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#16
December 13th 07, 07:19 PM
posted to rec.radio.shortwave
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HD Radio
D Peter Maus wrote: David Eduardo wrote: "craigm" wrote in message ... David Eduardo wrote: A:B comparison of HD and a CD is nearly indistinguishable, but with Analog FM it shows coloring. How about something more quantitative? Radio listenening is based on perception, not statistics. S/n is only important if the noise is audible... the big difference is the very perceptable difference between preemphasized analog FM audio, vs. non-preemphasized digital audio in the HD stream. Not even close to being true. Not much of what 'Eduardo' says is... I did some perceptual studies in Texas, this was about 1984, to make a point to my chief engineer who was trying to say the same things. Without going into numerical analysis, we discovered that, though the test subjects, and two of the testers, couldn't put language to it, they did prefer sounds with the highest S/N, even though in a dead room with no program applied, they couldn't distinguish between various noise floors. The results surprised everyone, at how sharp the perceptions were. Not only did the listeners prefer, all other parameters being equal, the higher S/N, but they did so by an overwhelming majority. In two tests, as high as 78%. The tests were quadruple blind, and conducted over several weeks, with a subject field of 100 participants. The tests were done in several acoustically variable environments...a common living room, a music listening room, a studio listening room, a recording performance space, a theatre, a stationary vehicle, a moving vehicle, and an open area outdoors. Actually, a game preserve. Acoustic outlets included Klipschorns, Heresy's, AR58's (don't hold me to that one), KLH-23's, KEF 104's, JBL L200's, and headphones including Sennheiser 414's, Pioneer SE-L40's, Koss Pro4AA, and a pair of Radio Shack, the model of which I've forgotten. All acoustic devices were used in all acoustic environments, except the vehicles, where Jensen auto speakers were used, and each of the headphones. Even where the respondents could not distinguish between baseline noise floors, they expressed opinions of preference for the programs with higher S/N values. Even though, in most cases, they could not explain what it was they were hearing that was different. More detailed analysis of this phenomenon has been written about in engineering texts for years. The best of them by Harry Olson. As part of the same tests, we did comparisons of broadcast exciters, using the same models and configurations of exciters used by all the stations in town, and compared them, again quadruple blind A/B tests into single receivers, and there was no discernable pre/de-emphasis difference. We did this with a number of test receivers, as well. Receivers included those by Yamaha, H-K, Sansui, and Pioneer, and tuners by Nakamichi, Pioneer, and Kenwood. There was no statistical perception of any pre/de-emphasis error by the same test subjects who could discern S/N differences in a moving Cadillac. And Fanfare Electronics at the Consumer Electronics Shows, when they were in Chciago, stunned audiophiles by playing a CD through an unmodified Broadcast Electronics exciter over the air into their FT-1 tuner, into a Jadis amplifier, and B&W speakers and in an A/B with a direct feed from the Studer A730, audiophiles from all over the country could not tell the difference. Statistically, no preference between the CD over the FM and the CD direct. Zero. Over 10 days, with thousands of subjects. This test had been done also by Magnum Dynalab at CES, and has been repeated at every CES where Fanfare has shown up since it's inception. So, your claims of pre/de-emphasis coloration are nonsense. The pre/de-emphasis complex is 100% complementary and of no discernable impact on the output. Opening heavy drapes in the listening room will have more impact on the listening experience than pre/de-emphasis tracking errors. The difference between HD and analog FM audio, is 100% a factor of the processing done to the audio. Which is dynamic and spectral in analog, and digital in HD. What's more, is that, with your engineering experience, you should know that. One more thing that raises questions. |
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