Noise exposure limits and measurements for earphones

Abstract

There are noise exposure concerns regarding the use of audio earphones and telephone receivers. The permissible noise exposure limits have been defined for the occupational environment for many years, for instance, the US Code of Federal Regulations, 29CFR1910.95, Occupational noise exposure and the Directive 2003/10/EC of European Parliament on Minimum Health and Safety Requirements. Those permissible noise exposure limits are defined for noise exposure in an ‘‘open-field’’ environment. An open-field environment is an environment where the noise sources are at a distance from a person’s ear. The sound or noise field can be a combination or any of a free field, or partially reflected, diffused, and reverberant fields. Nonetheless, the noise exposures from earphones are not in an open field. They are localized at or inside the user’s ear. Conventional open-field noise exposure measurement methods do not apply. During the last 15 years or so, a few different test methods for measuring noise exposure from earphone or telephone receivers were developed. The standards of ITU-T P.360, UL 60950-1, IEEE 269, and EN 50332 were developed mostly by the telephone industry. This presentation addresses the common permissible noise exposure limits, how to relate the limits to earphones, and how to measure them.