Not-So-Ancient Mariners and Noise-Induced Hearing Loss

HHTM Staff: Noise-induced hearing loss (NIHL) has been the subject of many posts at HHTM and we have discussed that not everyone self-induces their NIHL.  Those who serve in our armed forces get theirs the old fashioned way — by daily exposure to hazardous levels of workplace noise or as warfighters in high noise combat conditions.  Today’s post looks at those in maritime environments who comprise a substantial portion of the 4 million people in the US exposed daily to hazardous noise. 

We have individuals who provide their subscriptions at appointments; one was an ex-Naval Officer.  The September 2013 SeaPower magazine issue is a Special Report on the U.S. Marine Corps, including a 3-page section on NIHL and the mouse model. Here are some interesting facts and quotes that were gleaned from reading the Sea Power article and an article from MarineLine.com.

Some Maritime Noise Facts and Factoids

One Need: Protect Crew’s Ears

• NIHL is the “most common work-related illness in the United States.”
• The Coast Guard characterizes NIHL by “The Three Ps:  painlessly, progressively and permanently.”
• Onboard ship, noise levels in engine rooms and ventilation systems reach 120 dB.
• Noise levels average 85 dB on 55-60 meter trawlers over 14-day trips.
• Aircraft carrier decks reach noise intensity levels of 126-150 dB during flight operations — greater than rock concert: 2 orders of magnitude  (10²⁾  
• Regular hearing protection via ear plugs and muffs may be inadequate in such noise environments, placing crew members at risk. 
• Continuous noise exposure has been linked to aggressive behavior and sleep disturbances.

Another Need:  Ensure Crew’s Safety

• Shipboard high noise levels put crew members at risk by reducing speech audibility and masking warning signals.
• 80% of maritime accidents result from human error, one of the most common being “lack of communication.”
• 69% of 1250 UK Royal Marines Commandos suffered NIHL as the result of combat service in Afghanistan.
• All regular hearing protection devices “have nuances that will not be helpful in combat.”

You can see the problems: How to ensure good communication and safety in the moment without compromising hearing in the long run?  And vice versa?  To quote from the SeaPower article,

“In a land combat situation, you have to be able to hear faint sounds that could mean danger, while at the same [time] being protected against the onslaight of noise in a fire fight.”

A Multidisciplinary Approach

The Office of Naval Research (ONR) provides some answers and many of the facts listed above as part.  They are heavily involved in multidisciplinary, comprehensive research on practically all aspects of sound:  acoustics, psychoacoustics, ear pathology, cell biology, neurophysiology, and genetic engineering.  As diverse examples:

• The US Navy’s Atlantic Undersea Test and Evaluation Center (Bahamas): measured radiated noise to develop unique acoustic “signatures” of individual ships at sea.
• Ships are “groomed” to isolate and reduce/eliminate sources of sound and vibration. Grooming results are used to engineer quieter future ship designs.
• ONR’s Noise-Induced Hearing Loss Program ensures that sailors working in high-noise environments are fitted with custom molded ear protection (Personal Hearing Protection, PHP) that “only fit one way–the right way.”
• Ongoing research to develop electronic ear wear that simultaneously protects against loud noises, reduces noise and amplifies sounds of importance.
• Ongoing research in hair cell regeneration by gene manipulation in the mouse model.
• Studies of other non-mammalian species with natural hair cell regeneration capability (fish, amphibians, birds).

The Final Word(s)

Sharp-eyed readers may have noticed that the 4th bullet above described our goals for hearing aids:  eliminate the noise, protect the ears and — above all — amplifying only the sounds that are important.  Bravo for the US Navy for helping make this dream a reality. From my reading of the articles, it seems that the present designs are in the form of hands-free wireless headsets.  Those won’t fit into hearing aids, nor are those we want to talk to all wearing mics that communicate wirelessly to the headsets.  But, it’s a start for us and a better solution for those on flight decks and in combat than what they had before.  And we can be confident that all the research will eventually find its way into consumer products from which we all will benefit.

In the meantime, we leave you with these words from Kurt Yankaskas, Director of ONR, on ear protectors:

“Pick them correctly. Wear them correctly.  And stick them in your ear(s).”

Yes Sir!

photo courtesy of wikimedia