Cross Correlation of two sound signals


by sampathkumarm
Tags: correlation, cross, signals, sound
sampathkumarm
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#1
Jan2-13, 01:04 AM
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Hello!
We are trying to verify if an acoustic standing wave has been established in a cavity. In order to do so, we are giving a constant frequency signal to a speaker. We are picking up the signal at two locations, one very close to the speaker(reference signal) and at a particular location(captured signal). We are cross correlating them. Ideally, we are supposed to get a zero phase difference between the two signals for the frequency sent in, proving that the reference and captured signals are varying simultaneously in time. However, we are getting a jump from -pi to pi at that frequency ?(here,its 520Hz). Could anyone explain what is happening? Thank you for taking your time for this!
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berkeman
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Jan3-13, 06:45 PM
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Quote Quote by sampathkumarm View Post
Hello!
We are trying to verify if an acoustic standing wave has been established in a cavity. In order to do so, we are giving a constant frequency signal to a speaker. We are picking up the signal at two locations, one very close to the speaker(reference signal) and at a particular location(captured signal). We are cross correlating them. Ideally, we are supposed to get a zero phase difference between the two signals for the frequency sent in, proving that the reference and captured signals are varying simultaneously in time. However, we are getting a jump from -pi to pi at that frequency ?(here,its 520Hz). Could anyone explain what is happening? Thank you for taking your time for this!
Welcome to the PF.

Could you also post a diagram of your cavity, showing the speaker location and the locations of the microphones?
AlephZero
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Jan3-13, 09:16 PM
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Quote Quote by sampathkumarm View Post
Ideally, we are supposed to get a zero phase difference between the two signals for the frequency sent in, proving that the reference and captured signals are varying simultaneously in time.
Why do you think that should happen? And why do you think it should happen only at a resonance?

Also, what are you measuring (or calculating) on the plot that looks like an amplitude?

The sudden change in phase suggests the system has a mode (or resonance) at that frequency, but without a drawing of the complete setup it's hard to guess what is happening.


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