How do I modify this code so that it can remove background noise from the 'drop 3.WMA' file?

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David Mabwa
David Mabwa 2017-1-10
评论： Michael Abboud 2017-1-13
How would I modify the following code so that it would delete background noise from the drop 3 file?
The image is the plotted audio data. The code is:
a=audioread('drop 3.WMA'); l=size(a); l=l(1); sound(a,44000) b=a(1:l); x=linspace(0,1,l); plot(x,b);

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回答（1 个）

Michael Abboud
Michael Abboud 2017-1-13
To remove background noise from a signal, you will most likely need to know more about either the signal, or the noise. In particular, it can be helpful to know more about the frequencies of your signal or noise, as most filtering operations separate signals by frequency range. It can often be helpful to perform a Fourier Transform
For example, if the background noise is a low hum of a car or airplane, then you may want to use a highpass filter to reduce these low frequencies. If the background noise is a specific interference at 60 Hz, you can use a notch filter to attenuate a small range around 60 Hz. However, just by looking at your image there is no way to tell what is the signal and what is the noise.
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For more information and some great examples on filtering noise from signals, I would suggest you refer to the following documentation page:
Removing Unwanted Spectral Content from a Signal
  2 个评论
David Mabwa
David Mabwa 2017-1-13
Oh my mistake. The sound is that of a bouncing golf ball on concrete. I would like to keep the sound of the bouncing ball only. It is intended to be a plot of amplitude against time.
Michael Abboud
Michael Abboud 2017-1-13
In this case, I would guess that the 'signal' is likely at a higher frequency than any background noise. I would suggest that you try performing a Fourier Transform on the signal to try and determine what frequencies are present. eg: Audio Signal Frequency Analysis
Then you can proceed to design a filter as demonstrated in the first link (perhaps a highpass filter) to attenuate the appropriate frequencies. Good luck! :)

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