Amy Behrman
NAVAIR Technology and Intelligence Office
September 13, 2004

The F-35 Joint Strike Fighter program is sponsoring the development of advanced hearing protection technologies designed to prevent noise-induced hearing loss for Navy, Marine Corps, and Air Force JSF maintenance personnel.
Under the Lockheed Martin F-35 JSF contract, earplug designer Adaptive Technologies, Inc. (ATI) would produce about 40 test units, enough to qualify and demonstrate the system’s utility as an F-35 platform solution for hearing protection. Officials are hopeful that a successful fleet demonstration will strengthen the case for broader application and funding.
According to ATI, the “QuietCommTM” Digital Active Noise Reduction (ANR) earplug “provides breakthrough hearing protection for military personnel in extremely high noise environments, where in some carrier deck locations, three seconds of unprotected exposure can cause permanent hearing damage. Designed for military jet support personnel, the custom earplug offers protection in high intensity ambient noise, and clear communication with improved speech intelligibility.”
“This active noise reduction earplug, coupled with the ATI microphone, new ear cushions from David Clark Company, and a new ATI foam insert, offers a breakthrough advancement in hearing protection technology … the likes of which haven’t been seen for deck crew and flight line personnel in close to 50 years,” said Jim D’Andrade, NAVAIR senior systems engineer and Air Vehicle Systems Engineering Integration (AV-SEIT) Environment Team Lead for the Navy and Air Force JSF program office.
The unique earplugs contain a miniature microphone and speaker used to conduct the active cancellation portion of the attenuation, as well as provide communications capability. Sound inside the ear canal is actively “canceled” through a process known as active noise reduction (ANR).
While the concept of ANR is pervasive in headsets, this is the first practical application of the technology for deep-insert earplug devices. The real benefit is realized through extending the bandwidth of active control performance from the traditional 800 Hz to as high as 3000 Hz.
Because speech contains frequency content up to and beyond 3000 Hz, extending the control bandwidth to this range enables the technology to realize improvements in speech intelligibility that are not possible with current technologies.
ATI has also worked closely with David Clark Company Incorporated to demonstrate passive noise reduction improvements using a new ear seal and interior foam in a retrofit package. When coupled with the new passive ear seal and interior foam, the ANR earplug technology will provide more effective hearing protection than ever before.
According to James Wilt, technical point of contact (TPOC) for NAVAIR’s hearing protection project, integration of the new earplug with state-of-the-art passive protection technologies leads to a total hearing protection package that can provide attenuation nearing 46 dB – enabling effective communication and hearing protection for up to 60 launch and recovery sequences before exceeding the total safe daily exposure limit.
“This is significant when you consider that a single launch in a 24-hour period can exceed the safe noise dose,” said Wilt.
Tactical jet engine noise is one of the loudest sounds in the world, and can reach an “ear aching” 150 dB(A) for carrier aircrew standing along the foul line during a catapult launch.
According to the National Institute for Occupational Safety and Health (1998), continued exposure to noise above 85 dB(A) will likely cause permanent hearing loss. The maximum exposure time at 85 dB(A) is 8 hours, which should be followed by 16 hours of quiet recovery time. At 110 dB(A), the maximum exposure time is approximately one minute and 29 seconds.
According to the March/April 2004 edition of “Approach” Magazine, today’s 1950’s vintage, double protection earplugs and earmuffs provide only 30 dB of total attenuation or noise reduction – that is, only if the double protection is properly worn for the entire duration on duty.
This leaves the average maintainer, landing signals officer (LSO), or landing signals enlisted (LSE) with a near continuous exposure of up to 120 dB(A). Consequently, life on a carrier can mean progressive and permanent hearing loss.
In a recent NAVAIR ear protection survey of 301 deck crew personnel on 6 ships, a surprising 47 percent reported never wearing earplugs. Only 14 percent reported always wearing double hearing protection, and a mere 7 percent inserted their earplugs fully (which would provide 22 dB attenuation). Inserting a plug half way takes protection down to a mere 16 dB.
Hearing loss is the number one Veterans Administration disability claim, amounting to over $5.5 billion since 1977 for all Services. The US Navy and Marine Corps represent about 28 percent of total claims. Aside from hearing loss, prolonged exposure to jet noise could cause a pilot to miss a radio call, resulting in an aviation mishap, or worse – loss of aircraft and crew. In terms of aviation safety, the ability to hear is no less important than 20/20 vision.
Clearly, new technology isn’t the only answer. Better policies, documentation, training, and enforcement of hearing protection safety guidelines are needed.

In an effort to increase awareness of the consequences of unprotected noise exposure, NAVAIR Human Systems representatives continue to meet with Fleet Fail Safe Teams (FSTs), Air Medical Safety Officers (AMSOs), Squadrons, Operational Advisory Groups (OAGs), Integrated Management Panels (IMPs), and similar aviation life support forums – while documenting earplug usage aboard carriers and LHA-class amphibious ships.

The goal is to increase awareness and strengthen the case for improved policy, training, and enforcement, as well as to secure funding for advanced hearing protection technologies for the Fleet.

Captions:

anrsystem1.jpg: QuietComm Digital Active Noise Reduction (ANR) Earplugs

Cranial_new.jpg: QuietComm Digital Noise Canceling Communication Microphone

Foam2.jpg: Cranial Headset custom Contoured Acoustic Foam Insert