issue05

EMUSIC-L Digest                                      Volume 59, Issue 05

This issue's topics:
	
	high freqs
	K2000 Sample Playback Problem (10 messages)
	The trouble with digital.

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Date:         Tue, 28 Dec 1993 17:45:30 EST
From:         ronin 
Subject:      high freqs

be very careful how you put your understandings of empirical evidence, john.
the 20 KHz threshold is a norm, not a physical absolute. if you choose
to assert otherwise, please reference the appropriate article on cochlear
microphonics. further, the debate on whether or not phase interference
of >20 KHz components can have audible effects on normal listening is just
that... a debate. no psychoacoustics conference that i am aware of has
been definitive on that question. on a more circumstantial note, while i
have conventionally assumed as you have that anything above 20 KHz really
didn't matter, i have also been very surprised by the discrimination abilities
of some listeners... particularly blind people. it may be suggested that,
barring actual damage, everyone' hearing range is higher than is thought, but
that like cats and color-sense, it's just not useful for normal operations
and so is effectively filtered out.
on the other hand, i also came into this conversation late (au was down
somewhere in there). i notice that you refer to mass-marketing and esthetics,
neither of which i'm talking about here. so my apologies if i'm not addressing
the original point.
i have, btw, heard the difference between sound sampled at 32KHz and 44 KHz.
to me, it is subtle but it is there. actually, i suspect that it may even have
less to do with the sampling itself than the input and output filters, but
they are part of the process, you know. like analog, digital recording has
its compromises. the higher sampling rate allows some of those compromises to
be shunted well out of the normal hearing range - in particular the
nonlinearities of the filters. although i gotta tell ya, 48KHz makes no
sense to me at all.

-----------< Cognitive Dissonance is a 20th Century Art Form >-----------
Eric Harnden (Ronin)
 or 
The American University Physics Dept.
4400 Mass. Ave. NW, Washington, DC, 20016-8058
(202) 885-2748  (with Voice Mail)
---------------------< Join the Cognitive Dissidents >-------------------

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Date:         Fri, 24 Dec 1993 07:32:00 EST
From:         Robert C Graham Jr 
Subject:      K2000 Sample Playback Problem

Hello!

I am concerned about the information I have been seeing about the 18K
High Frequency rollof of the K2000's playing of samples.  How pronounced
is this rolloff?  Is there a company that does a mod that corrects
this problem?  If such a company exists, can those K2000 users tell me
about their experiences?  I do not want this problem to get in the way
of using what is otherwise such a fine machine as the K2000!

P.S.  By the way, does this rollof occur both through the seperate and the MIX
ouytputs?

Thanks!

RCG

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Date:         Tue, 28 Dec 1993 10:40:21 -0500
From:         William Matthews 
Subject:      Re: high frequencies

Yes, but....  there are hearable acoustic difference tones that result from
frequencies higher than those we can hear at any age.   Pauline Oliveros once
made a piece -- in the good olde tone generator studio days -- entirely from
difference tones made with (as I remember her anecdote) radio frequency
generators!  And there are demonstrable acoustic parallels.

This phenomenon is one of those which results in the difference between
acoustic instrument sound and loudspeaker sound.  If you're going to work with
electronic sound, you've already decided to accept sonic limitations...  all
circuit 'n' loudspeaker sound is "colored" because of frequency limitations.

  We just prefer to think of ourselves as members of some musical rainbow
coalition...

Bill
wmatthew@abacus.bates.edu

------------------------------
Date:         Tue, 28 Dec 1993 10:49:00 EST
From:         "DRCV06::GRAHAM" 
Subject:      Re: High frequencies.

I was off for a week, so am coming in the middle of this discussion, but I
am very interested in the issues of high frequencies, overtomes, and
differences between live acoustic performances and electronic reproductions
of them.

I will never forget the first time I heard a symphony orchestra after
having been raised listening to them on the hi-fi.  After spending some
time as a recording engineer and sound technician, I began to learn the
restrictions that electrnics place on true reproduction of acoustic
instruments.

Can somebody tell me why the frequency standard for compact disks was
chosen at 22 khz?  I have wondered very often why we are to be deprived of
many overtones because of that restriction.  Being blind, cd's are easier
for me to use than lp's, but I'd gladly go back to the lp with its better
response curve if it could be made as dynamically responsive as a cd ...
not to mention the ease of cd use ... it would mean less data, but how
about a 40 khz cd standard, would be great.

Dan Graham

------------------------------
Date:         Tue, 28 Dec 1993 10:13:00 PST
From:         "Rossi, John" 
Subject:      FW: K2000 Sample Playback Problem

>I am concerned about the information I have been seeing about the 18K
>High Frequency rollof of the K2000's playing of samples.

Why are you concerned about this information?  If you are over 20 you have
probably been rolling off frequencies above 18K for quite some time.  If you
are over 30 you probably haven't heard a frequency over 16K in quite some
time.  If you are over 40, chances are that you are substantially rolling
off frequencies above 12K.  While it is true that Kurzweil probably could
have increased the quality of its converters, it probably would have added
to the cost of the unit.  Judging by the response of almost everybody who
has used a K2000, one would have to guess that they made the right move.  It
has always been much more concerning to me that people consider the absense
of frequencies they cant hear problematic.  While there probably is a
psychoacoustical effect of supra-audio frequencies, it apparently doesn't
convey a lot of 'quality' meaning in most people.  After all, there is
nothing magical about the difference between 18K and 22K (about 3
semitones), and CD players have a brick wall filter at about 20K.  Most
people don't complain about some preceived lack of frequency response
(although some such as Neil Young do).  Anyway, there is no convincing
research (except one Japaneese study) which suggests that supra-audio
frequencies are meaningful, at all.

John

------------------------------
Date:         Tue, 28 Dec 1993 13:56:00 PST
From:         "Rossi, John" 
Subject:      Re: High frequencies.

 ----------
>it would mean less data, but how
>about a 40 khz cd standard, would be great.

>Dan Graham

The point I was trying to make is that frequencies higher than those which
can be 'heard' do not contribute significantly to the asthetic appeal of the
music.  Actually, if people were not media hyped to believe otherwise, I am
sure that a 15K standard would be accepted as a norm.  A/B tests do not
revela anything about mass market asthetics.  Also, differences in A/B tests
have not been observed in comparing CD standard music to analog recordings
with up to 40K of frequency bandwidth.  Concordantly, populations of people
who have little (if any) hearing above 15K (most people over 30) do not
differentiate between 15K and 20K digitally encoded music.

John

------------------------------
Date:         Tue, 28 Dec 1993 23:30:14 CDT
From:         Henry B Throop 
Subject:      FW: K2000 Sample Playback Problem

JROSSI writes:

> Anyways, there is no convincing research (except one Japanese study) which
> asserts that supra-audio frequencies are meaningful, at all.

Could you give a source for this?  I'm interested.

-henry
throop@ac.grin.edu

------------------------------
Date:         Wed, 29 Dec 1993 14:54:00 PST
From:         "Rossi, John" 
Subject:      Re: high freqs

My point wasn't that some (many?) people cannot discriminate frequency
content between 15 and 20K Hz (or even higher than that).  What I was trying
to point out is that in many A/B tests, done by the
recording-music-manufacturing industries, people were unable to discern a
difference between a CD and an identical analog recording with all
frequencies present up to 40K.  However, one Japaneese group found that if
you look at the EEG of people listening to a digital (20K cut) source vs an
analog source with frequencies to 50K replreente you see an amplitude shift
which occurrs about 10 seconds after the change from analog to digital or
vice versa.  I am going to be looking at these kinds of functions for the
next two years at Bowling Green State University.  There I will have access
to the only Brain IRD EEG analysis system in the US.  That equipment will
allow me to look at things like analog vs digital in addition to frequency
response and dynamic range factors using a unique analytical method.  This,
however, has little practical application for the public because all of the
critical tests which matter have been done and the correctness of their
interpretation proved by the mass acceptance of CDs and other digital media.

John

------------------------------
Date:         Wed, 29 Dec 1993 14:59:00 PST
From:         "Rossi, John" 
Subject:      Re: K2000 Sample Playback Problem

>> Anyways, there is no convincing research (except one Japanese study)
which
>> asserts that supra-audio frequencies are meaningful, at all.

> Could you give a source for this?  I'm interested.

> -henry
> throop@ac.grin.edu

I found it referenced in a Dave Moulton article in Home and Studio Recording
about 8 months ago.  The article was a pragamatic defense of digital media
in light of Neil Young's trashing of digital media.  Dave pointed out that
that study was the only one in which differences were found.  Incidentally,
Dave has agreed to participate in the design of my research effort at BGSU.
 He sold me my first synthesizer in 1972.

John

------------------------------
Date:         Thu, 30 Dec 1993 01:29:53 +0200
From:         Matias Dahl 
Subject:      Re: High frequencies.

*>many overtones because of that restriction.  Being blind, cd's are
*>easier for me to use than lp's, but I'd gladly go back to the lp
*>with its better response curve if it could be made as dynamically
*>responsive as a cd ... not to mention the ease of cd use ... it
*>would mean less data, but how about a 40 khz cd standard, would be
*>great.

  Yup.. I agree, BTW dows anyone know what the responce curves are for LPs,
 C-cassettes, etc..
    DAT 48kHz sampling speed
    CD  44.1kHz sampling speed

  Be careful.. you sounded like CDs would have sampling rate of 20Khz..

  I was tought way back that if you double the sampling rate and take away one
 bit, the sound quality would remain the same.. eg
    20khz 8 bit would be same sound wuality as 40kHz 7bit ?!? is this true ?!?

------------------------------
Date:         Thu, 30 Dec 1993 03:55:05 -0500
From:         David HAUBENSACK 
Subject:      Re: High frequencies.

>   I was tought way back that if you double the sampling rate and take away one
>  bit, the sound quality would remain the same.. eg
>     20khz 8 bit would be same sound wuality as 40kHz 7bit ?!? is this true ?!?
>

Not at all !

The number of bit is the amplitude resolution of the signal and it gives
the noise/signal ratio. The highest is this number, the better is the N/S
ratio.

The sampling frequency is the time resolution.

How would you manually sample ? If N is the number of bit and f the frequency,
it is the same as discretizing the signal Amplitude(t) thru a grid that has
2^N levels in the Amplitude direction and steps of 1/f seconds in the time
direction. Then you store these results on a CD... Of course, you must adjust
the recording level in order that the signal just fits in the height of the
 grid.

David.

------------------------------
Date:         Wed, 29 Dec 1993 06:46:28 -0800
From:         Michael O'Hara 
Subject:      The trouble with digital.

The filters.  Thats the problem.

At 44.1 KHz there is *theoretically* enough data, but real world filters
cannot deal with what I will call for clarity a "rapidly changing spectral
content" as well as the old analog disc can.  Most analog filters have
group delay problems, most oversampling-type filters have transient
ringing problems... "near perfect" filters are available - and I have even
HEARD one that works well - It costs a fortune, however.

In short, it is the *PHASE* resoulution that is digitals' problem.

A *twice* as high sampling rate would help a fair amount. And I would
have to agree with the man who wanted the 40KHz (80KHz) CD format.

But the difference would be most noticible with well recorded, complex
acoustic music.. and only as a feeling of increased "smoothness" in the
sound.

As I have mentioned before, the designer of the CD only classified it
as "Mid-Fi" - (well, I assume this was ONE of the designers) and as
such, true Hi-Fi performance is a difficult thing to achieve with the
format. period.

Oh, the "audia digi-master" used a very fast microcomputer that generated
64x "oversampled" signal... It used a "splining" algorithim instead of
the usual cheapo "sin (x)" based feedback type digital filter.

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