82ND MEETING ß ACOUSTICAL SOCIETY OF AMERICA

partment of Physics, Brigham Young University, Provo, Utah 84601.--A scheme has been developed for calculating the input impedance at the reed end of woodwind structures. The scheme is based on representing the bore and fingerholes of an instrument with 1ossy cylindrical sections. The log of the im- pedance is calculated and plotted at 10-Hz intervals over the range from 0 to 3000 Hz for each specified fingering of the instrument. Impedance curves have been calculated for the following oboe-like bores: (1) simple truncated cone, (2) smooth bores of one and five conical joints, (3) bores with dis- continuities at the reed staple, (4) oboe with fingerholes and no losses, and (5) oboe with fingerholes and losses. Dr. Arthur Benade provided experimentally measured impedance curves for the oboe used as the basis of the calculations for case (5). The experimental and numerical results are compared and discussed.

AfTrill, between its upper and lower tones. The form of fre- quency modulation of the sinusoidal signals was a square wave for the trill, and, for the vibrato, either a triangular or a 50% steady-state trapezoidal wave. Both trill and vibrato had identical center frequencies, fc, and duration (750 msec). Within the range tested (4-12 Hz), the modulation frequency had no effect on Af¾ibr. However, the adjusted Af¾ibr were consistently higher for the triangular modulation of the vibratos. The function relating •Xfvibr to AfTrill was monotonic with an average slope of 1.72 for the triangular vibrato and 1.07 for the trapezoidal vibrato. No difference could be ob- served as an effect of two different center frequencies 0re-- 705 or 2330 Hz) when frequency ratios AfTrin/f½ and Af¾ibr/fe were considered. The width of the observers' internal filter was estimated from the data. [Supported by NINDS Grant No. NS03856.'1

9:20

EEl-3. Vocal Cord Model for Singing. INGO R. TITZE AND WILLIAM J. STRONG, Department of Physics, Brigham Young University, Provo, Utah 84601.•A thick membrane is ap- proximated by a set of 16 masses, allowing for 32 degrees of freedom. The restoring forces are a combination of longitudinal tension and material elasticity. Thus the vibration becomes stringlike for high frequencies (high tension in the ligaments, or cord edges) and springlike for low frequencies (elastic properties of the vocalis muscle). Longitudinal tension and medial compression define the statics of the system of coupled masses, and the air flow determines the dynamics. Vibrato can be introduced by slowly modulating either the subglottal pressure or the cord length, i.e., the crico-thyroid muscular tension. Registration is accomplished by manipulating the elastic properties and the tension on the vocalis muscle. Various falsetto modes, including horizontal phasing along the edge of the cord, are set up by a medial compression ad- justment. The set of coupled equations is programmed on a small computer which includes a graphic display.

9:40

EEl-4. Pitch Change in Trills and Vibratos. P. L. DIVENYI AND I. J. HIRSH, Central Institute for the Deaf, St. Lous, Missouri 63110.--Musically trained subjects adjusted the absolute frequency change in a vibrato, ZXfVibr, to match the pitch change in a trill having a constant frequency separation,

9:50

EEl-5'. Musicians' Learning Perceptual Skills Using a Com- puter-Based Teaching Machine. W. J. DOWLING, Department of Psychology, University of California, Los Angeles 90024.•As part of a university program in innovation in instruction, music students in an introductory ear training course learn to reproduce tonal patterns using a computer-based teaching machine. The kinds of patterns involved are intervals of two tones, brief melodies, simultaneous combinations of tones in chords, and chord progressions. The basic procedure involves presentation of a stimulus pattern by the computer. The stu- dent then attempts to reproduce the pattern on a keyboard. The computer provides feedback and presents another pattern. Problems can be graded for difficulty and are designed to com- plement classroom experience in the course. The computer, a Hewlett-Packard 2116B, produces tone patterns directly through a digital-to-analog converter using a 3-kHz sampling rate. This sampling rate was chosen to provide sufficient fre- quency resolution and bandwidth for the musical pitches em- ployed, while at the same time leaving the computer able to attend to other users in a time-sharing system. The advantage of digital synthesis of tones lies in flexibility in choice of waveform and pitch scale. Students respond on an electronic organ keyboard monitored by the computer. The computer keeps a complete record of stimuli presented and students' performances. It is expected that this tool will prove to be of great value to both the teaching of perceptual skills of music and for studying the psychology of learning those skills.

FRIDAY, 22 OCTOBER 1971 GRAND BALLROOM, 10:00 A.M.

Session EE2. Demonstrations in Acoustics

WILLIAM J. STRONG, Chairman

Invited Papers (variable time)

10:00

EE2-1. Cochlear Blood Flow. M. LAWRENCE AND F. NUTTAL, Kresge Hearing Research Institute, University of Michigan, Ann Arbor, Michigan.--A movie illustrating blood flow through the vas spirale as discussed in paper L4 is shown. ß

EE2-2. Sound Wave Demonstration Apparatus. IRVIN G. BASSETT, Department of Physics, Brigham Young University, Provo, Utah 84601.--The apparatus described in this paper consists of four loud-

138 Volume 51 Number 1 (Part 1) 1972

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