Reverse the effects of a Chebyshev type 2 filter on a 1-d sound file.

Hi fellow Matlab users,

Currently I am using a Chebyshev type 2 filter to high-pass filter a sound file sampled at 44.1 kHz. I obtain the filter coefficients using [b,a] = "cheby2(n,Rs,Ws)", with n=1, Rs=3 and Ws = 2*fc/fs. Cut-off frequency fc is 4 kHz in this case. After this I apply the coefficients using the filter function.

After this I want to do some manipulations to the signal, and then undo the effects of the high-pass filter. So I want to amplify each frequency by the same amount it has been attenuated by the Chebyshev filter. Any ideas on how to do this? Using a Chebyshev low-pass filter didn't yield me any results. Deconv won't work because Chebyshev filters don't use convolution.

Thanks in advance,

Lucas

Answer 1

[Abhiram Bhanuprakash]

Hi Lucas,

Since you obtain the numerator and denominator coefficients using 'cheby2', I think you can reverse this effect by passing the manipulated signal through the "inverse filter", that is, through the filter which has the numerator and denominator coefficents interchanged.

To do this, you can use the 'filter' function. Doc here

Hope this helps,

Cheers!

Abhiram

[Lucas]

Hi Abhiram, Works very well. Thanks for the input! Lucas