BehindTheMedspeak: How loud is too loud?

In her September 18, 2007 New York Times "Q&A" column C. Claiborne Ray explored just how loud noise has to get before you start to go deaf; the piece follows.

Cover Your Ears!

Q. At what decibel level does noise start to do irreparable hearing damage? Are regular subway commuters in danger, for example?

A. The risk of hearing loss from loud noises depends on both the level of sound and the length of exposure, and at least one study of New York City subways has found that the hearing of commuters may be in danger if they ride a noisy train or wait in a noisy station for long enough.

According to the National Institute on Deafness and Other Communication Disorders, an extremely loud sound of about 120 to 150 decibels, like a nearby clap of thunder or a gunshot, can damage hearing right away, and sounds of 85 decibels or more can cause damage if there is long or repeated exposure, say for 45 minutes a day.

A study last year, published in The Journal of Urban Health, found that potentially damaging noise levels had been recorded on some platforms and on some moving subway trains.

On the 17 subway platforms where measurements were taken, the mean maximum noise level was 94 decibels. The highest level, 106 decibels, was recorded in Union Square station. On the trains, one-fifth of the lines checked exceeded 100 decibels, and two-thirds exceeded 90 decibels.