Noise-canceling vs. noise-isolating headphones: What's the difference?

We compare these two often confused headphone types on the New York City subway system to determine which works better at blocking out the noise.

The Etymotic ER-4PT (left) and Bose QuietComfort 15 (right) headphones Steve Guttenberg

I have to admit I never really bought into noise-canceling headphones.

The name was a turnoff, they don't really cancel or eliminate noise, they reduce noise--and that's great--but so do most in-ear headphones. Better yet, those headphones don't need batteries and don't run the music signals through the noise-canceling electronics. My favorite isolating headphones sound better than noise-canceling headphones, but I haven't tested a noise-canceling headphone for a long time.

So I borrowed a pair of Bose QuietComfort 15 Acoustic Noise Cancelling headphones ($299) from CNET editor David Carnoy. I headed down into the New York subway with the Bose and three in-ear headphones, the Velodyne vPulse ($89), Etymotic ER-4PT ($299), and the Westone ES5 ($950) to discover which was the quietest of them all.

The Bose headphones were extremely comfortable, and their noise-canceling powers were impressive, so it's easy to understand why they're popular. I stood on the platform of a busy subway station to get the maximum sonic assault and switched between the four headphones as trains entered and exited the station. The screeching, metal-against-metal roar of the subway trains was reduced to a remarkable degree, and the Bose set a high standard indeed, but after just a few comparisons I learned the Etymotic and Westone were more or less on par with the Bose. The character/sound of the noise was different on all three headphones, so there was no clear winner; all three did a good job. I wasn't playing music at this stage of the testing, I wanted to concentrate on noise-hushing capability and was concerned music would mask some of the noise.

The Etymotic ER-4PT (left), Velodyne vPulse (center). and Westone ES5 (right) headphones Steve Guttenberg

The Velodyne vPulse failed to block as much noise as the other three headphones, probably because its dome-shaped silicone ear tips aren't designed to go as far into the users' ear canals as the ER-4PT or the ES5 headphones do. The upside to the vPulse's shallower penetration is it's more comfortable than the ER-4PT or ES5. Those two require a bit of fussing to insert and seal out the noise; the QuietComfort 15 is hassle free. It's easier to quickly pop on and off your head.

Ah, but I also found the Bose's noise-canceling signals produced what felt like "pressure" against my eardrums. The effect was very mild, and some people notice it more than others; in-ear headphones don't have that problem. On a more positive note, the QuietComfort 15's noise-hushing was more effective over a broader range of bass, midrange, and treble frequencies than the other three headphones. They let a bit more of the high-frequency screech and squealing noises from the subway train's wheels grinding against the tracks than the Bose did.

Then I boarded a train and it was significantly quieter inside, compared to standing on the station platforms. The whoosh of fan noise was reduced by all four headphones, and I noted the Bose was a wee bit quieter than the Etymotic and Westone, and much better than the Velodyne. I got off the train at Pennsylvania Station, went upstairs and took an uptown bus. The road rumble and heavy thuds of the bus' tires traversing potholes wasn't reduced all that much, though the Westone was slightly better than the others.

Once I started to listen to music on the bus, and the subway on the return trip back home, the noise-reducing differences were harder to detect, but the Velodyne was still in last place. With music, the Bose sounded better than the Velodyne, but the Etymotic and Westone were even better, with superior overall clarity to the Bose. That headphone seemed to compress music's soft-to-loud dynamic range swings. The Westone's bass power and definition were easily the best of the four headphones.

Sitting in my fairly quiet (for New York) living room, I compared all four headphones again, but this time I just listened for their sound quality with a wide range of music. The differences were easier to hear at home, which underscores the fact that all headphones--including noise-canceling and noise-isolating--pass a large amount of environmental noise to the listener. That said, the Bose's sound with music was at its best on the train and bus, in my apartment the sound took on a hollow/recessed character, and the treble was a little coarse. The Etymotic was much smoother and clearer overall. The Westone had by far the strongest bass and dynamic punch. It's the best sounding of the four headphones.

So, where you listen to headphones changes their sound. Indoor versus outdoor versus on the train, bus, or plane, a given set of headphones will sound different in each location. If you listen to more music on headphones while commuting than in quieter environments, go for a noise-canceling headphone. I have a newfound respect for what the Bose QuietComfort 15 does well, and it's very comfortable, I just wish it sounded better at home. If you listen 50/50 while commuting and in quieter environments, consider a noise-isolating headphone. If you only listen at home, consider full-size headphones, like the Hifiman HE-300 ($249) or Philips Fidelio L1 ($299) (review in the works).

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