Types and Effects of Noise exposure in Aviation

In one of my previous articles we talked about the Sound, Hearing and Noise in aviation. You can read that article by clicking here. Let’s talk now about the types and effects of noise.

Types of Noise

Steady: Continuous noise of sudden or gradual onset and long duration (more than 1 second). Examples: aircraft power plant noise, propeller noise, and pressurization system noise. According to the Occupational Safety and Health Administration (OSHA), the maximum permissible continuous exposure level to steady noise in a working environment is 90 dB for 8 hours.

Impulse/blast: Noise pulses of sudden onset and brief duration (less than 1 second) that usually exceed an intensity of 140dB. Examples: firing a handgun, detonating a firecracker, backfiring of a piston engine, high-volume squelching of radio equipment, and a sonic boom caused by breaking the sound barrier. The eardrum may be ruptured by intense levels (140dB) of impulse/blast noise.

EFFECTS OF NOISE EXPOSURE

Physiologic

• Ear discomfort: May occur during exposure to a 120 dB noise.
• Ear pain: May occur during exposure to a 130 dB noise.
• Eardrum rupture: May occur during exposure to a 140 dB) noise.
• Temporary hearing impairment. Unprotected exposure to loud, steady noise over 90 dB for a short time, even several hours, may cause hearing impairment. This effect is usually temporary and hearing returns to normal within several hours following cessation of the noise exposure.
• Permanent hearing impairment: Unprotected exposure to loud noise (higher than 90dB) for eight or more hours per day for several years, may cause a permanent hearing loss. Permanent hearing impairment occurs initially in the vicinity of 4,000 Hz (outside the conversational range) and can go unnoticed by the individual for some time. It is also important to remember that hearing sensitivity normally decreases as a function of age at frequencies from 1,000 to 6,000 Hz, beginning around age 30.

Psychological

• Subjective effects: Annoying high-intensity noise can cause distraction, fatigue, irritability, startle responses, sudden awakening and poor sleep quality, loss of appetite, headache, vertigo, nausea, and impair concentration and memory.
• Speech interference: Loud noise can interfere with or mask normal speech, making it difficult to understand.
• Performance: Noise is a distraction and can increase the number of errors in any given task. Tasks that require vigilance, concentration, calculations, and making judgments about time can be adversely affected by exposure to loud noise higher than 90 dB.

Find more like this: Aeromedical Factors, Educational, Pilots , aeromedical, fit for flight, flight fitness, headsets, hearing, noise