| Abstract: | In the course of measuring the real-ear attenuation at threshold (REAT) of experimenter-inserted E-A-R foam earplugs on 100 subjects, a statistically significant correlation was observed between attenuation and hearing level (for normal listeners, HTL less than or equal to 20 dB) at test frequencies from 2-8 kHz. Listeners with more sensitive hearing obtained better protection. The relationship was most robust at 6 and 8 kHz. For hearing levels greater than 20 dB, attenuation appeared independent of hearing level. A hypothesis was developed to explain the relationship for the normal listeners, based upon the fact that the high-frequency attenuation of the earplug was nearly bone-conduction limited. The hypothesis suggested that the attenuation of a hearing protector that provided substantially lower protection would not exhibit the same relationship. Data for such a device were collected for 70 subjects, and indeed demonstrated reduced correlation between attenuation and hearing level. Implications of the results of the experiments are discussed with regard to hearing level requirements for hearing protector attenuation test subjects, utilization of hearing-impaired listeners to measure REAT at suprathreshold (with respect to normal listeners) sound pressure levels, and linearity of hearing protector attenuation as a function of sound level. |
