Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hplabs!hpl-opus!hpnmdla!hpsad!toma
From: toma@hpsad.HP.COM (Tom Anderson)
Newsgroups: comp.dsp
Subject: Re: Re: Pitch shift / offset and FFT
Message-ID: <9520003@hpsad.HP.COM>
Date: 28 Sep 89 19:12:58 GMT
References: <4384@internal.Apple.COM>
Organization: HP Signal Analysis Division - Rohnert Park, CA
Lines: 16

> Taking the real part of both sides:

I don't know much about ears, but I believe that they hear:

sqrt(Real_part^2+Imaginary_part^2) 

and so it is incorrect to just look at the real part.

Also, if you look at two tones on a spectrum analyzer, you just see two
tones and no beat notes in a linear system.  (I just tried this to make
sure :-)).  It takes a nonlinearity to generate the "mixing products" in
the frequency domain.

Tom Anderson       "It's only hardware"
Hewlett-Packard    Signal Analysis Division
Opinions expressed are my own and not HP's.