If you believe the advertisements Bose puts out about these headphones, you can slip them on and instantly enjoy blissful quiet. Well, don't believe the advertisements. The headphones are able to actively cancel *some* noise, but nothing that comes close to warranting the $300 price tag. Examples:

* Sitting in front of my computers (I have two), I put the headphones, thinking that the white noise of the power-supply fans and hard drives will be easy to cancel. Nope... It does get quieter, the lower frequency noise is greatly attenuated, but you can still hear the whine of the drives. It's more like someone turned the treble way up.

* Riding to bus to work - I ride a commuter bus that takes the highway and there are three main components to the noise: the wind/tire noise, the engine noise, and the transmission. If you count other people talking, that makes 4. When you put on the headphones, the engine noise is reduced fairly well, but the transmission noise is reduced to far lesser degree, which means that it's *more* noticable. You can also clearly hear conversations around you. Playing music through the headphones doesn't help, since they seem to be actively passing the higher frequency noise sounds on to you together with the music.

* On a plane trip - the exact application that Bose crows about - the same comments as the bus apply, and the really annoying thing is that with the engine noise gone, you can hear the conversation of others very clearly. If I'm trying to sleep and it's between the roar of a jet engine or the inane babbling of the people sitting in front of me, I think I'd prefer the jet noise.

I contacted Bose customer support, thinking that perhaps I just had a defective unit, but the response (which was very friendly) basically said that the headphones only "reduced* noise and that different amounts of attenuation for different frequency noise was normal. I had gotten the headphones as a present for my wife, so they sat in a box for the first two weeks - which is to say that I would have returned them if the 30 days weren't up by the time that I realized what a rip-off they are.

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