Performance of New Acoustical Test Fixtures Complying with ANSI S12.42-2010, With Particular Attention to the Specification of Self Insertion Loss

摘要

ANSI/ASA S12.42-2010 specifies how to measure the insertion loss of hearing protection devices (HPDs). It requires use of acoustical test fixtures (ATFs) that are similar to existing ATFs but differ in terms of the earcanal length, inclusion of a simulated flesh lining the earcanal, and a heater to bring the fixtures to approximate body temperature. These features were necessary for the devices to provide insertion loss data with better correspondence to measurements on human heads. This was important as use of an ATF is the standard’s preferred method for tests on certain electronic earplugs and for all impulse testing. At least two ATFs [one from G.R.A.S. Sound and Vibration and the other from the Institute of St. Louis (ISL)] are intended to comply with the standard. The studies reported herein are part of an ongoing evaluation of these heads in which ATF insertion-loss measurements for a sample of passive earplugs and earmuffs are compared to real-ear attenuation at threshold data per ANSI S3.19-1974. This study will include discussion of recent modifications to one of those heads intended to address issues that were reported in an initial evaluation that was previously presented [Berger, Kieper, and Stergar (2011). J. Acoust. Soc. Am. 130(4) Pt. 2, p. 2434].