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Noise and Hearing Loss in the Metal Manufacturing Industry

Noise and Hearing Loss in the Metal Manufacturing Industry. David Welch Gareth John Alla Grynevych Peter Thorne. Research Protocol. Day 1: Tour of facility Employees interviewed individually - Explanation of project - Interview - Disposable earplug assessment ( Veri -Pro)

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Noise and Hearing Loss in the Metal Manufacturing Industry

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  1. Noise and Hearing Loss in the Metal Manufacturing Industry David Welch Gareth John Alla Grynevych Peter Thorne

  2. Research Protocol • Day 1: • Tour of facility • Employees interviewed individually • - Explanation of project • - Interview • - Disposable earplug assessment (Veri-Pro) • Sound level meter measurements • Day 2: • Hearing tests (otoscopy, tympanometry, and audiometry) • Dosimetry

  3. Participants • 27 Companies • 160 Employees • 155/160 Male • 11/160 Clerical staff (including all 5 females)

  4. Noise Levels

  5. Noise Levels by Company Size(Production workers only) There was no difference in mean noise level (F(2,135)=1.257, p=0.288)

  6. Noisy Equipment Top Ten

  7. Impulse Noise Top Ten

  8. The mean age was approximately 40 years. Age (years)

  9. Lifetime Work Noise Exposure

  10. Noise Exposure and Age

  11. Hearing Thresholds by Age

  12. Audiogram Notch Criteria: • Poorer threshold at 4 or 6 kHz than at 2 kHz AND • Better threshold at 6 or 8 kHz than at 4 kHz AND/OR • Better threshold at 8 kHz than at 6 kHz AND • Notch depth >20 dB HL AND • Bilateral notches

  13. Audiogram Notch 15 people had bilateral notches according to the criteria • 0/40 (0%) 18-30 years • 4/39 (10%) 31-40 years • 6/54 (11%) 41-50 years • 5/27 (19%) 51 years or more

  14. Hearing Threshold by Age and Notch

  15. Hearing Threshold by Age and Notch

  16. Hearing Threshold by Age and Notch

  17. Hearing Disability vs Hearing LossAbility to hear in noisy backgrounds was impaired in 25% of participants

  18. Tinnitus Responses to the question: “In the last 12 months, when you are awake and it is quiet, have you experienced tinnitus . . .?”

  19. Hearing Protection • 160 workers interviewed • 86 (54%) used earmuffs • 75 (47%) used earplugs • 13 (8%) used either • 12 (8%) used neither (Of these 12, 5 were production workers with Leq scores : 89.7, 86.6, 84.2, 81.9, and 71.6 dB(A). )

  20. Lifetime Noise Exposure without HPE (Overall, there was a correlation between age and years spent working in noise without HPE (r=0.480, p<0.001))

  21. Poorly Fitted Earplugs

  22. Older Workers Tended to Fit Earplugs Less Well

  23. Poorly Fitted Earplugs = Poorer Hearing

  24. Conclusions • High noise levels in metal manufacturing • Half of production workers exposed >85dB(A) • NIHL was not widespread (15/160 with measureable notch) • Hearing disability was present in a quarter of workers – but not well linked with hearing loss • HPE used by almost all production workers • HPE used always by younger workers (up to approximately 40 years) • Suggestive of greater awareness of the impact of noise in younger workers • Poor fitting of foam earplugs was common • Poor fitting of foam earplugs was associated with NIHL

  25. Acknowledgements • Thanks to the many companies and individuals who gave their time to participate in this research. • Thanks to Dr John Wallaart, ACC Programme Manager, for his friendly advice and assistance. • Thanks to John Skudder, ACC Workplace Safety Programme Manager, for his invaluable help in getting the research started and for sharing his knowledge along the way. • Thanks to Zaneta Schumann, Department of Labour Service Manager, and the Auckland North Office of the Department of Labour for their kind help and interest in the research. • Thanks to Sperian for the generous loan of the VeriPro system.

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