Dr. Tom's Reply to: Geoff Weiss

[<gbmaidsf@wco.com>]

Subject: Re: Who's Dr. Tom? From: iigs@wam.umd.edu (Geoff Weiss) Date: 6 Sep 1995
01:42:22 GMT Message-ID: <42iu9u$dn6@cville-srv.wam.umd.edu>
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Well, Geoff - here's my detailed reply to your request for some answers. Please
note: My answers are marked with (*) Geoff Weiss wrote, as noted by Paragraph -
followed by a number in parenthesis:

Paragraph (1) - I, like many, still question the validity of your claims with the
VAMPS. I got a book from the school's library (3-D Sound For Virtual Reality and
Multimedia. Begault, Durand R.  AP Professional, Boston, 1994.) on the subject of
3-D sounds and it appears that the GS is unable to support 3-D sound with the
software that is available.  Before I go into why I think this is the case, I
want Dr. Tom to explain (in one paragraph or less) the following terms (to see if
he knows anything about this subject):  IHL, HRTF, and R/D ratio. Concepts like
these are what should be explained with the VAMPS documentation. Words like
"Digital Audio Transmutation" are complete nonsense.  How can you change digital
audio?  It is all 1's and 0's.

(*) Taking grammar, spelling and word omissions into consideration, your
paragraph (1) above, had no breaks for subject changes. It's too complex -
compound in structure and would be given a grade of D, by any English teacher
that reviewed it.  Your paragraph (2) below, has several spelling errors and word
omissions.

The GS is indeed able to support 3-D sounds, as is any computer, which can play
music in stereo, with more than 6 tracks in the music score, if the samples are
coded and/or score-scaped as such, then ported to that computer for use with the
music programs it supports.  The 3-D ported samples can be additionally localized
with the scores soundscape, by using simple and standard 3-D special effect
procedures like; volume fade-in and volume fade-out, vibrato, tremolo,
pitchbend-up and pitchbend-down, reverb, echo and double track/position stager of
the track/sample/scores, to create azimuth.  Azimuth refers to left/right tilt.

I'll try to contain the explanations of;IHL, HRTL, and R/D ratio within one
paragraph or less. However, if you wish a concise definition of these terms, it
would exceed one paragraph. Thus, for additional understanding of these and many
other terms, you should refer to the references, obtain and read them, as indexed
at the end of this post. HRTL is head-related transfer function. IHL is "in-head
localization'. R/D ratio is both; reverb distance ratio and reverberant-to-direct
sound ratio.

With respect to "Digital Audio Transmutation" being complete nonsense, please
allow me to explain. Digital Audio Transmutation, a term that I invented, (DAT
for short) refers to the standard and well established effects of sound
hetrodyning.  Where you take two different audio signals, patterns, frequencies
or sounds, apply them together, to get a third and unique sound, signal, pattern
or frequency. All sound is converted (or transmutated) from digital to analog,
before it can be perceived by the human ear. Now, does that sound like complete
nonsense?

Paragraph (2) - Now here some of the reasons why I don't you can make 3-D sound
on the GS.  1) One way to produce 3-D sounds is with 2-4 DSP boards and a mixer. 
No GS Stereo cards have that.  2)  Another way to produce 3-D sounds is with a
"convolvotron"--the hardware in the Gravis Ultrasound card for the PC.  No GS
stereo card has that. 3)  For a sound to appear to come from a specific
direction, you need to play the same sound at the same time in both ears AND to
process the result through a FIR filter (this is what the convolotron does).  I'm
100% positive that the ensonique chip inside the GS does not have any FIR
filters.  If anything, any modifications you made to these songs were the FIRST
step to produce 3-D sound.  These songs do not have the 3-D characteristics that
you claim.

(*) Items 1, 2 and 3, as outlined above are indeed correct.  With respect to your
abstract and blanketed conclusions that the GS can't produce 3-D sound, well you
are vastly under-rating the GS sound abilities!  No, the GS has no FIR filters.
Such filters are not required to achieve 3-D soundscapes, as presented in the
VAMPS music modules and the playback basic JukeBox program, using Noise Tracker
GS, versions; 1.0, 1.3, 1.4 or 2.0. As Dr. Begault has stated in his publication
"CYBERARTS - EXPLORING ART & TECHNOLOGY, page 80, paragraph 1 - "The idealistic
goal of 3-D audio technology is to control every act of spatial hearing, using
nonspecialized playback systems".

I've discussed the VAMPS and Noise Tracker GS program abilities for designing and
presenting 3-D and psychoacoustic soundscapes, in 8-bit audio stereo output, with
Dr. Begault, at length. He agrees - that it is very possible to do such with the
IIGS, a stereo card, ported and processed 3-D samples, the structured score
abilities of Noise Tracker GS and also with SoundSmith, by using standard
psychoacoustic special effects, as I've outlined above for your review. VAMPS
music modules, as I have presented them are indeed the idealistic goal of 3-D
audio technology to present and control every act of spatial hearing, using
nonspecialized playback systems. I trust you will not argue with Dr. Begault!

Paragraph (3) - I'm going to state for the record that I am in no way an expert
in 3-D sound. All of this information is directly from the one book I checked
out.  I did not read the book in its entirety--I skimmed it to find out about the
theory and practical applications.  Also, I do not have a stereo card in my GS. 
I believe others who say that they do not hear 3-D sound with the VAMP pieces.  I
have given reference information about the book for anyone for anyone who wants
to verify this subject matter.

(*) With respect to your comments in the above paragraph 3, You are not an expert
in 3-D sound.  On that, I agree. However, for the record I'd like to make it
known that I do consider myself an expert in 3-D sound.  I've been involved with
3-D sound technology, have researched and applied it's abilities from 1967 to
date!

During this period of time, I've amassed an extensive library and collection of
books, research reports, personal papers and publications on all aspects of 3-D
sound, sound applications, theory and use, in many fields of audio research and
interest.  When I read something, I don't skim read it, as so many people that
use the Apple II and post to Usenet - csa2 seem to do. I read it completely, over
and over again, until I understand it thoroughly. If I don't understand any
aspect of any of it, then I'll research the issues until I do!

The fact that you do not have a stereo card in your GS and state that the VAMPS
are not 3-D is an absurd and illogical personal conclusion. How could you
possibly hear a 3-D sound of any sort from a IIGS, with no stereo card. You also
need a stereo system, a set of over-the-ear, high-intensity, electrostatic
headphones and any SRS sound system, as the final filtering, amplification and
output unit, to connect your headphones to, in order to listen to the VAMPS and
perceive the 3-D soundscapes.

You are obviously basing your conclusions on the collective, ignorant, biased and
untrained expressions of others. They may very well also, not have a stereo card.
Is this a fair basis to conclude that my VAMPS are not 3-D?  You believe other
who say - indeed!  To be able to hear 3-D sounds requires a trained ear, an
acquired sense of trained and skilled depth, distance and sound localization
perception, in both the vertical and horizontal sound plains, as any expert in
the field of 3-D sound and/or Psychoacoustics would tell you!  Perceiving 3-D
sound is an acquired skill, that requires time and practice to develop your
abilities to perceive all aspects of 3-D soundscape designs.  Again any expert in
the field of 3-D sounds and/or psychoacoustics will tell you this, if you ask
them. I've clearly stated most of the above in my VAMPS, NTV and MegaMODS
documentation files.

If you are still in doubt, concerning any of the above - please give Dr. Begault
or myself a call.  I'm sure he will be only to happy to discuss all these issues
with you.  And, I certainly will.  You should be able to reach Dr. Begault via;
(415) 604-5000, the main number for NASA-Ames Research Center and ask for his
extension. That's the number I reached him from, about 6 months ago.  You can
contact me at (415) 468-1609.

You may also wish to obtain and read/review the following references, to gain a
more through understanding of 3-D sounds and Psychoacoustics.

GS Sounds; Parts 1-5, C. Turley, Available on ftp/grind/apple2/1WSW

Spatial Hearing: The Psychophysics of Human Sound Localization, J. Blauert
(M.I.T. Press, Cambridge, MA, 1983)

"Control of Auditory Distance", D. R. Begault, dissertation, Univ. of Ca., San
Diego (1987)

A Virtual Display System for Conveying Three-Dimensional Acoustic Information. in
Proc. Human Factors Society 32nd Annual Meeting (1988), pp 86-90

Headphone Simulation of Free-Field Listening. II: Psychophysical Validation, J.
Acoust. Soc. Am., Vol. 85, 868-878

Localization of Nonindividualized Virtual Acoustic Display Cues, Proc. CHI 91 ACM
Conf. on Computer-Human Interaction (1991), pp. 351-359

Headphone Simulation of Free-Field Listening. I: Stimulus Synthesis, J. Acoust.
Soc. Am., vol. 85, pp. 858-867

Perceptual Effects of Synthetic Reverberation on 3-D Audio Systems, presented at
the 91st Convention of the Audio Engineering Society, New York, 1991 Oct. 4-8,
preprint 3212

Digital Simulation of Sound Transmission in Reverberant Spaces, M. R. Schroeder,
J. Acoust. Soc. Am., vol. 47. pp. 424-431 (1970)

Music, Sound and Sensation - A modern Exposition, Fritz Winckel, (Translated from
the German by Thomas Binkley), Dover Publications, Inc. New York, (1967)

The Psycho-acoustical Analysis of Structure as Applied to Electronic Music, F.
Winckel, Music Theory, 7:194 (1963); New Haven, Yale School of Music Publication
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Geoff -- preferred email address: geoff@the-hermes.net <a
href=http://www.the-hermes.net/~geoff/>Home Page</a>