In the area of noise cancellation, the JVC HA-NC250 works as advertised. Due to the design of the ear cups, the headphones even manage to block out some higher-frequency sounds, such as the tappity-tap of the keyboard--but only when music is playing as well. Even with music off, flipping on the active noise-cancellation feature eliminates low-frequency noises, such as the hum of an air conditioner, meaning the HA-NC250s are perfectly suited to air travel. However, during testing I did notice a faint, cyclical static sound in the right ear cup, which is where the noise-cancellation circuitry is located. For the most part, it's not noticeable when music is playing, but it could irritate some users.
Sound quality in general proved quite good in testing, and I like that you can listen to music with or without the noise-cancellation feature engaged. In general, music sounds a bit clearer, more open, and considerably amplified with the noise-cancellation feature on, but sound quality overall was great. Bass response in particular was impressively tight, yet it didn't overshadow other ranges of sound. Audio response was pleasantly even, with rich mids, sparkly highs, and nice undertones. For 200 bucks, the JVC HA-NC250 makes an acceptable alternative to the Bose QuietComfort 3.
