# Homework Help: Analysis or results of FFT

1. Nov 21, 2012

### JJ91

1. The problem statement, all variables and given/known data

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 ?

2. Relevant equations

2. Nov 21, 2012

### Staff: Mentor

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?

3. Nov 22, 2012

### JJ91

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.

4. Nov 22, 2012

### Staff: Mentor

I don't think this makes sense.

Well, where is the difference between a phase of x and x+2n*pi?

Me neither, so why do you care about the phase?

5. Nov 22, 2012

### JJ91

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.