Frequencies of standing wave in pipe

[susdu]

Homework Statement

A speaker is placed near the open end of a 0.5m pipe (closed on the other end).
what is the speed of sound if the pipe resonances at 600Hz for n=2?

Homework Equations

fn=(2n+1)*V/4L
Or?
fn=(2n-1)*V/4L

The Attempt at a Solution

I saw both versions of the formulas above, which one is correct?

 

[TSny]

Both formulas are correct. The first one assumes that the possible values of n are 0, 1, 2, 3, ... The second formula assumes the values of n are 1, 2, 3, ... So both formulas will produce the same set of resonant frequencies.

However, since the formulas produce a different frequency for the same n, you would need to know which formula the problem wants you to use. It's probably the same formula that was used in class or in your textbook.

 

[susdu]

Thanks for the clarification!

 

[cepheid]

Well, the bottom version of the formula obviously doesn't work for n = 0, whereas the top one does, so I'm assuming the two versions are just dependent on where you start counting from. They both generate identical harmonics if you let n be 0, 1, 2, 3, ... for the top one and 1, 2, 3, ... for the bottom one.

EDIT: I was sitting there too long with my compose window open while doing something else and got beaten to the punch!

 

[susdu]

Thanks anyway cepheid.