Speakers for High Frequency Sound

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"John Woodgate"

> 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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"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..

 

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Tommi M. <tomppaaREMOvE@kolumbus.fi> wrote:
>"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..

If you get a full test done, you'll see that the high end response drops
off slowly enough that you can't really say there is a limit. You can say
"My hearing is down 30 dB at 16 KC" which is pretty dramatic a drop, but
even so you might still hear something at 16 KC if it is loud enough.

Now, the question of course, is how many different mechanisms are involved
in that top end corner. And it's certainly more than just one or two.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

 

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"Tommi M." <tomppaaREMOvE@kolumbus.fi> wrote in message
news:cunt2o$n9$1@phys-news1.kolumbus.fi...
>
> "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..

D'oh, you apparently meant that the highest audible frequency varies with
the intensity of the sound, but there is always an upper limit to human
hearing and that limit is individual.

 

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Thanks, Arny. I'll look at what Vifa has to offer.

 

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Earthworks' founder David E Blackmer using a study of the human hearing
mechanism

< http/www.earthworksaudio.com/f_wpapers/beyond20khz.html >

dale

 

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"Tommi M." <tomppaaREMOvE@kolumbus.fi> wrote in message
news:cunt2o$n9$1@phys-news1.kolumbus.fi
> "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?

Well, its just not just one number.

> If you have any links or info on that, I'd certainly be interested..

Isn't that what the Fletcher Munson curves show?

 

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"dale" <dallen@frognet.net> wrote in message
news:1108382187.974836.152180@f14g2000cwb.googlegroups.com
> Earthworks' founder David E Blackmer using a study of the human
> hearing mechanism
>
> < http/www.earthworksaudio.com/f_wpapers/beyond20khz.html >

I think this paragraph summarizes pretty well:

"TO FULLY MEET the requirements of human auditory perception I believe that
a sound system must cover the frequency range of about 15Hz to at least
40kHz (some say 80kHz or more) with over 120dB dynamic range to properly
handle transient peaks and with a transient time accuracy of a few
microseconds at high frequencies and 1°-2° phase accuracy down to 30Hz. This
standard is beyond the capabilities of present day systems but it is most
important that we understand the degradation of perceived sound quality that
results from the compromises being made in the sound delivery systems now in
use. The transducers are the most obvious problem areas, but the storage
systems and all the electronics and interconnections are important as well."

He's says that this is part of his belief system, and I think he's telling
it like it is. Thing is, the paper really doesn't provide evidence that
supports his stated belief.

 

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We have an AMC near my home, but I rarely go to a movie theater. Most
of the movies that I watch are on DVD, played on my computer. That
high-pitched sound that I hear, the "TV sound," is recorded on home
video, among other places.

Heh, wouldn't it be funny if someone were using it as copy protection?
More likely, I think, it is accidental, though I don't know why it so
regularly shows up for scary scenes.

 

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In article <w4Odnfss1qv6Do3fRVn-1w@comcast.com> arnyk@hotpop.com writes:

> > Earthworks' founder David E Blackmer using a study of the human
> > hearing mechanism

>
> "TO FULLY MEET the requirements of human auditory perception I believe that
> a sound system must cover the frequency range of about 15Hz to at least
> 40kHz (some say 80kHz or more) with over 120dB dynamic range to properly
> handle transient peaks and with a transient time accuracy of a few
> microseconds at high frequencies and 1°-2° phase accuracy down to 30Hz. This
> standard is beyond the capabilities of present day systems but it is most
> important that we understand the degradation of perceived sound quality that
> results from the compromises being made in the sound delivery systems now in
> use. The transducers are the most obvious problem areas, but the storage
> systems and all the electronics and interconnections are important as well."
>
> He's says that this is part of his belief system, and I think he's telling
> it like it is. Thing is, the paper really doesn't provide evidence that
> supports his stated belief.

Unfortunately that's the tough part. A theory can lead you to tests to
prove a hypothesis, but until you can actually conduct those tests,
it's still just a theory. In the mean time, "sounds pretty good to me"
will have to do when I'm evaluating loudspeakers.



--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo

 

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I read in sci.electronics.design that dale <dallen@frognet.net> wrote
(in <1108382187.974836.152180@f14g2000cwb.googlegroups.com>) about
'Speakers for High Frequency Sound', on Mon, 14 Feb 2005:
>Earthworks' founder David E Blackmer using a study of the human hearing
>mechanism
>
>< http/www.earthworksaudio.com/f_wpapers/beyond20khz.html >

Having described how the system works, he just states his opinion that a
bandwidth wider than 20 kHz is necessary. I, too, did experiments with
tweeters, when I could hear properly. The response above 20 kHz matters
IF there is any signal up there. The point is that there is **amplitude
non-linearity** in any transducer, so that spectrum components above 20
kHz intermodulate to produce difference-frequency signals which are
quite audible.
--
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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"Arny Krueger" <arnyk@hotpop.com> wrote

> Isn't that what the Fletcher Munson curves show?

Though widely quoted as gospel, I was under the impression F&M have been
discredited.
ISTR that F&M were also responsible for the (also bogus) finding that anything
less
than 3% distortion is inaudible.

From rane.com:

"In the '30s, researchers Fletcher and Munson first accurately measured and
published a set of curves showing the human's ear's sensitivity to pure tone
loudness verses frequency ("Loudness, its Definition Measurement and
Calculation," J. Acoust. Soc. Am., vol. 5, p 82, Oct. 1933). They conclusively
demonstrated that human hearing is extremely dependent upon loudness. The curves
show the ear most sensitive to pure tones in the 3 kHz to 4 kHz area. This means
sounds above and below 3-4 kHz must be louder in order to be heard just as loud.
For this reason, the Fletcher-Munson curves are referred to as "equal loudness
contours." They represent a family of curves from "just heard," (0 dB SPL) all
the way to "harmfully loud" (130 dB SPL), usually plotted in 10 dB loudness
increments.

D. W. Robinson and R. S. Dadson revised the curves in their paper, "A
Redetermination of the Equal-Loudness Relations for Pure Tones," Brit. J. Appl.
Phys., vol. 7, pp. 156-181, May 1956. These curves supersede the original
Fletcher-Munson curves for all modern work with pure tones. Robinson & Dadson
curves are the basis for ISO: "Normal Equal-Loudness Level Contours," ISO
226:1987 -- the current standard.

Users of either of these curves must clearly understand that they are valid only
for pure tones in a free field, as discussed in the following by Holman &
Kampmann. This specifically means they do NOT apply to noise band analysis or
diffused random noise for instance, i.e., they have little relevance to the real
audio world. A good overview is T. Holman and F. Kampmann, "Loudness
Compensation: Use and Abuse," J. Audio Eng. Soc., vol. 26, no. 7/8, pp. 526-536,
July/August 1978.

For real audio use, the Steven's curves are more applicable: S. S. Stevens,
"Perceived Level of Noise by Mark VII and Decibels (E)," J. Acoust. Soc. Am.,
vol. 51, pp. 575-601, 1972. [Used to create ISO 532:1975 and ASA S3.4-1980] See
Holman & Kampmann above for discussion. "

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
To reply, remove spaces: n o lindan at ix . netcom . com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

 

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"Nicholas O. Lindan" <see@sig.com> wrote in message
news:ZN8Qd.656$9J5.524@newsread2.news.atl.earthlink.net
> "Arny Krueger" <arnyk@hotpop.com> wrote

>> Isn't that what the Fletcher Munson curves show?

> Though widely quoted as gospel, I was under the impression F&M have
> been discredited.

I think that orthodox wisdom is that F&M are accurate and representative as
far as they go.

> ISTR that F&M were also responsible for the (also bogus) finding that
> anything less than 3% distortion is inaudible.

I don't know how you made that leap. My diving board isn't that springy, it
seems.

> Users of either of these curves must clearly understand that they are
> valid only for pure tones in a free field,

Obviously you're way behind on your reading, as I've made many posts in the
recent and distant past about putting the F&M numbers into context. If you
take them simplistically, they are usually very optimistic about what might
be heard in most real world contexts, if for no other reason that they
ignore masking.

 

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< http/www.earthworksaudio.com/f_wpapers/beyond20khz.html >

>He's says that this is part of his belief system, and I think he's
telling
>it like it is. Thing is, the paper really doesn't provide evidence
that
>supports his stated belief.

here are the texts he gives as reference found at bottom of paper

An Introduction to the Physiology of Hearing, 2nd edition
James O. Pickles, Academic Press 1988
ISBN 0-12-554753-6 or ISBN 0-12-554754-4 pbk.

Spacial Hearing, revised edition
Jen Blauert, MIT Press 1997
ISBN 0-262-02413-6

Experiments in Hearing, Georg von Békésy
Acoustical Society of America
ISBN 0-88318-630-6

Hearing, Gulick et al
Oxford University Press1989
ISBN 0-19-50307-3

dale

 

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"Nicholas O. Lindan"
> "Arny Krueger"
>
>> Isn't that what the Fletcher Munson curves show?
>
> Though widely quoted as gospel, I was under the impression F&M have been
> discredited.


** Neat how you eliminated the context so you could change it to your
hobby horse.


> ISTR that F&M were also responsible for the (also bogus) finding that
> anything
> less than 3% distortion is inaudible.
>

** Think there is a decimal point missing.


> From rane.com:

> They represent a family of curves from "just heard,"


** The only on topic bit.


> Users of either of these curves must clearly understand that they are
> valid only
> for pure tones in a free field,


** Seems to apply to folk with headphones on OK.

Audiology relies on it.



> This specifically means they do NOT apply to noise band analysis or
> diffused random noise for instance, i.e., they have little relevance to
> the real
> audio world.


** I note this is your totally whacko opinion and not a quote as you are
trying to pretend.

The threshold SPLs and frequency limits of human hearing are ENORMOUSLY
important to "real audio world ". It is hardly possible to design a piece
of audio equipment or an audio system without taking them into account.





............ Phil

 

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dale wrote:
>
> < http/www.earthworksaudio.com/f_wpapers/beyond20khz.html >
>
> >He's says that this is part of his belief system, and I think he's
> telling
> >it like it is. Thing is, the paper really doesn't provide evidence
> that
> >supports his stated belief.
>
> here are the texts he gives as reference found at bottom of paper
>
> An Introduction to the Physiology of Hearing, 2nd edition
> James O. Pickles, Academic Press 1988
> ISBN 0-12-554753-6 or ISBN 0-12-554754-4 pbk.
>
> Spacial Hearing, revised edition
> Jen Blauert, MIT Press 1997
> ISBN 0-262-02413-6
>
> Experiments in Hearing, Georg von Békésy
> Acoustical Society of America
> ISBN 0-88318-630-6
>
> Hearing, Gulick et al
> Oxford University Press1989
> ISBN 0-19-50307-3
>
> dale

Ignoring the mumble concerning construction of the ear, nerves,
etc--it is known that one can easily detect *phase* differences that
could be interpreted as a 100KHz+ frequency.
Easily described using "first principles" as "where is that damn tiger
that might be stalking me".

 

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Robert Baer> wrote:

> Ignoring the mumble concerning construction of the ear, nerves,
> etc--it is known that one can easily detect *phase* differences that
> could be interpreted as a 100KHz+ frequency.

That claim runs counter to what I've read from some folks with good
credentials regarding human hearing. Could you provide a citation for
me? Thanks.

--
ha

 

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>>"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.

Could be. I took it to be the scanning frequency of a special,
experimental peripheral. I never completely figured out how general the
article's statement could be applied to other equipment.

>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).

I've been getting a lot of polemic, lately, and not just on this
thread, or in these newsgroups. It's odd to see it, because it is only
a few people who appear to have an external agenda. But, on this
thread, I think I can chalk it up to just plain hard-headedness on the
part of the antagonists.

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

Thanks. I won't.

>Good fortune in your exploration,

Thank you, Chris. I appreciate your encouragement.

 

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In article <1108165220.798267.223400@c13g2000cwb.googlegroups.com>,
<pooua@aol.com> wrote:
>Some people can hear an extremely high-pitched sound generated by
>television CRTs and television cameras. I have long wondered what
>frequency this sound is. So, I am looking around for test equipment to
>help me measure it. I plan to use an audio generator (which I can buy
>for about $200), but I need to find a set of headphones that can
>produce sound at these high frequencies. The low end frequency should
>be about 12 kHz, and I would like to be able to go at least to 50 kHz.
>I am guessing the sound is somewhere around 40 kHz.

Your guess is way out - what you're hearing is the line frequency
which on European PAL TVs is about 15 kHz. I could hear it until
my mid to late twenties; now at age 32 I can't hear it at all.
However, that might be because new TV's aren't as noisy

I'd be VERY surprised if you could hear anything at all above 20 kHz.

David.

 

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D.M. Garner <dmg@eng.cam.ac.uk> wrote in message
news:cvgb04$2tt$1@gemini.csx.cam.ac.uk...
> In article <1108165220.798267.223400@c13g2000cwb.googlegroups.com>,
> <pooua@aol.com> wrote:
> >Some people can hear an extremely high-pitched sound generated by
> >television CRTs and television cameras. I have long wondered what
> >frequency this sound is. So, I am looking around for test equipment to
> >help me measure it. I plan to use an audio generator (which I can buy
> >for about $200), but I need to find a set of headphones that can
> >produce sound at these high frequencies. The low end frequency should
> >be about 12 kHz, and I would like to be able to go at least to 50 kHz.
> >I am guessing the sound is somewhere around 40 kHz.
>
> Your guess is way out - what you're hearing is the line frequency
> which on European PAL TVs is about 15 kHz. I could hear it until
> my mid to late twenties; now at age 32 I can't hear it at all.
> However, that might be because new TV's aren't as noisy
>
> I'd be VERY surprised if you could hear anything at all above 20 kHz.
>
> David.

Piezo tweeters will generally go to above 20KHz. I've worked a lot with
ultrasonics - way above audible range - you 'hear' it from time to time due
to subfrequencies generated by mechanical nonlinearities around the
transducers, at a much lower frequency.