Klarinet Archive - Posting 000481.txt from 1997/11

From: Josias Associates <josassoc@-----.com>
Subj: Re: Recording Quality of Clarinet
Date: Wed, 12 Nov 1997 19:43:58 -0500

On Tue, 11 Nov 1997, Mark Charette wrote:

> Jrykorten@-----.com wrote:
> >
> > Regarding the degredation that occurs during the recording process: I agree
> > whole heartedly. For me, ever since CD's predominated the market, I have had
> > a great deal of difficulty listening to either the piano or the clarinet.
> > Turns out the CD wipes out all the upper harmonics! (A 10kHz sine wave on a
> > CD looks like a triangle wave). It's probably for this reason that I can't
> > get excited about any clarinetists sound from a CD. In fact Shifrin's sound -
> > which used to excite me so - now sounds like anybody else when I listen to
> > him on CD. And I'm sure this is because of the CD recording process.
> >
> > The piano on the other hand sounds like some cartooon version of a piano with
> > "boingy" sounding strings to me.
>
> Jerry,
> If a triangle's what you're seeing off the end of your CD player then
> it's time to get it fixed. Even though the CD is recorded at
> 44 Khz/channel (so that 22Khz is it's maximum recordable frequency)
> it goes through a resonably sophisticated digital->analog conversion.
> At 10Khz there's no statistically significant difference in the
> output waveform from digital recordings.

> Mark Charette, Webmaster - http://www.sneezy.org/clarinet
> Web/Personal - charette@-----.org
> Business - charette@-----.com
>
Mark, Jerry,

In 1987, I attended a lecture-demonstration by Caltech
Audio-Engineering Prof. Boyck, who was also a concert pianist. The lecture
dealt, in part, with quantitative limitations on (then) current
parameters used in commercial digitization of audio signals. The audience
was composed of high-powered engineers and scientists, who were so
hostile to Prof. Boyck's controversial assertions that I worried
that someone might attempt to organize a lynch party. Being one of the
rabid doubters myself, I thought, "Who does this guy think he is,
the Billy Mitchell of Audio Engineering?"

Conceding at the outset the superior noise performance of the
digital approach, Boyck then attacked the inferiority of the reconstructed
digital-to-analog signal when compared to some straight analog storage
approaches. He temporarily smoothed some ruffled feathers by saying that
he wasn't attacking the digital approach, per se, as being inferior, just
the digital parameters then currently being used to make commercial CDs.

As if he hadn't yet gotten our attention, he announced that
the source analog waveforms were grossly undersampled -- that is, the
sampling rate at ca. 40 kHz was at least an order of magnitude (factor of
ten) too low. Similarly, he contended that the quantizing resolution of the
linear analog-to-digital converters (ADCs) currently in use was too small
for the dynamic range of the human ear. He finished drawing the battle
lines by asserting that the commercial producers of audio digitization
equipment knew all this and would not change the designs and associated
production tooling until commercial competition forced them to do so. (If
that were true, I thought, it would also apply to high-definition TV, which
the U.S. had been flying in satellite cameras since the early 1960s.)

Since nearly everyone in the audience knew Information Theory,
Boyck then immediately acknowledged that the Nyquist Frequency, the
highest-frequency component measurable without aliasing (seeming to be
of a different frequency, like the difference between the source and
sampling frequencies), was half the sampling frequency, or 20 kHz.
But that component would be reconstructed not as a sine wave, but as a
two-point triangular wave with artificial and unpredictable amplitude
reduction and phase displacement. And a 10-kHz component would have
appreciable stair-case-type amplitude distortion as well as phase
distortion.

The hue and cry from the audience included, "Who cares? My
middle-aged hearing doesn't even go up to 10 kHz."

Boyck told those people that, even with their compressed
frequency range, they could somehow perceive higher components and that,
like most other people, their hearing would be adversely affected by
subtle additions of high-frequency phase distortion associated exclusively
with the digitizing process.

He then presented the results of several experiments that
involved making music recordings, digital and analog, from the
same analog audio feeds. Everyone agreed that the digital recordings,
which used commercial sampling rates and resolution were inferior
soundwise to the analog recordings. The digital recordings, to be sure,
were quieter and of generally good quality. But everyone agreed that
an indefinable something was missing. In a remarkably sobering moment,
a large majority of the audience agreed that, for want of a more
quantitative term, the analog recording had superior "presence."

Unfortunately, there were no solo clarinet passages to critique.
But if there were, I would not expect to have heard intermodulation
distortion in the clarinet sound, because there were no weak links in
his recording/playback setup. However, the quality of the clarinet sound
might have been affected as were piano and voice tracks.

Professor Boyck concluded that part of his lecture by predicting
improved results from the digitizing process as sampling rates
approached 500 kHz. Although I don't follow the audio engineering field
closely, I am aware that contemporary commercial sampling rates are
increasing, which would affect the design of new CD and DAT players.

At the conclusion of Prof. Boyck's lecture, the audience's earlier
aggressive attitude about digital recordings was markedly subdued. Most
people seemed prepared to acknowledge at least qualitative (if not
quantitative) acceptance of the lecturer's thesis about digital audio
sampling parameters.

Connie

Conrad Josias
La Canada, California

   
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