filtering a wav file

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foxbrain

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hi
do u know how can i filter this wav file from the noise sound? i prefer using the wavelet theory
thanks
 

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Hi foxbrain
hi
do u know how can i filter this wav file from the noise sound? i prefer using the wavelet theory
thanks
Click to expand...
Where this sound is coming from ? from an amplifier ? where is the input signal ? from a CD player ? or MP3 player ? more information is required .
Best Wishes
Goldsmith
 

i don't know ....
my professor gave this file to filter it as a project using matlab
 

i don't know ....
my professor gave this file to filter it as a project using matlab
Click to expand...
Ok , you need to analyze spectrum of this music and then understand what is frequency or BW of those noises . and then design a filter function for that BW . and then you'll get success ! that's all .
Good Luck
Goldsmith
 

i know that but how?
Click to expand...

If it was related to a circuit and if you wanted to remove those noises directly i would suggest to use a high order notch filter ( active filter of course ) . and it was easy . but sorry i'm not using matlab . so i can not guide you with matlab . but if you wanted a circuit for that i could guide .

Good Luck
 

1.first read the file from wavread.
2. see the spectrum by fft or sp tool in matlab.
3. realize what frequency of signal u dont want. if white noise is there use Gaussian window or averaging to reduce it.
4. check fdaTool to design the filter in matlab.

i didnt check ur file but it is general steps u can follow.
 

here the fft function to the signal.... how can i know where i should delete and how?
 

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1. u should know which type of noise it is.
2. for a wave file dont take fft to whole wave signal. you should divide the wave in small (22 ms) windows(frames) and see the fft of frame that will be better to understand.
 

download AudaCity - A Free Digital Audio Editor:
http://audacity.sourceforge.net/
you can hear and see all signal and analyze all or part of it!
You have 15s of music (sampled at 22050Hz) with 5000Hz noise on some parts......
 

Hi foxbrain

im not saying wavelet (you can also use the wavelet for analysis or compression)

take 22 ms or 15 ms of small audio frame analyze (do fft or whatever signal processing you want in a frame) the signal than only u can implement filters or bank of filters.
 

js:
thanks you for your program but i want to do it with matlab
lordy:
you can also use the wavelet
Click to expand...
do u know how can i do it?
take 22 ms or 15 ms of small audio frame analyze
Click to expand...
what is the instruction for this?and how can i know the noise from it?
 

[y, Fs] = wavread(filename);

suppose u have 10 sec wav file u stored it in variable y and ur sampling frequency is 20000(usually for audio it is 44.1kHz).

so for one second you will get 20000/10 = 2000 sample that is one second window and 1 ms 20 sample.

in 22.5 ms u will get 20*22.5 = 450 samples(thats is ur frame size).

that mean u r having around 44 frames( that is rectangular window people generally use hamming window).

x = y(450:900); will give u the second frame.

for wavelet put command

wavemenu in matlab( i hope this help).

moreover to remove noise from audio or speech is not the easy task 8-O
 
Last edited:

the file is : 352kbps and 14 seconds
anyway i read the file and i detected the noise signal at : x3 = y(17500:22500);
and i plotted it and it's fft as in the image attached.
what should i do next?
 

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1. what is ur signal sampling frequency ?
2. in x3 whether it is total noise or noise with audio ? u can check by wavplay.
3. in ur hole wave file x3 is the only noise patch ?
4 use command fft in command window and take the abs() and plot

like
x4 = abs(fft(x3));

plot(x4,fs);
 

There are much of term to study such as Supersampling, Supersymmetry, UP-Downsampling, ... etc.
You should build noise rating table.
 

I agree with phongphanp.

I listen your wave file today. noise is looks independent of audio you can try independent component analysis to separate out noise and audio but that will be little complex
so try out some filtering methods first that will be easy. If not succeeded than go for ICA.
 

what is ur signal sampling frequency ?
Click to expand...
352kbps
in x3 whether it is total noise or noise with audio ? u can check by wavplay.
Click to expand...
noise with audio
in ur hole wave file x3 is the only noise patch ?
Click to expand...
yes
use command fft in command window and take the abs() and plot
Click to expand...
here is the picture attached
.............
i tried many filter like min-max-mean-gaussian-laplacian ..... i didn't get any result.
 

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