Speakers for High Frequency Sound

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In article <1108241089.437689.216900@c13g2000cwb.googlegroups.com>,
pooua@aol.com says...
> How likely is it that a TV produces sound at more than one frequency?

Much less likely than when you post and say "My TV produces a really
high-pitched sound", and a whole bunch of people who work daily with
video and audio tell you that they, too, hear the high-pitched sound,
and tell you the exact frequency, and tell you the precise explanation
for what generates the sound, and their explanation in no way fails to
describe what you're hearing, that they're all talking about a different
sound.

If you want to do the experiment for experiment's sake, you should do
it. It's not a bad entry into the world of audio measurement, and a
curious itch is one you should always scratch. But it's pointless to
keep saying "Yeah, but it sounds higher", ignoring that pitch
discrimination at the edges is practically nonexistent, and coming up
with theoretical possibilities as to how it could possibly be higher,
and how if it were you could possibly theoretically hear it without
simultaneously noticing the very obvious pitch an octave or two lower
that we're all talking about.

--
Jay Levitt |
Wellesley, MA | Hi!
Faster: jay at jay dot eff-em | Where are we going?
http/www.jay.fm | Why am I in this handbasket?

 

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<pooua@aol.com> wrote in message
news:1108170172.822645.33210@c13g2000cwb.googlegroups.com...

> I am certain that just about any commercial audio signal generator is
> going to be callibrated well enough to distinguish the frequency I
> hear. It isn't that difficult to make a stable signal (particularly in
> commercial test equipment, which is what the signal generator is).

A much better way to measure it is with a small-diaphragm measuring
microphone, a preamp (most cheap ones will work) and a frequency counter. Or
do what the guy a few dozen posts back suggested: look at an oscilloscope.
Trying to match frequencies with an oscillator is less accurate than either
of those methods. And when you're done, odds are overwhelmingly in favor of
your result being equal to the horizontal sweep frequency of your TV system,
wherever you are.

> But, this is nothing. I would spend over a thousand dollars to test
> some of the other things about myself that I want to test. In
> particular, I can generate a sensation like electricity throughout my
> body, at will. I don't know what that is, but I would like to find out.
> As in, I would spend a thousand dollars to find out.

Make an appointment with a neurologist, or visit a friendly dept. of
neurology at your local medical school and ask someone how this works. It
might take graduate-level courses to understand the answers, which would
probably be the best use of the thousand bucks if that's what you want to
spend it on. Me, I'd buy season tickets for the symphony, if they weren't
locked out.

Peace,
Paul

 

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"George Gleason" <g.p.gleason@worldnet.att.net> wrote in message
news:NwmPd.197878$w62.65230@bgtnsc05-news.ops.worldnet.att.net...
>
> It sounds like a defect in his hearing, imagine if someone could see
> outside one octave of visual information
> that would also be considered abnormal, and actually possibly harmful to
> their existence

Some people can. Folks who have had certain kinds of cataract surgery no
longer filter out UV, and their retinas are sensitive, so they can see
things other people can't. Not much real harm, and most of the time they
wear glasses with UV filters in them. I'm told that during World War II
people who'd had that kind of surgery were used by British spy services;
they'd hang out on ships off the coast of occupied Europe, and spies would
flash signals to them using flashlights that emitted only UV. They could see
it, others couldn't. (I've always wondered whether the story was urban
legend, since the slightest fog or haze would cut the UV level drastically,
and the North Sea and English Channel are always well-supplied with both.)

"Fog in Channel -- continent isolated!"

Peace,
Paul

 

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> I am looking for a speaker that will produce sound waves from 12 kHz to
> 50 kHz.
>
>
Ribbon HF drivers can easily do that
contact SLS loudspeakers
they can sell you a unit for about 100$ that will go to 40K
george

 

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I read in sci.electronics.design that pooua@aol.com wrote (in <110824108
9.437689.216900@c13g2000cwb.googlegroups.com>) about 'Speakers for High
Frequency Sound', on Sat, 12 Feb 2005:

>How likely is it that a TV produces sound at more than one frequency?
>
Both 0% and 100%. 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.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http/www.jmwa.demon.co.uk Also see http/www.isce.org.uk

 

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> 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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On Sat, 12 Feb 2005 12:27:12 -0800, pooua wrote:
[and excised all attribution]

>>>It does not at all tell us that no one could hear
>>>higher frequencies than 20 kHz.
>
>>That's a different question.
>
> It's the same question. Someone said that humans cannot hear above 20
> kHz. I said there is no physical mechanism that prevents them from
> hearing higher frequencies.

Well, then, what you said is wrong. Of course there's a physical mechanism
that prevents humans from hearing higher frequencies. The mechanism of the
eardrum itself, as well as the limit of the "shortness" of the cochlear
cilia. And don't forget the inertia of the malleus, incus, and stapes, and
the resonance of the sinuses and eustachian tubes, and the mass and
resonant frequency of the skull itself, and the massive amount of damping
afforded by all of that soft tissue.

>You were not
>addressing the same subject as
> we had been discussing.

Hope I cleared that up!

>>There are some pretty obvious ways to find
>>people who can hear frequencies above 20 KHz.
>>One is to simply jack up the intensity, and another
>>is to use young people whose ear structures are
>>simply smaller.
>
> So, there are people who can hear above 20 kHz. That is the point I am
> making.

OK, there are people at the extremities of the bell-shaped curve.

So, other than that, do you have a point?

Thanks,
Rich

 

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On Sat, 12 Feb 2005 08:35:36 +0000, John Woodgate wrote:

> I read in sci.electronics.design that William Sommerwerck
> <williams@nwlink.com> wrote (in <110qinrklm6ss4b@corp.supernews.com>)
> about 'Speakers for High Frequency Sound', on Fri, 11 Feb 2005:
>
>>If humans can hear it, it can't possibly be at 40kHz, because the best
>>human hearing extends to only a bit above 20kHz.
>
> Some young children can hear at least up to 40 kHz. I've done the tests.

I took a hearing test once while high on drugs, and had trouble
distinguishing the test tone from the ringing in my ears that was there
presumably from the drugs. When the test was complete, the young nurse
looked at the readout, and said, "Well, it's kind of erotic..." That
is, she mispronounced "erratic", but at that point I kind of lost track...
%-}

Cheers!
Rich

 

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On Sat, 12 Feb 2005 07:05:24 -0500, Arny Krueger wrote:
>
> 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.

That's a mistake that is very broadly applied. The idea that everybody is
supposed to fit into the same box. "Oh, numbers don't match? Take a pill
and conform!"
--
The Pig Bladder From Uranus, Still Waiting for
Some Hot Babe to Ask What My Favorite Planet Is.

 

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On Sat, 12 Feb 2005 14:04:49 -0800, pooua wrote:

> 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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In article <1108241089.437689.216900@c13g2000cwb.googlegroups.com>,
<pooua@aol.com> wrote:
>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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<pooua@aol.com> wrote:
>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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<pooua@aol.com> wrote:

> They should have tested you with more than just headphones. The
> headphones measure eardrum response. The nerve conduction test is done
> through the skull. When they tested me for nerve conduction, I wore a
> loop with a mass at either end (I did not get a good look at it). One
> end was placed ahead of my left ear a few inches, and the other end
> was behind my right ear an inch or two.

I've only heard the term "bone conduction", not "nerve conduction."

there's also otoacoustic emissions testing, which exploits the ear's
acoustic impedance matching mechanism. but AFAIK it isn't used for
threshold testing.

--
Aaron J. Grier | "Not your ordinary poofy goof." | agrier@poofygoof.com
The United States is the one true country. The US is just. The US
is fair. The US respects its citizens. The US loves you. We have
always been at war against terrorism.

 

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<pooua@aol.com> wrote in message
news:1108239493.320200.308470@c13g2000cwb.googlegroups.com

> 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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<pooua@aol.com> wrote in message
news:1108245889.496045.275540@c13g2000cwb.googlegroups.com

> 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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On 12 Feb 2005 21:58:58 -0800, pooua@aol.com wrote:

>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

I think you've possibly misinterpreted this.

You obviously have a scientific intent. Science's most basic tenet is
to ruthlessly shed extra BS. IMO that category would include much
of the polemic that's been cross-posted into r.a.p. Ideaologies
run deep,(and even deeper, apparently, in some newsgroups).

Please don't be dissuaded from your exploration by polemics, by
others' prejudices or by a priori models.

The map is not the world. Science is the search for the map. No
scientist pretends to know the world.

Good fortune in your exploration,

Chris Hornbeck

 

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<pooua@aol.com> wrote in message
news:1108245889.496045.275540@c13g2000cwb.googlegroups.com...
> 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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In article <420F377E.3070207@netscape.net>, mike <spamme0@netscape.net> wrote:
>
>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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> So that's the weird spike I always notice on the FFT
> window on some CD-ripped WAVs...

Yes, and you see it in Stereophile's FFT displays.

When I did FFTs myself I had the same problem. I had to make sure the monitor
was out-of-range of the mic.

 

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I read in sci.electronics.design that Tommi M.
<tomppaaREMOvE@kolumbus.fi> wrote (in <cunt2o$n9$1@phys-
news1.kolumbus.fi>) about 'Speakers for High Frequency Sound', on Sun,
13 Feb 2005:
>
>"Arny Krueger" <arnyk@hotpop.com> wrote in message
>news:LqqdnSQSBe9hbZDfRVn-hQ@comcast.com...
>> 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..
>
What happens is that at some sufficiently high frequency the threshold
of hearing gets up to the 130-140 dB level, and equals the threshold of
pain. So you can't hear it until it's loud enough to hurt ****and liable
to damage your hearing across the whole range****. DON'T experiment.

You have done at least temporary damage if you get 'ringing in the ears'
and a temporary loss of hearing sensitivity. You may have done permanent
damage if you get a 'tickling' in the ear.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http/www.jmwa.demon.co.uk Also see http/www.isce.org.uk