# Homework Help: Compressions and rarefactions of a sound wave

1. Oct 17, 2008

### Nauraushaun

1. The problem statement, all variables and given/known data
Well it's not so much a direct question as it is several.
I'm very confused about sound waves. I know that, when modelled as a transverse wave on a set of axis, a compression is a maximum and a rarefaction is a minimum. But where do nodes and antinodes fit into this? Which is a node, which is an antinode?
What's more, I'm even more confused about actual loud points. Are compressions and rarefactions considered to be loud points, meaning the point in the middle is a quiet point?

3. The attempt at a solution
See attached image.
You can see that I had a go at labelling the wave myself. Could someone please replace my labels with the correct ones?
Thanks very much.

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2. Oct 20, 2008

### cristo

Staff Emeritus
Well, what are the definitions of a node/antinode?

What's plotted on the y axis of this graph?

3. Oct 20, 2008

### Nauraushaun

I'm not sure about the definitions! Therein lies the problem :D

Well, it depends how you interpret it. It's got the X axis, which could be seen as 0. On a Voltage vs. time graph, both maximums and minimums are 'high' points of voltage, so this could be the same.
On the other hand, the notion of a minimum suggests it's very little sound, and I was sure rarefactions were quiet points, being the absence of particles, but it's hard to visualize.