The exposure at the ear in response to a forward-propagating wave depends upon the angle of incidence at the head, the nominal sound pressure level of the impulse and the attenuation of hearing protection (if worn). The unoccluded and occluded responses of an acoustic test fixture equipped with two G.R.A.S. IEC 60711 couplers ¼-inch microphones were measured in 15° increments for impulses with nominal peak sound pressure levels of 150 and 160 decibels. The attenuation was assessed in a variety of ways: Impulse Peak Insertion Loss (IPIL), change in A-weighted Equivalent Energy, and change in the Auditory Hazard Unit. Generally, the LAeq was quite similar to the (IPIL). However the change in AHUs predicted less attenuation than was actually observed. The lower performance for AHUs may be attributable to the nonlinear hazard growth for the unoccluded ear.

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