November 01, 2010
Like many pilots, my headset was my first big aviation purchase. The David Clarks were expensive for me in those days but turned out to be great value for money. 25 years later they are still going strong and until a month ago I would have said they would last me until my landing gear gives out.
But then Bose asked me to try out their new A20 headset and I am afraid the David Clarks may now end up being relegated to the co-pilot seat. The A20 is Bose’s most advanced pilot headset yet. It replaces Bose’s very popular Aviation Headset X the first and most widely sold active noise reduction (ANR) headset in the world.
Attempts to reduce the din in the cockpit have been going on since the 1950s when aeroplanes and helicopters started to become very noisy working environments. A bloke called Lawrence J. Fogel in the US was the first to develop an ANR headset but it wasn’t until the founder of the Bose Corporation Dr. Amar Bose, got into the act, that the field started to really quiet down.
In 1978 Dr Bose was apparently on an international flight and was provided with a set of headphones he felt were crappy at keeping out the noise. He declared that he could do better.
But it turned out to be a difficult problem to solve. It took him 10 years of research before he released his first noise cancelling headphones and shouted down the competition. Nowadays, Bose has 5 factories, more than 150 retail stores worldwide and Dr Bose is still there as the company’s technical director. His headsets are the equipment of choice for NASA and are also connected to a special communications system on the International Space Station so astronauts can make phone calls home to their families. You don’t get a much better endorsement than that.
Most other headphone manufacturers have since jumped on the ANR bandwagon including Telex , Lightspeed and David Clark. The competition between them is fierce so the products they offer us pilots are getting better and better. Noise-cancelling headphones work by placing one or more microphones near the ear to pick up ambient sounds. The A20 has them both inside and outside each earcup. The electronic circuitry analyses those sounds and generates its own waves but 180° out of sync with the original noise. When the two waves collide, the interference cancels the noise before it gets to your ear. The first few times you use it, the lack of noise is scary.
I know what my aeroplane sounds like and that constant growl is comforting. On the rare occasion I hear the growl change, it gets my attention immediately. Flying along without hearing that growl was disconcerting for a while. But the silence grew on me.
The silence also makes it possible to hear every radio call with crystal clarity. It is very noticeable how much more clearly I hear others speaking on the radio.
The other new feature I enjoyed was the plug for my iPhone. Having Elvis, Pet Shop Boys and Andre Rieu belting out in my ears at Bose quality is terrific as I while away the hours in the air. The A20 also has Bluetooth connectivity with my phone. But along the east coast, trying to make a phone call at altitude is always a hit and miss proposition so I don’t know how often I would use it. Bose also claims the A20 has improved cushion materials for the earcups. My head has not complained once about wearing it but my old David Clarks are just as comfortable. I’ve been told some pilots replaced the earcups on earlier Bose models with more comfortable brands. But these seem fine even over my sunglasses. Bose also says this model has one third less clamping force than other headsets which makes for a more comfortable ride.
For pilots of heavy metal machines, the A20 features Intercom/AUX priority switching. Many pilots will use this for dedicated GPS and traffic warning systems. Audio priority can also be set to mute the auxiliary input completely when intercom signal is detected, or to simply lower the auxiliary volume. Noise-cancelling headphones aren’t perfect of course. Unlike my old David Clarks, they can’t stay in the aeroplane when I go home. They are much too expensive to be left lying around.
They consume power. I have to remember to carry spare batteries (although I have flown with the things turned off and the noise level is still terrific so that issue is not a big one).
Active noise reduction headsets also work well for sounds that are continuous, such as the growl of my engine, but they are not effective at damping out rapidly changing audio signals. Again a small problem in an aeroplane. And occasionally I get a high-frequency hiss which I cancel out by switching my avionics off and back on. For years, pilot friends have been badgering me to switch to an ANR headset. But my internal noise reduction system always cancelled out their nagging, primarily I guess because of the cost and the fact that my old headset was doing a good job. But having used the A20 now for a couple of months I’ve changed my opinion.
In fact, the noise reduction in the A20 headset is so good, that when Bose ask me to return it, I’m pretty sure I won’t hear anything.
