Research on the Characteristics of Noise Exposure on Workers Wearing Acoustic Devices

Introduction
There are hundreds of thousands call center workers wearing acoustic device in Korea. However, researches and noise exposure measurements on the noise transmitted from acoustic devices have seldom been performed due to the difficulty of measurement and to the absence of the measuring method in Korea. The aim of this study is to set up management measures to protect hearing loss on the call operator by acquiring noise exposure data and hearing test data.

Methods
Noise exposure measurements of 17 operators were performed in 7 call centers and Head and Torso Simulator method in compliance with the ISO Standard 11904-2 was used for the measurement. The hearing loss of 101 workers of 5 call centers was investigated by executing pure-tone audiometry, tympanometry, distortion product otoacoustic emission and questionnaire.

Results
Sound pressure levels(SPL) transmitted from the headset were 73.2~86 ?(A). The operator exposed to the highest SPL set up his volume control at 9 which was the highest volume level. As a result of Pearson Correlation Analysis, the correlation between volume level and SPL transmitted from the headset showed high relation as significance at the 0.794 level(p<0.05).
Pure-tone thresholds by frequency of call center workers were 9~30 ?(A). As a result of tympanometry for the left and right ears, "A type" meaning normal condition was 88% and 92% respectively. In a distortion product otacoustic emission, "pass" meaning normal condition was 93% and 97% respectively.

Discussion
To protect hearing loss of call center operators, it is more practical and effective measure to limit the volume level below the noise exposure level, i.e. 85 ?(A), rather than to carry out noise monitoring considering cost-effective aspect.