April 30, 2003, is International Noise Awareness Day. The Sight & Hearing Association, in conjunction with other hearing-related organizations worldwide, is promoting the day to educate the public about the dangers of noise to hearing and health.

Noise is the leading cause of hearing loss, affecting an estimated 10 million people and putting 30 million more at risk.

Noise-induced hearing loss can be caused by occupational noise exposure (factories, construction sites, etc.) and/or recreational and environmental noises (e.g., loud music, guns, power tools, and household appliances). That last concert you went to? You may have been exposed to music exceeding 120 decibels (dB). At that level, you risk hearing damage in less than seven minutes.

To know whether you are listening at a safe level, a few general rules exist. According to the Occupational Safety and Health Administration (OSHA), for every five decibel (dB) increase, cut the exposure time in half. For example, at 90 dB, you are safe for eight hours. At 95 dB, your hearing is safe for four hours. Another organization, the National Institute for Occupational Safety and Health (NIOSH), has instituted an even stricter standard. Starting at 85 dB at eight hours, for every 3-dB increase, reduce your exposure time in half. For example, 88 dB = 4 hours, 91 dB = 2 hours, 94 dB = 1 hour.

Noise-induced hearing loss (NIHL) is caused by exposure to sound levels or durations that damage the hair cells of the cochlea, a tiny organ in the inner ear. Initially, the noise exposure may cause a temporary threshold shift ‹ a decrease in hearing sensitivity that typically returns to its former level within a few minutes to a few hours. Repeated exposures to loud noise lead to a permanent threshold shift, which is an irreversible sensorineural hearing loss.

To ward off noise-induced hearing loss, follow three simple steps: avoid loud noise, turn it down or wear hearing protection. In addition, have your hearing checked regularly.

In Minnesota, the Sight & Hearing Association is coordinating free hearing screenings statewide on April 30. Click here to find a site near you.

To find a screening or activities related to International Noise Awareness Day outside Minnesota, go to the League for the Hard of Hearing¹s Web site at www.lhh.org.