Snoring!

I once read of a woman who divorced her husband of thirty years, because his incredibly loud snoring kept her awake, even though she was sleeping in a different room that wasn't contiguous with his! If the device could be unintrusive enough not to interfere with the snorer's sleeping, then it could save a lot of marriages!

- Hoytster

There might be the risk that irresposible parents would use this device to ignore their baby's crying when there is a serious problem.

it would require a great deal of amplification to output a sound of the equivilent intensity to a babies scream or dog bark. so the gadget would have to be pretty large. bose headphones have the advantage of only having to output to earphones. but mabye for movie theaters baby equiped seats could have a microphone in the arm rest that pulls out or something.

I'm just guessing, but I think that the source of the anti-sound would have to be very close to the original sound in order to neutralize it at all. Could anyone with expertise in the area commment?

It's a very appealing idea, if it could be made to work. I organize the volunteer ushers in my church, and the absolute worst part of the job is having to ask a parent with a crying baby to leave. The amount of tension this can create is incredible.

What about working with a small headset connected into your computer, wich runs a program to cancel the noise ? It should be possible for people who work in an noisy environment to plug 2 microphones into the PC and a lightweight headset for the cancelled noise ? (the one from Bose is quite expensive and too heavy)

Computers are so fast these days that it should be possible !

Anyway noise cancelation is a good invention or should I call it a discovery ?

Good idea, unfortunately it won't work. As you stated, active noise cancellation works by inverting the sound so that the original + the inverse = zero. This results in silence, in theory; or a reduction, in practice. It works well in small spaces, so headphones are perfect.

When you try to use it on a larger scale, the sounds reverberate off their surroundings in all directions. When the inverse bounces off different surfaces at different distances from the listeners, there will be different phases of the wave reaching the listener at various locations.

Now you have the original + (inverse, but out of phase) does not = zero.

The result would be either a sound that seems to change volumes, periodically; or just louder than the original.

If it worked, there would be a lot less loud stereos on the road around my car.

Thisexperiment lets you test the theory on various scales, if you are really interested. I found this link about four years ago, and haven't used it since. It all worked then, so good luck now.

I guess that's whynot.net