brent@itm.UUCP (Brent) (01/20/85)
X
OK folks, let's cover this ground again. Opinionate all you
want, I'll stick to experimental fact:
KEF labratories in England do an extensive amount of psychoacoustic
research in the design of their speaker systems. They do things like
have a person and a pair of speakers behind a screen, and do double-
blind listening comparisons of the person and a tape recording of that
person. They double-blind switch in distorters, 9-th order elliptic
filters, etc. What have they learned after doing thousands of
tests on hundreds of subjects? Well, when the great digital debate
first came up in the Audio Engineering Socitey, KEF took their
equipment to one of the conventions, ran the tests for anyone who
wanted to participate, published the raw test scores and the
statistical conclusions. In short, it was an extensive research
project.
THE RESULT: (drum roll, please)
Nothing above 16 kHz makes any difference.
And so the professional audio community was convinced. Don't
argue with me, argue with KEF's numbers.
--
Brent Laminack (akgua!itm!brent)seifert@mako.UUCP (Snoopy) (01/22/85)
"Nothing above 16kHz makes any difference"
I *assume* they checked to make sure that the screens didn't
block freqs higher than that? And that background noise was
sufficiently low, etc etc.
If so, that's sort of interesting.
AR once did something similar, not to investigate bandwidth
requirements but just to prove that their speakers (10pi)
could fool people.
And someone else did a similar bandpass experiment with various
curtains/screens that *did* block various freqs, which proved
that high frequencies *did* matter. (These were done a *long*
time ago. I don't remember whether "high" was referring to over
16kHz at that time.)
I'd like to know what miking/speaker placement setups they
used to fool people in a live-vs-recorded test. Proper
imaging is hard to achieve, and could easily spoil such
a test. (right, Phil?)
_____
|___| the Bavarian Beagle
_|___|_ Snoopy
\_____/ tektronix!mako!seifert
\___/rentsch@unc.UUCP (Tim Rentsch) (01/23/85)
In article <itm.226> brent@itm.UUCP (Brent) writes: > > KEF labratories in England do an extensive amount of psychoacoustic >research in the design of their speaker systems. They do things like >have a person and a pair of speakers behind a screen, and do double- >blind listening comparisons of the person and a tape recording of that >person. They double-blind switch in distorters, 9-th order elliptic >filters, etc. What have they learned after doing thousands of >tests on hundreds of subjects? Well, when the great digital debate >first came up in the Audio Engineering Socitey, KEF took their >equipment to one of the conventions, ran the tests for anyone who >wanted to participate, published the raw test scores and the >statistical conclusions. In short, it was an extensive research >project. > > THE RESULT: (drum roll, please) > > Nothing above 16 kHz makes any difference. > >And so the professional audio community was convinced. Don't >argue with me, argue with KEF's numbers. The stated result strikes me as incomplete. Shouldn't it instead read: Nothing above 16kHz makes any difference to the test participants given the speakers (amplifiers, etc.) used in the test. Wonder if they were using KEF speakers by chance.... cheers, Tim "I prefer to hear my drum rolls on good equipment."
wunder@wdl1.UUCP (01/25/85)
The other A/B test was done long ago by RCA. Hi-Fi amplifiers were new, and many people thought that the extra high-frequency response made them sound worse. RCA used an acoustic low-pass filter with a cutoff of 7Khz. The filter was made of vertically mounted slats which pivoted so that the filter could be opened and closed, sort of like a sideways mounted Venetian blind. There was a live instrumental combo behind the filter and a curtain in front of it. Groups touring the RCA facility would come into the room, sit down, and do a blind A/B test. The results were overwhelmingly in favor of the high frequncies. RCA's explanation of why the Hi-Fi amps sounded bad was this: before anybody could play back thngs in Hi-Fi, nobody put much effort into recording things in Hi-Fi -- thus the high frequencies were badly distorted and really did sound bad through good equipment. I read about this in Pop Electronics or some such. The article was titled something like "The Experiment that Saved Hi-Fi". Many times I have wished that somebody would bring back that neato acoustic low-pass filter technology and wrap televisions in something that cut the flyback whine (what? you can't hear it? but that's only 15KHz!). wunder
brent@itm.UUCP (Brent) (01/25/85)
X
mako asked about early experiments that showed high frequencies
did matter. The classic example is the Olson experiments during the
'30s (I think). The big hoopla of that day was whether or not high
frequencies caused listener fatigue, and generally unrealistic sound.
Olson had a live group perform on stage and moved cloth battans around
to cut off high frequency sounds from the listeners. He found that high
frequency sound wasn't the cluprit, but high frequency distortion was.
(I believe he had something to do with The Labs, anyone who haunts
building 15 at Murry Hill care to comment?)
But in those days, high frequencies were, I believe, in the
8-12 kHz range.
--
Brent Laminack (akgua!itm!brent)rzdz@fluke.UUCP (Rick Chinn) (01/31/85)
> > RCA used an acoustic low-pass filter with a cutoff of 7Khz. The > filter was made of vertically mounted slats which pivoted so that > the filter could be opened and closed, sort of like a sideways > mounted Venetian blind. There was a live instrumental combo behind > the filter and a curtain in front of it. Groups touring the RCA > facility would come into the room, sit down, and do a blind A/B test. Actually, it was Harry F. Olson, while he was at RCA. The date was circa 1947. You can read more about it in Musical Engineering (now called Music, Physics and Engineering and reprinted by Dover). Just a bit of trivia. Rick Chinn John Fluke Mfg. Co MS 232E PO Box C9090 Everett WA 98206 ihnp4!uw-beaver----\ decvax!microsof \ ucbvax!lbl-csam \ +====!fluke!rzdz sun / sb1!allegra / ssc-vax------------/ (206) 356-5232
emrath@uiucdcsb.UUCP (02/07/85)
Oh yes, if anybody has tips or techniques for cutting down that flyback noise, I'd like to hear about them. My ears ring constantly at that frequency. I recently bought a new Hitachi and it had more noise than my old set. Actually, the high voltage supply (which I believe is driven off the horizontal yoke in your typical TV) seemed to add an amplitude modulation to the noise when a picture signal was present. I couldn't live with it and took it back and got a big Sony. This TV is awesome but it makes as much or more flyback noise as my old set (which I thought was too loud). 'course much of my problem is due to living around CRT terminals all day (or night). Solid state flat panels should be a blessing.