wmartin@brl-tgr.ARPA (Will Martin ) (01/06/86)
In article <1260@brl-tgr.ARPA> gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>) writes: >By the way, the fellow who got headaches in the room full of burning-in >monitor assemblies was probably being affected by the near-ultrasonic >sound generated by the horizontal circuits (often transformer laminations >vibrating). Even if he didn't consciously hear them, such whistles would >lead to irritability and headaches. For what it's worth, the latest issue (#28, I think) of The $ensible Sound, an "underground" audio magazine, has a report of a recent study which found that people could *really* hear up to 40 kHz, not the previously-believed 20 kHz limit. The older studies, according to the item, used transducers to reproduce the high-frequency sounds which were defective or inferior, masking the higher frequencies in distortion. There was no reference or citation; I wonder if some of the net.med people can locate the real study this item was based on, and post a reference or bibliographic note? This sort of info might be used to force terminal designers to finally eliminate all that nasty high-pitched noise their products emit! Will
dyer@harvard.UUCP (Steve Dyer) (01/07/86)
I don't know anything about so-called "Ultrasonic" hearing, but I do know that the flyback transformers on most monitors emit a buzz around 17-19 khz; the exact frequency escapes me right now. This is "ultrasonic" only for most people over 30 or 35 years of age. I can hear it, and I have several friends who can hear it. It doesn't bother me, but this does seem to be a point of contention for audiophiles who feel pushed headlong into a shotgun marriage of audio and video, since they claim that the sound of the monitor is especially disturbing during music, and makes any pretense to otherwise low distortion and noise figures quite silly. For example, the Pioneer CD/LaserDisc player has its programming display on the video monitor, eschewing low-tech LEDs. -- /Steve Dyer dyer@harvard.harvard.edu harvard!dyer
ark@alice.UucP (Andrew Koenig) (01/07/86)
> I don't know anything about so-called "Ultrasonic" hearing, but > I do know that the flyback transformers on most monitors emit a > buzz around 17-19 khz; the exact frequency escapes me right now. > This is "ultrasonic" only for most people over 30 or 35 years of age. I think it's 15,750 Hz: 525 lines on the screen times 60 Hz refresh rate, divided by 2 because of alternate scanning. People's ability to hear it seem to vary greatly by individual, even among children.
spp@ucbvax.BERKELEY.EDU (Stephen P Pope) (01/07/86)
I've never encountered a TV receiver or monitor that
didn't emit an annoying high pitched squeal at at least a
low audible level. I don't know (or care) whether this is
15.75, 17 or 19 KHz ( the three numbers people usually
throw out). I suspect it is there because the receivers
are not built real well. A real solid frame and chassis would
almost certainly help.
On a related subject, I understand that some native
tribes in quiet, undeveloped third-world areas have been
found to be able to hear well up to 40 or 50 KHz. Apparently,
the average westerner can hear only up to 12 to 20 Khz
mostly because of exposure to noise all his life.
steveabeles@mhuxm.UUCP (J. Abeles (Bellcore, Murray Hill, NJ)) (01/08/86)
> I do know that the flyback transformers on most monitors emit a > buzz around 17-19 khz; the exact frequency escapes me right now. about 15.75 kHz, actually.
alw@mit-eddie.UUCP (Alan Wu) (01/08/86)
In article <1280@brl-tgr.ARPA> wmartin@brl-tgr.ARPA (Will Martin ) writes: > ... This sort of info might be used to >force terminal designers to finally eliminate all that nasty high-pitched >noise their products emit! > Hear, hear! If you can't hear the nasty high-pitched noise emitted by most video terminals, think about what this says about your sense of hearing in the region of 15,570 Hz ...
oleg@birtch.UUCP (Oleg Kiselev) (01/09/86)
In article <11370@ucbvax.BERKELEY.EDU> spp@ucbvax.BERKELEY.EDU (Stephen P Pope) writes: > > I've never encountered a TV receiver or monitor that >didn't emit an annoying high pitched squeal at at least a >low audible level. I don't know (or care) whether this is >15.75, 17 or 19 KHz ( the three numbers people usually >throw out). I suspect it is there because the receivers >are not built real well. A real solid frame and chassis would >almost certainly help. I have heard it is usually the vibration of transformers and/or capacitors (fly-back transformer?????). THe worst offenders I have heard were tvi925 . Sometimes a sharp rasp on the side of the terminal would silence it for an hour or so ( and many people got so irritated by the squeal they did it routinely). And what about the fan noise in large micros? > On a related subject, I understand that some native >tribes in quiet, undeveloped third-world areas have been >found to be able to hear well up to 40 or 50 KHz. Apparently, >the average westerner can hear only up to 12 to 20 Khz >mostly because of exposure to noise all his life. It was also said that their 60-70 year-olds had hearing in exess of that of the early 30's-late 20's eurpean urban dwellers ( the researchers). The oldsters also were very alert and had no hart illnesses.... Whoops! I have just realized MY terminal started squealing! <RASP!> jd,bc, d||{~| -- Disclamer: I don't work here anymore - so they are not responsible for me. +-------------------------------+ Don't bother, I'll find the door! | STAY ALERT! TRUST NO ONE! | Oleg Kiselev. | KEEP YOUR LASER HANDY! |...!{trwrb|scgvaxd}!felix!birtch!oleg --------------------------------+...!{ihnp4|randvax}!ucla-cs!uclapic!oac6!oleg
fish@ihlpm.UUCP (Bob Fishell) (01/10/86)
> For what it's worth, the latest issue (#28, I think) of The $ensible Sound, > an "underground" audio magazine, has a report of a recent study which > found that people could *really* hear up to 40 kHz, not the > previously-believed 20 kHz limit. The older studies, according to the > item, used transducers to reproduce the high-frequency sounds which were > defective or inferior, masking the higher frequencies in distortion. > > There was no reference or citation[.] Sounds like more smoke blown up the wazoo by the anti-digital crowd to me. -- __ / \ \__/ Bob Fishell ihnp4!ihlpg!fish
carey@uiucdcs.CS.UIUC.EDU (01/10/86)
/* Written 5:27 pm Jan 7, 1986 by alw@mit-eddie.UUCP in uiucdcs:net.info-terms */ In article <1280@brl-tgr.ARPA> wmartin@brl-tgr.ARPA (Will Martin ) writes: > ... This sort of info might be used to >force terminal designers to finally eliminate all that nasty high-pitched >noise their products emit! > Hear, hear! If you can't hear the nasty high-pitched noise emitted by most video terminals, think about what this says about your sense of hearing in the region of 15,570 Hz ... /* End of text from uiucdcs:net.info-terms */ Sometimes the problem is not the frequency--subtraction between two frequencies.For example if the music you are listening to has frequencies say at 15,000 Hz then subtraction of the frequencies will give you (15,570 -15,000=) 570 Hz. This is in the audible range. I don't know how to calculate the loudness of subtraction tones. Does anybody else?
rab@well.UUCP (Bob Bickford) (01/12/86)
In article <251@birtch.UUCP>, oleg@birtch.UUCP (Oleg Kiselev) writes
about people being annoyed by the squeal put out by monitors and tv sets.
(BTW, it is [usually] the mechanical vibration induced in the flyback
transformer at 15,750 Hertz [B/W] which is audible.)
Then the discussion turned to Ultrasonic hearing.
On this subject, I used to work installing so-called "ultrasonic"
alarm systems and several times complained to my boss that I could
hear them (and they were giving me headaches). I finally convinced
him by doing a complete install and alignment of a system without
the usual test equipment, in a difficult location. I still (even
after several years of rock 'n' roll) have hearing up to around 20kHz.
(the alarms were between 25 and 40 kiloHertz) (I'm 27)
Robert Bickford (rab@well.uucp)
================================================
I doubt if these are even my own opinions.
================================================larry@kitty.UUCP (Larry Lippman) (01/12/86)
> I don't know anything about so-called "Ultrasonic" hearing, but > I do know that the flyback transformers on most monitors emit a > buzz around 17-19 khz; the exact frequency escapes me right now. > This is "ultrasonic" only for most people over 30 or 35 years of age. The frequency is 15,750 Hz - which is not that high, and is not `ultrasonic'. Whether or not you hear the flyback on a given monitor is a poor indication of your hearing ability, since better quality flybacks produce very little audio energy. ==> Larry Lippman @ Recognition Research Corp., Clarence, New York <== ==> UUCP {decvax|dual|rocksanne|rocksvax|watmath}!sunybcs!kitty!larry <== ==> VOICE 716/741-9185 {rice|shell}!baylor!/ <== ==> FAX 716/741-9635 {G1, G2, G3 modes} duke!ethos!/ <== ==> seismo!/ <== ==> "Have you hugged your cat today?" ihnp4!/ <==
edhall@randvax.UUCP (Ed Hall) (01/12/86)
>> For what it's worth, the latest issue (#28, I think) of The $ensible Sound, >> an "underground" audio magazine, has a report of a recent study which >> found that people could *really* hear up to 40 kHz, not the >> previously-believed 20 kHz limit. The older studies, according to the >> item, used transducers to reproduce the high-frequency sounds which were >> defective or inferior, masking the higher frequencies in distortion. >> >> There was no reference or citation The fact is plausible, but the explanation is absurd. Nonlinearities in reproduction may add harmonics to the acoustic signal, and for an especially bad transducer might even excite resonances at sub- harmonics of the test frequency. But if an appropriate amount of acoustic power is being generated at the test frequency, anything masking it would have to be as least as audible. As a personal note, at 31 I'm still bothered by TV and terminal horizontal frequencies--but not as much. It's one of the benifits of getting older... -Ed Hall ihnp4!sdcrdcf!randvax!edhall
rich@aoa.UUCP (Rich Snow) (01/16/86)
In article <11370@ucbvax.BERKELEY.EDU> spp@ucbvax.BERKELEY.EDU (Stephen P Pope) writes: > > I've never encountered a TV receiver or monitor that >didn't emit an annoying high pitched squeal at at least a >low audible level. Bothers me too. I used to work in a TV factory. The noise emenates from a coil in the horizontal oscillator of the Magnavox chassis we used. At one time a production line solution to sqeals of painful volume was to heatshrink the coil in question. Kind of like a straight jacket... In some sets, the flyback itself vibrates. I would not suggest surrounding it with heatshrink, maybe RTV? Does anyone out there have a "digital" tv, and assuming you are one of us that hears this noise (some don't) does your set squeal? a vidiot, Rich Snow AOA-----------------* ...!{decvax,linus,ima,ihnp4}!bbncca!aoa!rich ...!{wjh12,mit-vax}!biomed!aoa!rich