Correct Plot of FFT Phase for Audio File Analysis?

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Discussion Overview

The discussion revolves around the analysis of the phase plot obtained from the FFT computation of an audio file. Participants are examining whether the observed phase behavior is expected and discussing the implications of phase relative to amplitude.

Discussion Character

  • Homework-related
  • Debate/contested

Main Points Raised

  • One participant questions whether the phase plot should show a decrease as frequency increases.
  • Another participant asks for clarification on what the phase is relative to and expresses confusion about the phase range observed, which is from -2500 to +8500 radians instead of the expected -π to π.
  • A participant explains that the phase is relative to the amplitude at specified frequencies and mentions issues with the unwrap() function in MATLAB, which they believe is causing the unexpected phase range.
  • There is a discussion about the significance of phase, with some participants expressing uncertainty about its relevance and questioning why it is a focus of the analysis.
  • One participant notes that they submitted only the amplitude component of the analysis, indicating that the phase plot was not included due to the range issue.

Areas of Agreement / Disagreement

Participants express differing views on the relevance and expected behavior of the phase plot, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

There are unresolved questions regarding the expected behavior of phase in relation to frequency and the implications of the phase range observed. The discussion highlights potential limitations in the use of MATLAB for phase analysis.

JJ91
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Homework Statement



I would like get an advice whatever the plot of phase (in radians) of the FFT computation of audio file is correct.

Is it not supposed to show a decrease as the frequency increases ?

Homework Equations



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Phase relative to what? And why does it go from -2500 to +8500 and not from -pi to pi?
Where does the signal come from, why do you expect some specific phase?
 
Phase relative to what?
Relative to amplitude at specified frequencies

And why does it go from -2500 to +8500 and not from -pi to pi?
The command used unwrap() was supposed to make a range of -pi to +pi, however in MatLab it just doesn't work thus I assume it means -2500 rad to +8500 rad.

Where does the signal come from, why do you expect some specific phase?
The signal comes from the FFT of file audio.wav, I had no idea what I was expecting for "phase" the amplitude however makes clear sense.
 
Relative to amplitude at specified frequencies
I don't think this makes sense.

however in MatLab it just doesn't work thus I assume it means -2500 rad to +8500 rad.
Well, where is the difference between a phase of x and x+2n*pi?

I had no idea what I was expecting for "phase"
Me neither, so why do you care about the phase?
 
It was part of the question for analysis of an audio file. I end up submitting only amplitude component, the graph waveform however was correct, the range wasn't.
 

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