Safety and health newsletter for the Oregon construction industry

December 15, 2014


A simple way to lower noise levels: add distance

a graphic representing sound waves

Workplace safety and health specialists will tell you that engineering controls are the best way to control noise. When you replace a noisy machine with a quiet one, modify the machine to make it quieter, or change the sound path so that the sound is not as intense when it reaches the listener, you are using an engineering control.

Applying engineering controls to a noise problem can be challenging, however, because affordable off-the-shelf solutions are usually not available. When it is feasible, one of the simplest engineering controls is increasing the distance between the sound source and the listener. How does increasing the distance affect sound levels?

Sound pressure – the intensity of a sound – is measured in decibels at a given distance from a sound source. Thanks to a simple law of physics, we know that each time you double the distance from a sound source to the listener, you decrease the sound level by about six decibels. For example, if you are standing 10 feet from a source and the sound level where you are standing is 90 decibels, the sound level would be about 84 decibels at 20 feet. Nearby surfaces that might reflect the sound (or block it) can change the numbers, but this still a good rule of thumb for estimating sound levels at a distance.

See how distance affects the sound levels of a variety of workplace sounds with this interactive infographic from Oregon OSHA.

You can damage your hearing if you are continually exposed to noise greater than 85 decibels over eight hours, so it is important to know sound levels in noisy environments. Oregon OSHA's hearing protection rule, 1910.95, Occupational Noise Exposure, states that your workplace must have a hearing conservation program when employees are exposed to noise levels that are equal to or greater than 85 decibels, averaged over eight hours.

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But remember: the information in this newsletter is intended to highlight safe work practices, but it does not replace Oregon OSHA workplace safety and health rules.

For information about Oregon OSHA services and answers to technical questions, call (503) 378-3272 or toll-free within Oregon, (800) 922-2689.