Bose noise reduction earphones

[Jack Kretmar]

This thread may be a little off the subject of aircraft. In reading Marc Zeitlin's work profile, I see that he worked on a noise reduction project for the Bose corporation. Is this those new noise reduction earphones we hear about. If so, that's interesting because they would be great for the Cozy (even though they are very pricy). Is this the case, Marc? I'm no engineer, but I suspect they work by "reading" the noise signal and then instantly generating a reverse amplitude "mirror" signal to cancel out the noise. Do I have that right?

[Marc Zeitlin]

Originally posted by Jack Kretmar

Is this those new noise reduction earphones we hear about. If so, that's interesting because they would be great for the Cozy (even though they are very pricy). Is this the case, Marc?

 

Yes. When I was at Bose, I worked on the Bose X noise canceling headsets for pilots, as well as the first generation of noise canceling headsets for the mass market (they're now selling 2nd generation mass market headsets). Noise reduction headsets (called ANR, for "Active Noise Reduction") have been around since Bose invented them about 18 years ago, but only recently (5-10 years) has the price on many of them come down far enough for them to become very popular.

 

I have a pair of Bose ANR headsets, a pair of Lightspeed ANR headsets, and a couple of Peltor passive headsets. The Bose and Lightspeed are great - I won't wear passive headsets anymore - the Peltors are only used for the rare times there are people in the rear seats. The Bose X were the best headsets when they came out in 1999 - I don't know if that's still the case, but they're certainly still the most expensive :-). They are VERY good in the COZY - any ANR headset is better in any plane than any passive headset.

 

I'm no engineer, but I suspect they work by "reading" the noise signal and then instantly generating a reverse amplitude "mirror" signal to cancel out the noise. Do I have that right?

 

Pretty good guess, for not an engineer :-). There's a tiny microphone INSIDE the earcup, as close to your ear as they can get it. It picks up all the sound that ISN'T coming through the wires, and the circuit board inside the earcup generates the same noise, but 180 degrees out of phase, so it substantially reduces the incoming noise. It doesn't actually cancel it, because the microphone would have to be inside your ear to do that (which would be uncomfortable), and because the technology only works at the lower frequencies - generally there's no effect on anything above 300-400 Hz.

 

The Lightspeed Engineering website has an excellent tutorial on ANR headsets. See:

 

http://www.anrheadsets.com/

[Spodman]

Does anybody know if ANR has ever been tried in motorcycle helmets, or have I just given away an idea that'll make somebody rich:confused:

 

Erm, after a little more thought I suppose it may be inconvenient to miss out on ambulance sirens, the horn on the Kenworth on the intercept course or the cop asking the motor to be turned off or he will insert lead pellets into you...

 

On the other hand (having viewed Marc's link)

The frequencies we're canceling with ANR circuitry are low frequency propeller, exhaust, and wind noise that register at about 100Hz in the cockpit noise spectrum. 'True' engine noise is higher up the spectrum, and believe it or not you will likely hear the engine better.

 

I'm getting keen again:confused: