# Homework Help: Oscillation / Soundwaves Question - Phase difference?

1. Feb 16, 2013

An observer stands 3 m from speaker A and 4 m from speaker B. Both speakers,
oscillating in phase, produce 170 Hz waves. The speed of sound in air is 340 m/s.
What is the phase difference (in radians) between the waves from A and B at the
observer’s location, point P?

And I have no idea how to solve this :uhh:

Basically looks like:

P---------B (4m away)
|
|
|
|
A (3m away)

2. Feb 16, 2013

### tms

Think about what what a phase difference means, and then think about wavelengths and distances, and how all three are related.

3. Feb 16, 2013

I get that graphically a phase shift means it's literally shifted across the x-axis. But I can't think of an equation that would relate this an the distance.

4. Feb 16, 2013

### tms

If you draw two sine waves, one shifted a bit relative to the other, on the same graph, a distance should jump out at you.

5. Feb 16, 2013

But we don't know the phase...

I get that they're 1m apart and it covers 340 m every second so the phase would be out of sync by 1/340.. do I convert that to radians then?

6. Feb 16, 2013

### tms

The 340 m/sec is the speed of sound. You need to know the wavelength of the emitted sound, and compare that to the distance between the speakers.

7. Feb 16, 2013