Performance features of insert earphones.
Proceedings: 1992 hearing conservation conference, April 1-4, 1992. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, task order 91-37982, 1992 Apr; :121-124
The performance characteristics of insert earphones (IE) were reviewed. IE attenuations values ranged from about 28 to 37 decibels (dB) and 125 to 1000 Hertz (Hz), and from 33 to 42dB and 2000 to 8000Hz. Comparison of IE with TDH type earphones showed significantly more attenuation in the former, especially for the lower frequencies. IE calibration was done with an occluded ear simulator, HA-1 or HA-2 hearing aid coupler. Sound pressure levels (SPLs) were very stable for repeated intrasubject and intersubject measurements with both couplers. However, IE output SPLs differed between the couplers due to geometric differences between IE to coupler connections. Interim ANSI and International Standards Organization (ISO) threshold levels and reference equivalent threshold SPLs (RETSPLs) were discussed. For the HA-2 coupler, interim ANSI RETSPLs were slightly higher than the ISO RETSPLs, and were related to the database from which the RETSPLs were developed. A current IE threshold database, with adjusted and unadjusted mean thresholds, standard deviations, and threshold ranges across nine studies was presented. A five study database used to verify interim ANSI RETSPLs did not contain two studies used to develop ISO RETSPLs. Furthermore, the ANSI RETSPLs were based on the theory of adjusting, while the ISO RETSPLs were not adjusted. These differences in databases used were responsible for the discrepancies between ANSI and ISO thresholds. In clinical studies, earwax did not seem to be a major problem, and significant threshold differences between insert and TDH earphones were seen only in cases of conductive loss caused by a collapsing ear canal. The author concludes that research for specifying IE and supraaural earphone thresholds in both normal adults and children and those with middle ear pathologies is needed.
Audiometry; Ear-protectors; Hearing-disorders; Sensory-disorders; Noise-induced-hearing-loss; Performance-capability; Noise-measurement; Sound-attenuation
Proceedings: 1992 hearing conservation conference, April 1-4, 1992