電話交換手がヘッドホンから曝露される音圧の評価  [in Japanese] Assessment of Telephone Operators' Exposure to Sound Through Headphones  [in Japanese]

電話交換手がヘッドホンから曝露される音圧を,人工耳および音響測定用マネキンを用いた2段階の方法で測定した.スクリーニングとして実施した人工耳による測定では,非通話時間を含む8時間の等価音圧レベル(L_<eq>)が81.5dB,通話時間のみのL_<eq>が89.3dBと高かった.そこで,より作業者のヘッドホン着用に近い状態で測定でき,鼓膜付近での測定値を外耳道入口での音圧に換算可能なマネキンによる測定(ISO11904-2)を行ったところ,A特性による日本産業衛生学会の等価騒音レベル(L_<Aeq>)の許容基準と比較すると得られた修正L_<Aeq>は非通話時間を含む8時間で68.3dB,通話時間だけでは76.6dBであり許容基準を下回った.今回のような静かな作業場(51.3dBA)での通信業務では,80dB未満の音声でも良好な信号雑音(S/N)比が得られ,聴力への影響は小さいことが確かめられた.また,通話相手の性別,電話機の種類による曝露音圧の有意差はなかった.

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 (L_<eq>) of the total work hours was 81.5dB, whereas the L_<eq> of the total duration of phone calls was 89.3dB. 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 68.3dB, whereas the corrected L_<Aeq> of the total duration of call was 76.6dB, 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 (51.3dBA), 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