Bose replies to my observation about the hissing sound heard in quieter environments, and my observation that they are perhaps a little fragile.

My comments are in blue, their replies are in brown.  Updates subsequent to the initial review are in purple.

Conventional noise cancelling technology (most consumer noise cancelling headsets use feed forward processing) has serious limitations in the overall amount of reduction (dB) and the bandwidth of operation. These headsets don't have the desired effect on lower frequency noise, like a jet engine, or any effect on high frequency noise, like wind resistance.

Other noise canceling products available to consumers don't provide enough reduction to be able to hear the hiss from the electronics, but it is there. In an office environment, many users listen to music through the Bose headsets. This eliminates the hiss, and all extraneous noise is eliminated as well. On a plane, users can listen to music, airline programming, or silence.

I feel that Bose are being a bit disingenuous about this.  Yes, all electronics create a background noise, but better electronics have quieter background noise (as measured in a device's signal to noise ratio).  Suggesting that other noise canceling products hide their noise by less effective noise canceling is an unfair statement because I can hear the hiss in the Bose unit but not in other units in a totally silent environment when there are no other noises to obscure any potential hiss in the other unit.  Playing music does not 'eliminate the hiss' any more than playing music eliminates any other background noise!  I accept that the Bose units do work better overall than other units in a noisy environment, but the hiss is an unfortunate artifact that other devices have managed to avoid and which one would have thought Bose could also have done a better job of minimizing.

Update 2003 :  Although Bose claims, above, that their level of hiss is unavoidable, they are now proudly describing their new QuietComfort 2 as having a lower level of hiss!  Does this mean that Bose achieved the impossible?  Or does it mean that they were being economical with the truth when making the risible claim, above, that the hiss level in the earlier model was unavoidable!

Bose Acoustic Noise Cancelling technology works across the range of human hearing - if your ear can hear it QuietComfort will dramatically reduce it. QuietComfort technology is the result of 23 years of research, more than 10 US patents, and more than a decade of operation in mission critical applications with the United States military.

It is interesting to note that 3 out of 4 QuietComfort users report feeling less tired, even refreshed at the end of a flight. It turns out that low frequency noise (the predominant component of air travel) is linked to fatigue (independent medical studies confirm this). Since QuietComfort provides reduction of noise across the range of human hearing, it reduces the noise that cause fatigue.

You need not be concerned that the Bose headset is "potentially somewhat fragile." They are in fact robust, with an extremely low failure rate of 1/10th of 1 percent.

That is an excellent statistic for sure.  My comment was not meant as a criticism of the headphones, but rather a sad reflection on the real world of what goes on inside my airline carry-on bag.  By the time the bag has been stuffed full with a laptop, various other bulky and/or heavy objects, perhaps a couple of bottles of duty free spirits, then squeezed into an overhead bin, then suffered random attacks from other passengers putting things on top of it, I fear that anything inside it that isn't armor-plated is liable to be damaged, and particularly with a high value item such as these headphones, the idea of being more protective of them is probably quite appropriate!  :)

Update, 2003 :  Rather as anticipated and feared, on several occasions the headphone ear pieces have popped out of their frame.  Although I've been able to pop them back in on each occasion, I don't know how long this will remain feasible before the unit just simply snaps off.  Now that the headphones have been destroyed, further field testing is impossible.

It is also relevant to note that although Bose contested my claim that their headphones were potentially fragile, their new QuietComfort 2 has been completely redesigned.

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