“CAUSE YOU’RE HOT THEN YOU’RE COLD
YOU’RE YES THEN YOU’RE NO
YOU’RE IN THEN YOU’RE OUT
YOU’RE UP THEN YOU’RE DOWN
YOU’RE WRONG WHEN IT’S RIGHT
IT’S BLACK AND IT’S WHITE
WE FIGHT, WE BREAK UP
WE KISS, WE MAKE UP!”
Man I LOVE that song! I could just sing it all day long! On the train, on a plane, right beside you, in your ear-hole.
Supposin’ you don’t like the power-pop that my girl Katy likes to sing? Well then you’ve got two choices: 1) Challenge me to a sing-off. 2) Put on some noise-canceling headphones.
Trust me, you don’t want to challenge me to a sing-off.
So you’ve chosen to put on some noise-canceling headphones? Wise choice…
But how do they work? Don’t they have something to do with magnets?
Well, yes… most forms of speaker use magnets to… never mind, I dont talk to Juggalows.
I digress… “Noise Canceling” headphones are really just regular ol’ headphones with two small differences…
Regular headphones receive a signal from your iPod, CD player, 8-track, etc… and convert that signal into the vibration of a diaphragm, which creates noise which you interpret as bad music…. (No offense to your music tastes, but it’s just so cliche to have a favorite band that no one’s ever heard of… Katy Perry is all you need.)
Noise canceling headphones do the same, except that they also listen to the environment around you, and attempt to “cancel out” any noise that you might be hearing that isn’t from your desired audio source. In theory, this means you could be sitting on an airplane in flight, and not be able to hear the drone of the engines, or the whine of the baby down the aisle.
In reality though, they aren’t able to completely cancel ALL the noise around you. Even the super-high-end noise canceling headphones can only “cancel out” a certain percentage of the outside noise. There are a lot of complicated reasons for this, so I won’t go into them here, but suffice it to say…they ain’t perfect.
So a more accurate name for noise canceling headphones might be an “Active Noise Attenuator”. This is opposed to a “Passive Noise Attenuator”, which would simply be earplugs. In reality, if silence is what you want, earplugs are going to do much better than most noise canceling headphones.
Noise Canceling headphones operate on the Superposition Principle of wave mechanics. The idea is that when two waves encounter each other, they will “superimpose” their characteristics upon one another, creating a new wave that is a combination of the two original. The figure below shows the two extremes of superposition; 1) If the two waves are “in-phase” they add together, creating a larger amplitude wave, and 2) If the two waves are “out-of-phase” they subtract from one another, completely eradicating both original waves.
(FYI: This applies to particle/pressure waves like water and sound, as well as electromagnetic waves like light)
Your noise canceling headphones are using this concept to attempt to “cancel out” the sound waves from the outside environment via two simple components: 1) a microphone to listen to the outside noise, and 2) a small signal processor to create the waveforms necessary to cancel the outside noise.
That’s it. No fancy, super computer living inside your headphones… no complicated materials or wiring. Just a little microphone and a processor less sophisticated than the one in your 5$ Timex watch. So why are they so expensive?
Simple. They’re expensive because they sound expensive. “Noise Canceling” sounds really fancy, because most people don’t understand how it works, but in reality it’s just adding a little bit of extra noise to your headphones, which through some physics magic, results in reducing the perceived volume of the outside noise.
Are they a good idea? Certainly.
Are they worth it? Not at all. Earplugs can literally be bought with the change in your pocket, and do a much better job of creating silence for your ear-holes.
Maybe one day some company will figure out how stupid this is and starts selling noise-canceling headphones for 2$ more than regular headphones, then they’ll be worth it, but for now just listen to Katy Perry, sing really loud, and I’m sure you won’t be able to hear anything else for WEEKS.
Bonus: Although this technology is a sham for headphones, it’s being tested on a larger, 3-dimensional scale to reduce the noise of aircraft in communities near airports! Loudspeakers are set up around the airport that play the off-phase sound waves for the engine noises, and word-on-the-aerospace-street is that, after a lot of optimization, it works really well!