Hearing is second only to vision as a sensory mechanism to obtain critical information during the operation of an aircraft. All sounds have three distinctive variables: frequency, intensity, and duration. Normal conversation takes place in the frequency range from 500 to 3,000 Hz. Daily exposure to noise levels higher than 90dB can cause hearing impairment. This can go unnoticed initially because it occurs in the vicinity of 4,000 Hz (outside the conversational range). If the ambient noise level reaches 90dBA, you must use hearing protection equipment to prevent hearing impairment. Exposure to loud noise before flying (at home, while driving, at a party, etc.) can be as harmful as exposure to aircraft noise.
Hearing-threshold tests were made on flight personnel of several sorts, including aerial-application pilots, flight instructors, private pilots, stewa...
Forty-five attenuation spectra for earplugs were classified according to a simplified method designed to produce single-number ratings of noise reduct...
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