The effects of noise reducing earphone enclosures on audiometric thresholds and maximum permissible background noise level.
NIOSH 1992 Apr; :125-129
The effectiveness of noise reducing earphone enclosures on reducing background noise and masking effects on audiometric test signals was investigated. Two commercially available noise reducing audiometric earphone enclosures (Amplivox Audiocups and the Peltor AudioMate) were evaluated in terms of their attenuation characteristics, effects of audiometric thresholds, and maximum permissible background noise levels. Subjects were seven males and seven females, aged 20 to 41 years, with auditory threshold of 20 decibels (dB) or better at 500 to 8000 Hertz (Hz) in each ear. Each subject was tested at three sessions, with the Model 51 cushion alone, or encased in one of the earphone enclosures. Two sound field threshold tests (ears occluded and unoccluded) and one earphone threshold test were conducted. Real ear attenuation thresholds (REAT) were averaged and reference equivalent threshold sound pressure levels (RETSPLs) were calculated. Results showed that the AudioMate demonstrated the highest, and the Model 51 the lowest attenuation. The Audiocups attenuation values approximated those of Model 51 through 500Hz, and those of the AudioMate for frequencies of 1000Hz or higher. All three devices showed increasing REAT values with increase in frequency. Model 51 cushion alone, and Audiocups provided maximum attenuation at 4000Hz, beyond which it decreased, while the AudioMate continued to show small attenuation increases through 8000Hz. RETSPLs were reduced by both enclosure types at 125 to 250Hz. A table indicated ambient noise levels for frequencies of 500 through 8000Hz at which either Audiocups or AudioMate could be used without impact on audiometric thresholds.
Audiometry; Ear-protectors; Hearing-disorders; Noise-levels; Noise-induced-hearing-loss; Sound-attenuation; Noise-measurement; Sensory-disorders
Hearing Loss; Disease and Injury; Noise-induced-hearing-loss
Proceedings, 1992 Hearing Conservation Conference, April 1-4, 1992, Lexington, Kentucky, Office of Engineering Services, University of Kentucky and NIOSH