Digital signal Processing Filtering noise,convert to chipmunk sound

How to filter noise from an audio. When I built in matlab simulink, the noise can be filtered but the sound becomes lower. I am using FIR Equirriple low pass filter. Everyone know？？？ have any idea about it? Then, how can I change to chimpmunk sound and darth vader sound.... Thanks

Answer 1

[Walter Roberson]

When you use a low-pass filter, then by definition only the frequencies lower than the cutoff are passed through (beyond a threshold amount.) This will lower the frequency distribution relative to the original sound, so what you are observing is expected for the filter you have implemented.

This should suggest to you that you are not using the correct filter technology for what you want to do. I am not sure it can be done with FIR or IIR, but I do not know much about either. See http://en.wikipedia.org/wiki/Frequency_multiplier

We seem to have some confusion over what the Vader family of sounds consists of; see http://www.mathworks.co.uk/matlabcentral/answers/43003-dark-vader-effect-help