Validation of an Acoustic Head Simulator for the Evaluation of Personal Hearing Protection Devices

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Authors
  1. Abel, S.M.
  2. Odell, P.
  3. Dunn, G.
Corporate Authors
Defence R&D Canada - Toronto, Toronto ONT (CAN)
Abstract
A study was carried out to assess the validity of using an acoustic test fixture (ATF) to assess the sound reduction afforded by personal hearing protection devices. The ATF under review consists of a head simulator, cast in silicone rubber and covered with artificial skin. Cavities milled out on either side allow for the insertion of snap-in ear modules that incorporate a mechanical reproduction of human aural tissues. The ear canal is terminated by Zwislocki coupler and Etymotic ER-11 measurement microphone and models the impedance of the human ear. The experiment was carried out in a semi-reverberant chamber. On two separate occasions scheduled four months apart, the right ear of the ATF was fitted with an earmuff (E-A-R 3000), an earplug (E-A-R Classic foam plug), and the muff and plug in combination. The non test ear was fitted with the plug. The stimulus was a continuous pink noise, presented free-field at a level of 86 dB SPL using a bank of low, middle and high frequency speakers. Monaural sound level measurements were made under each of these conditions, as well as with the test ear unoccluded. These were replicated three times within session with two different settings of the measurement microphone, diffuse-field equalization and flat frequency response. Measurements were recorded and subsequently subjected to a third octave band analysis from 12.5 Hz to 20 kHz. The results showed that the measurements were highly stable within and across sessions. Differences due t

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Keywords
insertion loss assessment;human ear model
Report Number
DRDC-TORONTO-TR-2004-138 — Technical Report
Date of publication
30 Nov 2004
Number of Pages
52
DSTKIM No
CA025868
CANDIS No
523633
Format(s):
Electronic Document(PDF)

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