing machine). b. Narrow band noise – confined to a narrow range of frequencies (power tools). c. Impulsive noise – consists of transient pulses that can occur repetitively or not (jackhammer). Measurement 1. Sound intensity is measured using sound level meter, and the unit is called dB. Hazard levels and risks 1. Hazard due to excessive noise is hearing loss. This loss of hearing is a result of loss of receptors in the inner ear. 2. The ear will damage when frequency approaches 2,400 to 4,800 Hz. 3. Most important factors affect the risk of hearing loss are a. Intensity of noise b. Type of noise c. Duration of exposure d. Age on individual e. Coexisting hearing disease f. Nature of environment g. Distance from source h. Position of ears relative to the sound wave


Noise control 1. Engineering controls of noise focus on three ways a. Reduce noise level at its source – change machine / redesign b. Control along its path – isolate noisy equipment by install acoustical materials on walls, ceilings, and floors c. Control at the receiver level – earplugs / earmuffs 2. Administrative controls focus on a. Exposure management. Rotating and limiting exposure to noisy area and b. Education are the options within the administrative means. Hearing protection 1. The personnel in the area can wear hearing protection; i) Earplugs ii) Earmuffs Vibration hazards -


Closely related to noise hazards. Two types of injuries o Motion sickness to spinal injury when operating heavy vibrating equipment o Hand-arm vibration syndrome Injury prevention strategies o Use / purchase low vibration tools o Limit exposure o Change work habits

Figure 1 : Earplugs


Module 10_Noise and Vibration