Hearing deterioration in shipyard workers. Serial audiometry over a four-year period

Area of Science:

• Occupational Health
• Audiology
• Environmental Noise Impact

Background:

• Occupational noise exposure is a known risk factor for hearing loss.
• Understanding the rate of hearing threshold shift is crucial for preventative measures.
• Age-related hearing loss (presbyacusis) and noise-induced hearing loss can be difficult to differentiate.

Purpose of the Study:

• To quantify the yearly rate of hearing threshold change in workers.
• To differentiate hearing loss attributable to noise exposure versus presbyacusis.
• To investigate age-related differences in noise-induced hearing threshold shifts.

Main Methods:

• Annual audiometric measurements over 4 years for 58 workers (aged 20-65).
• Békésy sweep-frequency audiometry used for hearing threshold assessment.
• Calculation of yearly hearing threshold level change rates, separating noise and presbyacusis effects.

Main Results:

• A significant rate of threshold shift due to noise exposure was detectable for yearly changes as small as approximately 2 dB.
• Approximately 30% of investigated ears showed significant noise-induced hearing deterioration.
• Older workers exhibited a greater permanent threshold shift from noise than younger workers, contrary to expectations.

Conclusions:

• Békésy audiometry can detect subtle, significant noise-induced hearing shifts annually.
• Noise exposure is a significant contributor to hearing loss in the working population.
• Age influences the susceptibility to permanent threshold shift from occupational noise exposure.