Monitoring sound pressures within the ear: application to noise exposure.

A technique for monitoring sound pressures within the ear, particularly suited to studies of exposure to noise, has been developed based on a miniature microphone located in the cavum of the concha, and a calibrated, cassette tape recorder. By applying a frequency‐dependent pressure transformation during playback of data recorded at the concha, typical sound pressures at the center‐head position are recovered for comparison with accepted standards for hearing conservation, including those permitting increased exposure to interrupted noise. As an application of the technique, the sound levels experienced by forest workers operating timber skidders have been studied. It is found that near‐daily exposure to the noise of a typical harvesting operation will result in significant loss of hearing. The consequences of changing the sequence of work, and the noise of the machine, are discussed, as well as the wearing of ear protectors.