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Flights decks are hot, dirty and loud. Researchers at small businesses and universities across the country are taking the first steps to address one of these issues — jet noise — and the resulting hearing loss among sailors.
The Office of Naval Research’s Jet Noise Reduction Program is beginning basic research that could lead to both noise-dampening engine designs and ways to retrofit current aircraft with noise-reducing gear.
Though there have been studies on the impact of noise on war-fighter safety for about a decade, recent additions to the Navy’s aircraft inventory have increased awareness of the issue, said Joseph Doychak, the program officer for the air warfare and weapons division at ONR.
“It became more apparent as more advanced aircraft with higher-performing engines make their way into the fleet,” he said. “This isn’t just the F-35; it’s well before the F-35, too.”
The project is not looking at specific engines or changes to the fleet. Rather, it is studying the problem of noise from jets and learning how to collect better data that can lead to changes.
The biggest accomplishment so far has been creating a standard to measure noise and analyze data for tactical military aircraft.
Brenda Henderson, deputy manager for the project, could not predict when sailors will start seeing changes in the fleet as a result of this research. It took a few decades for commercial aircraft to begin adopting some changes, and “we hope that it won’t take us that long to transition our technology,” she said.
The Navy can’t just copy the changes made by the commercial sector, because the changes can also impact engine power and performance.
“We have to consider the impact of a noise-reduction device on the system,” Henderson said.
The jet noise from a tactical aircraft can reach 150 decibels on the flight line; a paint chipper can hit 100 decibels, and a forklift can top 85 decibels. The Navy considers anything above 84 decibels as “having the potential to cause hearing loss,” according to the Naval Safety Center’s website.
Doychak said it’s difficult to attribute hearing loss specifically to jet noise because sailors face so many other job-related noises, and their off-duty decisions also could cause hearing damage — attending rock concerts, for example.
Teams from Virginia Tech, Brigham Young University, California Institute of Technology, Cascade Technologies, Innovative Technology Applications Co., University of Illinois, University of Mississippi and Penn State University are working on aspects of the research, with about $4 million total funding from ONR. Many of the organizations are meeting for their first program review in mid-June.
Sailors currently wear both single and double ear protection, said Cmdr. Paul Durand, the force industrial hygiene officer at Naval Air Forces Atlantic.
Single ear protection includes foamy yellow earplugs, which can reduce noise levels by about 30 decibels, or the larger earmuff-style headphones, often called Mickey Mouse headphones; double protection means wearing both.
Areas are well-marked with signs stating whether single or double protection is required, Durand said. Areas that require double protection include the flight deck and engineering and machinery spaces; it’s also required when using certain tools, such as needle guns.
In addition to wearing protection, sailors are also regularly monitored for hearing loss. In 2012, 5 percent of those tested suffered clinically defined hearing impairment, a steady decline from almost 9 percent in 2013. The top three communities that suffered from hearing impairment in 2012 were aviation technicians, special operators and electronic technicians.