Using a sophisticated system of noise cancellation, the QZ/2000 headset significantly reduces the perceived noise level of static low-frequency sounds. In doing so, the headphones also cancel a portion of the music at those frequencies, but the net effect is unquestionably improved clarity in your music. The QZ/2000 works well for general noise dimming, even if you don't intend to listen to anything. Just put them on, switch the noise cancellation on, and enjoy your quieter environment.
Devices of this type have two functions: reducing noise, and playing program material. The QZs reduce noise very well, but a technical problem prevents the stock setup from playing music on an airplane.
I kind of like the Koss QZ approach a little better than the Bose (both from a cost standpoint and from the fact that you can hear conversation - the Bose earcups [passive quieting] preclude conversation). The active noise reduction, based upon a comparison that I made on a recent flight, is comprable.
The technical problem (and I wrote to Koss about this - we'll see what their reply is) is that due to the fact that the QZ's have an amplifier they are, in effect, a high sensitivity headphone (they are loud with very little input). The headphones on most airplanes are very low sensitivity, so you play them with the volume control set higher than you can with the Koss product. When you set the airplane's volume control very low, the program signal (the music) approaches the signal strenght of the underlying noise/static signal. What this means is that the signal/noise ratio is low, and you hear the annoying high-pitch noise. I think a simple low-tech solution is to put a volume control in the signal path. Koss sells these, but they should be included with the QZ.