Plane & Pilot
Tuesday, December 20, 2011

Headsets On Parade

Newer colors, better performance and more upgrade options lead the headset pack

The Clarity Aloft (left) features an MP3 jack; the Telex Ascend (right) is well-suited for turbine cockpits.
That's great news if you're sitting in a cockpit with consistent noise and it happens to be in the range of frequencies the ANR headset samples and attenuates (reduces).

But what if you're in a fabric-covered aircraft, a utility aircraft, a noisier LSA or even an open-cockpit aircraft? In those environments, the increased and constantly changing noise will confuse the electronics and cause "warbling" in the headset's speakers, making communication very difficult without the pilot knowing why. It's just enough that many pilots simply live with it. In those cases, a possible fix would be to switch to the right passive headset.

Passive headsets don't work based on narrow frequency ranges. They block noise by physically stopping it through various nonelectronic means. Many passive headsets attenuate much more noise than their ANR brethren, and do so across different frequencies. In the noisier environments outlined, a PNR headset could mean a world of improvement.

ANR does have its place though, and that's in quieter environments like small jets, any of the technically advanced aircraft (TAA) like Cirrus and Diamond, etc., and most larger turboprops. ANR is especially effective against low-frequency engine and propeller noise, and blocks it impressively. ANR headsets start to lose effectiveness in the higher frequencies generated by slipstream noise, and that's why some airline pilots prefer PNR sets in the cockpit. Each environment is unique and is best served by only one type of headset attenuation, and sometimes that's PNR.

What To Look For
Headset manufacturers spend millions of dollars researching ways to attenuate noise. The discovery they've made is that it's the sum of many little things that yields the best attenuation and sound. It's these features that you should compare when shopping for a new headset. A headset's ear cups are the first line of defense against noise. The key here is the shape. Sure, they all look oval, but closer inspection reveals slight differences. Sennheiser's new S1 headset uses the largest cups we've seen, while Pilot USA's ANR headset features an indent on top of each cup. Meanwhile, Bose and Lightspeed use squared-off ovals or fat, round ear cups. The real-world difference between these is found by looking at the noise-reduction ratings provided by each manufacturer.

Sound attenuation is offered in "decibels" (noted as "dB"), which is a measurement of volume (sound intensity). The higher the number, the better the attenuation. For reference, a human conversation has a volume of about 60 dB.

Many manufacturers list only a fixed attenuation number, such as "-24 dB," and assume pilots don't want to know more detail. But we need to know at what frequency this attenuation happens. Is it 24 dB at 250 Hz or at 20,000 Hz? The attenuation should be at the frequencies we're most sensitive to (and can actually hear) in the cockpit. Attenuation at 30,000 Hz is no good to us humans since we hear mainly in the 20 to 20,000 Hz range, with speech in the 700 to 8,000 Hz realm.

Headset comfort is a function of the ear cup seals and the clamping mechanism. These days, ear seals come in gel, standard foam and "memory" foam.

The clamping mechanism is important because it affects the pressure on our temples. The biggest complaint pilots make is that the headset is uncomfortable due to pressure on their temples or ears. Metal clamping mechanisms usually produce the most pressure, but seal the best. Plastic produces less pressure but is more durable (especially carbon-plastic). Headsets with clamp connections in the center of the ear cup tend to be more comfortable than those that clamp in other areas. Again, this varies with each model and should be tested individually.

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