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Exposures from Headset Interference Tones
FEDERAL AVIATION ADMINISTRATION WASHINGTON DC OFFICE OF AVIATION MEDICINE
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This study evaluated the acoustic characteristics of interference tones as experienced by FAA Air Traffic Control Specialists ATCSs and pilots who wear headsets with insert type ear pieces. The Sound Pressure Levels SPLs of generated tones were measured through the headset at five randomly selected ATCS positions in each of seven Air Route Traffic Control Centers ARTCCs. The SPLs were compared within and between four frequencies .5, 1, 2, and 3 KHz over ten discrete signal power levels. The comparisons demonstrated that SPLs of tones could not be predicted for ARTCCs or for positions within an ARTCC, and that the durations of exposure were brief, i.e. limited to the time needed to remove the headset earpiece from the ear canal. Potential amounts of temporary threshold shifts TTSs also were evaluated in a laboratory by checking hearing levels following exposures to tones played with ATCSpilot communication through the same headset. Audiometric checks of 20 volunteer subjects indicated TTS could be detected following 1 KHz114 dB60 and 145 seconds, 2 KHz108 dB60 and 145 seconds, and 3 KHz99 dB145 seconds exposures, when hearing checks were made within the first 15 minutes. Such extended durations are highly unlikely for pilots and ATCSs and no TTS was detectable following exposures to shorter durations or to other frequencies with equivalent durations. headset, interference tones, insert type headset, hearing, threshold shifts.
APPROVED FOR PUBLIC RELEASE