Logic might tell you that the Sennheiser PXC 250 headphones can't possibly work—they're too small to seal out noise. But these compact, supraural (top-of-the-ear) phones with active noise reduction do a respectable job. They don't give you the tomblike isolation of the Bose phones, but they can do the voice-thinning trick too. In fact, these are the most compact active-noise-reduction phones we've tried that actually do the job.

The headphones are pretty flat up to 6.3 kHz; then they begin to tail off gradually. A glockenspiel concerto might sound thin, but the PXC 250s will deliver lots of good music in noisy places. The active electronics introduce a small amount of hiss, but it's inaudible below the music. The electronics module takes two triple-A batteries and has a belt clip. The zipper case includes both quarter-inch and two-prong airline adapters. Quieting: 15 dB; Frequency response: Almost great; Comfort: Excellent.