Noise-Canceling Headphones and Music Quality

Noise-canceling headphones are a great invention. Instead of walking down the street of a hectic city, being overwhelmed by the sounds of the million-footed beast, you can shut out much of din of traffic and conversation while listening to your favorite tunes. Another common use of noise-canceling headphones is plane trips; the constant sounds of an airplane can be fatiguing, and noise-canceling headphones – even with no music playing – can make for more restful traveling.

It may seem like these headphones use voodoo to silence background noise, but the technique is actually a pretty simple application of physics. They combine both passive and active noise cancellation.

To start with, each of the ear cups is well insulated, blocking out much of the noise around you. This passive noise cancellation blocks out many of the higher frequencies. In fact, you may find that good noise-canceling headphones block enough sound even before you turn on the active noise cancellation.

For this latter feature, each of the ear cups contains a tiny microphone that picks up the external sounds. The headphones process these sounds by flipping the sound waves upside down. When you play two sound waves at the same time – one inverted – they cancel each other out.

2000px Active Noise Reduction svg

A great example of effective noise cancellation is the Grateful Dead’s Wall of Sound. Back in 1974, sound man and chemist extraordinaire Owsley Stanley came up with a setup for the band that was distortion-free, and also served as monitors, so the band could hear themselves play without having blowback monitors on the stage in front of them.

Wall of sound

The Wall of Sound was the largest sound system ever built, and packed a lot of power: it weighed 75 tons, contained some 600 speakers, and put out more than 26,000 watts of sound. But there was a problem: since the microphones were facing backwards, toward all those speakers, wouldn’t they create a feedback loop?

Stanley set up microphones in pairs, out of phase, which worked exactly as active noise cancellation does. The singer sang into the top microphone, and the bottom microphone picked up the background sounds. This second microphone’s waves were flipped, canceling out the background.

Jerry microphone

As you can see in the first image above (from Wikipedia), there is still a remnant of the noise after the cancellation; this is unavoidable. As such, Grateful Dead recordings of the time – notably those officially released of the Grateful Dead Movie Soundtrack – have a bit of a hiss in the vocals.

The same is true with noise-canceling headphones today. If you stop playing music, you’ll hear a slight hiss in the background. Noise-canceling headphones may offer great sound, but they do have this limitation: anything you listen to, with active noise cancellation turned on, will be affected by this hiss. Because of this, no noise-canceling headphone will sound as good as regular headphones of the same audio quality.

So noise-canceling headphones are a trade-off. The sound quality of these headphones isn’t as good as standard headphones at the same price. But they’re great in noisy environments – planes, trains, busy city streets – where you really want to get rid of the background noise. If you use them in quiet areas, make sure to turn off the active noise cancellation; your music will sound better. (Some noise-canceling headphones only work with power; others will work without power, just like regular headphones.)

(If you’re curious, I have a pair of Audio-Technica ATH-ANC7B noise-cancelling headphones. (Amazon.com, Amazon UK) They’re a lot cheaper than Bose headphones, and are well rated. I don’t use them often, but when I do use them, they work very well, and have very good sound.)

14 thoughts on “Noise-Canceling Headphones and Music Quality

  1. Kirk, thanks for the explaination.

    If you want to avoid that hiss from noise-canceling headphones, you might consider some of the better in-ear monitors. They block sound very well and many easy outperform other options in terms of sound quality. Of course, it all depends on whether you can tolerate deeply-inserted earphones.

    My own Etymotic HF3 in ear headphones sound fantastic and can be used with the company’s “Awareness!” App for iPhone. This app permits only certain sounds to get to the listener based on that sound’s volume. By using the built-in microphone it allows, for example, for loud emergency-type sounds to get through, while letting the physical nature of the in-ear monitor to block the rest.

    • Yes, they are a good option. However, I can’t use in-ear monitors; I hear myself breathing, and it’s very annoying. (I have a custom-fit pair of Etymotics.)

      • That’s too bad. They’re such great sounding earphones.

        Maybe you should listen to louder music… some passages of Wagner’s come to mind, for ex. ;-)

    • I bought my first Ety ER-4Ps years ago & similarly find they have all the advantages of the 2 noise-cancelers I’ve bought and others I tried, plus their higher quality comes without the extra weight & size, without that tiresome hiss and without the need to have a separate set of batteries at hand. (Noise-cancelers’ batteries died more than once while flying: you’re SOL.)

      Any musician who values one of his most important capabilities, his hearing, will necessarily have SOME kind of noise-blocking if they’re on stage in front of any rock-volume sound system. Noise-canceling phones are really not the look you want, while unobtrusive plugs are just the ticket.

      PS: as a former audio engineer, I can say the 2nd mic is just a bit redundant: you already have a very good idea of the sound coming from the wall, and can negate it with modern circuitry (digital delay circuits are needed), just by the relative strength of the vocal versus all the other sound.

  2. I’m pretty fussy about excellent audio, but I recently purchase Bose QuietComfort 20i Acoustic Noise Canceling Earbuds. I’m very impressed with how well they cancel outside noise, without too badly ‘coloring’ the music. Admittedly, they do not offer what might be called high end sound, but the right setting, they’re a winner for me. They also do not seem to have that characteristic Bose sound – which is not my favorite sound signature.

  3. At first I didn’t really understand how the active noise cancelation works, but this makes much more sense to me now. Was really surprised when I put on my Sennheisers with active noise canceling on for the first time, really made a big difference.

  4. Its really important to understand the balance between Noise Cancelling and Issolation, becaue they both have their own effects on the Sound Quality.

  5. Thanks for clarifying how the active noise-cancellation feature works (ANC). I absolutely love my Bose QuietComfort 35 headphones that they just released. It has such a good ANC technology equipped!

  6. Thank you very much Kirk.

    I have been using many kinds of noise-cancelling headphones but I haven’t know how it works compared to other normal headphones until reading this well-explained article. Thanks

  7. Yeah I wish I’d bought a pair of Bose Quiet Comfort 35s now. I went for the Plantronic Backbeat Pros instead and although they are awesome, the ANC is not as good. Still quite happy with my purchase though.

  8. Interesting read about the wall of sound – I began the NC lifestyle with ATH-ANC7B’s and eventually upgraded to the Bose Quietcomfort series. Sound quality is comparable in both, but I have yet to find another product that can compete with the Bose as far as the noise-cancelling technology goes.

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