If you work in a noisy environment or know someone who suffers from hearing loss, you may need to know these terms common in hearing loss prevention.
Basic terminology:
Acoustic trauma is a single incident that causes a sudden hearing loss. Examples of acoustic trauma are blows to the head and loud explosions.
Decibel ( dB ) is the unit that expresses the intensity of a sound. The threshold for discomfort is between 85 and 95 dB and the threshold for pain is between 120 and 140 dB. A dosimeter measures sound levels over a specified interval.
Hertz ( Hz ) is the unit for measuring audio frequencies. Human hearing ranges between 20 Hz and 20000 Hz, but is most sensitive between 500 and 4000 Hz.
Continuous noise can be measured for at least one second. Hazardous noise is any sound that is capable of causing permanent hearing loss. Impulsive noise is a sound that rises to a peak and quickly fades, like striking a hammer on a metal plate, or a gunshot.
Hearing loss in the workplace:
Action level is the sound level at which OSHA requires activities to reduce the risk of noise-related hearing loss.
Administrative and engineering controls are efforts to limit noise exposure. This can be done through schedule modification, location changes, or by changing the operating schedule of noisy machinery.
Exchange rate refers to the relationship between intensity and dose of sound. If the intensity of a sound increases by 5 dB, the dose of noise doubles. (Also called the doubling rate.) OSHA uses a 5 dB exchange rate; the U.S. Armed Forces use a 3 or 4 dB exchange rate.
Hearing tests:
Attenuation is the testing of sound protection, and can be done in calibrated sound fields or in the “real world”.
An audiogram measures hearing thresholds. A baseline audiogram is taken after a quiet period to give the best estimate of a person’s hearing ability. Subsequent audiograms can be compared to the baseline audiogram.
Presbycusis is natural, gradual hearing loss attributed to aging.