Noise attenuation characteristics of the MX-41/AR and the Telephonics circumaural audiometric headsets.

Masking from background noise is often a serious problem when hearing levels are measured at or near the low reference threshold levels specified in the American National Standards Specifications for Audiometers, ANSI S3.6-1969. Since background noise limits for audiometric test rooms are inversely related to the noise reduction characteristics of the earphone/cushion assemblies, it is important that these units have significant and consistent attenuation properties. This paper reports the noise reduction characteristics measured for the conventional TDH-39 earphone mounted in the supra-aural MX-41/AR cushion and for the new TDH-50 Telephonics circumaural headset. The circumaural headset was found to produce an average of about 10 dB more noise attenuation than did a well-adjusted supra-aural device, and the circumaural headset provided much more consistent test-retest noise reduction characteristics. Theoretical aspects of headband force as well as the implications of attenuation measurements for test room recommendations are discussed.