# sound processing, fft

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PRIYANK SHAH on 24 Jan 2012
My project is related to sound processing. I am taking sound signal into matlab simulink using audio input block,
In my project, the basic idea is to transform the time domain signal into the frequency domain, then amplify the frequency bands of interest and then transform the signal back to the time domain.
how can i do this?
please guide me or give me some reference or any idea. i don't know signal processing operation very well.
thank you...
[Merged information from comment]
Aim: filtering of the input sound signal and amplify according to the given gain plot.
(note: here sound signal is general talk of two three persons with environmental noise.)
( here input sound signal is not any pure tone.it is a mixer of different frequencies.)
Gain plot:
Amplication gain at different frequencies:
(Graph: Amplify the signal at 250 to 500 freq 8 to 15 db linearly.,…,4k to 8k 22db .)
Problem:
1. Give me some direction. Windowing? What is windowing? And how to apply?
2. I am right now working on Matlab. Taking the signal through audio input block in simulink. Then filter the signal with 5 band pass filters(250-500, 500-1000, 1k-2k, 2k-4k, 4k-8k band pass filters) and amplify them directly by gain block.
But my main problem is that it amplifies equally with all frequencies. I have to amplify them such that it should be amplify at 250 frequency with 20 db, at 300 freq with 25 db, at 350 freq with 30 db… , at 500 freq with 40 db so on. and we can’t make filters for all frequencies. So is it possible to make equation such that signal is amplified with given frequency. or any fft operation is possible?   Main program:
main problem:
In my project, the basic idea is to transform the time domain signal into the frequency domain, then amplify the frequency bands of interest and then transform the signal back to the time domain. how can i do this?

Wayne King on 24 Jan 2012
Hi Priyank, I gave you advice in your other identical thread.
Please give specifics, sampling frequency, frequency band of interest.
Also do you have the DSP System Toolbox?
Walter Roberson on 4 Feb 2012
I moved your long description in to your Question.

Walter Roberson on 4 Feb 2012
On Windowing: Please have a look at http://signal.ece.utexas.edu/~arslan/courses/dsp/lecture17.ppt . I glanced at it, and it appears to cover useful ground.