[sdiy] Phase shifts and instantaneous frequency

[harrybissell at wowway.com]

Remember that Ian has assumed SINE waves of 100Hz and 201Hz.
they will NOT beat, because there are no harmonics at all
(so nothing to beat).

You need a non-linear mixer, which the ear provides.

There may be something of the 'missing fundamental' detection
that human beings have.  The 100Hz and (presumed) ~almost~ second
harmonic might give some perceptual effect.

I'm just trying to set this straight before Ian comes back and
spanks you. You know that Ian was born before Physics books existed...
at least those printed with movable type...  :^P

H^) harry



On Tue, 15 Jul 2008 15:00:54 +0100, cheater cheater wrote
> No, the beats are a normal physical phenomenon. Back to physics 
> books, Ian ;)
> 
> The original thread's question was about a constant phase 
> relationship - not a variable one. Of course you can hear a variable 
> phase relationship, which is called pitch bending. :P
> 
> Cheers
> D.
> 
> On 7/15/08, Ian Fritz <ijfritz at comcast.net> wrote:
> > You can *easily* demonstrate to yourself that differences in phase are, in
> > fact, audible.  To do this, make a signal with two sine waves at 100 and 201
> > Hz.  This is a signal with a slowly varying phase difference between the two
> > components.  If the phase differences don't matter, then you will hear a
> > steady tone.  If they do matter, then you will hear beats.  In fact, you
> > *do* hear beats.  Yes, you can easily detect phase differences between two
> > tones.  (I learned about this from one of the websites I ran across during
> > our previous discussion of this topic.)
> >
> >  What's going on?  The beats are a result of nonlinear mixing in the ear!
> > They do not occur at low volume levels, or if the signals are presented
> > separately to each ear.  You can easily demonstrate this to yourself, also.
> > The nonlinear mixing produces a difference tone at 101 Hz, which beats
> > against the 100 Hz signal.
> >
> >  Try it!
> >
> >   Ian
> >
> >
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Harry Bissell & Nora Abdullah 4eva