The human ear and examples of natural heterodynes

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Topic:	Science > Physics
User:	"greysky"
Date:	03 Jan 2008 12:36:29 AM
Object:	The human ear and examples of natural heterodynes

One night I fell asleep while watching the late movie and when I woke up,
the channel had gone off the air, and there was the usual pattern of
circles on the tv, along with a rather annoying steady tone. Curious to see
how close I could whistle and perhaps match the tone from the TV, I noticed
a quite clear heterodyne tone produced in my ears. The third tone would
start out low (or was it high, I can't quite remember because this was 25
years ago) and would increase in frequency the closer I got to the center
frequency. The next day I asked my physics professor about the human ear's
ability to produce a heterodyne in this manner, and he stated flat out that
it was impossible. Now, I wasn't gonna argue with the guy because finals
were going to start and he held my grade in his hands and he was a bit of a
hothead.... but I couldn't figure out why he thought it wsa impossible.
Since then I've asked around a few more times, butthe general idea ws that
the human ear could not produce a heterodyne signal - yet I quite clearly
remember how easily my ears created one. Now, 25+ years later, my ears are
not as good as they one were - tinnitus, some frequency selective deafness,
and general ageism have taken their toll and I can no longer produce the
heterodyne signal. So does anyone have any theories as to whether the human
ear can produce a heterodyne signal? If you are a young'un I innvite you to
do this experiment for yourself. All you need is a steady tone and the
ability to whistle. Use a tone generator set to about 1.5 Kilocycles coming
from a single speaker 3 - 5 meters away. Begin to whistle and slowly try to
match the tone generator and then go a bit higher and lower. You should
clearly be able to hear a third tone -the beat frequency- varying as the
inverse of your whistled tone. Give it a try and tell us your results...
Greysky
.

User: "Androcles"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 02:41:20 AM

"greysky" <greysky@sbcglobal.net> wrote in message
news:Kn%ej.2661$pr6.738@nlpi070.nbdc.sbc.com...
: One night I fell asleep while watching the late movie and when I woke up,
: the channel had gone off the air, and there was the usual pattern of
: circles on the tv, along with a rather annoying steady tone. Curious to
see
: how close I could whistle and perhaps match the tone from the TV, I
noticed
: a quite clear heterodyne tone produced in my ears. The third tone would
: start out low (or was it high, I can't quite remember because this was 25
: years ago) and would increase in frequency the closer I got to the center
: frequency. The next day I asked my physics professor about the human ear's
: ability to produce a heterodyne in this manner, and he stated flat out
that
: it was impossible. Now, I wasn't gonna argue with the guy because finals
: were going to start and he held my grade in his hands and he was a bit of
a
: hothead.... but I couldn't figure out why he thought it wsa impossible.
: Since then I've asked around a few more times, butthe general idea ws that
: the human ear could not produce a heterodyne signal - yet I quite clearly
: remember how easily my ears created one. Now, 25+ years later, my ears are
: not as good as they one were - tinnitus, some frequency selective
deafness,
: and general ageism have taken their toll and I can no longer produce the
: heterodyne signal. So does anyone have any theories as to whether the
human
: ear can produce a heterodyne signal? If you are a young'un I innvite you
to
: do this experiment for yourself. All you need is a steady tone and the
: ability to whistle. Use a tone generator set to about 1.5 Kilocycles
coming
: from a single speaker 3 - 5 meters away. Begin to whistle and slowly try
to
: match the tone generator and then go a bit higher and lower. You should
: clearly be able to hear a third tone -the beat frequency- varying as the
: inverse of your whistled tone. Give it a try and tell us your results...
:
: Greysky
The tinnitus is a defect in the nervous system, the nerve ending is sending
a false signal to the brain. Frequency selective deafness is a result of
fine hairs in the cochlea breaking off. It is these hairs that vibrate in
sympathy (resonate) with the sound and stimulate the nerve endings.
They fracture with age and with use.
Your physics teacher was right, ears do not whistle. Perhaps
he misunderstood your question as I first did, I had it to read
it through twice because you seem to imply that the ear causes
sound to be emitted.
There is no good reason why a young and healthy ear should not
detect a heterodyne tone.
.

User: "Tim Williams"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 04:11:13 AM

"Androcles" <Engineer@hogwarts.physics_c> wrote in message
news:Qc1fj.129713$cJ3.85514@fe2.news.blueyonder.co.uk...

The tinnitus is a defect in the nervous system, the nerve ending is

sending

a false signal to the brain.

As I recall, the fine hairs are regenerative recievers, so "a defect in the
nervous system" could certainly include a miscalibrated amount of feedback.
It's known that tinnitus sufferers literally do have "ringing in the ears".
Let's see what Wikipedia says about it:
http://en.wikipedia.org/wiki/Tinnitus#Mechanisms_of_subjective_tinnitus

There is no good reason why a young and healthy ear should not
detect a heterodyne tone.

Not a hetrodyne, but a difference easily. The amplitude modulates with an
apparent cusp (not sine wave) envelope. I would suppose the ears aren't as
great at detecting the phase between cycles, making it appear to modulate.
Tim
--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms
.

User: "Androcles"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 04:51:05 AM

"Tim Williams" <tmoranwms@gmail.com> wrote in message
news:Sx2fj.496$d56.191@newsfe06.lga...
: "Androcles" <Engineer@hogwarts.physics_c> wrote in message
: news:Qc1fj.129713$cJ3.85514@fe2.news.blueyonder.co.uk...
: > The tinnitus is a defect in the nervous system, the nerve ending is
: sending
: > a false signal to the brain.
:
: As I recall, the fine hairs are regenerative recievers, so "a defect in
the
: nervous system" could certainly include a miscalibrated amount of
feedback.
:
: It's known that tinnitus sufferers literally do have "ringing in the
ears".
:
I suffer from it, I don't need anyone to tell me I do, Tim.
: Let's see what Wikipedia says about it:
: http://en.wikipedia.org/wiki/Tinnitus#Mechanisms_of_subjective_tinnitus
Trusting wackypedia, the crap anyone can write, is like trusting a
politician.
:
: > There is no good reason why a young and healthy ear should not
: > detect a heterodyne tone.
:
: Not a hetrodyne, but a difference easily.
Let's see what wackypedia says about it.
http://en.wikipedia.org/wiki/Heterodyne
"This article or section contains too much jargon and may need
simplification or further explanation."
"heterodyning is the generation of new frequencies by mixing two or more
signals "
: The amplitude modulates with an
: apparent cusp (not sine wave) envelope. I would suppose
We'll ignore suppositions and "not sine waves"
and go directly to simple sine wave addition.
http://www.androcles01.pwp.blueyonder.co.uk/Sagnac/Sagnac2.JPG
Looks to me as if Greysky (whom you rudely snipped even it is his
post I was answering) experienced heterodyning as he claimed.
Yes a difference, and a heterodyne, easily.
.

User: "Glen Walpert"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 10:55:57 AM

On Thu, 03 Jan 2008 10:51:05 GMT, "Androcles"
<Engineer@hogwarts.physics_c> wrote:

"Tim Williams" <tmoranwms@gmail.com> wrote in message
:
: Not a hetrodyne, but a difference easily.

Let's see what wackypedia says about it.
http://en.wikipedia.org/wiki/Heterodyne

"This article or section contains too much jargon and may need
simplification or further explanation."

"heterodyning is the generation of new frequencies by mixing two or more
signals "

: The amplitude modulates with an
: apparent cusp (not sine wave) envelope. I would suppose

We'll ignore suppositions and "not sine waves"
and go directly to simple sine wave addition.
http://www.androcles01.pwp.blueyonder.co.uk/Sagnac/Sagnac2.JPG

Looks to me as if Greysky (whom you rudely snipped even it is his
post I was answering) experienced heterodyning as he claimed.
Yes a difference, and a heterodyne, easily.

Sorry, simply summing two signals to obtain an amplitude beat
frequency is not hetrodyne.
------------
http://glossary.its.bldrdoc.gov/fs-1037/dir-018/_2566.htm
heterodyne: 1. To generate new frequencies by mixing two or more
signals in a nonlinear device such as a vacuum tube, transistor, or
diode mixer. (188) Note: A superheterodyne receiver converts any
selected incoming frequency by heterodyne action to a common
intermediate frequency where amplification and selectivity (filtering)
are provided. 2. A frequency produced by mixing two or more signals in
a nonlinear device. (188)
---------------
In order to get sum and difference sine waves via the hetrodyne
effect, nonlinear mixing is required. This is explained in pretty
much any primer on the subject, and has been hashed to death here on
SED in the past few years. With sound levels and frequencies within
the range of human hearing the propogation of sound in air is linear,
and therefore hetrodyning cannot occur. Greysky's physics professor
was right.

.

User: "Androcles"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 12:07:16 PM

"Glen Walpert" <gwalpert@notaxs.com> wrote in message
news:f03qn3p6vickphpbjtcqgr5286tf32n9ls@4ax.com...
: On Thu, 03 Jan 2008 10:51:05 GMT, "Androcles"
: <Engineer@hogwarts.physics_c> wrote:
:
: >
: >"Tim Williams" <tmoranwms@gmail.com> wrote in message
:
: >:
: >: Not a hetrodyne, but a difference easily.
: >
: >Let's see what wackypedia says about it.
: > http://en.wikipedia.org/wiki/Heterodyne
: >
: >"This article or section contains too much jargon and may need
: >simplification or further explanation."
: >
: >"heterodyning is the generation of new frequencies by mixing two or more
: >signals "
: >
: >
: >
: >: The amplitude modulates with an
: >: apparent cusp (not sine wave) envelope. I would suppose
: >
: >We'll ignore suppositions and "not sine waves"
: >and go directly to simple sine wave addition.
: > http://www.androcles01.pwp.blueyonder.co.uk/Sagnac/Sagnac2.JPG
: >
: >Looks to me as if Greysky (whom you rudely snipped even it is his
: >post I was answering) experienced heterodyning as he claimed.
: >Yes a difference, and a heterodyne, easily.
:
: Sorry, simply summing two signals to obtain an amplitude beat
: frequency is not hetrodyne.
:
: ------------
: http://glossary.its.bldrdoc.gov/fs-1037/dir-018/_2566.htm
:
: heterodyne: 1. To generate new frequencies by mixing two or more
: signals in a nonlinear device such as a vacuum tube, transistor, or
: diode mixer. (188) Note: A superheterodyne receiver converts any
: selected incoming frequency by heterodyne action to a common
: intermediate frequency where amplification and selectivity (filtering)
: are provided. 2. A frequency produced by mixing two or more signals in
: a nonlinear device. (188)
: ---------------
Oh, a linear op-amp won't add two signals?
http://www.markallen.com/teaching/images/electronics/opamp_block.jpg
: In order to get sum and difference sine waves via the hetrodyne
: effect, nonlinear mixing is required.
: This is explained in pretty
: much any primer on the subject, and has been hashed to death here on
: SED in the past few years. With sound levels and frequencies within
: the range of human hearing the propogation of sound in air is linear,
: and therefore hetrodyning cannot occur. Greysky's physics professor
: was right.
:
Oh really? I'll throw away all I ever learned about analogue computing,
then. It won't matter, Concorde has been scrapped now anyway
after 30 years of success. If I'd know it wouldn't work because SED
said so I'd have never got involved. Pity it did or I could have saved
myself the trouble.
.

User: "Army1987"
Title: Re: The human ear and examples of natural heterodynes	04 Jan 2008 07:06:59 AM

Glen Walpert wrote:
[about beating between tinnitus and a real sound]

Are your ears a linear device? Can you tell the difference between a
0.2 pascal sound and a 0.4 pascal sound (i.e. 80 dB and 86 dB) with the
same ease you can hear the difference between 0.22 Pa and 0.02 Pa
(i.e. 80.8 dB and 60 dB), or 2 Pa and 2.2 Pa (i.e. 100 dB and 100.8 dB)?
--
Army1987 (Replace "NOSPAM" with "email")
.

User: "Glen Walpert"
Title: Re: The human ear and examples of natural heterodynes	04 Jan 2008 08:23:41 AM

On Fri, 4 Jan 2008 13:06:59 +0000 (UTC), Army1987 <army1987@NOSPAM.it>
wrote:

Glen Walpert wrote:

[about beating between tinnitus and a real sound]

While neither the ears or any other sensor in existence are truly
linear, the nonlinearity of human hearing has nothing to do with the
beat frequency effect caused by the linear addition of two signals.
You can see the effect clearly with a microphone and oscope while
carefully keeping both in their essentially linear range. You do not
even need to mix the two sounds in air, you could add the signal from
two microphones in different anechoec chambers and see the effect, or
simply add the signals from two signal generators, same beat frequency
effect is clearly visible. But this has nothing to do with hetrodyne.
Serach for the thread "multiplying two signals" to find the last SED
discussion of why addition is not the same as multiplication. Or
better yet find a basic signal processing text and learn how nonlinear
mixing (e.g. multiplication) produces sum and difference signals, and
linear addition produces only a beat frequency.
It is possible to produce a true hetrodyn effect in air, commercial
products are even available which use the effect to produce audible
sound from the mixing of two ultrasonic sounds, but this requires that
the two sounds be at frequencies and amplitudes where the propogation
of sound in air is significantly nonlinear, well outside the range of
human hearing, and is entirely different from the beat frequency
effect which occurs in the linear hearing range.
.

User: "Glen Walpert"
Title: Re: The human ear and examples of natural heterodynes	04 Jan 2008 12:10:53 PM

On Fri, 4 Jan 2008 13:06:59 +0000 (UTC), Army1987 <army1987@NOSPAM.it>
wrote:

Glen Walpert wrote:

[about beating between tinnitus and a real sound]

Actually I was writing about beating between two real sounds. Beating
between tinnitus and real sound may or may not be similar.

Let me try an example to explain the difference between a beat
frequency effect and hetrodyne mixing of two real sounds in air:
Consider two directional sound sources A and B directed so as to cross
each other. Within the human hearing range where propogation is
essentially linear, close to either source before the crossing zone
you hear only the individual source A or B. In the crossing zone you
hear both sources simultaneously, and a beat frequency caused by
alternating constructive and destructive interference at the detector
(ear or microphone) can be heard or measured. Neither sound beam is
altered by this however, and beyond the crossing again only the
individual sources can be heard, completely unmodified by the
crossing. Turning one source on or off has no effect on the other.
This is a beat frequency, not hetrodyne mixing.
Now crank both sources up into the nonlinear range, where sound
pressure is not very small compared to atmospheric pressure
(oversimplifying a bit). Since these levels will damage your hearing,
we will listen with a microphone. Now, not just in the crossing zone
but emmanating from the crossing zone are sum and difference
frequencies. Now the sound beams are actually interacting, so that
turning off either source causes the sound level of the other source
beyond the crossing zone to increase, decreasing when both are on
because some of the sound energy is actually being converted to the
sum and difference frequencies. This is hetrodyne mixing.
Both effects are equally real, but they are not the same thing.
.

User: "Army1987"
Title: Re: The human ear and examples of natural heterodynes	04 Jan 2008 03:28:04 PM

Glen Walpert wrote:
[...]

Let me try an example to explain the difference between a beat
frequency effect and hetrodyne mixing of two real sounds in air:

Consider two directional sound sources A and B directed so as to cross
each other. Within the human hearing range where propogation is
essentially linear, close to either source before the crossing zone
you hear only the individual source A or B. In the crossing zone you
hear both sources simultaneously, and a beat frequency caused by
alternating constructive and destructive interference at the detector
(ear or microphone) can be heard or measured. Neither sound beam is
altered by this however, and beyond the crossing again only the
individual sources can be heard, completely unmodified by the
crossing. Turning one source on or off has no effect on the other.
This is a beat frequency, not hetrodyne mixing.

Now crank both sources up into the nonlinear range, where sound
pressure is not very small compared to atmospheric pressure
(oversimplifying a bit). Since these levels will damage your hearing,
we will listen with a microphone. Now, not just in the crossing zone
but emmanating from the crossing zone are sum and difference
frequencies. Now the sound beams are actually interacting, so that
turning off either source causes the sound level of the other source
beyond the crossing zone to increase, decreasing when both are on
because some of the sound energy is actually being converted to the
sum and difference frequencies. This is hetrodyne mixing.

Both effects are equally real, but they are not the same thing.

Ok, I misunderstood the meaning of hetrodyne, I thought it simply meant
distorted beating sound, as if I played a G# and a A together on the
electric guitar with distortion on.
--
Army1987 (Replace "NOSPAM" with "email")
.

User: "Richard Henry"
Title: Re: The human ear and examples of natural heterodynes	04 Jan 2008 11:07:08 AM

On Jan 4, 5:06=A0am, Army1987 <army1...@NOSPAM.it> wrote:

Glen Walpert wrote:

[about beating between tinnitus and a real sound]

Sorry, simply summing two signals to obtain an amplitude beat
frequency is not hetrodyne.

------------
http://glossary.its.bldrdoc.gov/fs-1037/dir-018/_2566.htm

heterodyne: 1. To generate new frequencies by mixing two or more
signals in a nonlinear device such as a vacuum tube, transistor, or
diode mixer.

No, but I can hear echoes sometimes.
.

User: "Army1987"
Title: Re: The human ear and examples of natural heterodynes	04 Jan 2008 07:06:59 AM

Glen Walpert wrote:
[about beating between tinnitus and a real sound]

User: "John Larkin"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 11:17:14 AM

On Thu, 03 Jan 2008 16:55:57 GMT, Glen Walpert <gwalpert@notaxs.com>
wrote:

On Thu, 03 Jan 2008 10:51:05 GMT, "Androcles"
<Engineer@hogwarts.physics_c> wrote:

"Tim Williams" <tmoranwms@gmail.com> wrote in message

:
: Not a hetrodyne, but a difference easily.

Let's see what wackypedia says about it.
http://en.wikipedia.org/wiki/Heterodyne

"This article or section contains too much jargon and may need
simplification or further explanation."

"heterodyning is the generation of new frequencies by mixing two or more
signals "

: The amplitude modulates with an
: apparent cusp (not sine wave) envelope. I would suppose

We'll ignore suppositions and "not sine waves"
and go directly to simple sine wave addition.
http://www.androcles01.pwp.blueyonder.co.uk/Sagnac/Sagnac2.JPG

Looks to me as if Greysky (whom you rudely snipped even it is his
post I was answering) experienced heterodyning as he claimed.
Yes a difference, and a heterodyne, easily.

Sorry, simply summing two signals to obtain an amplitude beat
frequency is not hetrodyne.

------------
http://glossary.its.bldrdoc.gov/fs-1037/dir-018/_2566.htm

heterodyne: 1. To generate new frequencies by mixing two or more
signals in a nonlinear device such as a vacuum tube, transistor, or
diode mixer. (188) Note: A superheterodyne receiver converts any
selected incoming frequency by heterodyne action to a common
intermediate frequency where amplification and selectivity (filtering)
are provided. 2. A frequency produced by mixing two or more signals in
a nonlinear device. (188)
---------------

In order to get sum and difference sine waves via the hetrodyne
effect, nonlinear mixing is required. This is explained in pretty
much any primer on the subject, and has been hashed to death here on
SED in the past few years. With sound levels and frequencies within
the range of human hearing the propogation of sound in air is linear,
and therefore hetrodyning cannot occur. Greysky's physics professor
was right.

Get two sinewave generators and two loudspeakers and try it. You
certainly *will* hear the near-zero-beat difference frequency. The ear
is acting as an envelope detector.
Try it.
John
.

User: "Androcles"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 12:11:48 PM

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:uv5qn3le43g74plrid8oask2v9ljoh1lao@4ax.com...
: On Thu, 03 Jan 2008 16:55:57 GMT, Glen Walpert <gwalpert@notaxs.com>
: wrote:
:
: >On Thu, 03 Jan 2008 10:51:05 GMT, "Androcles"
: ><Engineer@hogwarts.physics_c> wrote:
: >
: >>
: >>"Tim Williams" <tmoranwms@gmail.com> wrote in message
: >
: >>:
: >>: Not a hetrodyne, but a difference easily.
: >>
: >>Let's see what wackypedia says about it.
: >> http://en.wikipedia.org/wiki/Heterodyne
: >>
: >>"This article or section contains too much jargon and may need
: >>simplification or further explanation."
: >>
: >>"heterodyning is the generation of new frequencies by mixing two or more
: >>signals "
: >>
: >>
: >>
: >>: The amplitude modulates with an
: >>: apparent cusp (not sine wave) envelope. I would suppose
: >>
: >>We'll ignore suppositions and "not sine waves"
: >>and go directly to simple sine wave addition.
: >> http://www.androcles01.pwp.blueyonder.co.uk/Sagnac/Sagnac2.JPG
: >>
: >>Looks to me as if Greysky (whom you rudely snipped even it is his
: >>post I was answering) experienced heterodyning as he claimed.
: >>Yes a difference, and a heterodyne, easily.
: >
: >Sorry, simply summing two signals to obtain an amplitude beat
: >frequency is not hetrodyne.
: >
: >------------
: >http://glossary.its.bldrdoc.gov/fs-1037/dir-018/_2566.htm
: >
: >heterodyne: 1. To generate new frequencies by mixing two or more
: >signals in a nonlinear device such as a vacuum tube, transistor, or
: >diode mixer. (188) Note: A superheterodyne receiver converts any
: >selected incoming frequency by heterodyne action to a common
: >intermediate frequency where amplification and selectivity (filtering)
: >are provided. 2. A frequency produced by mixing two or more signals in
: >a nonlinear device. (188)
: >---------------
: >
: >In order to get sum and difference sine waves via the hetrodyne
: >effect, nonlinear mixing is required. This is explained in pretty
: >much any primer on the subject, and has been hashed to death here on
: >SED in the past few years. With sound levels and frequencies within
: >the range of human hearing the propogation of sound in air is linear,
: >and therefore hetrodyning cannot occur. Greysky's physics professor
: >was right.
: >
: >
:
: Get two sinewave generators and two loudspeakers and try it. You
: certainly *will* hear the near-zero-beat difference frequency. The ear
: is acting as an envelope detector.
:
: Try it.
:
: John
Nah, it has been hashed to death on SED in the past few years, it
can't possibly do that if SED says so. Beats me how piano tuners
did their job when they can't hear a beat because SED hashed it
to death.
.

User: "Glen Walpert"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 04:41:04 PM

On Thu, 03 Jan 2008 09:17:14 -0800, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Thu, 03 Jan 2008 16:55:57 GMT, Glen Walpert <gwalpert@notaxs.com>
wrote:

On Thu, 03 Jan 2008 10:51:05 GMT, "Androcles"
<Engineer@hogwarts.physics_c> wrote:

"Tim Williams" <tmoranwms@gmail.com> wrote in message

Sorry, simply summing two signals to obtain an amplitude beat
frequency is not hetrodyne.

------------
http://glossary.its.bldrdoc.gov/fs-1037/dir-018/_2566.htm

heterodyne: 1. To generate new frequencies by mixing two or more
signals in a nonlinear device such as a vacuum tube, transistor, or
diode mixer. (188) Note: A superheterodyne receiver converts any
selected incoming frequency by heterodyne action to a common
intermediate frequency where amplification and selectivity (filtering)
are provided. 2. A frequency produced by mixing two or more signals in
a nonlinear device. (188)
---------------

In order to get sum and difference sine waves via the hetrodyne
effect, nonlinear mixing is required. This is explained in pretty
much any primer on the subject, and has been hashed to death here on
SED in the past few years. With sound levels and frequencies within
the range of human hearing the propogation of sound in air is linear,
and therefore hetrodyning cannot occur. Greysky's physics professor
was right.

Get two sinewave generators and two loudspeakers and try it. You
certainly *will* hear the near-zero-beat difference frequency. The ear
is acting as an envelope detector.

Of course you will hear the beat frequency, but that does not make it
the result of hetrodyning.
.

User: "John Fields"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 05:25:25 PM

On Thu, 03 Jan 2008 22:41:04 GMT, Glen Walpert <gwalpert@notaxs.com>
wrote:

On Thu, 03 Jan 2008 09:17:14 -0800, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

Get two sinewave generators and two loudspeakers and try it. You
certainly *will* hear the near-zero-beat difference frequency. The ear
is acting as an envelope detector.

Of course you will hear the beat frequency, but that does not make it
the result of hetrodyning.

---
Indeed.
If it were truly the result of heterodyning then f1 + f2 would also
be heard if it was within the range of hearing.
I've tried it and I've heard no upper sideband.
--
JF
.

User: ""
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 07:45:49 AM

Your physics teacher was right, ears do not whistle. Perhaps
he misunderstood your question as I first did, I had it to read
it through twice because you seem to imply that the ear causes
sound to be emitted.

Well actually they can and do!
For example:
http://bmb.oxfordjournals.org/cgi/reprint/63/1/223.pdf
Otherwise, just search for "otoacoustic emissions".
John
.

User: "Androcles"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 08:16:41 AM

<jrwalliker@gmail.com> wrote in message
news:de0eb65e-5fe6-4b21-ab80-452a8cdc164f@d21g2000prf.googlegroups.com...
:> Your physics teacher was right, ears do not whistle. Perhaps
: > he misunderstood your question as I first did, I had it to read
: > it through twice because you seem to imply that the ear causes
: > sound to be emitted.
:
:
: Well actually they can and do!
:
: For example:
:
: http://bmb.oxfordjournals.org/cgi/reprint/63/1/223.pdf
:
: Otherwise, just search for "otoacoustic emissions".
:
: John
Yeah, and bullets can fly.
Whistle:
1 a: a small wind instrument in which sound is produced by the forcible
passage of breath through a slit in a short tube <a police whistle> b: a
device through which air or steam is forced into a cavity or against a thin
edge to produce a loud sound <a factory whistle>2 a: a shrill clear sound
produced by forcing breath out or air in through the puckered lips b: the
sound produced by a whistle c: a signal given by or as if by whistling3: a
sound that resembles a whistle; especially : a shrill clear note of or as if
of a bird
If I notice a puff of air coming from the side of your head then
I'll probably conclude the cavity is filled with air and not vacuum :-)
.

User: ""
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 09:01:49 AM

sound that resembles a whistle; especially : a shrill clear note of or as if
of a bird

I guess this is the definition you had in mind.
In particular, the ear can generate difference frequencies between two
simultaneously presented acoustic sine waves which are detectable with
a probe microphone placed in the ear canal.
It is also possible to detect an echo from a click stimulus using a
probe microphone.
Both of these responses are diminished or absent when the cochlea is
damaged by noise exposure or ototoxic drugs.
John
.

User: "Androcles"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 09:25:17 AM

<jrwalliker@gmail.com> wrote in message
news:378517bb-d72b-43b2-a684-3c89875d2eb0@l6g2000prm.googlegroups.com...
:> sound that resembles a whistle; especially : a shrill clear note of or as
if
: > of a bird
:
: I guess this is the definition you had in mind.
Definitions are indeed important, English is vague. However,
the intent is generally understood from the context.
:
: In particular, the ear
: It is also possible
:
: Both of these
Which although interesting isn't relevant to Greysky's post.
What is less interesting is that you didn't respond to Greysky's
post, probably because like so many others you have a short
attention span and prefer to snip, making it more difficult for
others to know what Greysky's post was about and so it all
crumbles into triviality while you spout what interests you
and fail to answer the original post.
.

User: "oldcoot"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 10:11:20 AM

Speaking of heterodynes, there's a clever stunt anyone can do using
radio frequencies instead of acoustics. It's a quick-and-dirty
'Theremin' using three broadcast-band radios:
Radio# 1 is set to any *blank spot* in the upper end of the band,
anywhere around 1300-1600 khz. It is now prepared to receive on that
'clear channel'.
Radio# 2 is *manually tuned* (not digital) and is the "transmitter".
It is placed in close proximity to Radio# 1 for close coupling. Back-
to-back usually gives the strongest coupling. Tune Radio# 2 slowly
through the lower portion of the band until its local oscillator* (LO)
is heard as a strong 'rushing' sound on Radio#1. Leave it set on that
spot. This unmodulated carrier is now the victim of our
attention. :-)
Radio# 3 is a Walkman type, also *manually tuned* (not digital). It is
brought into close proximity to Radio# 2 for close coupling. Tune it
slowly thru the lower portion of the band until its LO is heard as a
whistle 'beating' (heterodyning) against Radio# 2's LO. Tune for zero
beat. You'll hear a a "Weeeoooop..." as the tone approaches zero
beat. Now you can play the 'Theremin'.
Squeeze and massage Radio# 3 (the Walkman), which causes its LO
frequency to vary enough to produce a large, warbling shift of the
beat note, which is heard on Radio# 1. 'Tremolo' (amplitude shift) is
done by rapidly moving the Walkman away from / toward the other pair.
With minimal practice you can play 'spook music' rivaling anything
heard in sci fi genres or by the Beach Boys.
*In American practice at least, the local oscillator (LO) frequency is
pretty much standardized as 455 khz, which means it tracks 455 khz
above the received signal. F'rinstance, if you're listening to a
station at 900 on the dial, the set's LO is running at 1355khz.
.

User: "Androcles"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 10:37:17 AM

"oldcoot" <oldcoot7074@sbcglobal.net> wrote in message
news:d3ddc67b-20b7-4cff-899a-f8e646cdcb96@i7g2000prf.googlegroups.com...
: Speaking of heterodynes, there's a clever stunt anyone can do using
: radio frequencies instead of acoustics. It's a quick-and-dirty
: 'Theremin' using three broadcast-band radios:
:
: Radio# 1 is set to any *blank spot* in the upper end of the band,
: anywhere around 1300-1600 khz. It is now prepared to receive on that
: 'clear channel'.
:
: Radio# 2 is *manually tuned* (not digital) and is the "transmitter".
: It is placed in close proximity to Radio# 1 for close coupling. Back-
: to-back usually gives the strongest coupling. Tune Radio# 2 slowly
: through the lower portion of the band until its local oscillator* (LO)
: is heard as a strong 'rushing' sound on Radio#1. Leave it set on that
: spot. This unmodulated carrier is now the victim of our
: attention. :-)
:
: Radio# 3 is a Walkman type, also *manually tuned* (not digital). It is
: brought into close proximity to Radio# 2 for close coupling. Tune it
: slowly thru the lower portion of the band until its LO is heard as a
: whistle 'beating' (heterodyning) against Radio# 2's LO. Tune for zero
: beat. You'll hear a a "Weeeoooop..." as the tone approaches zero
: beat. Now you can play the 'Theremin'.
:
: Squeeze and massage Radio# 3 (the Walkman), which causes its LO
: frequency to vary enough to produce a large, warbling shift of the
: beat note, which is heard on Radio# 1. 'Tremolo' (amplitude shift) is
: done by rapidly moving the Walkman away from / toward the other pair.
: With minimal practice you can play 'spook music' rivaling anything
: heard in sci fi genres or by the Beach Boys.
:
: *In American practice at least, the local oscillator (LO) frequency is
: pretty much standardized as 455 khz, which means it tracks 455 khz
: above the received signal. F'rinstance, if you're listening to a
: station at 900 on the dial, the set's LO is running at 1355khz.
Yes, the LO tracks to produce a constant frequency for the IF
amplification stage prior to detection of the audio signal.
No matter what station the radio is tuned to, the IF strip only
sees one frequency (which is why heterodyning is done, of course).
Interesting that moving the Walkman rapidly is producing Doppler
shift, so it is motion dependent and not position dependent.
.

User: "oldcoot"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 11:34:14 AM

On Jan 3, 8:37=A0am, "Androcles" <Engin...@hogwarts.physics_c> wrote:

Interesting that moving the Walkman rapidly is producing Doppler
shift, so it is motion dependent and not position dependent.

No, the effect is not Doppler at this small scale. The 'tremolo' is
just amplitude shift caused by varying distance.
The frequecy shift of the Walkman's LO is due to
minute component movements caused by squeezing/'massaging' the
Walkman.
.

User: "Androcles"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 01:02:43 PM

"oldcoot" <oldcoot7074@sbcglobal.net> wrote in message
news:0586ea96-1dc7-47db-9eff-7e36d4c792e1@d4g2000prg.googlegroups.com...
On Jan 3, 8:37 am, "Androcles" <Engin...@hogwarts.physics_c> wrote:

Interesting that moving the Walkman rapidly is producing Doppler
shift, so it is motion dependent and not position dependent.

User: "John Larkin"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 10:24:30 AM

On Thu, 03 Jan 2008 08:41:20 GMT, "Androcles"
<Engineer@hogwarts.physics_c> wrote:

"greysky" <greysky@sbcglobal.net> wrote in message
news:Kn%ej.2661$pr6.738@nlpi070.nbdc.sbc.com...
: One night I fell asleep while watching the late movie and when I woke up,
: the channel had gone off the air, and there was the usual pattern of
: circles on the tv, along with a rather annoying steady tone. Curious to
see
: how close I could whistle and perhaps match the tone from the TV, I
noticed
: a quite clear heterodyne tone produced in my ears. The third tone would
: start out low (or was it high, I can't quite remember because this was 25
: years ago) and would increase in frequency the closer I got to the center
: frequency. The next day I asked my physics professor about the human ear's
: ability to produce a heterodyne in this manner, and he stated flat out
that
: it was impossible. Now, I wasn't gonna argue with the guy because finals
: were going to start and he held my grade in his hands and he was a bit of
a
: hothead.... but I couldn't figure out why he thought it wsa impossible.
: Since then I've asked around a few more times, butthe general idea ws that
: the human ear could not produce a heterodyne signal - yet I quite clearly
: remember how easily my ears created one. Now, 25+ years later, my ears are
: not as good as they one were - tinnitus, some frequency selective
deafness,
: and general ageism have taken their toll and I can no longer produce the
: heterodyne signal. So does anyone have any theories as to whether the
human
: ear can produce a heterodyne signal? If you are a young'un I innvite you
to
: do this experiment for yourself. All you need is a steady tone and the
: ability to whistle. Use a tone generator set to about 1.5 Kilocycles
coming
: from a single speaker 3 - 5 meters away. Begin to whistle and slowly try
to
: match the tone generator and then go a bit higher and lower. You should
: clearly be able to hear a third tone -the beat frequency- varying as the
: inverse of your whistled tone. Give it a try and tell us your results...
:
: Greysky

The tinnitus is a defect in the nervous system, the nerve ending is sending
a false signal to the brain. Frequency selective deafness is a result of
fine hairs in the cochlea breaking off. It is these hairs that vibrate in
sympathy (resonate) with the sound and stimulate the nerve endings.
They fracture with age and with use.
Your physics teacher was right, ears do not whistle. Perhaps
he misunderstood your question as I first did, I had it to read
it through twice because you seem to imply that the ear causes
sound to be emitted.

google "SOAE" and you'll fine stuff like...
http://www.otoemissions.org/definitions/SOAE.html
John
.

User: "Androcles"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 10:54:59 AM

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:603qn3pnnac6obb3gv1vktdf6h53c90gdn@4ax.com...
: On Thu, 03 Jan 2008 08:41:20 GMT, "Androcles"
: <Engineer@hogwarts.physics_c> wrote:
:
: >
: >"greysky" <greysky@sbcglobal.net> wrote in message
: >news:Kn%ej.2661$pr6.738@nlpi070.nbdc.sbc.com...
: >: One night I fell asleep while watching the late movie and when I woke
up,
: >: the channel had gone off the air, and there was the usual pattern of
: >: circles on the tv, along with a rather annoying steady tone. Curious to
: >see
: >: how close I could whistle and perhaps match the tone from the TV, I
: >noticed
: >: a quite clear heterodyne tone produced in my ears. The third tone would
: >: start out low (or was it high, I can't quite remember because this was
25
: >: years ago) and would increase in frequency the closer I got to the
center
: >: frequency. The next day I asked my physics professor about the human
ear's
: >: ability to produce a heterodyne in this manner, and he stated flat out
: >that
: >: it was impossible. Now, I wasn't gonna argue with the guy because
finals
: >: were going to start and he held my grade in his hands and he was a bit
of
: >a
: >: hothead.... but I couldn't figure out why he thought it wsa impossible.
: >: Since then I've asked around a few more times, butthe general idea ws
that
: >: the human ear could not produce a heterodyne signal - yet I quite
clearly
: >: remember how easily my ears created one. Now, 25+ years later, my ears
are
: >: not as good as they one were - tinnitus, some frequency selective
: >deafness,
: >: and general ageism have taken their toll and I can no longer produce
the
: >: heterodyne signal. So does anyone have any theories as to whether the
: >human
: >: ear can produce a heterodyne signal? If you are a young'un I innvite
you
: >to
: >: do this experiment for yourself. All you need is a steady tone and the
: >: ability to whistle. Use a tone generator set to about 1.5 Kilocycles
: >coming
: >: from a single speaker 3 - 5 meters away. Begin to whistle and slowly
try
: >to
: >: match the tone generator and then go a bit higher and lower. You should
: >: clearly be able to hear a third tone -the beat frequency- varying as
the
: >: inverse of your whistled tone. Give it a try and tell us your
results...
: >:
: >: Greysky
: >
: >The tinnitus is a defect in the nervous system, the nerve ending is
sending
: >a false signal to the brain. Frequency selective deafness is a result of
: >fine hairs in the cochlea breaking off. It is these hairs that vibrate in
: >sympathy (resonate) with the sound and stimulate the nerve endings.
: >They fracture with age and with use.
: >Your physics teacher was right, ears do not whistle. Perhaps
: >he misunderstood your question as I first did, I had it to read
: >it through twice because you seem to imply that the ear causes
: >sound to be emitted.
:
: google "SOAE" and you'll fine stuff like...
:
: http://www.otoemissions.org/definitions/SOAE.html
:
: John
How much should I fine it? Does 50 bucks sound ok?
.

User: "John Larkin"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 11:13:06 AM

On Thu, 03 Jan 2008 16:54:59 GMT, "Androcles"
<Engineer@hogwarts.physics_c> wrote:

Nobody will ever convince you of the existance of things that you are
determined to not believe. And nothing will likely ever improve my
typing. As disabilities go, I prefer mine.
John
.

User: "Androcles"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 11:47:16 AM

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:9o5qn3lvijo2j8j7r9mnuve4b85a15qpbq@4ax.com...
: On Thu, 03 Jan 2008 16:54:59 GMT, "Androcles"
: <Engineer@hogwarts.physics_c> wrote:
:
: >
: >"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
message
: >news:603qn3pnnac6obb3gv1vktdf6h53c90gdn@4ax.com...
: >: On Thu, 03 Jan 2008 08:41:20 GMT, "Androcles"
: >: <Engineer@hogwarts.physics_c> wrote:
: >:
: >: >
: >: >"greysky" <greysky@sbcglobal.net> wrote in message
: >: >news:Kn%ej.2661$pr6.738@nlpi070.nbdc.sbc.com...
: >: >: One night I fell asleep while watching the late movie and when I
woke
: >up,
: >: >: the channel had gone off the air, and there was the usual pattern
of
: >: >: circles on the tv, along with a rather annoying steady tone. Curious
to
: >: >see
: >: >: how close I could whistle and perhaps match the tone from the TV, I
: >: >noticed
: >: >: a quite clear heterodyne tone produced in my ears. The third tone
would
: >: >: start out low (or was it high, I can't quite remember because this
was
: >25
: >: >: years ago) and would increase in frequency the closer I got to the
: >center
: >: >: frequency. The next day I asked my physics professor about the human
: >ear's
: >: >: ability to produce a heterodyne in this manner, and he stated flat
out
: >: >that
: >: >: it was impossible. Now, I wasn't gonna argue with the guy because
: >finals
: >: >: were going to start and he held my grade in his hands and he was a
bit
: >of
: >: >a
: >: >: hothead.... but I couldn't figure out why he thought it wsa
impossible.
: >: >: Since then I've asked around a few more times, butthe general idea
ws
: >that
: >: >: the human ear could not produce a heterodyne signal - yet I quite
: >clearly
: >: >: remember how easily my ears created one. Now, 25+ years later, my
ears
: >are
: >: >: not as good as they one were - tinnitus, some frequency selective
: >: >deafness,
: >: >: and general ageism have taken their toll and I can no longer produce
: >the
: >: >: heterodyne signal. So does anyone have any theories as to whether
the
: >: >human
: >: >: ear can produce a heterodyne signal? If you are a young'un I innvite
: >you
: >: >to
: >: >: do this experiment for yourself. All you need is a steady tone and
the
: >: >: ability to whistle. Use a tone generator set to about 1.5 Kilocycles
: >: >coming
: >: >: from a single speaker 3 - 5 meters away. Begin to whistle and
slowly
: >try
: >: >to
: >: >: match the tone generator and then go a bit higher and lower. You
should
: >: >: clearly be able to hear a third tone -the beat frequency- varying as
: >the
: >: >: inverse of your whistled tone. Give it a try and tell us your
: >results...
: >: >:
: >: >: Greysky
: >: >
: >: >The tinnitus is a defect in the nervous system, the nerve ending is
: >sending
: >: >a false signal to the brain. Frequency selective deafness is a result
of
: >: >fine hairs in the cochlea breaking off. It is these hairs that vibrate
in
: >: >sympathy (resonate) with the sound and stimulate the nerve endings.
: >: >They fracture with age and with use.
: >: >Your physics teacher was right, ears do not whistle. Perhaps
: >: >he misunderstood your question as I first did, I had it to read
: >: >it through twice because you seem to imply that the ear causes
: >: >sound to be emitted.
: >:
: >: google "SOAE" and you'll fine stuff like...
: >:
: >: http://www.otoemissions.org/definitions/SOAE.html
: >:
: >: John
: >How much should I fine it? Does 50 bucks sound ok?
: >
: >
:
: Nobody will ever convince you of the existance of things that you are
: determined to not believe.
This is true, but not relevant. I made no statement of disbelief.
: And nothing will likely ever improve my
: typing. As disabilities go, I prefer mine.
I'm sorry to hear you are disabled but that too is irrelevant regarding
"The human ear and examples of natural heterodynes"
.

User: "John Larkin"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 12:10:35 PM

On Thu, 03 Jan 2008 17:47:16 GMT, "Androcles"
<Engineer@hogwarts.physics_c> wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:9o5qn3lvijo2j8j7r9mnuve4b85a15qpbq@4ax.com...
: On Thu, 03 Jan 2008 16:54:59 GMT, "Androcles"
: <Engineer@hogwarts.physics_c> wrote:
:
: >
: >"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
message
: >news:603qn3pnnac6obb3gv1vktdf6h53c90gdn@4ax.com...
: >: On Thu, 03 Jan 2008 08:41:20 GMT, "Androcles"
: >: <Engineer@hogwarts.physics_c> wrote:
: >:
: >: >
: >: >"greysky" <greysky@sbcglobal.net> wrote in message
: >: >news:Kn%ej.2661$pr6.738@nlpi070.nbdc.sbc.com...
: >: >: One night I fell asleep while watching the late movie and when I
woke
: >up,
: >: >: the channel had gone off the air, and there was the usual pattern
of
: >: >: circles on the tv, along with a rather annoying steady tone. Curious
to
: >: >see
: >: >: how close I could whistle and perhaps match the tone from the TV, I
: >: >noticed
: >: >: a quite clear heterodyne tone produced in my ears. The third tone
would
: >: >: start out low (or was it high, I can't quite remember because this
was
: >25
: >: >: years ago) and would increase in frequency the closer I got to the
: >center
: >: >: frequency. The next day I asked my physics professor about the human
: >ear's
: >: >: ability to produce a heterodyne in this manner, and he stated flat
out
: >: >that
: >: >: it was impossible. Now, I wasn't gonna argue with the guy because
: >finals
: >: >: were going to start and he held my grade in his hands and he was a
bit
: >of
: >: >a
: >: >: hothead.... but I couldn't figure out why he thought it wsa
impossible.
: >: >: Since then I've asked around a few more times, butthe general idea
ws
: >that
: >: >: the human ear could not produce a heterodyne signal - yet I quite
: >clearly
: >: >: remember how easily my ears created one. Now, 25+ years later, my
ears
: >are
: >: >: not as good as they one were - tinnitus, some frequency selective
: >: >deafness,
: >: >: and general ageism have taken their toll and I can no longer produce
: >the
: >: >: heterodyne signal. So does anyone have any theories as to whether
the
: >: >human
: >: >: ear can produce a heterodyne signal? If you are a young'un I innvite
: >you
: >: >to
: >: >: do this experiment for yourself. All you need is a steady tone and
the
: >: >: ability to whistle. Use a tone generator set to about 1.5 Kilocycles
: >: >coming
: >: >: from a single speaker 3 - 5 meters away. Begin to whistle and
slowly
: >try
: >: >to
: >: >: match the tone generator and then go a bit higher and lower. You
should
: >: >: clearly be able to hear a third tone -the beat frequency- varying as
: >the
: >: >: inverse of your whistled tone. Give it a try and tell us your
: >results...
: >: >:
: >: >: Greysky
: >: >
: >: >The tinnitus is a defect in the nervous system, the nerve ending is
: >sending
: >: >a false signal to the brain. Frequency selective deafness is a result
of
: >: >fine hairs in the cochlea breaking off. It is these hairs that vibrate
in
: >: >sympathy (resonate) with the sound and stimulate the nerve endings.
: >: >They fracture with age and with use.
: >: >Your physics teacher was right, ears do not whistle. Perhaps
: >: >he misunderstood your question as I first did, I had it to read
: >: >it through twice because you seem to imply that the ear causes
: >: >sound to be emitted.
: >:
: >: google "SOAE" and you'll fine stuff like...
: >:
: >: http://www.otoemissions.org/definitions/SOAE.html
: >:
: >: John
: >How much should I fine it? Does 50 bucks sound ok?
: >
: >
:
: Nobody will ever convince you of the existance of things that you are
: determined to not believe.

This is true, but not relevant. I made no statement of disbelief.

: And nothing will likely ever improve my
: typing. As disabilities go, I prefer mine.

I'm sorry to hear you are disabled but that too is irrelevant regarding
"The human ear and examples of natural heterodynes"

You chose to mention it. Most people gloss over obvious typing errors,
when the meaning is obvious in context.
John
.

User: "Androcles"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 01:02:43 PM

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:b69qn31tnuqnps8ldaan58tpg8ba83a47g@4ax.com...
: On Thu, 03 Jan 2008 17:47:16 GMT, "Androcles"
: <Engineer@hogwarts.physics_c> wrote:
:
: >
: >"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
message
: >news:9o5qn3lvijo2j8j7r9mnuve4b85a15qpbq@4ax.com...
: >: On Thu, 03 Jan 2008 16:54:59 GMT, "Androcles"
: >: <Engineer@hogwarts.physics_c> wrote:
: >:
: >: >
: >: >"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
: >message
: >: >news:603qn3pnnac6obb3gv1vktdf6h53c90gdn@4ax.com...
: >: >: On Thu, 03 Jan 2008 08:41:20 GMT, "Androcles"
: >: >: <Engineer@hogwarts.physics_c> wrote:
: >: >:
: >: >: >
: >: >: >"greysky" <greysky@sbcglobal.net> wrote in message
: >: >: >news:Kn%ej.2661$pr6.738@nlpi070.nbdc.sbc.com...
: >: >: >: One night I fell asleep while watching the late movie and when I
: >woke
: >: >up,
: >: >: >: the channel had gone off the air, and there was the usual
pattern
: >of
: >: >: >: circles on the tv, along with a rather annoying steady tone.
Curious
: >to
: >: >: >see
: >: >: >: how close I could whistle and perhaps match the tone from the TV,
I
: >: >: >noticed
: >: >: >: a quite clear heterodyne tone produced in my ears. The third tone
: >would
: >: >: >: start out low (or was it high, I can't quite remember because
this
: >was
: >: >25
: >: >: >: years ago) and would increase in frequency the closer I got to
the
: >: >center
: >: >: >: frequency. The next day I asked my physics professor about the
human
: >: >ear's
: >: >: >: ability to produce a heterodyne in this manner, and he stated
flat
: >out
: >: >: >that
: >: >: >: it was impossible. Now, I wasn't gonna argue with the guy
because
: >: >finals
: >: >: >: were going to start and he held my grade in his hands and he was
a
: >bit
: >: >of
: >: >: >a
: >: >: >: hothead.... but I couldn't figure out why he thought it wsa
: >impossible.
: >: >: >: Since then I've asked around a few more times, butthe general
idea
: >ws
: >: >that
: >: >: >: the human ear could not produce a heterodyne signal - yet I quite
: >: >clearly
: >: >: >: remember how easily my ears created one. Now, 25+ years later, my
: >ears
: >: >are
: >: >: >: not as good as they one were - tinnitus, some frequency selective
: >: >: >deafness,
: >: >: >: and general ageism have taken their toll and I can no longer
produce
: >: >the
: >: >: >: heterodyne signal. So does anyone have any theories as to whether
: >the
: >: >: >human
: >: >: >: ear can produce a heterodyne signal? If you are a young'un I
innvite
: >: >you
: >: >: >to
: >: >: >: do this experiment for yourself. All you need is a steady tone
and
: >the
: >: >: >: ability to whistle. Use a tone generator set to about 1.5
Kilocycles
: >: >: >coming
: >: >: >: from a single speaker 3 - 5 meters away. Begin to whistle and
: >slowly
: >: >try
: >: >: >to
: >: >: >: match the tone generator and then go a bit higher and lower. You
: >should
: >: >: >: clearly be able to hear a third tone -the beat frequency- varying
as
: >: >the
: >: >: >: inverse of your whistled tone. Give it a try and tell us your
: >: >results...
: >: >: >:
: >: >: >: Greysky
: >: >: >
: >: >: >The tinnitus is a defect in the nervous system, the nerve ending is
: >: >sending
: >: >: >a false signal to the brain. Frequency selective deafness is a
result
: >of
: >: >: >fine hairs in the cochlea breaking off. It is these hairs that
vibrate
: >in
: >: >: >sympathy (resonate) with the sound and stimulate the nerve endings.
: >: >: >They fracture with age and with use.
: >: >: >Your physics teacher was right, ears do not whistle. Perhaps
: >: >: >he misunderstood your question as I first did, I had it to read
: >: >: >it through twice because you seem to imply that the ear causes
: >: >: >sound to be emitted.
: >: >:
: >: >: google "SOAE" and you'll fine stuff like...
: >: >:
: >: >: http://www.otoemissions.org/definitions/SOAE.html
: >: >:
: >: >: John
: >: >How much should I fine it? Does 50 bucks sound ok?
: >: >
: >: >
: >:
: >: Nobody will ever convince you of the existance of things that you are
: >: determined to not believe.
: >
: >This is true, but not relevant. I made no statement of disbelief.
: >
: >
: >: And nothing will likely ever improve my
: >: typing. As disabilities go, I prefer mine.
: >
: >I'm sorry to hear you are disabled but that too is irrelevant regarding
: >"The human ear and examples of natural heterodynes"
: >
: >
: >
:
: You chose to mention it. Most people gloss over obvious typing errors,
: when the meaning is obvious in context.
:
: John
This is getting dreary. Over and out.
.

User: "John Larkin"
Title: Re: The human ear and examples of natural heterodynes	03 Jan 2008 03:26:59 PM

On Thu, 03 Jan 2008 19:02:43 GMT, "Androcles"
<Engineer@hogwarts.physics_c> wrote:

OK, but google the SOAE stuff. Ears can produce sounds.
John
.

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