<i><b>Editor's note:</b> We have changed the rating in this review to reflect recent changes in our rating scale. Click <a href="http://www.cnet.com/4520-6022_1-6207800-1.html?tag=txt">here</a> to find out more. </i> <br><br> Koss's Quiet Zone QZ-2000 headphones are capable of surprisingly efficient noise cancellation over a relatively broad frequency spectrum: from midbass to upper midrange. This effectively hushes much of the sound made by planes, trains, and buses. We even subjected the QZ-2000s to a full-frontal New York City sonic assault, consisting of subways, noisy restaurants, and--worst of all--the unyielding din of midtown traffic. The noise-cancellation process pumps up the midrange to help the music cut through noisy conditions, which suggests that this unit is best for canceling fairly consistent noise. <br><br> We found the QZ-2000 earphones extremely comfortable, although they don't look as cutting-edge as they could, considering their advanced noise-cancellation technology. The circuitry that cancels the noise is housed in a small external box; this also holds twin AA batteries, which Koss claims last more than 200 hours at a stretch. You can fold the QZ-2000s into a compact bundle and store them in a neat little carry bag--a good idea for travel. <br><br> The relatively large and heavy battery pack lacks a belt clip, and its two wires (a thick one to the headphones and a skinny one to the portable audio device) are prone to getting tangled with each other. One more nitpick: The QZ-2000s, like some other noise-canceling headphones, produce a slight sense of pressure on the eardrum. Listeners sensitive to this effect may find them mildly uncomfortable. <br><br> The QZ-2000s' warm and round sound is adept at pumping up music. The headphones sounded best with rock tunes, but for a retail price of $199, Koss should offer more midrange detail and high-frequency resolution. DVD movies were less affected by the overmellow sound, but we still much preferred the less expensive <a href="/electronics/0-6342422-1304-20604867.html?tag=txt">Sony MDR-NC11</a> earbud headphones for their better sonics and noise cancellation.