Question about Sound Waves - Help Needed

[student85]

I have a question regarding sound waves. Can someone clear up the following if anything is wrong:
Sound waves have parts of high pressure and low pressure. The medium in which the sound is being transmitted vibrate backward and forward, being their maximum displacemente from rest "smax".
I get very confused with the terms because I believe there are two parts which need to be analyzed in waves: the movement of the medium and the movement of the wave. So, particles in the air go back and forths, while the wave goes only forth?
Damn sorry I think ur like "wow this guy is confusing himself even more." But I am really confused about sound waves. Can anybody give me some quick notes about the movement of sound in air. THANKS A LOT IN ADVANCE.

 

[quinn]

Sound is a disturbance in a physical medium (air). Sound waves in air are regions of pressure differences that move in tandem, but there is no net movement of the air. The movement of the pressure "trains" is far slower than the individual molecules in the air.

 

[student85]

Thanks quinn. I didnt understand what you said about the zero net movement of the air. If there is no movement then how do high and low pressure sections form?

 

[russ_watters]

Consider waves on the ocean. The wave moves linearly (propagates), while individual molecules of water move only up and down (actually, kinda in an oval pattern). In the ocean and in sound, the movement of one molecule disturbs the molecule next to it, which causes that molecule to move, etc, etc, etc.

 

[jtbell]

The air in a sound wave moves on a small scale, probably a fraction of a millimeter, because that's what produces the pressure variations. But the air doesn't move on a large scale. When you talk to someone, the air next to your lips doesn't end up next to your listener's ears. Unless you're very close to your listener, that is!

 

[student85]

thanks jtbell!
I think I am cleared up now.