Led by research associate Alberto Behar and electrical and computer engineering professors Hans Kunov and Willy Wong, the team found that while general noise exposure over the course of an average day is marginally acceptable, noise levels during teaching periods could damage the inner ear. "The hair cells of the inner ear simply crumble under the load, and they don't grow back again," says Kunov.

According to Ontario's Occupational Health and Safety Act, noise levels on the job should not exceed 90 decibels (dB)-the equivalent of a power lawn mower-over eight hours of a 24-hour period. Wong and his colleagues used noise dosimeters to measure exposure for 18 teachers from 15 Toronto high schools and found that the peak noise level exceeded 85 dB for 78 per cent of the teachers. During an average eight-hour exposure, the team determined that 39 per cent of the teachers faced potentially harmful noise levels.

Most of the classrooms are constructed with concrete blocks and linoleum, providing a highly reflective sound surface. "The world is louder than we think," says Wong. "Schools might consider protective measures such as sound baffling and carpet and teachers might also wear protective earplugs and consider periodic hearing checks."

The study, which was funded by Natural Sciences and Engineering Research Council of Canada and the Canada Foundation for Innovation, was published in the April 2004 issue of the Journal of Occupational and Environmental Hygiene.

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Contact: Prof. Willy Wong
willy@eecg.utoronto.ca
416-978-8734
University of Toronto
18-May-2004