Spectral-motion aftereffects and the tritone paradox among Canadian subjects is the title of a paper published in the journal Perception and Psychophysics on research conducted by John Platt, Lloyd Dawe, and E. Welsh.
Have you ever spun yourself around for a while and then noticed that, when you stopped, the world seemed to spin slowly in the opposite direction? (OK, so maybe it's been a few years since you had occasion to try it, but try to think back...) This is known in perceptual circles as a motion aftereffect, and it has something to do with fatiguing the neurons that detect motion in a certain direction. Platt and his colleagues hypothesized that the same might be true for a more abstract kind of motion--motion up or down in musical pitch! They speculated that, if they could fatigue the sensory system by always playing it nothing but ascending intervals for a while, that, when they stopped, the next interval they played might be interpreted as descending! Of course, in order to do this, they had to use intervals that were a little ambiguous in the first place, and they found such a class of intervals described in the work of Diana Deutsche on what she called the "tritone paradox"--synthetic timbres composed of octave-harmonics-only used to play an ascending or descending tritone (i.e. 6 half steps or one half of an octave).
What were their results? You'll just have to pick up a copy of Perception and Psychophysics at your local newsstand to find out... OR, you could visit http://www.cameron.edu/~lloydd/webdoc1.html for some clues...
John Platt, professor of psychophysics at McMaster University, has been using his Kyma system to provide sound manipulation for the research projects of number of his colleagues in the psychology department at McMaster, among them:
An experiment to attract rats by playing back the sound made by lots of rats eating. Apparently, it is quite a distinctive (though not entirely pleasant) sound.
An experiment to alter the pitch of fathers' singing voices. Apparently, infants are more attentive to their mothers' singing than to their fathers', so the researchers tried shifting the fathers' voices up in pitch to see if that would attract the babies' attentions.
For a lucid and entertaining explanation of several "auditory illusions" like circular pitch, the tritone paradox, and auditory motion after effects, visit psychoacoustic researcher (and Kyma-ite) Lloyd Dawe's website http://www.cameron.edu/~lloydd/webdoc1.html. Dr. Dawe and his colleague Dr. John Platt make use of Kyma in their psychoacoustic research in these and other areas.
Professor John R. Platt has placed the course notes for an undergraduate course on human audition that he is teaching at McMaster University on the web
http://www.science.mcmaster.ca/Psychology/psych3a03/psy3a03.html
This is a great resource for those who would like to teach themselves more about the human auditory system as well as for those in related fields (like music) who would like to tie some of the findings of psychoacoustics in with work in their own field of study.
Kyma is referenced in Durand R. Begault's book 3-D Sound for Virtual Reality and Multimedia Applications. Intended for researchers, graduate students, and professionals in virtual reality, human-computer interaction, computer music, engineering, and psychoacoustics, the book focuses on the psychoacoustics, the design, and some applications of spatialized sound. The ISBN number is 0-12--084735-3. Click here to send Email to the publishers, or write/call them at:
Psychoacoustics researcher and professor John Platt has been using Kyma both in teaching his lecture and lab courses at McMaster University and in his own research in music perception and psychoacoustics. He writes about his uses of the system:
I initially bought the Kyma system for three main purposes. The first of these was to prepare demonstrations for an undergraduate course in auditory perception. The fairly technical nature of this course makes it difficult for most psychology students. This is particularly true if the material is not combined with numerous auditory examples illustrating the main points and demonstrating basic phenomena. It is very difficult to imagine sounds simply on the basis of verbal descriptions. We have thus prepared an increasing number of demonstrations of basic principles and phenomena in psychoacoustics and auditory perception for use in this course. These vary from simple illustrations of various waveforms and loudness levels through more complicated phenomena such as masking, critical bands and complex pitch processing to more cognitive phenomena such as auditory streaming and space perception. Most of these demos are simply presented to the students in the form of recordings, but in some cases it has been useful to provide the instructor (me) with interactive control of the sounds by way of virtual control panels. One such example is controlling the pitch, amplitude or location difference between two isocronous pulse streams to demonstrate fission and fusion of auditory streams.
Our second application of Kyma has been as the central instructional tool in a laboratory course I teach in psychoacoustics and music perception. In this course I begin by sitting around the computer with a small group of students and construct demonstrations of basic auditory phenomena that the students bring in so as to familiarize them with the operation of Kyma. We then proceed as a group to design a realistic auditory experiment. I help them implement it in Kyma, they run each other as subjects and then individually analyze the results and prepare a journal-style report of the findings. Finally, each student designs and executes his/her own auditory experiment, runs the other students as subjects and prepares a journal-style report of the findings. In these latter two stages of the course, virtual control panels are indispensable. They provide the interface between the subject and the experiment. Subjects use virtual push buttons to start trials and use virtual sliders or push buttons to subjectively match stimuli, report comparative judgments, rate stimuli on various psychological dimensions, make same-different judgments, etc.
Our third and most important reason for acquiring Kyma was to run our own research in psychoacoustics and music perception. Kyma has proved to be easily capable of implementing all the types of stimuli and experimental paradigms we employ, and virtual control panels are an ideal and flexible interface between the experiment and the subject.
Click here to visit Professor Platt's home page.
Jonathan Mackenzie presented a paper on his work with fractal sound synthesis and processing techniques using Kyma at the Edinburgh Science Festival in March 1997.
In December 1997, Eugenio Giordani is to present a lecture on Granular Synthesis to the faculty of Electrical Engineering at the University of Perugia (using Kyma for real-time demonstrations).
Starting in the fall of 1998, Lippold Haken will be assuming responsibility for the electrical and computer engineering courses that were previously taught by James Beauchamp at the University of Illinois (who has retired this year). The courses, on sound synthesis and audio engineering will be supplemented with a student lab that includes a fully-loaded Kyma system.
Composer Burt Fenner is working with a group of physics professors at Penn State University on a project to put a general physics course on CD-ROM. Fenner is providing not only music but also illustrative sonifications of some of the principles of physics discussed in the course. This mammoth project includes 11 units of 10 lessons each.