lance@uunet.UU.NET (Lance Norskog) (02/21/91)
ap207nra@venus.ycc.yale.edu writes: >If anyone knows where I can find more information on research being done >on "virtual sound", please let me know. The February 1991 issue of Computer Music Research contains an article on placing N speakers around you, controlled by N/2 MIDI synths with stereo reverbs. They put mikes in the center and calibrated against MIDI volume numbers. The article includes the mathematical model. The Midi comes out from a Mac sequencer, and the sequence player was modified to control the synths and reverb units according to math model and the calibrated sound inputs. They show a Mac application where you draw the sound placement over time in a 2D plane; the sequencer takes this into account during playback. Very slick. Their model is 2D, i.e. placed in a 2D plane. The last line says something to the effect that extending it to 3D should be easy. I'll go along with this just as soon as I understand the page of formulae they gave. If you stick to playing back pre-built sound samples, a separate processor could handle 3D sound placement. Antex in Gardena, CA (213-something) is advertising a PC card with stereo digital sound output, VGA with NTSC, a TI 32010, and 1Mb of RAM. Two of these could handle sound and video for a head-mounted rig, with 3 speakers around you and one overhead or 2 speakers in each ear mounted diagonally. Given that the functionality of $500 synths would take $5000 to add to an all-digital VR system, I think MIDI has a place in VR, especially in room-based systems. (As opposed to body-mounted systems.) On the subject: I brought up MIT's Csound package under 386 UNIX, and it takes 1-30 times real-time to compute scorefiles. That is, 1 minute of 8K/s samples takes 1-30 minutes to generate. Quadraphonic or 3D placement will take a little longer. (Now, if only I could find quadraphonic or octaphonic headphones.) Csound takes instrument and scorefile specifications, and generates sound samples with controllable sample rates and sound quality. The csound player is built around partial interpretation; it builds up an internal database of what you want done, then cycles through it. The code is pretty unreadable, but it looks like they're trying to be efficient. They claim a Sun-4 can generate in real-time. It has stereo and quad sound by panning volume; this is cheesy. Real placement needs phase control. Csound has a lot of neat stuff. You can take a sound sample, analyze it to death, and turn it into a frequency-based instrument specification. This apparently will do pitch-shifting correctly, with no hamsterization. I have long dreamed of an electronic "pan" or steeldrum; this might help. Also, CMusic and the CARL library from UCSD are available to researchers. F. Richard Moore, Mr. CARL, has a book out on CMusic. I haven't downloaded the package yet. Lance Norskog
txtj@vax5.cit.cornell.edu (Scott Glazer) (02/22/91)
I know Jaron Lanier's worlds (or some of them) have fairly realistic directional sound, stuff like a ticking clock that comes from the right direction and if you put your head read close it sounds louder in one ear (though come to think of it, this is a much easier trick than getting the phase differences correct and compensating for pinna distortions). I've thought for a while that virtual sound could provide a real inroad for a consumer application of virtual reality. If we could get all the sound processing neccessary on a chip, you could stick it into a walkman, mount a real cheap head-rotation sensor on one of the earphones, and produce some fairly interesting effects. It would work best with sound recorded binaurally, of course. The idea is that is you hear, say, a trumpet player in front of you and a drum to the right, you could turn toward the drum, and hear it in front. Give you some real interaction with whatever you are listening to. -Scott Glazer "Our universe is probably closed, its spacetime structure resembling a tremendous doughnut. Scientists have recently initiated the search for the cream filling."
dphaine@rose.waterloo.edu (Shaggy One) (02/26/91)
I am looking for any papers or articles on how to simulate 3D sound
using digital signal processing techniques. I would like to know
how an "earprint" is made and how the this information (a transfer
function?) is used to make a sound seem like its coming from a distinct
point in 3-Space.
This is for an application project in my DSP course which is why I
need some technical information.
Any info will be much appreciated.
--
Ajay Jindal. "Peace, Love, and Dye."
Disclaimer: This is a borrowed account. The views expressed do not represent
those of dphaine@rose. Replies, however, may be sent there.testarne@athena.mit.edu (Thad E Starner) (02/26/91)
In article <16816@milton.u.washington.edu> xhost91!lance@uunet.UU.NET (Lance Nor skog) writes: >On the subject: >I brought up MIT's Csound package under 386 UNIX, and it takes >1-30 times real-time to compute scorefiles. That is, 1 minute >of 8K/s samples takes 1-30 minutes to generate. Quadraphonic or >3D placement will take a little longer. (Now, if only I could .... >They claim a Sun-4 can generate in real-time. It has stereo and >quad sound by panning volume; this is cheesy. Real placement needs >phase control. Can vouch for the sun-4 stuff. The stuff I do was the original basis of the claim. I run a virtual drumset (polhemus, hidden line removal, etc.) and still have enough time to run csound real time option for the sound (on a SparcStation 1). In general sun 4's can handle csound real-time generation stuff easily (8k, mono). Thad Starner