The Math Forum

Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Math Forum » Discussions » Software » comp.soft-sys.matlab

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

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

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
Nasser Abbasi

Posts: 6,677
Registered: 2/7/05
Re: FFT function isn't working on signals greater than a second
Posted: Mar 23, 2013 3:32 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

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.


Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© The Math Forum at NCTM 1994-2018. All Rights Reserved.