The violent burst of noise made by airbags as they deploy could cause permanent hearing loss to 17 percent of the people exposed to them, a researcher at a national hearing conference said today.
The brief but sudden sound blast from an airbag is just one example of an impulse noise that people face, said auditory physiologist G. Richard Price, a consultant at Auditory Hazard Analysis in Charlestown, Md.
Unlike the continuous drone of a computer or washing machine in use, impulse sounds ratchet up the energy hitting your ears in a split second. In addition to the well-known dangers of impulse noises like gunfire, minor events like a hammer hitting a nail can produce hearing loss.
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Whether car windows are closed or open when airbags deploy affects the severity of hearing damage. Experts previously assumed sealed-tight windows led to more ear damage because they allow for higher pressure within the car cabin.
Price tested this idea by exposing models of ear structures to intense sounds above 130 decibels, or what you would hear if you were to stand on the runway as a jet takes off. The method is well established as an accurate predictor of hearing loss, 95 percent of the time. To simulate closed and open windows, Price altered the pressure surrounding the ear models.
As the pressure increased, hearing damage was reduced, overturning the previous thinking on the subject. The finding suggests that having car windows closed when airbags are activated is less hazardous to the ear than if the windows were open.
The higher pressure inside the cabin causes a stiffening of the middle ear, a small bone outside the inner ear. The stiffening blocks the sound energy from entering the inner ear where hearing damage takes place.
"Wearing hearing protection, designing equipment better, and being aware of the problem can all contribute to preservation of hearing," Price said.
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