DEVELOPMENT OF A UNIQUE PASSIVE HEARING PROTECTOR WITH LEVEL-DEPENDENT AND FLAT ATTENUATION CHARACTERISTICS

The nonlinear resistance of a small, sharp-edged orifice has been used for over twenty years to provide a level-dependent noise reduction in an earplug. It serves well in applications for which protection is required against high-level momentary impulses, such as gunfire, and when low noise reduction is needed between impulses for improved reception of speech and other low-level signals. An earmuff has been developed with similar performance characteristics, but designed to serve a wider range of applications. Its attenuation rises instantaneously for impulses above 120 dB, and approaches that of a conventional earmuff for impulses that reach 160 dB. Between or in the absence of impulses, it allows good reception of speech and similar signals by providing attenuation that is substantially flat from 400 to 8000 Hz and as much as 15 dB less than that of conventional earmuffs in this frequency range. This paper describes the development of this earmuff and presents performance data.