waveforms

Dana Nibby D_NIBBY at UNHH.UNH.EDU
Thu Feb 27 13:04:30 EST 1992


The following is a recent discussion from list MIND-L.
Would anyone here please comment on what's being said about
waveforms/entrainment?

   Thankyou

26-Feb-92 14:41:01-EST,1319;000000000001
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Date:    Wed, 26 Feb 1992 11:52:51 -0600 (CST)
From: "FNAL01::RAPH"@FNAL.FNAL.GOV (Jim Hawtree, MP9 Building Manager)
Message-Id: <920226115251.22e64013 at FNAL.FNAL.GOV>
Subject: RE:Hemisync waveform (Dana)
To: mind-l at asylum.sf.ca.us
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<Does anyone know which waveform is used in hemi-sync? Is it square?
<Sinusoidal? Etc.?
<
<   Which waveform is best, and which ones are commonly used?
<
<       Dana

IMHO it doesn't really matter.  Teh primary, fundamental frequency in
ALL of them is a sine wave.  Square and triangualar waveforms are actually
a series of sinusoidal waves, plus harmonics.  (A harmonic is an integral
multiple of the fundamental frequency - That is why different musical
instrumnts playing the same note sound different.  Their fundamental is the
same, but the harmonics and other higher frequencies are different.)

It is most probable that what the brain is responding to anyway is the leading
edge of the pulse, and not how it is shaped.

					Regards, Jim
26-Feb-92 15:55:21-EST,2853;000000000001
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To: mind-l at asylum.sf.ca.us
Cc: "Jim Hawtree, MP9 Building Manager" <"FNAL01::RAPH"@FNAL.FNAL.GOV>
Subject: Re: Hemisync waveform (Dana)
In-Reply-To: Your message of Wed, 26 Feb 92 11:52:51 -0600.
             <920226115251.22e64013 at FNAL.FNAL.GOV>
Date: Wed, 26 Feb 92 14:29:08 EST
From: "B.W. Dodson" <bdodson at NSF.GOV>
Message-Id:  <9202261429.aa29390 at Note.nsf.gov>


> <Does anyone know which waveform is used in hemi-sync? Is it square?
> <Sinusoidal? Etc.?
> <
> <   Which waveform is best, and which ones are commonly used?
> <
> <       Dana

> IMHO it doesn't really matter.  Teh primary, fundamental frequency in
> ALL of them is a sine wave.  Square and triangualar waveforms are actually
> a series of sinusoidal waves, plus harmonics.  (A harmonic is an integral
> multiple of the fundamental frequency - That is why different musical
> instrumnts playing the same note sound different.  Their fundamental is the
> same, but the harmonics and other higher frequencies are different.)
>
> It is most probable that what the brain is responding to anyway is the leadin
g
> edge of the pulse, and not how it is shaped.

> 					Regards, Jim

IMHO, this cannot be right.  Periodic non-sinusoidal waveforms
can be described as a Fourier series of sinusoidal waves having
integral multiples of the fundamental frequency.  As a result,
a 100 Hz square wave has a sine wave component at 100 Hz, 300
Hz, 500 Hz, etc.  Now, the idea in Hemi-Sync is to produce
effects within the brain at inaudibly low frequencies (e.g., 6
Hz) by putting 100 Hz into one ear, 106 Hz into the other, and
letting the hemispheric cross-talk within the brain produce the
6 Hz beat frequency.  (These numbers have no particular
significance.)  If this is done with a square wave, not
only does the 6 Hz beat appear between the 100 and 106 Hz
sinusoidal components, but also an 18 Hz beat from the 300 and
318 Hz components, 30 Hz from the 500 and 530 Hz components,
etc.  If the basic idea behind Hemi-Sync is close to correct,
this cannot be a good thing!  If some other waveform is chosen,
it will likely have 2nd harmonic content, which will make
things even worse with a 12 Hz beat.  I believe that a pure
sine wave is probably best for the Hemi-Sync effect.  This does
not say that other choices might not be more interesting from
an esthetic point of view, or easier to procude from hardware,
but Hemi-Sync should use sine waves.  (Another factor is that
square waves at slightly different frequencies probably sound
like a barrel of cats fighting! (:-))

Brian
26-Feb-92 16:34:00-EST,1936;000000000001
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From: mike at INTI.LBL.GOV (Michael Helm)
Date: Wed, 26 Feb 1992 12:28:26 PST
In-Reply-To: Dan Drumm <DRUMM at CNSVAX.UWEC.EDU>
       "RE:Hemisync waveform (Dana)" (Feb 26,  1:35pm)
Reply-To: mike at INTI.LBL.GOV
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To: mind-l at asylum.sf.ca.us
Subject: RE:Hemisync waveform (Dana)
Cc: Dan Drumm <DRUMM at CNSVAX.UWEC.EDU>

On Feb 26,  1:35pm, Dan Drumm wrote:
> It's getting a little thick again.
Oh, please.

> >Square and triangualar waveforms are actually
> >a series of sinusoidal waves, plus harmonics.
>
> Huh, where do you get this stuff?  A square wave is a square wave.
> I would like to see a function of sin waves that returns square or
> triangualar waveforms.

I recommend "Mathematical Methods For Physicists" 2nd Ed, George Arfken,
Academic Press (my copy is pre-ISBN but has LC# 73-119611).
Ch 14, "Fourier Series" p 643, & section 14.3 p 650 has all the info you
require.

> BTW: The harmonics can not be different.  Some harmonics can be more
 prevelent,
> or absent, but their frequency is always the same.

Only for idealized musical instruments -- or all violins would sound
the same, all the time.

Here's an experiment for you.  Sound a note on a stringed instrument,
say a guitar, on one of the top strings.  Then tape or remove all
the lower strings & sound the same note.  If it sounds different,
why?  If it doesn't sound different, you probably shouldn't be talking
about musical instruments anyway (your hearing isn't an adequate
test instrument).
26-Feb-92 17:05:19-EST,2327;000000000001
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From: David O. Dodge <dododge at WAM.UMD.EDU>
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To: mind-l at asylum.sf.ca.us
Subject: Re: waves and harmonics

<DRUMM at CNSVAX.UWEC.EDU> writes...
>>Square and triangualar waveforms are actually
>>a series of sinusoidal waves, plus harmonics.
>
>Huh, where do you get this stuff?  A square wave is a square wave.
>I would like to see a function of sin waves that returns square or
>triangualar waveforms.

Sorry if I'm missing your point, but I can assure you that square waves and
triangle waves ARE composed of sine waves. A pure square wave or triangle
wave will be made up of an infinite number of sine wave harmonics. I think
one of them is composed of all the odd harmonics. Any sound (even white noise)
can be specified as a bunch of sine waves added together.

>>(A harmonic is an integral
>>multiple of the fundamental frequency - That is why different musical
>>instrumnts playing the same note sound different.  Their fundamental is the
>>same, but the harmonics and other higher frequencies are different.)

Right. A sound is defined by it's harmonic makeup. There are mucho-expensive
additive synthesizers that produce very realistic sounds based solely on
specifying the amplitude envelopes for the harmonics. The principal behind
the more common subtractive synthesizers is that you pump out
waves like sawtooth, square, and triangle that have LOTS of harmonics and
then use filters to selectively remove them.

>BTW: The harmonics can not be different.  Some harmonics can be more
>prevelent, or absent, but their frequency is always the same.

Not sure what you mean here. Harmonics are sine waves relative to the base
pitch for a given sound.
                                       -Dave Dodge/dododge at wam.umd.edu
26-Feb-92 17:28:13-EST,1238;000000000011
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From: romkey at asylum.sf.ca.us (John Romkey)
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To: D_NIBBY at UNHH.UNH.EDU
In-Reply-To: Dana   Nibby's message of Wed, 26 Feb 1992 17:02:41 -0500 (EST)
 <699141761.840000.D_NIBBY at UNHH.UNH.EDU>
Subject: [Dan Drumm <DRUMM at CNSVAX.UWEC.EDU>: RE:Hemisync waveform (Dana)]
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