Speakers for High Frequency Sound

It's the horizontal scanning frequency, 15,734.25 Hz for American color TV. Trust me. You don't need to measure it.

If humans can hear it, it can't possibly be at 40kHz, because the best human hearing extends to only a bit above 20kHz.

transformer

televisions in the

vertical scan

X 525 =

That sounds likely, but I have a few questions about that.

1) Is this same sub-unit on a standard television camera? 2) What exactly is converting the electrical energy into sound? 3) If this sound is so square in the middle of normal human hearing (16 kHz is well-within the range of normal human hearing), why have I met so few people who can hear it?

Question 3 is perplexing, because my sister and I were always the only people in our classroom or in someone's home who could hear the television.

One time, when my sister was hospitalized, her nurse tried to turn on the television set for her, but the set did not appear to turn on. The nurse was about to leave the room for help with the TV, when my sister told him that the TV had just turned on. The screen was still black, so he did not know what to think. Then, the TV slowly produced a picture. My sister could tell the set was on because she could hear it. No one else in the room at the time could hear it.

I have worked in a computer call center for several years. At one time, we had CRT monitors in the room with us. I was the only person who could hear them. I liked to turn the CRTs off when not in use, because they hurt my ears. One time, I walked up to two of my associates and asked them if they would mind if I turned off the CRTs. One of them already knew I could hear the CRTs, but the other one did not. The one who did not know was surprised. Naturally, he reached up and turned off the set, and asked if I could hear the difference. Then, he turned it on. Then, off. Then, on. The other associate, who understood what I was experiencing, began to laugh, and called the guy a sadist.

an

Yes, that is what this is like. When I walk down the sidewalk, I can hear the television inside the homes I pass. I can tell if someone comes between the television and me, even if they are inside a closed room.

I was at a hospital recently. As I walked across the lobby, I heard a television. I looked around. Then, I noticed a television camera inside a security enclosure box, mostly hidden in the ceiling. It took me a little longer to find it than it used to, because I had to locate it with just one ear (as I said, I am mostly deaf in the other ear, now).

Your objective is not clear. If you're gonna measure your own hearing...

How much trouble/expense do you want to expend to measure something you can't fix?

How useful is a random measurement using unknown/uncalibrated equipment? I did some experiments 30 years ago trying to measure frequency response of speakers, rooms, etc. I NEVER got repeatable measurements at high frequencies...not even close.

One might have the tendency to crank up the level until you can hear something. That might not be the best thing to do. No need to destroy what hearing you have left. YMMV. mike

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I need to measure it, to be certain that is what I am hearing.

I think you are assuming some things that aren't necessarily so. One very important assumption you are making that is likely to be wrong is that no human can hear very much above 20 kHz. There are a number of ways that assumption could be wrong. In any event, there is no physical mechanism that would prevent a human from hearing higher frequencies.

Even so, I probably exaggerated the frequency of the sound. I estimate that the pitch is about double the highest frequency that I heard in the sound booth at the ENT. The highest frequency they tested was 12 kHz, so I should estimate the sound I hear from a television as 24 kHz. It's an ear-piercing shriek, in any event.

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.

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.

Did AES test your nerve conduction? I have a suspicion that the sound I hear is not coming through my eardrums. I am beginning to suspect that I hear it through my skull, which means nerve conduction.

Your eardrum may not be able to hear so well, but maybe your ear nerves are still able to pick up sounds normally?

My objectives are to find out what frequencies I can hear, and to match one of the calibrated frequencies from the signal generator against the sound I hear from televisions, so that I can finally know what that frequency from the television is.

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).

As for how much I would spend, well, I can justify some of the expense because I am an electronics hobbiest. So, I don't mind buying a $200 piece of test equipment as much as I might otherwise. And, I am going deaf, so I don't have forever to make this test.

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.

29.97

(16

16 kHz is not square in the middle. When you become an 'old fart' you will find that out. 16K is your top octave which you will lose as you age. Sorry, I don't like it either but I actually don't miss hearing the Horizontal. Been working in commmercial TV for 28 years and haven't heard the H in more than 10. GG

is

physical

frequencies.

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The tympanic membrane (the eardrum) can be bypassed; it is not absolutely essential in every case for hearing (indeed, there are hearing aids that do exactly that).

I don't know of a way around the cochlear cilia, short of replacing it with a functional equivalent (in contrast, the function of the tympanic membrane is not absolutely essential to hearing). 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.

far,

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.

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estimate

kHz.

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All the more reason to set up a test and measure it directly. I hate this guesswork.

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and

park.

take

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I suppose you would need to run a test to find out for certain?

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ears,

tell,

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I absolutely could hear the monitors with my eyes closed. I would be able to hear them in a pitch-dark room. I have been looking down at my desk when the instructor has turned them on from his control console, and I can definitely hear them when he turns them on. The sound of the televisions is distinct and loud, particular in my good ear. As I say, I wear earplugs in class to manage the sound.

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.

The difference is important, because eardrum hearing loss may be reversible or correctible. Nerve hearing loss is not. Also, the different types of hearing loss use different types of hearing aides. There are other differences, too, but I don't know what they all are. My doctor told me that they looked for my nerve conduction to match my ear conduction pretty closely.

I am getting "Connection refused" when I attempt to go to that URL.

The high pitched sound is usually from the yoke and flyback transformer (actually an inductor) feeding the television's CRT. For most televisions in the United States that frequency is right at 15,734 Hz because the vertical scan rate for NTSC is 29.97 times per second and it draws 525 lines. 29.97 X 525 =

15734.25 horzontal scanning frequency.

Old black and white televisions were slightly higher: 30 Hz vertical X 525 lines = 15,750 Hz.

I hear it loudly enough that I can tell when someone walks around in an adjacent room with a television set on.

John LeBlanc houston, TX

I can't answer question 1.

Question #2 is hard, because 16 kHz is at the edge of hearing, and that edge is heavily volume and age-dependent. Transmission of this stuff is dependent on the flexibility of your earbone joints, which craps out with age. So you see the same dependence and variability as you do in gymnastics, and for the same reasons. The older you are, the less likely you are to be able to detect high frequency at a given volume. But there are no firm limits.

Interestingly, your cochlea can hear tremendously high frequencies well into "ultrasound" above 20 kHz, so long as they are gotten in by bone conduction (putting the transducer on your skull). It's the earbones that are the block. Perhaps there are some people who have particularly good skull connections to their inner ear.

Question #3. Is related to why transformers and many other devices hum with the frequency of the energizing AC. The variable magnetic field generated by the coil causes Lorenz forces on the other wires of the coil, just as in a motor. They flex, and if they're not tacked down well, they vibrate. Air picks that up.

SBH

No need to measure it. In the US & Canada (and other NTSC countries such as Taiwan) the high-pitched sound that you can hear is either

15.75kHz (rare these days) or 15.734264kHz. That's when the TV is locked to a broadcast. If it's on an empty channel, the frequency will be a bit different.

When I was about 12 years old, I got into a trade show with my Dad where they had a demo of an ultrasonic welder. It just about took my head off when they turned it on, but none of the old farts could hear a thing. I'm now older than he was then. 8-( I can still hear the racket from a NTSC TV but it's not nearly as loud.

Best regards, Spehro Pefhany

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Yes, there is. The mass of the tympanic membrane and the sensitivity
of the cochlear cilia.

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.

Why not just do a google search for "NTSC video sweep frequency?" Hint: it's around 17 KHz.

Right, but most places cannot test that high accurately enough. I think the House Institute in LA can do up to 16 KHz accurately.

--scott

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Couldn't your hearing be down in the 8k range and still decent in higher frequencies? It's been quite awhile since I was tested but I remember that I had a dip in the high-midrange area (right where the loud guitars and cymbals are!) and then above that I was fine.

Al

Surely on vidicon tube cameras, which also have a yoke.

Mostly it's the magnetic field from the yoke vibrating things around, but to some extent it's also microphonic effects in electrolytic capacitors. Potting the yoke reduces most of it, though.

Because too many people today have poor hearing from living in a very loud environment. Try asking some children.

--scott

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point

sets

That would mean there is an upper limit. It does not at all tell us that no one could hear higher frequencies than 20 kHz.

I asked the tech who administered my hearing test last week what the highest frequency is that the machine could test. I watched as she touched the buttons on the control panel, and I saw the machine display the frequency on the monitor. The machine tests a maximum of 8 kHz for the eardrum, but it tests up to 12 kHz for nerve.