The science of acoustics is quite complex, particularly in the areas of psychoacoustics and psychomusicology. One of the first quagmires one encounters when studying acoustics is the difference between physical properties of sound, and human perception and processing of sound. The way one measures and analyzes sound is not the way one hears sound. Music educators are more likely to focus on the perception of sound and its interaction with the physical properties of sound, rather than just the physics of sound. Hence, there is a need for laboratories, graphic demonstrations, and experiments in these fields of study.

In the past, acoustics instructors used wave tanks and mass spring vibrators to illustrate various acoustical principles. This equipment was large, heavy and did not produce sound; rather, it illustrated the properties of sound through a variety of energy transfer mediums designed to approximate the actions of sound disturbances through air.

In the present zeitgeist, computer programs can graphically illustrate physical concepts as well as reproduce the sound creating the phenomenon. There are several programs on the market that will suit the needs of the acoustics instructor. Alchemy was one of the more sophisticated and robust programs. However, this program is no longer available and requires more than a Macintosh Classic or SE for optimum performance. There is also a software package called LabVIEW, designed for the engineering or physics department. This program is very expensive, user intensive, and requires a sophisticated computer. Sound Edit is a simple and inexpensive program that will, in most situations, meet the needs of the acoustics instructor or psychoacoustics researcher.

The Sound Edit programs were designed for the development of Hypercard stacks and multimedia presentations. However, there are aspects of the program that will allow one to maintain the degree of control over a sound stimulus that is necessary for psychological experimentation. Sound Edit has features for editing and mixing sounds and viewing sound waves. It also has a crude spectographic analyzer, which gives the user an approximation of a Fourier analysis.

This demonstration uses version 2.0.3 of Sound Edit. The newer version, Sound Edit Pro, (2.0.5) is now available (it is also much more expensive). There is not much difference between these programs in their abilities to analyze and create sounds. The main advantages of Sound Edit Pro over Sound Edit are in its ability to mix sounds. The earlier version (2.0.3) has a more intuitive sound spectrum analyzer, however it still is not as robust as one would like for Fourier analysis.

Both versions of Sound Edit are easy to use; and an experienced Macintosh user will seldom, if ever, need to refer to the manual. Sound Edit can either record sounds from the environment, or create sine, sawtooth, or pulse waves with a built-in tone generator. The program can now edit or mix these sound files in a variety of ways. One can then save the files, either as is, or as a sound resource on a Hypercard stack. When saved as a sound resource the sound can be played back with any of the appropriate Hypercard commands.

The main screen of Sound Edit may contain one or more windows for the creation and display of sound waves (figure 1). There are several scales for displaying the sound wave. The only one that would be of interest to the acoustics instructor is the most augmented one. The other window that displays information valuable to the acoustics instructor is the spectrogram (figure 2). The main problem with this feature of Sound Edit is the scale is fixed at increments or multiples of 125 Hz. There is also quite a bit of what appears to be random noise in the spectrogram display. This makes analyzing sound based on a different fundamental frequency awkward. However, one still may make use of it for demonstrating Fourier Analysis.

PRESENTATION

This paper focuses on the setup and delivery of two labs. The first lab illustrates the perceptual phenomenon of fundamental tracking, as well as how simple sine waves combine to make a complex wave. The second is an experiment on the importance of the attack in timbre recognition.

In the fundamental tracking lab three sine waves of 550 (C#), 660 (E) and 770 (G) Hertz are created using the Sound Edit tone generator. Each wave is played individually, and then the three waves are mixed. This creates a wave which sounds an "A" at 110 Hertz. Examination of this new wave also illustrates the way simple sine waves are combined to form a complex wave.

In the timbre recognition lab, three instrument sounds are recorded (trumpet, piano and clarinet). The sounds are then edited so the attacks (initial transients) are removed, leaving only the steady state sound. The subject is to identify the sounds both with and without the attacks. One will find that the sounds with attacks are easier to identify.

Sound Edit has several weaknesses for acoustics work. The sound spectrogram does not accurately represent the Fourier analysis of a musical sound; and Sound Edit can only mix four sounds at a time. Also, one should note that this program was designed to edit sounds for Hypercard stacks or multimedia presentations, not to illustrate acoustical phenomenon. However, Alchemy was designed to edit sounds in a recording studio. Only the software LabVIEW is specifically designed for scientific experimentation with sound.

A strength of Sound Edit is its user-friendly interaction with Hypercard, enabling an instructor to prepare elegant tutorials, classroom demonstrations, and experimental stimuli. Further, with the use of an external sound system, the 22 Hertz sampling rate will record and play back sounds of a quality suitable for trained musicians.