Hearing loss from exposure to loud sound affects millions of people. Noise-induced hearing loss is preventable, but most people do not know how long they can listen to loud sound without risking hearing damage. A single noise exposure may not result in hearing loss, but permanent damage to the inner ear from noise adds up over time. The accumulation of too much noise day by day, year after year, is the determining factor in hearing loss risk. A sound level meter is a device that measures noise at a particular point in time, while a dosimeter measures sound levels for many hours and calculates the cumulative noise dose in percent.

Daily noise dose is determined by both the intensity of the sound and the amount of exposure time. A 100% dose means that a person has reached the maximum noise exposure for the day, and continued exposure to loud sound could lead to hearing loss. Ideally, hearing protection should be used before the dose reaches 100% since dose limits are based on averages, and some ears are more susceptible to noise damage than others. When the noise dose exceeds 50% a person has reached half the maximum noise exposure for the day and it’s a good idea to use hearing protection to prevent over-exposure, particularly if a 50% dose reading is reached early in the day.