Plane & Pilot
Tuesday, October 5, 2010

Hearing Loss: Could It Happen to You?


The right headset and a little knowledge can save your hearing


Passive headsets block noise by physically stopping it. PNR sets clamp tightly to your head, preventing sound-pressure waves from reaching your ears. Insulation and different materials block sound waves or dissipate them. There’s no magic to PNR; using the fist-in-the-water analogy again, the waves you made with your left hand would simply be blocked by a dam—the PNR headset being that dam. One advantage of PNR sets is they’re great at blocking frequencies in the 1000-Hz-and-up range. They do it using clamping pressure and ear-cup design. That makes them less comfortable than ANR sets, but more effective in scenarios where your enemy is high frequency (like in an open-cockpit aircraft).

Ear Cups
Believe it or not, ear cups—the round things on headsets that go over your ears—make a big difference. In recent years, different materials have been found to be especially effective at blocking unwanted cockpit noise. Some manufacturers are using materials like magnesium, or modifying the ear-cup shape to enhance attenuation and performance. Related to the ear cup is the clamping pressure. While ANR headsets clamp lightly (they rely on the circuitry to reduce noise), PNR sets depend on clamping for noise reduction. So try on a headset for an extended period of time so you can detect any clamping pressure hotspots on your ears or head. Any headset worn in the store for 20 seconds feels good.

Ear Seals
Ear seals (the soft rings that attach to the headset’s ear cups) have been getting a lot of attention lately. Oregon Aero has been offering retrofit kits for various headsets for some time now, and pilots are beginning to appreciate the comfort and noise reduction available from good ear seals. The best ones are breathable to reduce sweat. That means organic materials like cotton and leather work best. Also, thick ear seals that elevate the ear cup away from your ear have been found to increase comfort on long flights.

Microphones
Headset microphones come in two basic flavors: dynamic and electret condenser. In recent years, more manufacturers have switched to electret-condenser microphones for general aviation headsets. An electret-condenser mic generates a powered signal that sounds louder and clearer and with less background noise. Dynamic microphones are nonpowered and still used on older—and especially military—aircraft. They cost less and handle abuse better, but are becoming nonstandard in today’s GA environment. As a general rule, use the same type of headset microphones in all your intercom outlets.

The Latest Thing
Just recently, pilots in noisy environments have discovered what musicians have known for some time: Doubling up on hearing protection is great insurance against hearing loss. That means using multiple forms of noise attenuation that won’t color the sound you’re accustomed to hearing. Several companies make special ear plugs that have a tiny removable sound filter that reduces noise in certain frequencies. Next time, instead of shoving those cheap foam plugs into your ears that block everything and make you feel like you have a monster head cold, use custom plugs. Since they only block harmful frequencies, normal sounds come through loud and clear. Using these custom plugs in addition to your regular headset adds 15 to 20 dB of additional noise reduction. Ask your audiologist for frequency-specific ear plugs or “musician’s ear plugs.” They normally run under $100, including the molds.

The most important fact from all of this is that headsets are a vital part of any pilot’s equipment. Among aviators, hearing loss seems to be a given. Caused by early neglect, improper headsets or infrequent use of them, it’s a loss that doesn’t have to exist. Hearing is a valuable sense considered second only to sight, and especially so for pilots. It makes sense to protect it at any cost. Don’t take hearing loss lightly and don’t think, “It won’t happen to me,” because if you fly long enough, it will.



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