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The 20kHz limit?

Author: Kevin Bowman
Date: 1999-08-12 15:06

Hiroshi wrote (in another thread):
As to CDs,they cut sounds above 20k Hz. There are machines to recover (Pioneer makes one of them) those ranges since we feel uncomfortable without those ranges of souds.
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Sorry, I had to take this issue out of the vibrato thread and slam it around a bit here. I don't wish to offend you, Hiroshi, but there are many myths surrounding recording, digital music, sampling, etc. that I must debunk.

First - there *may* be a psycho-accoustic effect on humans by frequencies over 20kHz and a *very* small percentage of people can hear frequencies up to 22kHz, albeit very faintly. But the fact remains that physical limit of the average (and most common) human ear is indeed 20kH.

Second - many audiophiles believe that digital recoding does not have the "warmth" of analog - this is partly true. I say digital recordings have more "brilliance"! This disparity is due not to the recording medium but the the advance in audio sensor technology (i.e. microphones). Since the advent of digital recording techniques, engineers have wanted to use the *entire* spectrum up to 20 kHz. Before digital, you would be very hard-pressed to find a microphone that had decent response above, say 18kHz. So what people started hearing with digital recordings was the frequencies they had never before heard from analog recordings - minus the "scratch", too.

Third - I've never heard of device to "recover" lost frequencies. Beside's, it's just not possible. Sampling an analog signal to a discreet medium (digital conversion) is a *lossy* process. There's absolutely no way to recover what the exact original values were. So if frequencies above 20kHz were not recorded, there's no way to "get them back". No matter what Pioneer's advertising hype might be.

It's my belief that recording technology has advanced sufficiently to bring near-real-life sound to listeners ears. But a recording will *never* be the same as hearing an orchestra, opera, big band, etc. live. There's so much involved in the recording process that can (and will) degrade the signal, even with the most expensive hi-tech equipment. Heisenberg's (sp?) uncertainty principle comes into play here which, basically, is this: the very act of observing something effect the outcome. In other words, you can't record sound without changing it.

Feel free to flame away (as I know this is a highly volatile subject) ...

Kevin Bowman

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