Measurements of earplug attenuation under supra-aural and circumaural headphones

Abstract

Objective: Supra-aural audiometric headphones are generally not recommended for use in measuring the attenuation of earplugs, because contact between the headphone and pinna and/or earplug could alter the attenuation obtained, and because of concerns of non-comparability between modes of excitation from supra-aural headphones and the sound-field procedure required by the standardized method. In this study, we compared measurements of earplug attenuation obtained under Telephonics TDH-50P supra-aural headphones with measurements obtained under circumaural headphones designed expressly for such testing. Design: The attenuation of three types of earplugs (foam, premolded quadruple-flange, and custom-molded) was measured in a repeated-measures design. Study sample: The study sample comprised 42 normal-hearing adults (21 females, 21 males). Results: With the foam earplugs, nearly all of the attenuation measurements under the supra-aural headphones fell within 10 dB of the measurements under the circumaural headphones. With the flange and custom earplugs, approximately 10% of individuals obtained spuriously high attenuation under the supra-aural headphones. Conclusions: We conclude that standard supra-aural audiometric headphones are suitable for measuring the attenuation provided by foam earplugs. However, supra-aural headphones should not be used to measure the attenuation of flange or custom-molded earplugs. The potential exists for substantial over-estimation of attenuation, especially of custom plugs.

Key Words::

• Hearing protection
• HPD
• earplugs
• attenuation
• fit-testing
• supra-aural
• circumaural
• headphones
• TDH

Acknowledgements

The authors thank two anonymous reviewers for their many helpful comments and suggestions. We acknowledge Angeli Mohanani, Sneha Parikh, and Kara Swan for their assistance with data collection. Results from this study were presented at the 2012 conference of the National Hearing Conservation Association in New Orleans, USA.

Declaration of interest: This work was supported by the Office of Naval Research through the Naval Submarine Medical Research Laboratory work unit 50814. The study protocol was approved by the Naval Submarine Medical Research Laboratory Institutional Review Board in compliance with all applicable Federal regulations governing the protection of human subjects. The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, nor the U.S. Government.

The first author is considered a part-time employee of the U.S. Government. This work was prepared as part of her official duties. Title 17 U.S.C. §105 provides that ‘Copyright protection under this title is not available for any work of the United States Government.’ Title 17 U.S.C. §101 defines a U.S. Government work as a work prepared by an employee of the U.S. Government as part of that person's official duties. The authors report no declarations of interest.