Bad Assumptions About Hearing Protection #3: An Ear Plug Halfway in the Ear Blocks About Half the Noise

Bad Assumptions About Hearing Protection #3: An Ear Plug Halfway in the Ear Blocks About Half the Noise

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It seems plausible that if a well-fit ear plug blocks 30 dB of noise, then a half-fit ear plug must block 15 dB of noise. Unfortunately, the math of hearing protection does not work that way. Instead, a half-fit ear plug is often providing 0 dB of attenuation.

Workers in noise levels of 85-95 dB (close to the OSHA Permissible Exposure Limit of 90 dB Time Weighted Average) are routinely offered ear plugs with Noise Reduction Ratings of 30 dB or more. When worn properly, that 30 dB hearing protector can make the worker feel isolated — unable to hear warning signals, co-workers, machine maintenance sounds, or communication radios.

To hear critical sounds, workers will sometimes remove their ear plugs about halfway, assuming they are still adequately protected. But in noise attenuation, any small channel or leak allows the noise to enter, and the protection quickly deteriorates from “all” to “none.” How do we protect a worker who does not need 30 dB of protection? Use hearing protectors with lower Noise Reduction Ratings. When used properly, a lower-attenuating ear plug will provide protection without sacrificing communication ability.

In a series of research studies designed to find out why workers do not use their ear plugs more consistently, NIOSH reports that the predominant reasons are inability to communicate (“I can’t hear my co-workers talking to me”), and interference with job performance (“I can’t hear the maintenance sounds from my machine, or warning signals”). The ideal hearing protector should not block all sound (overprotection), but rather reduce hazardous noise levels while still allowing a worker to hear the sounds that are critical to the job: coworkers, warning signals, and equipment maintenance sounds.

While there is no magic valve in hearing protectors that lets “good” sound in and keeps “bad” sound out, there are some hearing protectors that are more speech-friendly than others. These “uniform attenuation” hearing protectors attenuate all frequencies fairly equally, meaning speech and warning signals will sound more natural, rather than inaudible or distorted. Many users of uniform attenuation ear plugs, for example, report they can still hear what they need to hear for their job performance.

 

Next: Bad Assumption #4: Cut the NRR in Half to Predict Real-World Protection

 

Blog Author:  Brad Witt  
Blog Catagories:  Ear Plug  

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