Saving the World by Destroying Evil Sound Waves

Okay so I'm going to write my first post that actually contains some Physics - you have been warned!

So yesterday I talked about avoiding my Physics essay and this evening I actually finished it. It was quite interesting once I got into it and started using my other favourite website (since yesterday it is now demoted to second favourite...), howstuffworks and I actually understood what I was doing!

The essay was supposed to be all about noise and how to reduce it, I'm not exactly sure that my teacher wanted more than half of it to be taken up by noise cancelling headphones but it was so cool I just couldn't help myself!

The headphones 'destroy' background noise by using small microphones to pick up on the noise and then replicate the waves. The wave now has the same width and height (frequency and amplitude) as the original sound wave. However the wave is rotated by 180 degrees so when it is emitted the peaks (convex part) of our new wave aligns with the troughs (concave part) and vice versa so they look like the image where the orange line is one wave and the pink line is the other wave.

The noise is now cancelled! Of course I realise that sound waves are longitudal and not transverse so this must be a simplified explanation but this is cool right?! The sound practically disappears!

I guess maybe the title exaggerates slightly but Noise Induced Hearing Loss is a serious problem! At least thats what I read on the internet... Everyone knows the internet is always right!