The question of whether radio earmuffs provide protection or add damaging noise is addressed in a new Sound Source(tm) article recently released by Bacou-Dalloz Australia, parent company of the Howard Leight(R) and Bilsom(R) hearing protection brands.
Authored by Brad Witt, MA, CCC-A, who is Audiology and Regulatory Affairs Manager for the company, and available on their website, the Sound Source article discusses the difference between headset radios and hearing protector earmuffs equipped with AM/FM radios, and explains how to calculate effective noise exposure while wearing them.
"When headset radios first appeared in stores several decades ago, they were not marketed as hearing protectors," says Witt, adding that this was, "a good thing, since they offered very little attenuation of noise. At some frequencies, the headsets were even found to amplify background noise (with the radio turned off) due to resonance in the earcup."
To be a hearing protector, says Witt, an earmuff must be designed to be a hearing protector from the start.
The volume settings of typical portable stereo headsets have been measured as high as 96 dBA at 100% volume, "a hazardous noise level if listened to continuously for several hours.
Ideally, a radio headset should allow the enjoyment of music at safe levels, but also reduce the background disturbance in a noisy environment."
Today's new hearing protectors does just that, he reports. Built-in radios contain circuitry that limits their high radio volume. When the radio is turned on, for example, the sound output is electronically limited to 82 dB.
"When two noise sources are added together, the decibels are added logarithmically, not arithmetically," Witt explains.
"This means that the sum of two identical sound sources (90 dB + 90 dB) would equal 93 dB."
The Sound Source article goes on to provide a chart, illustrating the effective noise exposure levels for a typical radio earmuff worn in 90 and 100 dB of noise.
"Since the radio output is limited to a safe 82 dB maximum, the radio adds very little noise to effective exposures in high noise levels," Witt concludes.
"In a high-noise job that is also repetitive or monotonous, a radio earmuff can add significantly to worker satisfaction and enjoyment, without sacrificing hearing protection."