Like Sony's in-ear MDR-NC22 noise-canceling earphones, the new MDR-NC40's best feature is its price: Both pairs are only $100. The MDR-NC40 isn't an in-ear model but a supra-aural set of headphones, meaning that they sit on the ears without creating a seal. Comfortable and capable of delivering rich low-end sound, the MDR-NC40 isn't the most effective pair of noise-canceling headphones I've ever heard, but it does manage to eliminate a significant amount of noise. Anyone who thinks that $350 is an outrageous amount to spend for Bose's QuietComfort 3 should give the MDR-NC40 a whirl.

The supra-aural design is quite similar in feel to that of the Bose QuietComfort 3. The two pairs of headphones are roughly the same size and weight (the MDR-NC40 is 2.8 ounces), but Sony keeps the entire design black and simple in contrast to the silver ear cups on the QC3. The most significant difference in design, however, is the battery pack, which sits cozily in the right ear on the QC3, but in a compartment with a shirt clip about halfway down the 4.9-foot cable on the MDR-NC40. Also, the Sony pair takes one standard AAA battery; it doesn't have a rechargeable cell, so depending on how much you use them, you might want to stock a healthy supply of replacements. (Sony claims that one battery should last roughly 40 hours.)

Unlike the QC3, the MDR-NC40 can be used without active noise cancellation to preserve battery life—just switch the power off on the battery pack, but expect some loss of volume and bass response in the passive setting. The MDR-NC40 comes with a far more compact carrying case than the QC3, since the 'phones fold in half for storage.

Bose's QuietComfort 3 headset undoubtedly delivers better noise cancellation. For instance, there's an entire band of middle-high frequencies that the QC3 nearly eliminates but the MDR-NC40 doesn't quite stamp out. Even so , the MDR-NC40 is no slouch. Sony's noise cancellation should be sufficient for most; it definitely will help reduce airplane engine din and subway roar.

The MDR-NC40 is a decent-sounding pair of headphones with respectable low-end sound, particularly in deeper frequencies that a subwoofer might handle. There's a bit of added brightness, as well, that brings out certain guitar sounds and percussion hits. The Bose QuietComfort 3 sounds very different, with an even stronger boost in the mid-to-high frequency range that adds crispness in most scenarios but sometimes feels a bit too strong. The QC3 also has a bit more of a bass boost, but listeners starving for low-end won't go hungry with the MDR-NC40, and both pairs can handle high volumes quite well without distortion. For a $100 pair of headphones, the MDR-NC40 offer surprising audio performance.

From a pure noise-cancellation standpoint, if you can afford them, Bose's QuietComfort 3 or Sennheiser's $450 PXC 450 NoiseGard are the headphones to get. If you'd rather save some cash, the $100 MDR-NC40 is an excellent bargain.

Sony offers a one-year warranty on the MDR-NC40. For customer support, visit sony's website.