Army

Accelerated hearing protection fit-check software

Accelerated fit-check performs a rapid pass-fail by using information about the listener’s audiometric thresholds to construct broadband sounds that should be undetectable if the hearing protection is consistent with the advertised noise reduction rating of the device

Software & Information Technology Medical & Biotechnology

A U.S. Army researcher has invented a software improvement for commercially-available hearing protection fit-check testing software that saves time and money. A provisional patent application has been filed, and the software update is now available for license to companies that want to expand in a multi-million dollar market.

Existing fit-check systems for hearing protective devices (HPDs) come in two types- microphone in real ear (MIRE), and psychoacoustic systems. MIRE involves the placement of a microphone underneath the HPD to measure the amount of noise. Psychoacoustics use a listener test whereby the subject indicates the point where they just hear the sound with and without the HPD. Both of these approaches require some skill in administration and multiple measurements which are time-consuming and best done in a controlled lab.

The Army has improved on fitting HPDs with a fit-check protocol that replicates the functionality of a typical psychoacoustic system while saving time. The system relies on collecting the listener’s pure tone thresholds during an auditory test. These personal thresholds are used to adjust the levels of pulsed, one-third octave band noise to make them detectable only if the HPD under test provides less attenuation than two standard deviations below the mean values used in calculating the noise reduction rating of the device. These pulsed noises are combined into a single broadband noise, that will just be audible to the listener if the attenuation provided by the HPD is marginally acceptable. The method yields a quick HPD fit-check as it determines if the listener falls within the normal distribution of the HPDs frequency attenuations.

Where existing psychoacoustic fit check methods are intended to measure the amount of attenuation an HPD provides as a function of frequency, this new method is focused exclusively on determining whether an HPD provides enough attenuation to protect an individual from a noisy environment.

According to the National Institute for Occupational Safety and Health, 22 million U.S. workers are exposed to hazardous noise levels at work each year.

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