Do sound waves have an "upside down"?

Question

I know this sounds strange. Sound waves can be played backwards or forwards. Is there a way for them to be played "upside down"?

Answer 1

Yup, waves have an amplitude - how large the wave is. This is true for ripples in water, sound or any other sort of wave. If you have a wave and invert it, make the peaks the troughs and the troughs the peaks then you have what you refer to as an upside down wave. If the inverted wave meets the non-inverted wave they'll tend to cancel.



I've attached a fairly nice web page as a source. You might like to look at that.



I haven't tried this but if you have the kind of stereo with speakers which can be detatched if you play the same signal through both speakers and point them at each other and then reverse one of the speaker cables you should be able to hear a difference.

Answer 2

Yes.

Sound waves travel from the source radially. Think of the sound waves traveling in 3-D from the source. They can go in the x,y, and z planes both in the positive direction and negative('upside down' on your vertical axis) direction.There's a picture at:

http://www.treesfullofmoney.com/?p=1610

Answer 3

Everything John D told you is true, but he left out one important detail: If you listen to the original sound, by its self, and then you listen to the "inverted" sound by its self, you will not discern any difference. Interesting mathematical things happen (such as he described) if you play the sounds simultaneously through two different speakers, but the quality of being "inverted," all by itself, is not something that you are equipped to hear.



Those noise cancelling headseats that are promoted by a certain well-known speaker manufacturer work by picking up background sound and "inverting" it.



http://en.wikipedia.org/wiki/Active_noise_control

Answer 4

Inversion is the word you're looking for and yes, you can. Backwards obviously you hear everything in reverse order. Inverse, you hear it in funky reverse order.