Noise Cancellation?
 

I was sitting in an airplane Sunday night, N800 in hand, wishing I had brought along my noise canceling headphones. Then I looked down at my wondrous little IT and thought, "Now THERE would be a great IT app!" Use the built in mic to detect noise than process it to reproduce the same on a negative frequency and they balance out to silence.

Wouldn't something like that be great running in the background behind your favorite audio player? Giving you clean sound without the interruptions of background noise?

Now all we need are some acoustic engineers to write the code. Any takers?!? :D

Re: Noise Cancellation?
 

I think this is a bit complicated, since the IT is quite a way away from your ears. So the noise recieved by the Microphone would be different from the one recieved by your ears.
You have to match the frequency pretty well and time everything right, if you are off by even 1/4 of the period you can actually increase the noise. so for a standard background noise of 200 hz (Figure pulled right out of thin air) you would have to time everything right down to 0.00125 seconds.

But now i'm interessted in using a 2 Mic Setup to test how much difference this would make in a practical application.

This sounds like an interessting project.

Re: Noise Cancellation?
 

Hopeless, IMHO. But have fun, anyway...

Re: Noise Cancellation?
 

WHat if you were to use the microphone on the provided headphones? That's only like a foot away from the headphones...maybe a little easier.

Re: Noise Cancellation?
 

This really wouldn't work, I'm afraid. The reason noise-canceling headphones can work is that they can place microphones a known distance from each ear and in a position where they can assume they'll hear the noise before you do (i.e. immediately outward from the ear). If you're using one microphone located, say, in your lap on the N8x0, then if a sound comes from the left or right, the mic will pick it up before one ear, but after the other. There's no way it can cancel a noise after you've heard it, so it would only help one ear, and that's only if it could accurately guess how far away it is from you. Move the device and the cancellation stops working.

Re: Noise Cancellation?
 

Maybe you confuse this with something else. That's not how state-of-the-art active noise cancelling headphones work..

Re: Noise Cancellation?
 

Perhaps you could explain how they do work...

Re: Noise Cancellation?
 

The N8X0 isn't fast enough to do this within the time frame for this to actually be effective. It's easier just to play some gentle white noise in the background.

Re: Noise Cancellation?
 

There's plenty to read. Please use a search engine or a library.

Hint: Notice the part that those types of headphones work best for repetitive sounds, i.e. plane engines, train etc.

Re: Noise Cancellation?
 

Still, as far as I can see EvilBit got it pretty much right. Active noise cancellation won't work if you can't guarantee that the phase of the "anti-noise" sound is exactly opposite of the noise you want to cancel when both waves reach the eardrums.