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May 1981

Volume 69, Issue S1, pp. 31-S125

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back to top Session Q. Musical Acoustics I: Musical Instruments, Timbre and Temperament
Contributed Papers
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The effect of surface coatings upon brass‐instrument tone quality (A)

Robert W. Pyle, Jr.

J. Acoust. Soc. Am. Volume 69, Issue S1, pp. S37-S37 (1981); (1 page)

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An experiment was conducted to see if lacquer and silver plating have any measurable effect on the tone quality of brass instruments. A French horn fitted with a detachable bell was tested with two bells. One bell was initially lacquered, the other silver‐plated. The tests were repeated on the same bells after the lacquering and plating were chemically removed. Lacquer was found to decrease the acoustic output of the horn, more so at high frequencies than low; silver plating had no detectable effect. Anecdotal evidence from players qualitatively confirms the experiment and suggests that the effect of lacquering an instrument, though small, is not musically insignificant.
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Spectral similarities of tones from “especially useful” musical instruments (A)

A. H. Benade

J. Acoust. Soc. Am. Volume 69, Issue S1, pp. S37-S37 (1981); (1 page)

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In a room the ear can track pitch, tone color and dynamic nuances of musical instrument tones with quickness, stability, and precision, even in the presence of many similar tones or of noise (otherwise music would be impossible). It has been recognized that the ear is most effective with tones consisting of a set of harmonic components; with fairly strong lower partials and upper partials that rapidly fall away. This spectral rolloff apparently reduces intercomponent masking in the upper critical bands, a phenomenon that exists above the 6th harmonic. A study has been made of room‐average spectra for tones from instruments recognized as being especially useful in ensemble playing (oboes, violins, trumpets, pianos, saxophones, and bassoons). The spectra are remarkably similar: After a few srong lower harmonics each instrument shows an average rolloff of very nearly 18 dB/octave beginning at the 5th or 6th harmonic. There is no reason in physics why these diverse instruments share such spectral features. Instruments that “carry” less well (e.g., flute, cornet, or “vibes”) roll off earlier and/or more steeply. Tones with slower rolloff (e.g., the lowest note of an oboe sans lower joint) also show weakened trackability and pitch. [Work supported by NSF.]
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Bassoon spectrum transformation function (A)

A. H. Benade, J. C. Carman, and P. H. Barrett

J. Acoust. Soc. Am. Volume 69, Issue S1, pp. S37-S37 (1981); (1 page)

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Individual notes and also musical passages have been recorded with one microphone moved about the room, and the other probing the bassoon's reed cavity signal. Room‐averaged (“external”) spectra p‖(ext) and mouthpiece (“internal”) spectra p‖(lnt) are measured for the harmonic components of the mf level notes C2, F2, C3, F3. The precision is ±2 dB from all causes (player variability and room fluctuations). The smoothed transformation function 〈T(f)〉 = 〈pext/plnt〉 is calculated as a continuous function of frequency. This has a broad peak (30‐dB high, 500‐Hz wide at 15 dB down) centered at 600 Hz. Above this it fluctuates smoothly before rolling off steeply above 2000 Hz (20 dB down by 2500 Hz). The T‖′s of individual components differ from the corresponding values of 〈T(f)〉 by about ±6 dB. Loudspeaker playback of music using the internal signal via an electronic equalizer set to 〈T(f)〉 sounds like a bassoon but lacks “life.” Boosting or cutting several randomly chosen ⅓ octave bands by 4–8 dB improves the realism considerably, in the judgement of bassoonists and others. [Work supported by NSF.]
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Oboe normal mode adjustment via reed‐staple proportioning (A)

W. B. Richards and A. H. Benade

J. Acoust. Soc. Am. Volume 69, Issue S1, pp. S37-S37 (1981); (1 page)

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We have analyzed a model oboe consisting of a body cone of variable length and fixed truncation (of length x0) at the apical end. The missing apical cone is replaced. by a reed and staple model consisting of a tapered neck and a cylindrical cavity. Computer experiments searched for cavity and neck proportions giving an input admittance (seen at the junction with the main body) closely the same as that of the missing apical cone. It has already been shown that two major constraints on the cavity and neck proportions exist: Their total volume must match that of the missing cone, and their first mode frequency must equal that of the apical segment (fr2 = c/2x0). Subject to these constraints, cavity and neck lengths, diameters, and tapers can be found that make the first four modal frequency ratios harmonic within 5¢ as the length of the body is varied to sweep the first mode over its usual one‐octave range. Insight from this work plus study of the effects of small departures from these proportions provides practical guidance for the adjustments of reeds for real oboes, whose air columns are not quite conical in their acoustical behavior. [Work supported by NSF.]
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Standing waves in a flute (A)

William J. Strong, Ron Silk, and Neville H. Fletcher

J. Acoust. Soc. Am. Volume 69, Issue S1, pp. S37-S37 (1981); (1 page)

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Standing wave patterns for pressure were calculated and measured for two alternate A6 fingerings on a flute. For a fingering with the D# key open the calculated pressure distribution agreed well with a similar result from Coltman [J. Acoust. Soc. Am. 65, 499–506 (1979)] and with probe tube measurements made on the instrument when excited sinusoidally at resonance. For a fingering with the D# key closed the agreement among pressure distributions was much poorer. These results will be discussed in terms of the sensitivity of impedance matching in the open hole part of the tube as a function of frequency. [Work supported in part by Australian‐American Educational Foundation.]
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Cognitive correlates of musical similarity in chords for musicians and nonmusicians (A)

A. Lynne Beal

J. Acoust. Soc. Am. Volume 69, Issue S1, pp. S38-S38 (1981); (1 page)

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The perceptual and cognitive structures for music recognition possessed by trained musicians and musically naive listeners were examined through a similarity judgement task. Listeners rated chord pairs for perceived musical similarity. Chord pairs were identical or different in musical structure. Timbre, an acoustical property not related to musical structure, was manipulated independently by playing chords on harpsichord and guitar. Chord pairs involved the same or different instruments. Musicians' similarity ratings were unaffected by timbre differences. Attributes related to the musical structure of the chords (e.g., pitch equivalences and component intervals) determined their ratings. In contrast, nonmusicians did not separate musical similarity from acoustical similarity and used different criteria for rating chord pairs played on same than on different instruments. These results support earlier findings (Beal and Allard, Canadian Psychological Association Convention, June, 1980) that musicians develop cognitive structures for analyzing musical stimuli through formal study of music theory. Without this expertise, nonmusicians must process the sounds on a more cursory acoustical level.
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Perceptual discrimination of just and equal tempered tunings (A)

M. V. Mathews and Gregory Sims

J. Acoust. Soc. Am. Volume 69, Issue S1, pp. S38-S38 (1981); (1 page)

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Just and equal tempered intonations have been discussed for centuries. However, few perceptual comparisons have been made because it is difficult to repeat a musical performance exactly after changing the tuning. Pairs of short examples were synthesized on a computer in just and tempered intonation. Except for tuning, the two members of a pair were identical. Subjects listened to a pair and judged which tuning was played first. Results were complex. Highly trained musicians discriminated with high accuracy. Everyone else performed at close to chance levels. Harmonic (simultaneous notes) judgments were more accurate than melodic (sequential notes) judgments. Listeners typically based harmonic comparisons upon the strength of beats and used pitch memory for melodic judgments. Some intervals (3rds) were easy to discriminate, though others (5ths) were almost impossible.
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Multichannel digital synthesizer design using bit‐slice microprocessor architecture (A)

Blair D. McKay and Barry L. Wills

J. Acoust. Soc. Am. Volume 69, Issue S1, pp. S38-S38 (1981); (1 page)

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Real‐time synthesis of complex audio waveforms is required in a number of computer music applications. Digital synthesizers can achieve the desired complexity by additive means where multiple oscillators per voice are employed, each with controlled frequency and amplitude envelopes. In order to meet the real‐time requirements and also provide perceptually acceptable output signals a new multichannel synthesizer using bit‐slice technology has been designed and constructed. Concomitant control software, down‐line loaded from a supervising microcomputer, defines the number of active channels, their groupings (per voice), the sampling rate of each channel, and its particular amplitude and frequency control scheme. Parameters in the synthesizer are subsequently updated by the supervising microcomputer to create the desired audio outputs in real time. The versatility permitted by changing the control program together with improvements over other reported designs in signal‐to‐noise ratio, dynamic range and frequency resolution make this approach attractive for several applications.
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Study of the relations between instrumentist and instrument in computer music (A)

C. Cadoz and A. Luciani

J. Acoust. Soc. Am. Volume 69, Issue S1, pp. S38-S38 (1981); (1 page)

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Man‐machine communication is a very decisive point in digital synthesis of sounds used as a musical creation tool. We are concerned here with the instrumental gesture aspect of this problem where gesture is regarded as the most basic form of the relationship. Two complementary axes of study are necessary: (1) Analysis of gesture in instrument‐instrumentist relationship. An all important class of gestures is based on the energetical exchange between the instrumentist and his instrument. In such as case, the instrumentist receives information (by touch and dynamical perceptions) which determines his behavior and his listening. So we have built a special device for sound control, with mechanical feed‐back, taking into account the fact that the gesture is simultaneously a transmitter and a receiver channel. (2) The carrying out of sound synthesis by means of concrete source simulation. The simulation system relies on a first analysis of the instrument as a combination of an exciter structure connected to a vibrating structure. The latter are then decomposed into elementary mechanical components. Algorithmic models for mechanical components then allow a representation by the computer programs that we have elaborated of the main types of phenomena encountered in traditional instruments.
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