To Maverick:

I remember having read in one of your last threads, that to modulate male voice into female you have to use frequency-scaling instead of shifting, because the latter is inharmonic.
But couldn?t it be just done by getting rid of the fundamental, and leaving the harmonics. Then you would have a higher (female-like) pitch and it wouldn?t sound artificial (I think).

If there?s no response I?ll figure that this has been answered somewhere.
Posted on 2002-06-04 11:50:37 by slop
Hi Franz,

Sorry, it will not work.

Worst case: you shift the frequencies of an amount which is not a multiple or submultiple of the (now absent) fundamental: the sound will become totally inharmonic, because all the overtones will not be multiple of anything common anymore.

Best case: you carefully choose the amount of frequency to shift, and filter out the fundamental. It still won't work though, because the overtones are still spaced of an amount of Hz equal to the fundamental, and the brain *will* recreate the sensation that the fundamental is present (read a good book in psychoacoustics if you wish to go into depth, the acoustic brain is a wonderful machine).

The next possible technique to experiment with, e.g. to double the pitch, would be to filter the fundamental and all odd order overtones. That would leave only even overtones, effectively doubling the pitch.. but you can't do that for unvoiced (noisy) sounds like most consonants, etc.. You may also try a full wave rectifier to kill the odd overtones.. but it will sound distorted and crap.

Really, no use for frequency shifting for high quality voice pitch transformations, no use for distortion, you either do pitch shifting (i.e. frequency scaling), or some AI driven dynamic filtering, or even better advanced automatic analysis and resynthesis.
Posted on 2002-06-04 16:31:39 by Maverick
Then that?s really difficult.
I had never thought about psychoacoustics, but it really sounds like something important.
I was thinking about my experience with a violin: when I need an harmonic I just press the string softly, so that long = long/2, or l=3/4 l ...and it works. So I thought that it would probably be the same when trying to compute it.
But I didn?t take into consideration all the stuff going on, that the violin itself takes care of.

It?s very interesting.
Thanks a lot!
Posted on 2002-06-10 11:41:59 by slop