Human auditory response to an air bag inflation noise: Has it been 30 years?

Abstract

Once upon a time, over 30 years ago, 100 subjects volunteered for exposure to high level impulsive noises generated by the inflation of prototype automobile safety air bags. The government mandated that passive restraint systems, beyond seat belts, be introduced in passenger automobiles within 2 years. The only reasonable candidate was the air bag system, however, none were fully developed for automobile production. One concern was the effect of inflation noise on the auditory systems of vehicle occupants. Ninety-one volunteers qualified for the study; nine were rejected by an otolaryngologist because of head colds, congestion, and upper respiratory infections. Subjects facing forward in the rear seat of a small automobile experienced the noise of simultaneous inflation of a 9-cf passenger air bag and a 2.5-cf driver air bag. The median peak pressure level of the impulsive noises was 168 dB obtained with an overall measurement system ranging from 30 Hz (microphone low frequency cutoff) to 40 000 Hz. The dynamic range was 180 dB. Post-exposure auditory system evaluations included external auditory canals, eardrum membranes, verbal communications-auditory perception, aural discomfort, TTS, and PTS. Results are discussed in terms of the conditions of the exposures, the measurements, and the study population. [Work supported by DOT, National Highway Safety Bureau.]