[Assessment of telephone operators' exposure to sound through headphones]

We estimated the level of noise that telephone operators were exposed to through headphones by a two-step method using an artificial ear technique and a manikin technique. In the artificial ear technique, the sound pressure level (Leq) of the total work hours was 81.5 dB, whereas the Leq of the total duration of phone calls was 89.3 dB. Therefore, we conducted a more accurate measurement by the manikin technique (ISO11904-2). By this method, we could simulate the headphone-wearing condition of the workers and convert the measurements to a diffuse-field related L(Aeq). By this manikin technique, the corrected L(Aeq) of the total work hours was 68.3 dB, whereas the corrected L(Aeq) of the total duration of call was 76.6 dB, which was below the standard of the Occupational Exposure Limits of the Japan Society of Occupational Health. We confirmed that in a workplace where the background noise is low (51.3 dBA), a good signal-noise ratio is maintained so that operators don't have to listen to loud sounds through headphones. Neither the gender nor the type of the telephone equipment of the callers affected the sound pressure levels.