Airbag deployments are associated with loud noise of short duration, called impulse noise. Research on impulse noise from weapons firing, in particular that of G.R. Price & J.T. Kalb of the United States Army Research Laboratory, has led to the development of a mathematical model of the ear. This model incorporates transfer functions which alter the incident sound pressure through various ear parts. It also calculates a function, called the "hazard": a measure of mechanical fatigue of the hair cells in the inner ear. In this study, the repeatability of the model was examined by comparing its predictive behaviour for airbag noise impulses generated by nominally identical airbag systems. Calculations of potential "hazard" made by the model were also examined for reasonableness based on mechanical and biomechanical considerations. A large number of airbag noise pulses were examined using the model. The results provide some counter-intuitive insights into the mechanism of noise-induced hearing loss from deployment of airbag systems. Based upon testing of feline subjects (which are believed to be a good indicator of the risk to the more susceptible segment of the human population), the results indicate the following: there could be a risk of temporary and possible permanent threshold shifts in approximately 67% of the 1990-1995 model year vehicles from 19 manufacturers which were tested and assessed using the human ear model. For Part I see C 4525 (In: C 4511 S) (IRRD 879203).
Abstract