Takao Tsutsui

Technique for continuously monitoring core body temperatures to prevent heat stress disorders in workers engaged in physical labor.

Technique for Continuously Monitoring Core Body Temperatures to Prevent Heat Stress Disorders in Workers Engaged in Physical Labor: Chikage Nagano, et al. Department of Health Policy and Management, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan

Temporary threshold shifts at 1500 and 2000 Hz induced by loud voice signals communicated through earphones in the pinball industry.

To assess the risk of hearing loss among workers using earphones as communication devices at noisy worksites, we compared temporary threshold shifts (TTS) between ears on which workers wore earphones and ears on which no earphones were worn. We measured ambient noise and personal noise exposure as well as noise generated by and passed through earphones by applying frequency analysis at three pinball facilities during their hours of actual operation. We assessed hearing levels before and after a work shift (prework and postwork) of 54 workers by pure tone audiometry at six frequencies. The time-weighted averages for ambient noise and personal noise exposure exceeded 85 dB(A) and 90 dB(A), respectively. Overall sound pressure levels generated by and passing through earphones reached 109 dB(A). The one-third octave band spectrum of the earphone noise during the shift exceeded 90 dB(SPL) in the range of 315-2000 Hz. The number of ears demonstrating a TTS, defined as a shift of 10 dB or more in postwork over prework hearing thresholds, was significantly greater at 1500 and 2000 Hz among ears with earphones (P < 0.05 and P < 0.01, respectively) compared to those without. The reverse was observed at 4000 Hz for ears without earphones (P < 0.01). Workers wearing earphones or headsets as communication devices in noisy environments are exposed to high risk of hearing loss, particularly at the frequencies of 1500 and 2000 Hz. Ideally, hearing conservation programs for such workers should account for potential hearing losses at frequencies of 2000 Hz or lower frequencies induced by amplified voice signals.

Earplug-Type Earphone with Built-in Microphone Improves Monosyllable Intelligibility in Noisy Environments

Received Jul 18, 2007; Accepted Dec 7, 2007 Correspondence to: T. Nakao, Department of Health Policy and Management, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan, 1–1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan (e-mail: t-nakao@med.uoeh-u.ac.jp) Earplug-Type Earphone with Built-in Microphone Improves Monosyl lable Intelligibility in Noisy Environments

Optimum room temperature during rest periods between repetitive exercises under heat stress

Abstract Four healthy male volunteers (22.0±0.8 years) were asked to perform three repeats of 20 min of exercise, at a work rate of 75 W, on a bicycle ergometer for three times in a climatic chamber controlled at a dry-bulb temperature of 35°C, 60% relative humidity, and a wet-bulb globe temperature of 31.5°C. Between the work periods, they were asked to sit stationary for 15 min in an attached air-conditioned room. The experiment was repeated with the temperature of the attached room ( T a ) ranging from 20 to 30°C. The average increase in esophageal temperature ( T es ) was largest when T a was 20°C, followed by 22>26>30>24°C. At a T a of 24°C or less, most subjects showed an increase in T es even inside the air-conditioned room and a temporary decrease of T es right after the reentry to the climatic chamber. The lower the T a , the more the skin surface temperature decreased. The inverse elevation and initial drop of T es are likely to be caused by vasoconstriction on the skin surface and by subsequent recanalization between the skin surface and core. Considering that none of the results suggested that the optimum temperature should be 26°C or more, we suggest that the optimum room air temperature for short rests provided for heat-exposed physical workers should be around 22–24°C.

Assessment of exposure to voices and noise via earphones in manufacturing industry workers in Japan.

Assessment of Exposure to Voices and Noise via Earphones in Manufacturing Industry Workers in Japan: Tomo NAKAO, et al. Department of Health Policy and Management, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan—