Assessment of the attenuation provided by hearing protectors at high sound levels using reaction time and loudness estimation procedures

Abstract

Existing procedures for the evaluation of the attenuation provided by hearing protectors when worn by human subjects incorporate threshold‐level signals. An unresolved issue is whether the attenuation measured at threshold sound intensities is identical to that at the high intensities for which the protector was designed: Two procedures for providing real‐ear attention data at low and high sound levels were investigated here. The first of these, the reaction‐time (RT) paradigm, measures the time it takes a subject to respond to the presentation of an auditory stimulus. A function is then derived relating RT to simulus intensity in both the unprotected and protected conditions. From these two functions the attenuation provided at low and high sound levels can be determined. The second procedure, loudness magnitude estimation, is used in an identical fashion. Here, however, loudness‐intensity functions are determined in the unprotected and protected conditions with the difference between the functions for these two conditions reflecting the attenuation provided at various sound levels. Results obtained from ten normal hearers wearing ten different protectors (five muffs, five plugs) will be compared to attenuation estimates derived from the traditional real‐ear threshold procedure. [Research supported by grant 1‐R01‐OH00895 from the National Institute of Occupational Safety and Health.]