Second only to aging, loud noise is the leading cause of hearing loss among adults. A recent report by the Center for Disease Control and Prevention (CDC) found that 24% of adults have audiometric notches. This suggests a high prevalence of noise-induced hearing loss. Additionally, nearly one third of those who reported loud noise at work had a notch.
During an Audiometry, or behavioral hearing test, testers use an audiometer to create an audiogram. An audiogram is a graph showing the the frequencies at which the subject can hear. At specific frequencies, a dip may occur, which is where we get the term “notch”. Notches in an audiogram is a generally accepted indication of noise-induced hearing loss. However, more research is required.
The CDC’s report ultimately estimates that between 10 and 40 million Americans may have noise-induced hearing loss based on notches in their audiograms. The report does concede that other factors may contribute to NIHL, such as disease, certain drugs, and heredity. Because of this, some of the hearing loss in the report may be due to these factors, rather than noise.
Both the U.S. Department of Health and Human Services and World Health Organization have committed to raising awareness of NIHL and are developing guidelines on noise exposure. The CDC’s own National Institute for Occupational Safety and Health has suggested 85 dB averaged over an 8 hour day and 40 year career as a safety limit. They recommend hearing protection for noise over 85 dB.
Make sure you turn down that music, move away from prolonged loud noises, and wear hearing protection.