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Medical Forum / General / General / February 2005Speakers for High Frequency Sound
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. Incidentally, I just got my hearing checked by my ENT (Ear, Nose, Throat doctor). I measured in the 5-to-10 dB range on both the eardrum and nerve conduction tests across the entire measured frequency range (up to 8 kHz for eardrum, 12 kHz for nerve conduction). My doctor said that they want to see values less than 20 dB, so I am well-within the safe zone, as far as they are concerned. However, one reason that she scheduled this test for me is that I complained that I am going deaf in one of my ears. I have almost completely lost my sensitivity to the ultra-high pitched sound in that ear. I can hear that sound 100 times better from my other ear. People don't realize what a difference it makes to a person's perception when the range of hearing differs. I can walk into a room with other people, and they think they are in an empty room. If there is an operating television in the room, I will be aware of almost physical contact. Other people can hold a conversation in a normal voice, but I have to listen over a sound similar to a dentist's drill or a jet engine. After several minutes of that, I often feel dazed. No one else even notices anything, except maybe that I am acting a little more odd than normal. >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. 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. > So, I am looking around for test equipment to >help me measure it. I plan to use an audio generator (which I can buy [quoted text clipped - 23 lines] >one else even notices anything, except maybe that I am acting a little >more odd than normal. 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  Signature"it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com This is Spehro Pefhany for forever: > >Some people can hear an extremely high-pitched sound generated by > >television CRTs and television cameras. I have long wondered what [quoted text clipped - 5 lines] > locked to a broadcast. If it's on an empty channel, the frequency will > be a bit different. Do you know what are those frequencies for PAL-M? Sometimes I notice this high-pitched sound coming from my TV... (the 2 TV's I have at home: a 14" Toshiba and a 20" LG, so it's not a fault on the TV) []s SignatureChaos Master®, posting from Canoas, Rio Grande do Sul, Brazil - 29.55° S / 51.11° W / GMT-2h / 15m . "People told me I can't dress like a fairy. I say, I'm in a rock band and I can do what the hell I want!" -- Amy Lee (My e-mail address isn't read. Please reply to the group!) > 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. It's the horizontal scanning frequency, 15,734.25 Hz for American color TV. Trust me. You don't need to measure it. > 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. 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 people can hear an extremely high-pitched sound generated by >>television CRTs and television cameras. I have long wondered what >>frequency this sound is. > > It's the horizontal scanning frequency, 15,734.25 Hz for American color TV. > Trust me. You don't need to measure it. I can easily hear it and my hearing does not go near 16K > >>Some people can hear an extremely high-pitched sound generated by > >>television CRTs and television cameras. I have long wondered what [quoted text clipped - 5 lines] > I can easily hear it > and my hearing does not go near 16K Interesting. Maybe you're hearing some magnetorestriction related noise in the LOPT ? Maybe you underestimate your hearing ? Graham >>>> 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. >>> It's the horizontal scanning frequency, 15,734.25 Hz for American >>> color TV. Trust me. You don't need to measure it. Agreed. >> I can easily hear it >> and my hearing does not go near 16K It's a matter of intensity. > Interesting. Normal. > Maybe you're hearing some magnetorestriction related noise in the > LOPT ? I think that magnetostriction and related vibration in either the transformers or the deflection yoke is the usual explanation. > Maybe you underestimate your hearing ? 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. > 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!" SignatureThe Pig Bladder From Uranus, Still Waiting for Some Hot Babe to Ask What My Favorite Planet Is. > 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.. >> 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. 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: >> 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. SignatureRegards, 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 >> 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 Signature"C'est un Nagra. C'est suisse, et tres, tres precis." >> 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? > 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/ "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 >> 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. I read in sci.electronics.design that George Gleason <g.p.gleason@worldnet.att.net> wrote (in <DXbPd.28856$Th1.8953@bgtnsc04- news.ops.worldnet.att.net>) about 'Speakers for High Frequency Sound', on Sat, 12 Feb 2005: >I can easily hear it >and my hearing does not go near 16K The normal audiometry test measures your hearing sensitivity at threshold level. You can see from the Fletcher-Munson (Robinson/Dadson) curves, that the sensitivity of even an unimpaired ear varies with sound pressure as well as frequency. This means that you can hear LOUD sounds at much higher frequencies that you would expect from your threshold sensitivity curve. SignatureRegards, 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 > It's the horizontal scanning frequency, 15,734.25 Hz for American > color TV. Trust me. You don't need to measure it. I need to measure it, to be certain that is what I am hearing. > If humans can hear it, it can't possibly be at 40kHz, because > the best human hearing extends to only a bit above 20kHz. 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. >> It's the horizontal scanning frequency, 15,734.25 Hz for American >> color TV. Trust me. You don't need to measure it. [quoted text clipped - 9 lines] >ways that assumption could be wrong. In any event, 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. 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. --- >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. --- Unless you have perfect pitch, your estimates as to the frequency of what you heard are close to meaningless. --- >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. --- >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. SignatureJohn Fields > >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. --- > Yes, there is. The mass of the tympanic membrane and the > sensitivity of the cochlear cilia. 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. > I've done work trying to determine whether the nonlinearity of the > auditory system will allow beat notes which occur as a result of [quoted text clipped - 3 lines] > 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. --- > >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. --- > Unless you have perfect pitch, your estimates as to the frequency of > what you heard are close to meaningless. All the more reason to set up a test and measure it directly. I hate this guesswork. --- > >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? --- > >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. 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. >> >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 [quoted text clipped - 12 lines] >absolutely essential in every case for hearing (indeed, there are >hearing aids that do exactly that). --- Yes, but we're talking airborne sound here, aren't we? --- >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. --- Yes, in the sense that Ferraris and Fords are both cars. _But_ we're not discussing non-human hearing, are we? --- >> I've done work trying to determine whether the nonlinearity of the >> auditory system will allow beat notes which occur as a result of [quoted text clipped - 8 lines] >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. --- >> >Even so, I probably exaggerated the frequency of the sound. I >estimate [quoted text clipped - 10 lines] >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. Measure the period of the signal impinging on the microphone, take its reciprocal, and you'll have its frequency. --- >> >I can also hear LCD screens, but that's at a lower pitch, I think, >and [quoted text clipped - 7 lines] >> 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... --- >> >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 [quoted text clipped - 15 lines] >televisions is distinct and loud, particular in my good ear. As I say, >I wear earplugs in class to manage the sound. --- Ok, but I don't understand the point of all of this. Are you merely relating anecdotes, are you complaining about the sound, are you looking for some kind of an electronic way to make the noise go away, or what? SignatureJohn Fields >>>>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. I think we can hear airborne sounds (especially if they are intense) without the eardrum. --- >>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. 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. 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. --- >>> 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 [quoted text clipped - 5 lines] >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. The beat note is a perception generated in the brain from sounds it hears. There is no wave present at the beat frequency. [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. --- >> >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. --- >>>Now I am taking a college class in a room that has >>>3 television sets suspended from the ceiling. One [quoted text clipped - 4 lines] >>>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. I would like to find out what frequency of sound I am hearing from a television set. The sound I hear is not imaginary or merely a psychological effect. 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. > 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 > Ribbon HF drivers can easily do that > contact SLS loudspeakers > they can sell you a unit for about 100$ that will go to 40K Thanks, George. Ironically (considering the size of this thread), this is exactly the information that I need. I will check out SLS loudspeakers. >>>>>One very important assumption you are making that is likely >>>>>to be wrong is that no human can hear very much above [quoted text clipped - 16 lines] >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. --- >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. --- >>>But, what are the limits of the cochlear cilia? Certainly there >>>are animals that can hear higher frequencies, and they use [quoted text clipped - 10 lines] >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? --- >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. --- >An analogous situation would be Vitamin C production. There is no >physical limitation that would prevent humans from producing their own [quoted text clipped - 4 lines] >there are humans who are able to produce enough Vitamin C through >spontaneous oxidation to keep them alive without an external supply. --- f.ck vitamin C production, we're talking about acoustics. --- >>>> I've done work trying to determine whether the nonlinearity of the >>>> auditory system will allow beat notes which occur as a result of [quoted text clipped - 22 lines] >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? --- >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. --- >[snip] > [quoted text clipped - 15 lines] >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. --- >>> >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 [quoted text clipped - 12 lines] >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. --- >>>>Now I am taking a college class in a room that has >>>>3 television sets suspended from the ceiling. One [quoted text clipped - 18 lines] >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? --- >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. --- >The sound I hear is not imaginary or merely a psychological effect. --- How do you know that's true? --- > 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? SignatureJohn Fields > 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. Thanks, Arny. I'll look at what Vifa has to offer. Earthworks' founder David E Blackmer using a study of the human hearing mechanism < http://www.earthworksaudio.com/f_wpapers/beyond20khz.html > dale > 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. < 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 > < http://www.earthworksaudio.com/f_wpapers/beyond20khz.html > > [quoted text clipped - 23 lines] > > 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". 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. SignatureRegards, 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 > >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. [quoted text clipped - 3 lines] > --- > you may have crosstalk between your vision and auditory systems. You are probably hearing the backlight of the LCD. Some of them can be quite loud. Now that digital watches always use Indiglo backlights, I can hear them, and I actually had to get rid of a caller ID unit that lit up every day at 2am because the phone company reset the line. It kept waking me up. SignatureJay 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? > I actually had to get rid of a caller ID unit that > lit up every day at 2am because the phone > company reset the line. It kept waking me up. That would be a drag! >>It's the horizontal scanning frequency, 15,734.25 Hz for American >>color TV. Trust me. You don't need to measure it. [quoted text clipped - 3 lines] >>If humans can hear it, it can't possibly be at 40kHz, because >>the best human hearing extends to only a bit above 20kHz. It could easily be measured with Macfoh (www.macfoh.com) and DPA measurement mics george I am getting "Connection refused" when I attempt to go to that URL. >> It's the horizontal scanning frequency, 15,734.25 Hz for American >> color TV. Trust me. You don't need to measure it. [quoted text clipped - 7 lines] > very important assumption you are making that is likely to be wrong is > that no human can hear very much above 20 kHz. Yes and no. If the intensity is high enough, it may be possible to discern pure tones above 20 KHz. OTOH, hearing the removal of sounds is a different question, and the borderline frequency for most people is around 16 KHz. > There are a number of ways that assumption could be wrong. There are a probably an infinite number of ways that any assumption could be wrong, but that sheds little light on whether the assumption is correct or not. > In any event, there is no > physical mechanism that would prevent a human from hearing higher > frequencies. Sure there is. The perception of pitch is based on the activation of hairs in a coil-shaped structure in the ear. The finest hairs relate to high frequencies, but they don't go on forever. Basically, you run out of structure at some point in this part of the ear, and the extent and health of this structure sets the highest frequencies that you can perceive. It's not uncommon for this structure to be damaged by listening to excessively loud sounds. > > In any event, there is no > > physical mechanism that would prevent a human from hearing higher > > frequencies. > Sure there is. [snip] Basically, you run out of structure at some point > in this part of the ear, and the extent and health of this structure sets > the highest frequencies that you can perceive. 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. Shut up and play guitar. :) > Shut up and play(your) guitar. :) What was the name of the most tedious self absorbed, w.nker tour ever. George "George Gleason" >> Shut up and play(your) guitar. :) > > What was the name of the most tedious self absorbed, w.nker tour ever. ** Joe Cocker's " Mad Dogs and Englishmen " Toss up between Cocker, aka world's highest paid spastic and Leon Russell for the No 1 w.nker honours. ............ Phil >>> In any event, there is no >>> physical mechanism that would prevent a human from hearing higher >>> frequencies. >> Sure there is. [snip] Basically, you run out of structure at some >> point in this part of the ear, and the extent and health of this >> structure sets the highest frequencies that you can perceive. > That would mean there is an upper limit. Thus, I falsify the claim that "there is no physical mechanism that would prevent a human from hearing higher frequencies." That's all I set out to do. > It does not at all tell us > that no one could hear higher frequencies than 20 kHz. That's a different question. 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. > That's a different question. 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. Women, and especially black women, are able to hear at higher frequencies than men. >> That would mean there is an upper limit. >Thus, I falsify the claim that "there is no physical >mechanism that would prevent a human from >hearing higher frequencies." No, you would be falsifying a claim that there is no upper limit. But, that wasn't the statement you were challenging. You were challenging the statement that there is no physical mechanism preventing humans from hearing higher frequencies. These are not equivalent statements. >That's all I set out to do. Congratulations. >>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. You were not addressing the same subject as we had been discussing. >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. 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. [quoted text clipped - 4 lines] > 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. [quoted text clipped - 4 lines] > 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 > <pooua@aol.com> wrote in message ... >> In any event, there is no >> physical mechanism that would prevent a human from hearing higher [quoted text clipped - 7 lines] > not uncommon for this structure to be damaged by listening to excessively > loud sounds. A cochleal tsunami! =:-O On Fri, 11 Feb 2005 16:52:14 -0800, pooua wrote: >> It's the horizontal scanning frequency, 15,734.25 Hz for American >> color TV. Trust me. You don't need to measure it. > > I need to measure it, to be certain that is what I am hearing. Try just listening to it one time. In another post, you mentioned having to focus on a particular conversation or a particular flute. Do this to the sound, and ask what it's trying to tell you. It could be an attempt to communicate from a higher dimension. Good Luck! Rich for further information, please visit http://www.godchannel.com > In another post, you mentioned having to focus on a > particular conversation or a particular flute. I think you have me confused with someone else. I haven't said anything in this thread about focusing on a particular sound or conversation or flute. >>It's the horizontal scanning frequency, 15,734.25 Hz for American >>color TV. Trust me. You don't need to measure it. [quoted text clipped - 27 lines] > 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. I suspect that for the LCD screens what you are hearing are the power supplies for the backlight, and not the screen itself. Many of these have switching frequencies in the approx. 20kHz range, so when you light up the screen, you hear the squeal. SignatureCharlie -- Edmondson Engineering Unique Solutions to Unusual Problems You are probably corrrect. The sound of my Olympus C-3040 LCD display is not terribly high-pitched, but it is faint. > > Some people can hear an extremely high-pitched sound generated by > > television CRTs and television cameras. I have long wondered what [quoted text clipped - 12 lines] > If humans can hear it, it can't possibly be at 40kHz, because the best human > hearing extends to only a bit above 20kHz. Using a test generator I was able to *sense* rather than hear 22kHz when I was in my early 20s. Now I'm 50 - I seem to top out on 'hearing' at about 16kHz. That makes me quite lucky it seems. I do believe you can 'educate' your hearing btw. Be interested to hear - lol - other ppl's comments. Graham 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. SignatureRegards, 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 That is interesting. I have read that a newborn baby can hear the sound of a mosquito on the other side of a closed window. I've also read that ultrasounds on the fetus might harm the unborn child's hearing. But, I do not recall having read that some children can hear 40 kHz. > I read in sci.electronics.design that William Sommerwerck > <williams@nwlink.com> wrote (in <110qinrklm6ss4b@corp.supernews.com>) [quoted text clipped - 4 lines] > > 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 > Some people can hear an extremely high-pitched sound generated by > television CRTs and television cameras. I have long wondered what [quoted text clipped - 4 lines] > 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. 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 > 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. 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. > I hear it loudly enough that I can tell when someone walks around in an > adjacent room with a television set on. 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). >>The high pitched sound is usually from the yoke and flyback > [quoted text clipped - 21 lines] > kHz is well-within the range of normal human hearing), why have I met > so few people who can hear it? Most people can hear it, at least until they are 25 or so but most people do not know how to focus their listening and blank it out kind of like what my son does when I ask him if he did his homework > 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 [quoted text clipped - 7 lines] > 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. There is nothing special about hearing this my hearing is down 30 dB at 8 K(as high as the test at AES went) when compared to 3K and I can easily hear it george > 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 [quoted text clipped - 23 lines] > 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). > my hearing is down 30 dB at 8 K(as high as the test at AES went) > when compared to 3K and I can easily hear it 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 hearing is down 30 dB at 8 K(as high as the test at AES went) >>when compared to 3K and I can easily hear it [quoted text clipped - 5 lines] > Your eardrum may not be able to hear so well, but maybe your ear nerves > are still able to pick up sounds normally? I have no idea they gave us headphones and had us press a button when we heard sound this was end oct 04 but I also feel(subjectivly ) that I can hear things the tests say I should not be able to Because I can focus my listening and isolate sounds , like a single flute out of a flute section from 150 feet away from the orchestra george 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. > 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. SignatureAaron 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. > > my hearing is down 30 dB at 8 K(as high as the test at AES went) > > when compared to 3K and I can easily hear it [quoted text clipped - 5 lines] > Your eardrum may not be able to hear so well, but maybe your ear nerves > are still able to pick up sounds normally? I suspect that the brain compensates actually. I reckon also that the simple desire to use your ears effectively influences your result significantly. E.g. George Martin was a famed record producer but was essentially deaf in one ear ! Graham > E.g. George Martin was a famed record producer but was essentially deaf in > one ear ! > > Graham I knew I would be compared to Sir George Martin some day. :-) george >> E.g. George Martin was a famed record producer but was essentially deaf >> in [quoted text clipped - 5 lines] > :-) > george Excerpt from encyclopedia entry: "George Gleason has often been compared to Sir George Martin, due to both being named 'George'; and further, due to both men's surnames ending in the letter 'n' " :D Neil Henderson >>>E.g. George Martin was a famed record producer but was essentially deaf >>>in [quoted text clipped - 11 lines] > > Neil Henderson LOL Thanks G >There is nothing special about hearing this >my hearing is down 30 dB at 8 K(as high as the test at AES went) when >compared to 3K >and I can easily hear it >george 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 >>There is nothing special about hearing this >>my hearing is down 30 dB at 8 K(as high as the test at AES went) when [quoted text clipped - 8 lines] > > Al 8k was as high as the test measured so I am not aware of my measured abilities above that George > 8k was as high as the test measured so I am not aware of my > measured abilities above that 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. >>There is nothing special about hearing this >>my hearing is down 30 dB at 8 K(as high as the test at AES went) when [quoted text clipped - 6 lines] > 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. Hearing is selective. The last couple of years of my Dad's life, I was staying with him and Mom, as sort of "the guy who does everything around the house that they're too old and feeble to do". Mom's job was basically change Dad's diapers. I helped haul him out of bed and into his chair, or the car, etc. But when he was sitting in his chair, with Mom in the couch to his left, and me on the loveseat to his right, and the TV right in front of him, with the speakers pointed right at him, he had to turn it up uncomfortably loud, and Mom and I couldn't talk to each other or anything, or he couldn't hear the TV. But if I went into the kitchen and poured myself more than a shot of scotch, he could hear the sound of the overpour well enough to bitch about it. People decide what they want to hear. Good Luck! Rich for further information, please visit http://www.godchannel.com > most people do not know how to focus their listening and blank it out > kind of like what my son does when I ask him if he did his homework George ! Are you thinking of taking up a new role as a comedian ? I loved that response. :-) Graham > George ! > [quoted text clipped - 3 lines] > > Graham Well i got the looks for it :-) A face meant for a career in radio G the sound is caused by the magnetostriction of the power transfomer 16khz is not in the middle of the human range; voice is and it is around 3 khz >> The high pitched sound is usually from the yoke and flyback > transformer [quoted text clipped - 51 lines] > 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). >That sounds likely, but I have a few questions about that. > >1) Is this same sub-unit on a standard television camera? Surely on vidicon tube cameras, which also have a yoke. >2) What exactly is converting the electrical energy into sound? 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. >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? Because too many people today have poor hearing from living in a very loud environment. Try asking some children. --scott Signature"C'est un Nagra. C'est suisse, et tres, tres precis." > > The high pitched sound is usually from the yoke and flyback > transformer [quoted text clipped - 13 lines] > kHz is well-within the range of normal human hearing), why have I met > so few people who can hear it? 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 |
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