| Author |
Message |
Rich Grise
Guest
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 Posted:
Sun Feb 13, 2005 5:18 am Post subject:
Re: Speakers for High Frequency Sound |
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On Sat, 12 Feb 2005 14:04:49 -0800, pooua wrote:
| Quote: | You make good points, Jay. Please understand, though, that after 40
years of almost every person I've met (and I've worked with electronic
techs, too) telling me that they don't hear anything at the same time
that I hear a screaching loud sound, it is difficult for me to accept
that now everyone hears this sound.
|
DO YOU HEAR THAT NOISE WHEN THE TV IS OFF?????????
Will you please answer that question?
Three days now, you've been annoying people with speculation about what
that ringing in your ears is - TURN THE DAMN TV OFF! And _THEN_ see if
you still hear the ringing. If you do, you need medical attention.
Good Luck!
Rich
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Rich Grise
Guest
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| Posted:
Sun Feb 13, 2005 5:27 am Post subject:
Re: Speakers for High Frequency Sound |
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On Sat, 12 Feb 2005 12:38:29 -0800, pooua wrote:
| Quote: | if you look at a really shocking number of
commercial CD releases, you'll see a visible
peak at the video sweep frequency from
some monitor in the studio leak into something.
I've noticed several times over the last year that when I watch movies,
I hear the "television pitch" turn on during the movie. Usually, that
pitch is associated with specific angles in a scene. At first, I
noticed it just in horror movies, right when the spooky scenes begin. I
wondered if someone was using subliminal sound to make viewers tense.
But then I began to notice it in other types of movies and at times
when the movie wasn't supposed to be scary.
|
They can do amazing things with speaker systems in movie theaters these
days. Whenever I go to the movies around here, I go to the local AMC 20.
They're almost obsessive about quiet - they don't blast the viewers with
noise, even in loud scenes. It's no louder than, say, a live concert.
Anyway, just before they start the feature, they have a short-short of
some people in a crucial situation where quiet is absolutely necessary -
variously on a submarine, or some Indian hunting party that if they don't
get the buffalo, they're all going to starve - and a cellphone rings. The
ring is on the sound track, but the way they do the surround sound it
sounds exactly like some cell phone in the audience ringing. Everybody in
the scene turns and looks out at the audience, and and one says to
another, "It's in the audience." The point, of course, being "TURN OFF
YOUR CELLPHONE!"
Cheers!
Rich
n.b.: I don't work for AMC, I'm just a happy customer. :-) |
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Guest
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| Posted:
Sun Feb 13, 2005 5:28 am Post subject:
Re: Speakers for High Frequency Sound |
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| Quote: | DO YOU HEAR THAT NOISE WHEN THE TV IS OFF?????????
Will you please answer that question?
|
Sure.
No.
I said that I could hear the sound when someone turns on a TV. That
should imply that I don't hear it when the TV is off.
| Quote: | Three days now, you've been annoying people with speculation about
what
that ringing in your ears is - TURN THE DAMN TV OFF! And _THEN_ see
if
you still hear the ringing. If you do, you need medical attention.
|
I'm sorry that I've annoyed you. I have to say that I have found some
of the replies to my posts interesting and maybe even useful.
Thanks.
|
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Phil Allison
Guest
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| Posted:
Sun Feb 13, 2005 6:11 am Post subject:
Re: Speakers for High Frequency Sound |
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"John Woodgate"
| Quote: | The horizontal scan frequency of around 15.75 kHz is
'one frequency', but the waveform you hear is not sinusoidal; it is
quite rich in harmonics. Probably, the odd-order harmonics predominate.
Maybe I can measure it for you (on a British TV), but not tonight,
Josephine.
|
** I just did some tests with a condenser mic ( AKG CK2 omni + pre-amp )
on my PC - when viewing the output from a 60 dB gain mic pre on a scope I
immediately saw a high frequency sound buried in the LF room noise. Then I
added a parallel LC filter ( broadly resonant at 40 kHz) across the preamp
output and that cleaned it up allowing a frequency counter to lock on.
I thought it must be from the monitor until I saw the frequency was 30.723
kHz - while the monitor runs at 48.4 kHz.
Switched off the monitor - no change.
I found the tone was stronger near the ventilation slots on the PC case but
strongest if the mic was placed on the open CD rom drawer and pointed into
the box. The frequency is very steady while the SPL is critical on the
*exact* mic position - ie there are standing waves galore. I reckon it is
coming from either the main PSU or the HDD.
The sound would be around 50 dB SPL when on the CD rom drawer - and no, I
cannot hear it.
................. Phil |
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Guest
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| Posted:
Sun Feb 13, 2005 6:11 am Post subject:
Re: Speakers for High Frequency Sound |
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| Quote: | I found the tone was stronger near the ventilation slots
on the PC case but strongest if the mic was placed on
the open CD rom drawer and pointed into the box. The
frequency is very steady while the SPL is critical on the
*exact* mic position - ie there are standing waves
galore. I reckon it is coming from either the main PSU
or the HDD.
|
I did a quick Google search, and found that there are a lot of things
in a computer that would operate at 30.72 kHz.
"A bi-directional horizontal scanner must have a scanning frequency of
30.72 [kHz] to achieve SVGA resolution with a 60 [Hz] frame rate."
http://www.hitl.washington.edu/publications/tidwell/ch9.html
Also, several computer switching power supplies operate at 30.72 kHz.
The bearings in the hard drive produce a wide spectrum of noise,
especially on the high end. When their pitch drops down enough for it
to bother most people, it means the bearings are about to go out (from
my experience, that's true of your car's alternator as it is of your
computer's hard drive, and they both sound the same when they go bad). |
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Phil Allison
Guest
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| Posted:
Sun Feb 13, 2005 6:11 am Post subject:
Re: Speakers for High Frequency Sound |
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|
<pooua@aol.com>
** Hey - learn to quote properly !!!!!!
| Quote: | Phil Allison
I found the tone was stronger near the ventilation slots
on the PC case but strongest if the mic was placed on
the open CD rom drawer and pointed into the box. The
frequency is very steady while the SPL is critical on the
*exact* mic position - ie there are standing waves
galore. I reckon it is coming from either the main PSU
or the HDD.
I did a quick Google search, and found that there are a lot of things
in a computer that would operate at 30.72 kHz.
"A bi-directional horizontal scanner must have a scanning frequency of
30.72 [kHz] to achieve SVGA resolution with a 60 [Hz] frame rate."
http://www.hitl.washington.edu/publications/tidwell/ch9.html
|
** Got zero to do with what is inside a standard PC case.
| Quote: | Also, several computer switching power supplies operate at 30.72 kHz.
|
** " I reckon it is coming from either the main PSU or the HDD. "
| Quote: | The bearings in the hard drive produce a wide spectrum of noise,
|
** But not this one.
................ Phil
.............. Phil |
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Scott Dorsey
Guest
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| Posted:
Sun Feb 13, 2005 6:11 am Post subject:
Re: Speakers for High Frequency Sound |
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In article <1108241089.437689.216900@c13g2000cwb.googlegroups.com>,
<pooua@aol.com> wrote:
| Quote: | How likely is it that a TV produces sound at more than one frequency?
|
Very likely, but the sweep will be the loudest one. It will also produce
harmonics of the sweep (which you won't be able to hear) and some other
noises (especially modern TV sets which tend to have switching supplies
running at their own frequencies, rather than scan-derived supply voltages
for everything like older sets).
The Bruel and Kjaer 2804 microphone power supply whistles very audibly
around 18 KHz from the little switcher in there. Potting the transformer
in RTV helps a little bit. But it drives me up the wall since the supply
is normally close enough to the mikes that the sound gets picked up.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis." |
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Scott Dorsey
Guest
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| Posted:
Sun Feb 13, 2005 6:11 am Post subject:
Re: Speakers for High Frequency Sound |
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<pooua@aol.com> wrote:
| Quote: | You make good points, Jay. Please understand, though, that after 40
years of almost every person I've met (and I've worked with electronic
techs, too) telling me that they don't hear anything at the same time
that I hear a screaching loud sound, it is difficult for me to accept
that now everyone hears this sound.
|
Lots of electronic techs are deaf too. TV sweep is not subtle at all.
I had a noise on a Nagra III recorder once, and I couldn't tell if it
was brush noise (not to worry about) or bearing noise (to worry about).
I took it to the US service operation and nobody there could hear it.
A couple decades later, it's still making that sound, and it still
is annoying.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis." |
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John Fields
Guest
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| Posted:
Sun Feb 13, 2005 6:11 am Post subject:
Re: Speakers for High Frequency Sound |
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On 12 Feb 2005 12:18:13 -0800, pooua@aol.com wrote:
| Quote: | One very important assumption you are making that is likely
to be wrong is that no human can hear very much above
20 kHz.
[snip]
there is no physical mechanism that would prevent a human
from hearing higher frequencies.
---
Yes, there is. The mass of the tympanic membrane and the
sensitivity of the cochlear cilia.
The tympanic membrane (the eardrum) can be bypassed;
---
Yes, but we're talking airborne sound here, aren't we?
Must all perceived airborne sounds pass through the eardrum? I don't
believe so. I know that nerve conduction is sometimes explained as
physical contact through the skull, but I have always taken that as an
example, not as a limitation.
|
---
IOW, you don't want to be burdened with facts.
If you were underwater and a transducer was pumping 15kHz energy into
the water, (a medium which much more closely approaches the density of
the human body) then you could claim bone conduction, but in air at
the intensities which would typically come from magnetostriction
causing dimensional changes in a horizontal output transformer, I
think not.
---
| Quote: | I think we can hear airborne sounds (especially if they are intense)
without the eardrum.
|
---
Certainly it's possible, but at the frequencies and intensities you're
experiencing, it's not likely. I think what's more likely is that
you're experiencing an exaggerated example of the cocktail party
effect, especially if your statement that you can pick out individual
flutes in the flute section of an orchestra is true.
---
| Quote: | But, what are the limits of the cochlear cilia? Certainly there
are animals that can hear higher frequencies, and they use
the same basic equipment as humans do.
---
Yes, in the sense that Ferraris and Fords are both cars. _But_ we're
not discussing non-human hearing, are we?
At the moment, we are discusing physical limitations of humans hearing
higher frequencies, as opposed to differences in biological species.
The fact that there are animals that can hear higher frequencies than
20 kHz strongly implies that there is not a physical limitation on
humans hearing higher than 20 kHz. The limit is not physical, but
specific.
|
---
That's ridiculous. We're humans and the limitations on our hearing
are physical and based on what our bodies have adapted to. If they're
not physical, to what would you attribute the limitations?
---
| Quote: | It would then be possible for someone with an out-of-spec
hearing apperatus to hear higher than 20 kHz, even if no one else
could.
|
---
Yes, but then _their_ limitations would still be physical. A thinner
tympanic membrane could, conceivably, vibrate faster than a thicker
one and transmit the vibrations, with less attenuation than normal, to
the auditory ossicles which could, conceivably, be less massive and
transmit, with less attenuation than normal, the more frequent
vibrations into the cochlea, which could, conceivably, enclose cilia
which could, conceivably, be thinner, shorter, or whatever would be
required to make them be able to respond to the faster vibrations and
send their signals into the eighth nerve into the brain for
processing. Notice that everything leading up to the excitation of
the cochlear cilia is mechanical and it should be clear, even to you,
that the limitations imposed on our auditory system and, indeed, the
auditory systems of any species is physical.
---
| Quote: | An analogous situation would be Vitamin C production. There is no
physical limitation that would prevent humans from producing their own
Vitamin C. Lots of animals produce their own Vitamin C, and they have
the same basic machinery as we do for doing so. We can't, because of a
mutation that shut down the genes necessary for Vitamin C production,
but we still have the genes, and they could be re-activated. Besides,
there are humans who are able to produce enough Vitamin C through
spontaneous oxidation to keep them alive without an external supply.
|
---
Fuck vitamin C production, we're talking about acoustics.
---
| Quote: | I've done work trying to determine whether the nonlinearity of the
auditory system will allow beat notes which occur as a result of
exposure to the ear of ultrasonic signals which should result in
heterodynes being generated which can be heard, are heard
and, so far, the results have been negative. That is, if the ear is
exposed to a pair of frequencies, both of which are frequencies
higher than can be heard, the beat note won't be heard either.
That is interesting in its own way, but I don't believe that is
directly applicable in this case. The sensitive person may not be
hearing a beat note.
---
Of course it's applicable. The question you posed was whether there
was any physical limitation on human hearing and I gave the the
tympanic membrane and the cochlear cilia as examples. I further cited
the heterodyne experiment as an example which indicated that if the
low-frequency beat note generated by two ultrasonic signals being
mixed in the ear wasn't being heard, then in all likelihood the
physical structure of the ear was preventing the high frequency
signals from propagating to the point where they could be mixed,
preventing the beat note from being heard.
We already know that if a person cannot hear ultrasound, they could not
hear the beat note from that pitch.
|
---
I arrived at that conclusion from the results of my own work, but if
you have evidence of prior discovery I'd like to hear about it. Can
you cite a reference to support your statement?
---
| Quote: | The beat note is a perception
generated in the brain from sounds it hears. There is no wave present
at the beat frequency.
|
---
Au contraire! Outside of the brain, take two sinusoidal signals, f1
and f2, multiply them, and the result will be that two new signals
will be generated: f1+f2 and f1-f2. A filter will be needed to
isolate the desired signal from the melee in which it exists, and
that's the job of the brain, _but_ after the multiplication, that wave
will exist whether it can be detected or not.
---
| Quote: | [snip]
All the more reason to set up a test and measure it directly. I hate
this guesswork.
---
Then do it. It should be easy enough, just an electret microphone and
an oscilloscope ought to do it.
I am capable of hearing the sound I want to identify, and oscilloscopes
are expensive. A microphone will pick up sounds, but how would I know
if it is picking up the same sound that I hear? I'm sure that TVs
produce sound at more than one frequency.
What I need is something that will generate a calibrated tone that I
can adjust until it matches the pitch I hear from a television. Then I
will know that the two sounds are the same, and I will be able to
determine the frequency. Additionally, it costs a lot less money to
generate the audio signal.
|
---
You're assuming that the sound you hear is a simple sinusoidal signal.
It isn't, and depending on what you mix with it, what you interpret as
being the same frequency may well be something other than that.
---
| Quote: | I can also hear LCD screens, but that's at a lower pitch,
I think, and they are much quieter. I first noticed it when I
was in a nature park. It was very quiet outside, so as I
raised my digital camera up to take a picture, I could
distinctly hear the LCD screen.
---
you may have crosstalk between your vision and auditory systems.
---
I suppose you would need to run a test to find out for certain?
---
Yes, but _you_ would, not I...
I already satisfied myself that I am hearing the sound. You are the one
who is questioning whether I do or not.
|
---
Not at all. I'm sure that you're hearing something, and all I'm
suggesting is that you get tested in order to determine whether there
might be a link between your visual and auditory systems which causes
you to hear what you see.
Just as an aside, you might want to think about how much 15.75kHz
your mom and dad were exposed to before you were born.
---
| Quote: | Now I am taking a college class in a room that has
3 television sets suspended from the ceiling. One
man saw me putting earplugs in my ears, and
asked if I could hear the televisions. It turned out
that he is able to hear some televisions (the one in
his college dorm), but he could not hear the
televisions in the classroom. As far as I can tell, I
am the only person in the room who hears those televisions.
---
It might be instructive to determine whether you can "hear" the
monitors with your eyes closed.
I absolutely could hear the monitors with my eyes closed.
[snip]
---
Ok, but I don't understand the point of all of this.
I am looking for a speaker that will produce sound waves from 12 kHz to
50 kHz.
|
---
That's easy. I have, on hand, several transducers which can do that.
Wanna buy one or two?
---
| Quote: | I would like to find out what frequency of sound I am hearing from a
television set.
|
---
That's a little more difficult, and from the attitude you've displayed
so far it seems there's little chance you'd defer to what you would
consider to be an opinion different from your own.
---
| Quote: | The sound I hear is not imaginary or merely a psychological effect.
|
---
How do you know that's true?
---
| Quote: | I actually hear a very loud sound that most people of any age report they
have never heard. I am curious what this sound is, and why I am able to
hear it so well when so few other people can.
|
---
Maybe you're just special?
--
John Fields |
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Paul Stamler
Guest
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| Posted:
Sun Feb 13, 2005 2:37 pm Post subject:
Re: Speakers for High Frequency Sound |
|
|
<pooua@aol.com> wrote in message
news:1108245889.496045.275540@c13g2000cwb.googlegroups.com...
| Quote: | You make good points, Jay. Please understand, though, that after 40
years of almost every person I've met (and I've worked with electronic
techs, too) telling me that they don't hear anything at the same time
that I hear a screaching loud sound, it is difficult for me to accept
that now everyone hears this sound.
|
Electronic techs and recording engineers aren't the same thing. The folks
who hang out on this newsgroup are people whose job (paid or unpaid) it is
to listen very carefully to things. And we notice the high-pitched
squealing. I noticed it for the first time when I was nine, and we got our
first (B&W) television set. I don't hear it as much any more, because my
hearing isn't as sensitive as it used to be up there.
Is it possible you're hearing something other than the 15xxx Hz horizontal
sweep frequency? Yes. But it's not particularly likely, because THE
HORIZONTAL SWEEP FREQUENCY IS THERE. Known to be there, to a greater or
lesser degree, on damn near every television set made. There's a chance that
you're hearing other things, that you can hear >20kHz better than most
people, but the overwhelming *likelihood* is that you're hearing the
horizontal sweep frequency.
(If I had to guess, I'd say you have some sort of resonance going on in your
hearing apparatus that makes it unusually sensitive to tones at or near that
frequency, and that's why it's so easily audible, and why it's so annoying.)
So...Let's say you find out it's the horizontal sweep frequency, or
something else up there, after spending money for an oscillator, amplifier
and speaker, or whatever test gear you decide to use, then what? Knowing the
exact frequency you're hearing plus-or-minus a Hz won't make it any less
annoying. If I were spending money, rather than chase after numbers that
would satisfy my intellectual curiosity but not ease my discomfort, I'd put
the bucks into getting a set of really good, custom-fitted earplugs.
Peace,
Paul |
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Arny Krueger
Guest
|
| Posted:
Sun Feb 13, 2005 5:08 pm Post subject:
Re: Speakers for High Frequency Sound |
|
|
<pooua@aol.com> wrote in message
news:1108239493.320200.308470@c13g2000cwb.googlegroups.com
| Quote: | I am looking for a speaker that will produce sound waves from 12 kHz
to 50 kHz.
|
http://www.d-s-t.com/vifa/data/xt25tg30-04a.htm
http://www.madisound.com/vifa.html XT25TG30-04 $53.50
I've measured several samples, they do what the charts show. |
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Arny Krueger
Guest
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| Posted:
Sun Feb 13, 2005 5:10 pm Post subject:
Re: Speakers for High Frequency Sound |
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|
<pooua@aol.com> wrote in message
news:1108245889.496045.275540@c13g2000cwb.googlegroups.com
| Quote: | You make good points, Jay. Please understand, though, that after 40
years of almost every person I've met (and I've worked with electronic
techs, too) telling me that they don't hear anything at the same time
that I hear a screeching loud sound, it is difficult for me to accept
that now everyone hears this sound.
|
It's just a matter of speaking to the *right* people. This whole topic is
well-known and been around *forever* I think the first time I read about it
was in a copy of Popular Electronics in the late 1950s. |
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mike
Guest
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| Posted:
Sun Feb 13, 2005 5:18 pm Post subject:
Re: Speakers for High Frequency Sound |
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|
Phil Allison wrote:
| Quote: | pooua@aol.com
** Hey - learn to quote properly !!!!!!
Phil Allison
I found the tone was stronger near the ventilation slots
on the PC case but strongest if the mic was placed on
the open CD rom drawer and pointed into the box. The
frequency is very steady while the SPL is critical on the
*exact* mic position - ie there are standing waves
galore. I reckon it is coming from either the main PSU
or the HDD.
I did a quick Google search, and found that there are a lot of things
in a computer that would operate at 30.72 kHz.
"A bi-directional horizontal scanner must have a scanning frequency of
30.72 [kHz] to achieve SVGA resolution with a 60 [Hz] frame rate."
http://www.hitl.washington.edu/publications/tidwell/ch9.html
** Got zero to do with what is inside a standard PC case.
Also, several computer switching power supplies operate at 30.72 kHz.
** " I reckon it is coming from either the main PSU or the HDD. "
The bearings in the hard drive produce a wide spectrum of noise,
|
I've had some luck with a sound level meter hooked to a scope.
Have to get one with selectable weighting, cause the standard A
weighting used for industrial noise study etc. rolls off too fast.
I can get enough signal for tracing well above the normal frequency
range and well below the level that can produce a meter reading.
Another interesting toy is an ultrasonic frequency translator.
Used for leak detection and bearing noise detection.
Mine's made by GoPro, whoever they are.
There's a LOT of high frequency stuff coming out of my TV that I can't hear.
FWIW, I've never been able to correlate ultrasonic bearing noise coming
out of a hard drive with failure. Ideas?
mike
--
Return address is VALID.
Wanted, PCMCIA SCSI Card for HP m820 CDRW.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
http://nm7u.tripod.com/homepage/te.html
Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
Bunch of stuff For Sale and Wanted at the link below.
http://www.geocities.com/SiliconValley/Monitor/4710/ |
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Scott Dorsey
Guest
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| Posted:
Sun Feb 13, 2005 8:03 pm Post subject:
Re: Speakers for High Frequency Sound |
|
|
In article <420F377E.3070207@netscape.net>, mike <spamme0@netscape.net> wrote:
| Quote: |
FWIW, I've never been able to correlate ultrasonic bearing noise coming
out of a hard drive with failure. Ideas?
|
There is a recent paper on the subject in Sound and Vibration. Basically if
you plot the spectrum, you'll see one big peak at the rotational frequency and
a bunch of sidebands. When the sidebands get bigger and bigger and farther
from the fundamental peak, the drive is starting to fail.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis." |
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Tommi M.
Guest
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| Posted:
Sun Feb 13, 2005 9:51 pm Post subject:
Re: Speakers for High Frequency Sound |
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|
"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:LqqdnSQSBe9hbZDfRVn-hQ@comcast.com...
| Quote: | The mistake appears to be thinking that the limit of HF hearing is one
number that does not vary with the details and nature of the test.
|
Does this mean that any single person doesn't have a strict HF hearing
limit? If you have any links or info on that, I'd certainly be interested.. |
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