Standardized acoustic test fixtures for testing ear protection devices and noise cancelling headsets
G.R.A.S. Sound & Vibration A/S
Wednesday 3 june, 2015, 11:40 - 12:00
0.4 Brussels (189)
This paper is a study supported by practical tests on different methods and standards for measuring ear protection and the differences between these methods. Several acoustic test fixtures can be used for measuring the Insertion Loss of Hearing Protectors Devices (HPD) and Active Noise Cancelation (ANC) Devices. First, it is very important to have an Acoustic Test Fixture (ATF) with a very high self-insertion loss to insure that the measured insertion loss on the Device Under Test (DUT) is not influenced by false signals introduced in the ATF itself. Secondly, it is important to decide whether a more humanlike shape with a corresponding Head Related Transfer Function is needed, or a more simplified ATF can be used. In the first case, the ANSI standard s12.42 describes a proper method, while ISO 4869-3 describes the second method. The ANSI s12.42 ATF is designed with a special ear canal extension, which is longer than the standard extension, known from other ATFs like KEMAR, and is fitted with fleshlike material to better adapt In the Ear (ITE) devices. Thirdly, a large circum-aural pinna is included to ensure a perfect seal for all kinds of Over The Ear hearing protection devices. Furthermore, the total system consisting of ear simulator, ear canal extension and pinna are heated to body temperature. The ISO 4869-3 defines a more simple solution for circum-aural HPD’s, but can as well as the ANSI standardized ATF bee combined with pinnas, ear canal extensions and ear simulators for testing ITE devices. The two types of ATF are especially good when testing the new high quality ANC hearing protectors and headsets, which is why this presentation also looks at the challenges when measuring on ANC devices.
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