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I'm trying to reconstruct an audio signal, and below is what i got after rescaling.

enter image description here

How can i obtain centered audio signal such as below?

enter image description here

SOLVED:

ruoho ruotsi's answer addresses my problem :)

i found someone asked the similar question before

How to remove or filter the drift problem in measured Strain signal?

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  • $\begingroup$ Welcome to SE.DSP. You are reconstructing and rescaling a signal using unmentioned processing. They could influence the trend, background or baseline you are observing. Could you please be more specific about your reconstruction? $\endgroup$
    – Laurent Duval
    Dec 30, 2015 at 18:01
  • $\begingroup$ I was about to say... ;-( $\endgroup$
    – Peter K. ♦
    Dec 31, 2015 at 0:56

3 Answers 3

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"Center" isn't the word that I'd use to describe what you want to do. Your signal does not have a zero-mean, so like @Dole suggested you should use a DC-Blocker (DC-Offset removing) filter to get the job done:

Here are your references:

https://ccrma.stanford.edu/~jos/filters/DC_Blocker.html https://ccrma.stanford.edu/~jos/filters/DC_Blocker_Frequency_Response.html https://ccrma.stanford.edu/~jos/filters/DC_Blocker_Software_Implementations.html

the code (from the above links) can be as simple as this, where x is the current sample and y is the filtered sample, while xm1 and ym1 are the x,y from the previous step (i.e. x[i-1], y[i-1]):

  y = x - xm1 + 0.995 * ym1;
  xm1 = x;
  ym1 = y;
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    $\begingroup$ this is what i was looking for, thank you so much! :) $\endgroup$
    – anony
    Dec 31, 2015 at 0:42
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Use small High Pass filter. Usually it is suggested to remove the frequencies in the range of 0-200 Hz for speech signals.

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Remove DC offset. Either convert to frequency domain and remove bin 0 or just use a very low frequency high pass filter.

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