Pack a large number of people into a small, confined space, and you're bound to get noise. People talk, babies cry and engines drone — and all three combined is enough to drive any frequent commuter mad. Luckily, headphones are great for blocking such distractions out, but they too have their limits; there's only so much noise even Sonic Youth can drown out.
all external noise, but this is incorrect. Instead, their job is to filter noise. A built-in microphone on the outside of each ear cup samples ambient noise, which is then passed to a microchip on-board. Only consistent, repetitive waveforms — engine noise or construction work, for example — are removed from the final product.
However, even this approach to noise cancellation has its limits. Most models work poorly with high frequency noise, because their waveforms change much more quickly than a low frequency sound. And because most headphones have limited audio processing capabilities, these faster waveforms are harder to deal with.
So are there any scenarios in which noise-canceling headphones are actually worthwhile? Any location with a droning, low frequency noise will benefit most from a fancy Bose, Shure or other-branded headset, though your mileage may vary. Unfortunately, those talkative teens on the subway each morning will still remain as loud as ever.
really looking for is a sound-isolating model. This type of headphone cancels noise in a very different fashion, blocking it in the first place. There's no microphones or electronic trickery required here — simply foam, rubber or other insulating material that conforms to the shape of a listener's ear, blocking outside interference.
With this in mind, what sort of noise-canceling or blocking techniques do your own headphones use? Do they work as advertised, or are such technologies simply marketing gimmicks?
Images via Flickr user jquiz, Shure, Boze.