Employees of some nightclubs are being exposed to dangerously high noise levels, according to a study published recently in the International Journal of Noise & Health.

Researchers examined noise levels at nine different nightclubs in Ireland by placing a sound-level meter near the dance floor and attaching a dosimeter to the shirts of employees participating in the study. On average, the employees had worked in bars for five years.

The average daily noise exposure of these employees, who worked 20 hours a week on average, was 92 decibels, the study revealed. Between 11:30 p.m. and 1 a.m., the noise levels in the clubs rose by an average of 7 decibels. A 3-decibel increase is comparable to doubling the sound pressure level.

Study author Aoife Kelly, from the Dublin Institute of Technology, said that over time, noise exposure greater than 85 decibels for eight hours a day can cause permanent hearing loss.

Kelly also found that many nightclub managers in Ireland are unaware of noise regulations. Only two clubs involved in the study conducted noise risk assessments and provided the hearing protection required by the European Union for workers exposed to more than 85 decibels.  Only one actually required its employees to wear it.

Kelly said more people need to be aware of noise exposure regulations, and more club managers need to comply with the legislation.

The study findings echo those from similar surveys conducted in the United States, Britain and Australia. Noise-induced hearing loss is the most commonly reported occupational disease in Europe.