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Topic:
FFT function isn't working on signals greater than a second
Replies:
2
Last Post:
Mar 23, 2013 5:32 AM




Re: FFT function isn't working on signals greater than a second
Posted:
Mar 23, 2013 3:32 AM


On 3/22/2013 11:58 PM, sal22 wrote: > Greetings All > > I have an fft function in matlab/octave that works great on an imported mono > wav/audio signal that is 1 second long, but when the signal imported is more than 1 >second the frequency values become incorrect.
May be someone will read all this code below and better help you.
But I just wanted to say, that fft does not know any thing about seconds, frequency, hz, time, units, clock or any of this.
All what fft does is take a sequence of numbers, and returns back a sequence of numbers. that is all. It is a very dumb back box function (but very fast). Notice the input to fft?
Y = fft(x)
So when you say fft does not work when 'signal is more than 1 second' then this makes no sense. It must be a user error on how you are preparing the data to feed to fft or how you are using the result of fft.
If the signal is longer, this just means the sequence of numbers wil be longer. that is all. (assuming you sample at same rate).
>>Can anyone help me get this function to work with signals greater than just 1 second
fft does not care how long the sequence of numbers are.
Nasser



