[sdiy] Phase shifts and instantaneous frequency

[harrybissell at wowway.com]

I'm still not getting it...

cancellation would mean that for a period of one cycle
there is zero output signal (voltage, sound pressure, whatever).

I don't see from Tom's example that this ever goes to zero.

Of course it will cross zero but even a single sine wave
will do that periodically... I'm sure that isn't what you mean.

H^) harry



On Wed, 16 Jul 2008 15:14:50 +0100, cheater cheater wrote
> They will cancel after LCM(1/200, 1/201) seconds.
> 
> Ian:
> 
> Scientific qualifications: have started studying maths in the
> maths-phys department at 17 years old and studied since.
> 
> Why am I questioned about this?
> 
> If there's something you don't understand, ask, but please don't make
> it sound like I'm making stuff up?
> 
> ...
> 
> On 7/16/08, harrybissell at wowway.com <harrybissell at wowway.com> wrote:
> > You said "cancellation is incomplete" ???
> >
> >  That implies that there is some point at which the
> >  cancellation is complete. They will never cancel.
> >
> >  (I have not seen Tom's picture yet, so maybe I'm still
> >  not understanding what you mean by cancel...)
> >
> >  H^) harry
> >
> >
> >
> >
> >  On Tue, 15 Jul 2008 22:07:46 +0100, cheater cheater wrote
> >
> > > Harry,
> >  > wrong,
> >  > the 201 Hz partial and the 100 Hz partial start out at phase 0, but
> >  > after some time they'll be exactly out of phase, at which point they
> >  > cancel.
> >  > Until that happens, the cancelation is incomplete and goes from
> >  > minimum to maximum.
> >  >
> >  > The beating is 0.5 Hz because the lenght of a 200Hz wave is half of a
> >  > 100 hz wave's lenght. Or, the other way around, two lenghts of the
> >  > 201Hz wave are the lenght of a single 100.5 Hz wave. You should
> >  > experience beating at 0.5 Hz, so of a lenght of 2 seconds, which you
> >  > can clearly see on Tom's picture.
> >  >
> >  > What you don't experience is the fact that you should be hearing a
> >  > 0.5Hz fundamental instead of 0.5Hz beat *if your ears were perfect*.
> >  >
> >  > Whether or not laws of physics were written down already when you
> >  > were born, doesn't say that they did not exist. :P
> >  >
> >  > Cheers
> >  > D.
> >  >
> >  > On 7/15/08, harrybissell at wowway.com <harrybissell at wowway.com> wrote:
> >  > > 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
> >  > >
> >  > >
> >
> >
> >  Harry Bissell & Nora Abdullah 4eva
> >
> >
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Harry Bissell & Nora Abdullah 4eva