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'Headphones changing pitch automagically [OT]'
2000\04\07@104408 by M. Adam Davis

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face
Well, the act of moving the headphones away from you would cause a drop in
pitch, but it would normallize once the headphones stopped moving away from
you.  The pitch would rise while you bring the headphones towards you, but again
the pitch would normalize when they stopped moving (relative to your head).
The faster you move them, the higher (or lower) the pitch goes.

If the change does not follow this description, then you might be looking at the
inability for the headphones to send higher pitched notes very far, so they
become less-audible the further the headphones are away from you.  This would
make the spectrum of the music sound lower, and you might percieve that the
pitches shifted instead of the top ones disappearing.

Or your psycho.  Perhaps to gov't is beaming info into your head to make you
crazy.  You should try wearing an aluminum helmet (except in thunderstorms!).

-Adam

I respect faith, but doubt is what gives you an education. -- Wilson Mizner

Rich Leggitt wrote:
{Quote hidden}

2000\04\07@153412 by David E Arnold

picon face
This is known as the "Doppler Effect" or "Doppler Shift".  Look it up in the
encyclopedia or
a fundamental of physics textbook.

Think of when a fire engine drives by, recall how it seems to have a higher
pitch when approaching then a lower pitch after it passes and is going away.

-Dave





"M. Adam Davis" <spam_OUTadavisTakeThisOuTspamUBASICS.COM> on 04/07/2000 07:43:06 AM

Please respond to pic microcontroller discussion list <.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU>

To:   PICLISTspamKILLspamMITVMA.MIT.EDU
cc:    (bcc: David E Arnold/SYBASE)
Subject:  Re: Headphones changing pitch automagically [OT]




Well, the act of moving the headphones away from you would cause a drop in
pitch, but it would normallize once the headphones stopped moving away from
you.  The pitch would rise while you bring the headphones towards you, but again
the pitch would normalize when they stopped moving (relative to your head).
The faster you move them, the higher (or lower) the pitch goes.

If the change does not follow this description, then you might be looking at the
inability for the headphones to send higher pitched notes very far, so they
become less-audible the further the headphones are away from you.  This would
make the spectrum of the music sound lower, and you might percieve that the
pitches shifted instead of the top ones disappearing.

Or your psycho.  Perhaps to gov't is beaming info into your head to make you
crazy.  You should try wearing an aluminum helmet (except in thunderstorms!).

-Adam

I respect faith, but doubt is what gives you an education. -- Wilson Mizner

Rich Leggitt wrote:
{Quote hidden}

2000\04\07@205410 by Wagner Lipnharski

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The original post says clearly:
"...Then I take the headphones off and hold them away...", it means to
me he is NOT moving the phones, just holding them away, so, it is
impossible for doppler effect if the distance is fixed along the time.
Why the thread divert so much? probably in few days we will be talking
about the chicken counter in Australia is generating the pitch change at
his hearphones... :)
Wagner.

David E Arnold wrote:
{Quote hidden}

2000\04\07@221200 by Rob Brzykcy

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I *personally* think it has something to do with the total RMS power able to reach the ears
and the fact that the headphones may be tuned to compensate for the frequency response of
being used directly over the ear.. It seems like it would be something like listening to a
speaker in an enclosure, then removing it from the enclosure and letting it play in the open air.
There is a definite change in the sound without the enclosure. I believe the audio guys over
here agree that the ear canal resonates at 2-5Khz, depending on the individual, so that would
probably be enough to change the percieved pitch and make it seem higher when you put the
phones on.

Then theres always the phase cancellation of the two speakers facing each other.

Rob


{Quote hidden}

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{Quote hidden}

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2000\04\08@092133 by David Thompson

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Hi Richard,

I have noticed this affect also. Being a curious sort, I often wondered why
this could be. Rest assured, you are not psycho. The only thing that I can
add that it seems more obvious with higher volumes, and seems independant on
speed (i.e taking them off quicker or slower). Hmmm, I have just realised
that I've only noticed it with my full-size headphones, not the tiny in-ear
ones... whatever...

I will be interested in any theories that people might have.

Dave

{Original Message removed}

2000\04\08@101639 by Wagner Lipnharski

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face
My today's theory is sound waves interference.  Waves adding and
cancelation. When you remove the phones, each speaker is directly
pointing (and projecting sound waves) toward the other. Tunneling sound
waves and make them colide is an interesting experience that students
make with a glass pipe and small foam balls, where you can see the
resultant waves forming peaks with the foam balls, completely different
from the original waves, of course.  While the earphones are at your
head it doesn't happen, it is nice that our ears doesn't form a tunnel
:)

The most intense sound level has more power in this sound waves mixing,
so of course they are the ones which will be more noticed to change
pitch or frequency.  So, while you are removing the earphones, you will
be noticing a considerably change in pitch, as the phones goes sliding
away of your ears, face, nose, mouth, chim, and so on, more intense or
reduced sound intereference will be noticed while you handle the
earphones, since the arc is mostly in plastic, during the handling it is
common that the speakers get aligned for some time, disaligned for some
other time, almost aligned, etc, so different interferences can be
noticed for the loud frequencies.

I am not considering that LOTS of frequencies you will not hear anyway
with the phones away from your ears, what by itself could be confused
with change in the sound's pitch.

As an experiment, try to play with your home floor speakers, align them
face to face 1 meter apart, seat 3 meters 90 degrees from them, play a
song, ask somebody to change the alignment just 5 degrees of one
speaker, you will notice a very perceptive change in the sound, probably
also in the main base pitch.  A frequency spectrum analyser would show
you all this differences.

When you see a crazy dedicated sound specialist adjusting the speakers
angle at an auditorium, he is not a fanatic, he is just trying to get
the best overal frequency spread with the minimum sound waves
interference, so he expects after the show you say; "The sound was good,
isn't it?"

Wagner

David Thompson wrote:
{Quote hidden}

> {Original Message removed}

2000\04\09@155341 by Rich Leggitt

picon face
Thanks for the responses. After some casual experimentation, I've noticed
that this doesn't occur if the volume is reduced without removing
headphones, it continues to occur if volume is increased after removal,
and the effect of pitch shift seems to fade after about 20-30 seconds.

So I guess this is just an 'audio illusion'. Perhaps the ear+brain
attempts to correctively equalize audio signal, and this process is fooled
when the signal bandpass is greatly changed due to headphones on/off.

-- Rich

On Sat, 8 Apr 2000, Wagner Lipnharski wrote:

{Quote hidden}

> > {Original Message removed}

2000\04\09@160545 by Andy Kelley

picon face
Also known as 'doppler shift'

Andy.

On Sun, 9 Apr 2000 12:53:34 -0700 Rich Leggitt <EraseMErleggittspamCONCENTRIC.NET>
writes:
{Quote hidden}

> > > {Original Message removed}

2000\04\09@161218 by David VanHorn

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At 04:02 PM 4/9/00 -0400, Andy Kelley wrote:
>Also known as 'doppler shift'

I think if you work the math, you'll find that you can't induce noticable
doppler shift that way without breaking your own arms due to the
acceleration required.

It's an auditory illusion.

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2000\04\09@211946 by Brandon, Tom

flavicon
picon face
Don't see why phase cancelation would occur selectively based on frequency
unless it's a multiway system (i.e. the bass and treble come from different
places thus different angles). Need to be pretty precise for phase
cancelation. Although it does agree with more cancelation of high
frequencies as the larger (lower) waves require more physical accuracy to
cancel.

I'd say it's a result of the method used to produce the sound. With overear
phones, you're ear canal becomes a resonant chamber as someone mentioned. If
they're resonant at say ~5kHz, and you pump a 500Hz signal and a 5kHz signal
at the same level, the 5kHz will resonate and be louder, so you pump the
5kHz in lower.

Alternatively, bass is much more unidirectional, if you can, try detaching
the 2 earpieces (my overheads alllow this), know move them 30cm away from
your head but keep pointed at ears, I would guess the high rfrequency would
be dulled less as it has a path to your ear without bouncing off about 10
walls and thus going 10 times as far as the bass.

In-ear earphones don't produce bass in a quite normal way. They use
psychoacoustical methods and the fact they are plugging the ear canal to
obtain good bass from an impossibly small cone (and do major ear damage at
the same time), hence when you move them away from your ears the bass drops.

Tom.

{Original Message removed}

2000\04\09@223447 by Rich Leggitt

picon face
Not.

If I'm doing the arithmetic right then a half-tone doppler shift (say 440
A to 415.3 A-flat) requires a headphone velocity of 62 feet/sec directly
away from me. For the effect to last 20 seconds would mean that the
headphone cord must be ~1200 feet long. For the apparent volume to remain
constant from one foot to 1200 feet requires something like 200dB increase
in actual headphone output level.

10^18 watts? Maybe with a solar-powered audio amp, and I do mean 'powered
by a sun'.

And my headphones are rated for 100 mW.

And anyway, they aren't moving.

-- Rich

On Sun, 9 Apr 2000, Andy Kelley wrote:

{Quote hidden}

> > > > {Original Message removed}

2000\04\09@224249 by Robert A. LaBudde

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<x-flowed>At 12:53 PM 4/9/00 -0700, Rich wrote:
>Thanks for the responses. After some casual experimentation, I've noticed
>that this doesn't occur if the volume is reduced without removing
>headphones, it continues to occur if volume is increased after removal,
>and the effect of pitch shift seems to fade after about 20-30 seconds.
>
>So I guess this is just an 'audio illusion'. Perhaps the ear+brain
>attempts to correctively equalize audio signal, and this process is fooled
>when the signal bandpass is greatly changed due to headphones on/off.

This is most probably a psychoacoustic effect.

The ear has its own sensory 'graphic equalizer'. When you listen to load
sounds, some frequency sensors are reduced in sensitivity and others increased.

When you remove the earphones, there is a hysteresis period before the
sensors re-initialize. (The brain's interpretation of the sound is involved
in the sensor loop.)

The effect can be proven psychoacoustic by measurement with a microphone
showing the signal is unchanged in spectrum during the experiment.

The effect is similar to that felt with the eyes when moving from bright
lights to dim or vice versa. Sometimes spurious images are observed.

================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: spamBeGoneralspamKILLspamlcfltd.com
Least Cost Formulations, Ltd.                   URL: http://lcfltd.com/
824 Timberlake Drive                            Tel: 757-467-0954
Virginia Beach, VA 23464-3239                   Fax: 757-467-2947

"Vere scire est per causae scire"
================================================================

</x-flowed>

2000\04\10@003915 by Rob Brzykcy

picon face
> This is most probably a psychoacoustic effect.
>
> The ear has its own sensory 'graphic equalizer'. When you listen to load
> sounds, some frequency sensors are reduced in sensitivity and others increased.
>
> When you remove the earphones, there is a hysteresis period before the
> sensors re-initialize. (The brain's interpretation of the sound is involved
> in the sensor loop.)
>

Ill second this.. The ear, like many of our systems, compensates for our enviroment and
sometimes takes a little while to catch up when there is a sudden change.
Roughly the sonic equivalent to the "isometric lift-floating arm" trick. Push your arm outward
against a non-moving object for a while, then step away, and, without resistance, your arm
floats up without intervention. Same thing, only aurally.

Rob




Download NeoPlanet at http://www.neoplanet.com

2000\04\10@012528 by Alok Dubey

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face
yeah in college we called it dopplers effect
alok


-----Original Message-----
From: David Thompson [.....ranma21spam_OUTspamEISA.NET.AU]
Sent: 08 April, 2000 6:49 PM
To: TakeThisOuTPICLIST.....spamTakeThisOuTMITVMA.MIT.EDU
Subject: Re: Headphones changing pitch automagically [OT]


Hi Richard,

I have noticed this affect also. Being a curious sort, I often wondered why
this could be. Rest assured, you are not psycho. The only thing that I can
add that it seems more obvious with higher volumes, and seems independant on
speed (i.e taking them off quicker or slower). Hmmm, I have just realised
that I've only noticed it with my full-size headphones, not the tiny in-ear
ones... whatever...

I will be interested in any theories that people might have.

Dave

----- Original Message -----
From: M. Adam Davis <TakeThisOuTadavisKILLspamspamspamUBASICS.COM>
To: <.....PICLISTspamRemoveMEMITVMA.MIT.EDU>
Sent: Saturday, April 08, 2000 12:43 AM
Subject: Re: Headphones changing pitch automagically [OT]


> Well, the act of moving the headphones away from you would cause a drop in
> pitch, but it would normallize once the headphones stopped moving away
from
> you.  The pitch would rise while you bring the headphones towards you, but
again
> the pitch would normalize when they stopped moving (relative to your
head).
> The faster you move them, the higher (or lower) the pitch goes.
>
> If the change does not follow this description, then you might be looking
at the
> inability for the headphones to send higher pitched notes very far, so
they
> become less-audible the further the headphones are away from you.  This
would
> make the spectrum of the music sound lower, and you might percieve that
the
> pitches shifted instead of the top ones disappearing.
>
> Or your psycho.  Perhaps to gov't is beaming info into your head to make
you
> crazy.  You should try wearing an aluminum helmet (except in
thunderstorms!).
>
> -Adam
>
> I respect faith, but doubt is what gives you an education. -- Wilson
Mizner
>
> Rich Leggitt wrote:
> >
> > So I'm building this MP3 player, and I'm listening to the music through
> > headphones.
> >
> > Then I take the headphones off and hold them away so that I can still
> > faintly hear the music. And the strangest thing -- there's a very
dramatic
> > drop in apparent musical pitch. I put the headphones back on, and the
> > pitch goes back up. I take them off again and the pitch goes down again.
> >
> > Now, I don't think the frequency is actually changing (unless perhaps
the
> > bulb in the refrigerator is also staying on.)
> >
> > But I'm wondering what's going on? Is this a known phenomenon, i.e.
large
> > changes in apparent amplitude and/or apparent bandwidth translated by
some
> > psycho-acoustic process into changes in apparent frequency?
> >
> > Or perhaps I AM the psycho in 'psycho-acoustic'? :)
> >
> > -- Rich
>

2000\04\10@023922 by Darren King

flavicon
face
It couldn't be a doppler effect cause he wasn't swinging the headphones
around by the cord or moving fast enough to even be able to hear the wave
lengthen or shorten...  Did this get off topic?  Its most likely the type of
headphones that are creating a non dispersion wave.  (Sorry I forgot what
its really called, yeah college was a while ago).  So when far away from the
ear then most of the waves are not making it.  Try other headphones?

Darren King

----- Original Message -----
From: "Alok Dubey" <RemoveMEadubeyspamspamBeGoneWIPRO.CO.IN>
To: <spamBeGonePICLIST@spam@spamspam_OUTMITVMA.MIT.EDU>
Sent: Sunday, April 09, 2000 10:10 PM
Subject: Re: Headphones changing pitch automagically [OT]


> yeah in college we called it dopplers effect
> alok
>
>
> {Original Message removed}

2000\04\10@110134 by Wagner Lipnharski

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face
I wonder what power the earphones should be delivering to cause the ear
sensors to change so dramatically...

A simple way to test this:

a) Cut off the sound completely, take the earphones from your ears, hold
them 2 ft away, wait 1 minute of (music playing) silence, then turn the
audio volume level on, observe if you can notice any pitch change before
and after the 20 or 30 seconds period (as reported).

b) While listening to the sound, remove the earphones, you will notice
the pitch change... now, if you put back the earphones at your ears,
what you will notice?  immediate (good) pitch returns? or it takes some
time too?

Wagner.

"Rob B." wrote:
{Quote hidden}

2000\04\10@192606 by Rob Brzykcy

picon face
Well, being a person who produces music, I know there are a lot of ppl that dont like
headphones, and the reason people dont like headphones is because they cause severe ear
fatigue and they will make everything you try to mixdown and eq sound aweful after using
headphones for extended periods.. There are whole articles on this phenomena on the web ,
in books, and in magazines.
.
Needless to say, most producers use open air near field monitors to minimize the effects of
aural fatigue, which I have experienced first hand and I believe that this situation is another
manifestation.

Rob



{Quote hidden}

outward
> > against a non-moving object for a while, then step away, and, without resistance, your
arm
{Quote hidden}

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2000\04\10@194115 by William Chops Westfield

face picon face
Isn't this just a matter of transducer coupling effects?  I mean, an small
earphone-type headphone is similar in size to the ear canal itself, so if
they're close enough together, you might say they were "impedence matched"
in some sense.  Get them further apart and you start attenuating some of
the signals because of the mismatch between the earphone and "open air" and
again because of the mismatch between "open air" and the ear.  Or something
like that...

BillW

2000\04\10@200349 by Brandon, Tom

flavicon
picon face
Part of the fatigue of headphones is supposed to be psychoacoustical. The
brain is used to sounds coming from outside of the head from a certain
direction (binaural sound (headphones don't fall under this definition of
binaural sound as there are 2 sources)) while with headphones make the sound
appear to come from inside the head, a quite unnerving experience for the
simplistic (in one way) brain. Tests have shown that people who use auditory
cues (e.g. fighter pilots for radar) get far less fatigue when a binaural
sound is used rather than headphones.

The pitch change may also be psychoacoustical. Frequency spectra are used by
the brain for positioning. It works like this, inside the ear is a thing
called the pinna, when sound enters the ear canal it causes the pinna to
vibrate, the pinna vibration is related to the angle the sound entered the
ear. Thus, the frequency spectrum reaching the eardrum is altered based on
the direction. So if you take headphones off and move them in front of (or
behind) your head but keep them close to your body in the horizontal plane
you will create a very sharp angle to the ear and thus would get larger
modification of the frequency spectra. The pinna is only receptive to sounds
>3500Hz odd so you wouldn't notice the effect with bass, which is why bass
is more omnidirectional. The Aureal 3D system works by applying the HTRF (?
the impulse response of the pinna) to audio. So keep your head REAL straight
when using A3D or your own pinna will effect the calculated final HTRF
percieved by you.

Also, someone brought up bass reponse in in-ear style phones. These
headphones use psychoacpoustical tricks to make your brain hear frequencies
the phones can't produce. It's something like this, if you give the brain 2
sequential (non fundamental) harmonics then it will 'hear' the fundamental
harmonic as well. And if those fundamental harmonics were above 3500Hz (or
one was) then it would only work when the phones were pointed straight into
your ear or the pinna would throw it off.

(NB: All these facts are from memory, read the article last night while half
asleep. I'm quite sure all the ideas are right (as presented in the material
I read) but I apologise if any terms\details are incorrect).

Much of this info came from articles at http://www.headwize.com/ which have
a fair number of articles on the psychoacoustics of headphones\3D sound and
the like.

Tom.

{Original Message removed}

2000\04\11@092130 by Daniel Hart

flavicon
face
Wagner,
;-) -- >  This is known as the DUMBLER effect or DUMBLER shift. As a thread continues to exist is
becomes DUMBLER and DUMBLER until it degenerates into incoherent triviality. This is the newsgroup
equivalent of chaos, thereby reaffirming the theory of entropy. I, for one, get a warm feeling of
fulfillment each time I see a thread spiral into oblivion; and it is difficult to resist the
temptation to help it find its ultimate destiny. I can't explain, however, why the frequency appears
to increase as the thread moves away from the brain. An exercise for the student, I suppose. (Of
course I'm kidding, hope you accept this in good fun), -- Dan

Wagner Lipnharski wrote:

{Quote hidden}

--

Daniel Hart
Embedded System Design Engineer
NBS Technologies, Inc. (Card Technology Corp.)
70 Eisenhower Drive, Paramus, NJ 07652, USA
+1 201 845 7373 x183    EraseMEdhartspam@spam@nbstech.com

2000\04\11@121557 by Kevin Blain

flavicon
face
High frequency sounds are more directional than low frequency ones.
Therfore, when you hold the headphones STILL away from you, the low
frequency sounds are the ones that you hear LOUDER than the HF ones. Point a
cup at your ear from further away, and you should notice the HF pick up
again.
----- Original Message -----
From: Alok Dubey <@spam@adubeyspam_OUTspam.....WIPRO.CO.IN>
To: <spamBeGonePICLISTEraseMEspamMITVMA.MIT.EDU>
Sent: Monday, April 10, 2000 6:10 AM
Subject: Re: Headphones changing pitch automagically [OT]


> yeah in college we called it dopplers effect
> alok
>
>
> {Original Message removed}

2000\04\12@085846 by Alok Dubey

flavicon
face
yeah .. in fact that is why the difference in shape of the woofer and the HF
speaker,.,.. i though it was doppler he was talking abt but what u say makes
more sense
Alok



> {Original Message removed}

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