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I have a noisy audio file, available here (It is safe to download if you wish to) https://ufile.io/pstrt

Now, I inspect it in matlab: enter image description here

And then i plot it on normalised frequency: enter image description here

Now I need to filter this signal to remove the noise. However, I have no idea what is causing the noise in the first place. Perhaps it is obvious even from the two figures I have shown but unfortunately not for me. I could play a guessing game and apply different configurations of lowpass, highpass and bandpass filters, but I have quite a few of such audio files to analyse. Thank you for any help.

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  • $\begingroup$ Ideally you would know something about the original signal, and/or about the noise. What if it's a non-noisy recording of noise, and there's nothing to remove? $\endgroup$ – MBaz Dec 17 '18 at 17:38
  • $\begingroup$ It is given as homework/coursework and when playing it you can hear a "proper" sound and some bass over it (which i presume is noise).So there is definitely something to remove, I just don't know what. $\endgroup$ – Scavenger23 Dec 17 '18 at 17:40
  • $\begingroup$ Is there a reason you can't ask this question to your TA/professor? They're in the best position to help you. $\endgroup$ – MBaz Dec 17 '18 at 19:34
  • $\begingroup$ Your link to the audio file didn't work for me. Does that website require membership to work? $\endgroup$ – johnnyvsx May 16 at 19:35
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Since it's home work, I can't give the full solution.

  1. The noise seem to have been artificially added. This type of noise doesn't happen normally
  2. The noise is basically two sine waves that really don't belong there
  3. The best filter type to eliminate these are notch filters.
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  • $\begingroup$ Thank you for the answer but it doesn't help. In order to apply the notch filter I need to know where to apply it. Can you at least partially explain how did you come up to your conclusion about the two sine waves? Thank you. $\endgroup$ – Scavenger23 Dec 17 '18 at 18:03
  • $\begingroup$ a) Listen to it. There is an obnoxious tone in the signal. b) Look at the peaks in your spectrum $\endgroup$ – Hilmar Dec 17 '18 at 20:41
  • $\begingroup$ Thanks, i still don't know at what frequencies the said sine waves are. Perhaps I will ask my professor. $\endgroup$ – Scavenger23 Dec 17 '18 at 21:35
  • $\begingroup$ peaks means strong up shoot in amplitude of the signal you have one that has amplitude of 13000. $\endgroup$ – Ch.Siva Ram Kishore Dec 30 '18 at 4:13

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