Abstract
It is widely accepted that for continuous noise, a relationship exists between the energy of sound (A-weighted) and its deleterious effects on hearing. However, when the exposure is to high intensity short duration impact or impulse noise, a hitherto unpredictable degree of damage can occur to the inner ear. The present study has set out to establish damage risk criteria for a variety of impulsive waveforms.
A mathematical model of the auditory periphery has been developed and verified for sinusoidal stimulation using existing experimental data. Experimental results, obtained using guinea pigs under impulsive stimulation, were used to calibrate the model. Once calibrated the model was used to give information as to the damage likely to occur from other types of impulsive stimuli, hence reducing the need for extensive animal experimentation.
It has been shown that the model can predict the potential auditory hazard from various impulsive stimuli, quantitatively in the guinea pig and qualitatively in man. Both the experimental and theoretical results indicated that the intensity of the first pressure wave of an impulse, above a certain value, is the most significant determinator of hearing damage.
The machine designer thus has guide lines as to where to concentrate his efforts in reducing potentially traumatic machine noise.
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