Bad Assumptions About Hearing Protection #6: There’s No Way to Measure the Dose of a Worker Under HPDs Throughout Their Workday

Bad Assumptions About Hearing Protection #6: There’s No Way to Measure the Dose of a Worker Under HPDs Throughout Their Workday


Ideally, the best way to know if a worker is protected from hazardous noise is to take a noise dosimetry measurement under the hearing protectors — that is, place a microphone at the eardrum. This concept of in-ear dosimetry is now available in a product called QuietDose™.

Noise dosimetry is typically measured by clipping a microphone on the collar of a noise-exposed worker. The dosimeter samples the noise levels throughout the day, and accurately gives a reading at end of shift showing the noise dose of the worker for that day. A dose over 100% exceeds OSHA’s Permissible Exposure Limit of 90 dB for an 8-hour TWA, while a noise dose of 50% is defined by OSHA to be the Action Level at which Hearing Conservation measures are implemented (generally at an 8-hour TWA). But such ambient dosimetry measurements tell us nothing about the noise level reaching the eardrum under the hearing protectors.

QuietDose uses dual miniature microphones, each inserted under the ear plug or ear muff, to measure the noise dose at the eardrum. If a worker has a proper fit of the hearing protectors, the noise dose will be safe — under 50% for the workshift. But if the worker has an inadequate fit, or removes the protectors repeatedly in high noise, the resulting noise dose at the end of the workshift will be excessive. This immediate feedback gives the worker (and safety manager) the critical information to make immediate corrections. In a typical Hearing Conservation Program, it takes several years of audiometric testing to ascertain whether a worker has lost hearing due to workplace noise. But using in-ear dosimetry, any worker can know immediately and precisely whether hazardous noise levels are reaching the eardrum. And if we can stop the noise exposure at the eardrum, we have stopped the hearing loss.


Bad assumptions sink many well-intentioned safety initiatives. But avoiding these simple bad assumptions about hearing protection helps a Hearing Conservation Program stay on solid ground, and do just what it is designed to do: prevent noise-induced hearing loss.

By the way, if you’ve found this series helpful, you can download the complete “Bad Assumptions About Hearing Protection” discussion as a white paper in PDF format from at:



Blog Author:  Brad Witt  
Blog Catagories:  QuietDose  

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