Noise cancelling headphones?

Question

I know noise canceling headphones cancel out noise by reading the sound then adding another noise 180 degrees out of phase of the original, but does it physically cancel out the noise you hear, or does that noise still reach your eardrum? I guess what I'm thinking is the noise still has to reach your eardrum, but the headphones "trick" your mind into thinking there is no noise. I work in a very noisy environment and am concerned the noise is still getting to my eardrums.

Answer 1

You can read a write-up about how the noise cancelling head phones work.  Go to:

http://www.heilsound.com  

Click on Amateur Radio then click on headsets and then click on the Quiet Phone headset to read the write-up about how it works.  

If you have further questions, and I think you will, contact Chip Margelli or Bob Heil.  By the way Bob Heil was the sound guy for the Eagles band so he knows his audio.

Answer 2

noise canceling is fairly easy.

to cancel noise, you feed the source you want into an op-amp on one side, and the noise source in on the other side, the result will be the source less the noise.

I like the LM741 since it has fair freq response and zero gain.

Answer 3

If you can't hear it, it isn't hurting your ears. That simple really. It's not that your ears are fooled, it really is that the sound waves cancel each other out precisely at the point in the ear where the hearing occurs. So there is literally NO noise at that point.