title: Combined effects of hand-arm vibration and noise on temporary threshold shifts of hearing in healthy subjects.
abstract: OBJECTIVE
  To investigate whether hand-arm vibration and noise have a combined effect on temporary threshold shift (TTS) of hearing among healthy subjects.
  
  
  METHODS
  Nineteen healthy subjects with an average age of 25.7 (SD 7.7) years were exposed to vibration (30 m/s2, 60 Hz), noise [90 dB(A)] and both, respectively. The subject's right hand was placed on the plate of a vibrator and the right ear exposed to noise via headphones. Subjects were exposed to vibration and/or noise for 3 min and after a 1-min pause the exposure was repeated five times. Hearing thresholds at 1, 4 and 6 kHz were measured during the time periods before, between (during pauses) and after exposure.
  
  
  RESULTS
  Exposure to vibration alone caused almost no hearing threshold changes at every frequency tested. But exposure to noise or a combination of vibration and noise caused a significant increase in TTSs at 4 and 6 kHz. Moreover, exposure to a combination of vibration and noise caused significantly higher TTSs than exposure to noise at 4 and 6 kHz.
  
  
  CONCLUSIONS
  The present results demonstrate the combined effects of hand-arm vibration and noise can enhance exposure to hand-arm vibration and noise can enhance the TTS of hearing more than noise exposure, though hand-arm vibration alone may hardly affect TTS.
authors.affiliation: Department of Public Health, Nagoya University School of Medicine, Japan. h44785a@nucc.cc.nagoya-u.ac.jp
authors.forename: S
authors.initials: S
authors.lastname: Zhu
authors.forename: H
authors.initials: H
authors.lastname: Sakakibara
authors.forename: S
authors.initials: S
authors.lastname: Yamada
mesh_terms: D000328:Adult; D001132:Arm; D001305:Auditory Fatigue / Q000502:physiology*; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D006225:Hand; D006801:Humans; D008297:Male; D009622:Noise / Q000009:adverse effects*; D012307:Risk Factors; D013997:Time Factors; D014732:Vibration / Q000009:adverse effects*