title: The effect on the temporary threshold shift in hearing acuity from combined exposure to authentic noise and hand-arm vibration.
abstract: OBJECTIVE
  This study examined and compared the effect on temporary threshold shift in hearing (TTS) in healthy subjects of noise and hand-arm vibration (HAV) combined and separately using controlled and authentic exposure conditions. This study also investigated the effect on TTS in hearing in relation to gender after such exposures.
  
  
  METHODS
  Twenty-two healthy subjects (11 men/women, mean age 22 years, range 18-31 years) were exposed both separately and in combination with HAV (6.7 m/s(2)), using vibrating handles and to noise (99dB(A)) using headphones, for 20 min. The HAV and noise were reproduced from recordings from angular grinder in operation. Hearing thresholds at 1, 4, and 8 kHz were measured before and up to 30 min after exposure.
  
  
  RESULTS
  Combined exposure to noise and HAV created significantly greater TTS in hearing than HAV exposure at 4 and 8 kHz alone. After exposure to HAV, there was no significant change in hearing threshold. At 1 kHz, there was a significant difference between noise and HAV exposure in TTS in hearing. There was no significant difference between combined exposure and noise exposure for any test frequency. There was no significant difference in TTS in hearing in relation to gender for 1, 4, and 8 kHz for HAV, noise, or a combined exposure.
  
  
  CONCLUSIONS
  The results indicate that there is no difference in the TTS in hearing after combined exposure compared to noise exposure alone. HAV exposure did not change the hearing threshold. The TTS in hearing did not differ significantly in relation to gender after HAV, noise, or combined exposure.
authors.affiliation: Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine, Umeå University, 901 87, Umeå, Sweden. hans.pettersson@envmed.umu.se
authors.forename: Hans
authors.initials: H
authors.lastname: Pettersson
authors.forename: Lage
authors.initials: L
authors.lastname: Burström
authors.forename: Tohr
authors.initials: T
authors.lastname: Nilsson
mesh_terms: D000293:Adolescent; D000328:Adult; D001309:Auditory Threshold / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009623:Noise, Occupational / Q000009:adverse effects*; D009784:Occupational Diseases / Q000209:etiology* / Q000503:physiopathology; D016273:Occupational Exposure / Q000009:adverse effects*; D012737:Sex Factors; D011795:Surveys and Questionnaires; D014732:Vibration / Q000009:adverse effects*; D055815:Young Adult