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Prescoring based upon the material contained in abstracts was used to allocate presentation times for the papers in Speech Communication submitted for presentation at the 80th Meeting of the Acoustical Society. After the papers were actually presented, their technical content, presentation quality, and discussion quality were judged. No casual relationships could be established between the prescoring and postjudging of the paper, although the papers allocated 15 min were judged statistically better in technical content than the papers allocated 5 or 10 min. It is hoped that this letter might entice others to conduct further experimentation and subjective assessment of different methods for improving professional meetings. [ABSTRACT FROM AUTHOR]

It has been previously determined that precompressed onionskin paper may be used as an acoustic decoupler. In our evaluation, compressional-wave measurements were made on various types of paper, and in particular onionskin typing paper, at 32 and 1000 kHz. At the lower frequency, a composite material technique was used to allow pressurization of the samples. The velocity of sound and attenuation were found to vary nonlinearly with pressure over the range from 0 to 2000 psi. This nonlinearity introduces a nonlinear acoustic loading of the transducer elements and is the main disadvantage of onionskin paper. However, it was confirmed that the onionskin paper should be more stable with pressure than the other papers, provided that it has been properly precompressed. Most of the insertion loss provided by onionskin paper is caused by the mismatch in acoustic impedance. Thus, a fairly wide variety of materials should provide equivalent acoustical properties. [ABSTRACT FROM AUTHOR]

The acoustic decoupling behavior of onionskin paper is examined, with emphasis on sonar transducer applications. Nonlinear changes in the sound velocity of onionskin paper with pressure are used to predict the degradation of both frequency and directional response. These results are obtained by computer analysis of a longitudinal-vibrator equivalent circuit. The results are in reasonable agreement with the measured characteristics of a specific transducer configuration. [ABSTRACT FROM AUTHOR]

This paper is a reply to views on aircraft noise in the community and in the passenger cabin of modern jet aircraft presented in three papers at the 86th Meeting of the Acoustical Society in Los Angeles, Nov. 1973 (Papers MM1, MM3, and MM11). It is argued that procedures used by the author of paper MM-1 can result in EPNL values subject to errors of as much as 8 to 15 EPN dB. Recent measurements by Boeing are quoted that are substantially in agreement with those officially determined in 1971 for 727 aircraft on take-off. It is anticipated that landing noise will show similar agreement with published data. Other Boeing measurements using an aircraft in which engine noise was essentially eliminated indicate that it is technologically impossible to achieve the low community noise levels suggested in MM3 at the present time with a viable commerical airplane. Measurements together with widely accepted hearing conservation criteria indicate that travellers are not being exposed to hazardous noise levels inside passenger cabins of modern jets as claimed in paper MM11. [ABSTRACT FROM AUTHOR]

The recent paper by Hueter et al. on ultrasonic lesions in the central nervous system, which appeared in a recent issue of this Journal (March, 1956), presents a rather limited view of this field and may lead to some misunderstandings. This note is a critical analysis of the Hueter paper. Some of the more important points discussed are: (1) The unique advantages of producing ultrasonic lesions in the brain by using dosages appropriate for selective action combined with focusing of the beam in contrast to the use of focusing alone. (2) The choice of an irradiation procedure in experiments designed for the elucidation of physical mechanisms of the action of ultrasound on tissue. (3) The specification of the acoustic variables required for a dosage description. (4) The inapplicability of Eyring's theory of viscosity, plasticity, and diffusion to the elucidation of observed dosage relations. (5) The clarification of the usage of the terminology, nontemperature effects. (6) The applicability of the reciprocity method for the calibration of thermo-couple probes. [ABSTRACT FROM AUTHOR]

Critiques by A. Cohen, H. Davis, B. L. Lempert, and W. D. Ward of my paper 'Impairment to Hearing from Exposure to Noise' are treated individually. Questions raised by the reviewers are discussed and areas for further discussion are noted. [ABSTRACT FROM AUTHOR]

A program for computer retrieval of papers in acoustics is being used to search titles of all papers that have appeared in four journals over the past 13 years. Title words and author surnames are truncated to five letters. The search may be weighted Boolean, fractional, or for associated words needed to formulate a request. [ABSTRACT FROM AUTHOR]

The impact damper reduces the vibration amplitude of a mechanical system through momentum transfer by impact and conversion of mechanical energy into heat. The fundamental configuration consists of a single mass particle moving in a container fixed to the primary single-degree-of-freedom vibrating system which is driven by a simple harmonic force. A number of years ago, the author developed the (basic) solution for the steady-state two-impact/cycle symmetric motion for the fundamental configuration. More recently, S. F. Masri has published in this journal some interesting extensions of the basic solution for the fundamental configuration, as well as studies of other configurations, Using his results it is shown herein that the basic solution for the fundamental configuration is, in general, the only combination of practical interest. [ABSTRACT FROM AUTHOR]

Response curves of loudspeakers have irregularities, mostly not visible in the case of a loudspeaker of good quality and measured with normal equipment. By enlarging the ordinate scale these small peaks and dips of ±2 db become visible, but with the design of a cone it is considered that these irregularities are more or less inevitable and not so serious. This opinion is strengthened because by listening tests with a variable audio-frequency nothing abnormal can be detected. It is also impossible to measure any distortion in the region of these peaks and dips. By introducing short and sharp bursts of sine waves, however, all sorts of spurious oscillations between the bursts are visible on a cathode-ray tube. The amplitude of these phenomena depends on the internal damping of the diaphragm, the choice of the fiber, and the degree of beating of the pulp. The purpose of this paper is to raise the following question: Is this phenomenon the cause of the apparent harshness, etc., when listening to high-level high-note reproduction? [ABSTRACT FROM AUTHOR]

Dr. Ingard will lead the summary and open discussion of the papers presented in this session. Questions and points deserving further discussion will be directed to individual authors, after which questions will be accepted from the floor. [ABSTRACT FROM AUTHOR]

Two highlights of musical acoustics of the past twenty-five years are the advent of practical electrical musical instruments and research on deviations from the regular in music. Included in the latter are studies of the vibrato, transient modifications of tone quality, departures of intonation from rigid scales. The 'steady-state' concepts of the past now need refurbishing in the light of 'deviation' evidence. An analysis of papers directly related to music and published in the first twenty-five volumes of the Journal of the Acoustical Society of America reveals a steadily increasing interest in musical acoustics until World War II. In common with other subjects the publication rate dropped sharply during the war. Publication in acoustics as a whole increased rapidly after the war, but interest in musical acoustics (at least as evidenced by papers in the Journal) did not revive. Patents on musical devices, however, now constitute a significantly larger percentage of the annual output of the U.S. Patent Office than was the case in 1941. Technology is outstripping research in musical acoustics; interest in research must be revived immediately for the benefit of those who will listen to music in the next twenty-five years. [ABSTRACT FROM AUTHOR]

Last fall this writer described two designs for a low frequency horn adapted to operate in the corner of a room. The data presented consisted of experimental and computed performance on an experimental model and the computed performance of an improved design. The present paper describes the measured impedance of the new design and shows that this new design is a practical answer to the requirements of a speaker of this type. Minor discrepancies between the computed and measured performance are explained. Such discrepancies as exist are more of academic than practical interest. The improved design possesses all the characteristics which are desirable in a device of this class. This speaker, which is about the size of an ordinary radio console, has good response down to 40 cycles and an average efficiency from 40 to 400 cycles of about 30 percent, and a maximum variation of efficiency in this frequency range of only 2 decibels. Its normal environment, a room corner, utilizes room space which is ordinarily wasted. Observers have commented favorably upon both the artistic use of the space in the corner of the room and the acoustic performance of the instrument. With its high efficiency it is suitable for large scale sound reproduction. [ABSTRACT FROM AUTHOR]

For the power series expansion of the shift of the relaxation rates of a gas by admixtures, new coefficients are given. They were applied on measurements of Monkewicz [J. Acoust. Soc. Am. 42, 258-266 (1967)] in methane with water vapor admixed. The resulting rate constants differ considerably from those obtained by the use of the Tuesday-Boudart coefficients. [ABSTRACT FROM AUTHOR]

For several years we have used in this laboratory a set of steel bars, each mounted on a resonating box and respectively tuned to the frequencies 110, 220, 330, 440, 550, 660, 770, 880 and so on in the Fourier series, to and including 1760 c.p.s. This gives in effect it fundamental tone with the succeeding Fourier harmonics tip to the 16th inclusive. By repeated experiment with many students taking courses in the theory and practice of tuning pianos in equal temperament, during the last three years, we have found that, if we sound several of the bars simultaneously, choosing the members of the series in their regular succession, that is to say, such a series as 220, 330, 440, 550, 660, we always hear clearly and, as it were, beneath the simultaneous sounds, blended together into a chord, the fundamental tone 110. When again we take such a series as 440, 660, 880, 1100, we hear the fundamental 220. When we take 660, 990, 1320, 1560, we hear the fundamental 330. When again we have taken an irregular series, such as 330, 550, 660, 880 and 900, we have always heard a tone of pitch corresponding with the frequency of the smallest number of beats between any pair of the bars, namely 110. In the case above mentioned, the 110 is very distinct, with 220 existing simultaneously, and traces of 330 also. The most important fact however seems to be that the lowest frequency deducible, namely 110, is always, in the cases mentioned, definitely and distinctly heard. It should be understood that these bars are excited simply by blows delivered with felt-covered hammers, and that the beat-tones, as I shall call them, are therefore feebler than they would be if the bars were excited electrically at relatively large amplitudes, and were steadily sustained thereat. Phenomena such as these described have been explained by the Koenig theory of beat-tones, which states that when the number of beats between two frequency-generating units exceeds the minimum number of atmospheric pulses sufficing to arouse a sensation of sound (that is to say, when the number exceeds 16 or thereabouts), sensations of tone are aroused and identified, giving sensations of pitch corresponding to the beat-frequencies. Presumably such sensations may be described as having subjective origin, although it appears that the psycho-physiological foundation of any such theory has hardly yet been laid firmly. What seems more important for the moment is that our experiences corroborate the observations made, and conclusions reached, by Fletcher, as shown in his paper. We do not overlook the fact of Fletcher's experiments pointing to the fundamental tones being regarded as the actual pitch-sensation generators for the groups of simultaneous harmonic sounds used by him, while in our case we recognize the fundamental tones as forming weak but very distinct roots to the chords which are constituted by the simultaneous harmonic tones. The distinction however does not appear to be essential. [ABSTRACT FROM AUTHOR]

The rate of energy flux in an ultrasonic beam, propagating in a fluid medium, may be expressed for a single frequency and longitudinal oscillation by E[lowercase_phi_synonym] = 1/T0T A pudt, where T is the period of oscillations, A the cross section of the beam, p the instantaneous value of pressure oscillations, and u represents particle velocities causing the pressure oscillations. This is the basic equation with which, at the turn of the century, Lord Rayleigh calculated acoustic intensities in gases. Almost half a century later, Langevin was first to measure ultrasonic intensities in liquids by evaluating radiation pressures created by these intensities. A simple theoretical basis to these evaluations was already established two decades prior to his experiments. Further theories were later developed to express more closely the relationship between the radiation pressure and sonic intensities. The complexity of wave propagation phenomena in real media, however, has been preventive in establishing an exact theory, especially in cases of intense or pulsed radiations. Therefore, there is a serious need for alternative methods to determine sonic intensities without resorting to debatable postulations. Only after compilation of reliable data will it be possible, through these methods, to validate or modify the existing theories. The only reliable method, which can avoid debatable assumptions, appears to be the conversion of sonic energy into heat. The heat-conversion method is one of the oldest known to physics in terms of determining a multitude of radional energies. The so-called bolometers or radiometers were the standard instruments used in evaluating heat or light radiation more than a century ago. The purpose of this paper is to review various kinds of calorimetric methods and explore their feasibility to ultrasonic power measurements. Thus we hope to revive and perfect at least one of these classical methods as a primary standard toward the evaluation of newly established methods and theories. [ABSTRACT FROM AUTHOR]

Acoustic decoupling behavior of onionskin paper is examined with emphasis on sonar-transducer applications. Effects of changes in the acoustic impedance of a decoupling support structure are discussed in detail. Nonlinear changes in sound velocity with increased uniaxial pressure are shown to degrade both frequency and directional response of the transducer. Predicted characteristics obtained by computer analysis of a longitudinal-vibrator equivalent circuit are compared to measured characteristics of a specific transducer configuration. [ABSTRACT FROM AUTHOR]

Small linear phase changes introduced in a uniform linear array of point sources do not cause any appreciable change in the energy radiated until the phase variation along the line becomes equal to that which occurs in the wave in space. Then the efficiency begins to drop rapidly. The efficiency will, of course, be a periodic function of the phase shift. If the excitation of the point sources is due to regularly recurring pulses whose timing varies linearly along the array then the phase variation will be directly proportional to the frequency of the different components. This sort of excitation may be made to occur in paper mill suction rolls. (These are hollow cylindrical shells which are perforated with a pattern of holes through which water is drawn from the paper by means of stationary suction boxes.) Models in which the phase between adjacent holes is varied by the use of different drill patterns have been studied for arrays of sources one foot and 20 feet long. The experiments agree qualitatively with theory on all points and indicate that a noise reduction of at least 15 db can be obtained by choice of a suitable drill pattern. [ABSTRACT FROM AUTHOR]

In the usual formulation of the equations of motion for dynamical systems, position and velocity coordinates are chosen as dependent variables. In some problems, however, the forces in the system may be of greater interest than the configuration coordinates. This paper concerns the problem of writing equations of motion in which forces are dependent variables. It is shown that such equations arise from a 'loop analysis' of the mechanical schematic diagrams, as contrasted with the 'nodal analysis' which leads to the ordinary equations of motion. The analytic treatment of certain classes of mechanical systems, without reference to schematic diagrams, can lead to these 'force equations of motion' under conditions which are discussed. Some of the considerations which are required in extending this analytic treatment to more general systems are indicated. [ABSTRACT FROM AUTHOR]

It is proposed that the classical treatment that predicts the generation of a scattered wave of frequency (ω1 -ω2) as the result of the interaction of two plane elastic waves of frequencies ω1 and ω2 has its quantum mechanical analogy if a phonon-'splitting' process is considered. [ABSTRACT FROM AUTHOR]

The filtering action of a spectral filter changes when the filtering functions of the transducers, of which it is composed, change. Practical transducers possess filtering functions that exhibit inherent deviations from the nominal forms that are assigned to them. This paper presents an assessment of the influence that such deviations have on the filtering action of a spectral filter. Of particular interest are deviations that have statistical distributions so that ensemble average of the filtering action can be defined and estimated. Also assessed in the paper is the influence of variations in the filtering functions of the transducers on the filtering action of a spectral filter. Variations are the changes that are introduced by design. Of particular interest are statistical variations in the positions of the centers of the transducers. It is argued that such variations may, in certain cases, be advantageous. Numerical examples that illustrate the analytical formalism are cited. [ABSTRACT FROM AUTHOR]

The high frequency translation losses in record reproduction which Professor Hunt has quoted from a former paper of mine apply only to soft plastic-coated recording disks such as are used for instantaneous play-back recording. They do not hold and are very much less on the relatively hard material of which commercial transcription records are pressed. The RCA reproducer was designed and primarily intended for use with these hard commercial pressings. With reference to the frequency characteristic which is to be adopted and which is being used for the new Orthocoustic broadcast transcription records and which Professor Hunt contends represents too much high frequency pre-emphasis, let me say that this program was started solely with the idea of producing ultra-high quality disks. It seems inconsistent that such a characteristic would be used if it resulted in objectionable distortion. The direct purpose in accenting the high frequency range in recording and attenuating it in reproduction is of course to reduce surface noise. Our object in demonstrating such a record at this meeting was not only to show how far the surface or background noise can be reduced but also to direct attention to the absence of distortion. As Mr. Robert Morris, of the National Broadcasting Company, indicated, the requirements for low surface noise on broadcast records are rather severe. Low distortion is not alone of paramount interest. The noise level too must be below a commercially acceptable value. This level is far below that which would be tolerated in home record reproduction. Assuming that it were possible to make a record totally free from wave form distortion the broadcasters would immediately insist on raising the recording level until the distortion was brought up to but not beyond the acceptable amount just mentioned. Thus the signal to noise ratio would be improved and no harm done. I cannot argue with Professor Hunt's calculations on distortion but think perhaps he based them upon a higher recorded level than we propose to use in Orthocoustic disks. It is intended of course that the distortion will be objectionable to no one, and for all practical considerations not audible. By this method of recording it has been found possible to make ultra-high quality lateral transcription records which, in side-by-side comparison with the output from a high quality monitoring loudspeaker operating on 'live' programs, defy detection, from the standpoints of frequency range, background noise and low distortion. That is all we can expect from any recording system. [ABSTRACT FROM AUTHOR]

This paper reviews the impact of digital computers on acoustics research since their introduction about a decade ago. The influential ro⁁le that computers have attained in acoustics has resulted from their imaginative use as research tools for analysis, control of experiments, modeling, and simulation-rather than from straightforward calculating applications. Illustrative examples discussed in this paper include modeling of the human speech-production process and the mechanical and neural aspects of hearing, speech analysis and synthesis, automatic speech and speaker recognition, generation of musical sounds and psychoacoustic test stimuli, study of the perceptual correlates of acoustic stimuli, multidimensional scaling, simulation of ray propagation in the deep ocean and in reverberant enclosures, acoustic measurements in concert halls, digital modeling of auditorium designs. Monte Carlo simulation of wave propagation in multimode transmission media, and acoustic image reconstruction of unknown objects by 'inverse diffraction' on the computer. [ABSTRACT FROM AUTHOR]

The probability of a correct answer, P(C), is not a valid index of sensitivity in the detection and localization (DAL) experiment although the DAL experiment is itself valuable. A table of d' exists for the DAL experiment with k = 2. In the construction of the table, Gaussian distributions of the critical variable were assumed, but no assumption was necessary about the relative variance of noise-alone and of signal-plus-noise distributions. [ABSTRACT FROM AUTHOR]

In a previous paper [J. Acoust. Soc. Am. 53, 719 (1973)] we discussed the calculation of the scattered field for scalar plane-wave incidence on a type of filled periodic corrugated surface. The surface consisted of parallel half planes, alternate adjacent pairs of which were filled with a material having different density, and supporting waves of different velocity structure from those in the surrounding medium. This paper considers a related problem with plates of finite rather than semi-infinite depth. Both soft- (Dirichlet) and hard- (Neumann) boundary conditions are considered. Limiting cases of the problems considered here correspond to the results of Deryugin. The most characteristic effects observed are the Brewster-angle and resonance anomalies. [ABSTRACT FROM AUTHOR]

There were two significant themes in this session. The first theme concerned vibration control and noise reduction. The first paper (Ruzicka) reviewed fundamental vibration control concepts for reducing undesirable mechanical vibration and noise. Other papers discussed: sound-structural interaction and the use of statistical energy analysis in predicting response and noise radiation (Lyon), vibration control and noise reduction by means of damping materials (Jones), and reduction of machine noise by vibration isolation (Crocker and Hamilton). The second theme concerned biodynamics. One paper discussed active vibration isolation for seated personnel and its particular use to isolate pilots from low frequency vibration in aircraft (Calcaterra). Two other papers (Reynolds and Soedel) and (Abrams and Suggs) discussed hand impedance measurements on human subjects. The motivation behind this work was the growing concern in recent years with the effects of vibrating hand-held tools on the human operators. One remaining paper (Collins, Keller, and Kosmakos) discussed the physiological effects of mechanical vibration, the experimental studies being conducted on male rats. [ABSTRACT FROM AUTHOR]

This paper discusses the papers presented in the two sessions on aircraft noise at Purdue. The first session on Aircraft and Rotor Noise included invited papers on airport noise (MCK. ELDRED) and rotor noise (REETHOF) and several contributed papers on the prediction of rotor noise both from propellors and from compressors. Two papers also discussed the problem of propagation and absorption of compressor noise in ducts. The second session on Jet Noise and Sonic Boom included an invited paper on response to jet noise (Clarkson) and several contributed papers on supersonic jet noise and on rocket noise. Three papers also discussed the prediction of sonic boom overpressures. [ABSTRACT FROM AUTHOR]

This session consisted of nine contributed papers all dealing with different aspects of noise and vibration control. St. Hilaire and Vaidya described the mechanism of sound generation caused by the metal reed in a reed organ, and in another paper described the response in a small room due to a sound source in a larger room connected by an opening between them. Davies applied statistical energy analysis to systems with strong but point coupling. Tseo presented a farfield formulation for sound pressure and radiation intensity from a simply supported rectangular plate. Jai-Lue Lai showed mean-square displacement responses of an axially moving belt for loadings of special random processes. Prediction methods for sound power radiated by several classes of rigid flow-discontinuities in low-speed air ducts were presented with experimental evidence by Hayden. Requirements on scanning rate and detection time constant were presented for space-averaged acoustic measurements by Wooten and Cary. Nitsche presented a survey of spectral analysis techniques for moving sound sources. The use of Helmholtz resonators for acoustic absorption was presented by Czarnecki. [ABSTRACT FROM AUTHOR]

It has been shown by Safar that a theory of rectified diffusion when combined with a linearized analysis of the bubble dynamics gives an adequate description of threshold phenomena. The value of an explicit formula for the process is emphasized. [ABSTRACT FROM AUTHOR]

A brief analysis is given on the contribution of surface scattered sound to the reverberation measurements of Urick and Saling [J. Acoust. Soc. Am. 34, 1721 (1962)] and of Mackenzie [J. Acoust. Soc. Am. 33, 1498 (1961)]. It is demonstrated for Mackenzie's result that surface scattering intensities are the same order of magnitude as his measured reverberation level. This may account for the descrepancy in their scattering coefficients and those measured by different means. [ABSTRACT FROM AUTHOR]

It is suggested that the hearing threshold shift found in underwater subjects indicates that the human ear is basically a velocity-sensitive device. [ABSTRACT FROM AUTHOR]