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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]

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]

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]

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 data I reported were from slow-response measurements, and EPNL values were derived using appropriate factors (for specific aircraft type, altitude, and operating conditions) determined from large samples of measurements obtained according to the FAR 36 certification method; hence the data were within normal tolerances of ±2 or 3 dB or EPNdB and were not subject to the 8- to 15-EPNdB error suggested by Callaway. My data were consistent with recent data published by other investigators. In regard to passenger cabin noise levels in commercial jet aircraft, measurements by myself and others show that during high-altitude cruise (28 000 to 35 000 feet) passengers near windows and in the mid and rear sections will be exposed to noise levels above 80 dBA. [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]

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]

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]

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]

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]

Spectrograms as normally produced by the 'sound spectrograph' are three dimensional. Time is portrayed along the length of the spectrogram paper, frequency across it, and amplitude by the blackness of the marking. The time and frequency scales thus provided are adequate for most analysis purposes. The amplitude scale, however, is poorly defined, first because inherent characteristics of the spectrogram paper limit the amplitude portrayal to a highly non-linear and limited range, secondly, because reading degrees of blackness by eye is inaccurate. This inadequacy in determining amplitude led to the development of a method for portraying amplitude which was independent of the characteristics of the paper or of the ability of the eyes to delineate grades of blackness of marking. The device developed and herein described provides an auxiliary presentation which portrays, at any preselected point in time, a two-dimensional spectrogram with axes of amplitude and frequency. This device delineates a 35-db amplitude range with the scale in uniform logarithmic steps. [ABSTRACT FROM AUTHOR]

The levels of the difference bands, fh - fl and 2(fh - fl), generated by a pure tone and a narrow band of noise, have been estimated in a manner reported in previous papers (Greenwood, 1971a, 1972a, 1972b). Results and conclusions follow: (a) Combination bands of the form fh - fl and 2(fh - fl) vary in level as functions of stimulus parameters in ways very similar to the variation in level of the difference tone, fh - fl, produced by tonal primaries, as measured by cancellation techniques. Difference band levels are rather insensitive to increases of primary frequency ratio in the ranges explored (about 1.35-1.85). Difference band level obeys different functions of primary intensity depending on whether one or two, and whether the upper or the lower, primaries are varied. When the lower primary level is varied alone, square-law behavior is observed, in agreement with Goldstein (1967) and with Zwicker (1955); when the upper primary or both primaries vary, curves depart from square-law behavior in near agreement with Goldstein. Békésy's 1934 observations (1960) and Wenner's (1968) results suggest a conceivable explanation that might resolve some apparent discrepancies among results of Goldstein, Zwicker, and this paper when both primaries vary. (b) At primary levels exceeding about 60 dB SPL, combination tones of the form n(fh - fl) and combination tones of the form (n + 1)fl - fh will exist simultaneously, and since they lie in the same frequency region they will interchange places, with varying interactions, as primary ratios are varied-producing perceptual effects relevant to higher-level phenomena of consonance generally and to the beats of mistuned consonance specifically. [ABSTRACT FROM AUTHOR]

The paper summarizes the sonic-bang studies that have been made in the United Kingdom since 1965, which embrace flight trials, field experiments, and laboratory studies. The main flight trial concerns the measurement of the sonic bang from the Concorde. It is shown that, when the Concorde is flying at 45 000 ft, the waveform at the ground has attained its farfield N-wave shape, although this is not quite so when it is flying at 37 000 ft. The measured characteristic overpressures for these two altitudes and a Mach number of 1.3 are 110 N/m2 and 120 N/m2, respectively. The effects of sonic bangs on cathedrals are discussed and the vibrational responses likely to be induced by the sonic bang are compared with those already arising from other environmental causes. Finally, the results of a study of the effects of simulated sonic bangs on some greenhouses are discussed; these results seem to indicate that most damages can be ascribed to a triggering effect. [ABSTRACT FROM AUTHOR]

The far-field acoustic pressure generated by an infinite plate driven by a point and a line force are computed. This paper constitutes an extension of previous computations [G. Maidanik, J. Acoust. Soc. Am 42, 27-31 (1967)]. The plate considered in this paper is covered uniformly and completely by a compliant coating which is applied in turn to the front and back of the plate. The formalism accounts for different fluids' occupying the space in front of the plate and in the cavity back of the plate. [ABSTRACT FROM AUTHOR]

Ferroelectric ceramic materials are often used in underwater sound transducers by stacking a number of identical pieces together. In this paper, the theoretical behavior is derived for a ferroelectric, cylindrical tube consisting of any number of longitudinally polarized coaxial segments. The effects due to lateral dimensions, which may not be negligible, are included. Electromechanical equivalent circuits are developed that greatly simplify and improve the analysis of composite resonators in transducer design. The theoretical parameters are related simply to experimentally measured quantities so that the parameters can be evaluated even though the lateral dimensions are large relative to the length of each individual segment. The dielectric, piezoelectric, and elastic losses are included in the general theory but losses are not considered explicitly. [ABSTRACT FROM AUTHOR]

The geometry of a rectangular enclosure is examined from the viewpoint of the absorption of reverberant energy. For diffuse sound, the significant quantity is not what is implied by the term mean free path but rather the mean reciprocal of the pathlengths. For particular modes, the reciprocal of the pathlengths can vary widely from its mean value and introduce a corresponding uncertainty in the relation of decay rate to absorption coefficient. Although no simple expressions have been found for enclosures of general shape, the range of variation from mode to mode seems to be nearly as great as for rectangular enclosures. This paper was written independently of a related one by F. V. Hunt [J. Acoust. Soc. Am. 36, 556-564 (1964)] and their simultaneous appearance is purely a coincidence. Hunt's paper is concerned primarily with reconciling the various formulations of the mean free path, whereas this paper stresses the variation of mean free path and the inversely related collision frequency for isolated normal modes. [ABSTRACT FROM AUTHOR]

The paper deals with the problem of estimating the sound field generated by a limited region of turbulence containing foreign bodies of arbitrary shape and arbitrary composition. According to the Lighthill-Curle acoustic analogy, the aerodynamically-generated sound is the same as that due to a distribution of quadrupole and dipole sources within the fluid and over the surfaces of the bodies. It is known that the presence of foreign bodies will usually convert some of the intense nearfield energy of Lighthill's quadrupoles into the form of sound attributal to dipole and monopole sound whose amplitude is much greater than that of the free-flow noise. Current trends towards more sophisticated theories have again focused attention on this problem with drastically different results. Calculations are here presented to determine the extent whereby this multipole-conversion process actually is taking place. It is shown that a method involving matching of inner and outer expansions yields intensity laws of different orders of magnitude comparing favourably with observed results. Curle and Powell's attempts to solve the problem have been reexamined to show inconsistencies their analysis. In particular, Curle's retarded-wave solutions are recasted by use of Fourier synthesis. It is suggested that much of the discrepancies between the results in the present paper and the predictions of Curle's theory can be explained by a more carefully conducted analysis, throwing emphasis on various possibilities by which pseudosound tuned to the presence of foreign bodies may give way to sound fields being many orders of magnitude stronger than those emerging from Curle's analysis. [ABSTRACT FROM AUTHOR]

Two wavevector filters were designed for investigating the nature of the pressure field induced on a flat boundary by a highly subsonic turbulent boundary layer. The wavevector filters were designed specifically for investigation in the spectral range where the spectral density of the pressure field is high. Preliminary experiments have been carried out, and the results relating to the convection velocity are reported. The major objective of the paper is, however, to present an analysis that makes it possible to properly interpret the results and allows for a more satisfactory comparison between the results reported in the paper and the available data in the literature. [ABSTRACT FROM AUTHOR]

This paper considers the response of thin elastic plates to sinusoidal acoustic excitation. A theoretical method for obtaining the dynamic deflection and stress in the nonlinear region is given. The theory is compared with test results showing rather good agreement. The application of the theory to the design of panels to withstand acoustic fatigue is discussed in the latter part of the paper. [ABSTRACT FROM AUTHOR]

The transducer design described in this paper employs a mercury column of variable length intimately coupled to an electrically driven piezoelectric element so that a composite vibrating system is formed whose resonant frequency is capable of continuous variation. A large radiating area is realized by combining a number of such composite elements in the form of a matrix. This matrix arrangement is attached to a container which supports the mercury column. One dimension of this column is varied by means of a mechanically driven piston. The entire assembly is enclosed in a steel tank with a sound rubber window to permit its use as an underwater sound transducer. [ABSTRACT FROM AUTHOR]

The conventional sound spectrograph affords the analysis of short signal samples and considerable flexibility in the construction of amplitude sections. Other major interests in sound spectrography are in the instantaneous portrayal of signals, and in the permanent record display of continuous linear and logarithmic analyses. This paper suggests instrument methodology for carrying out these operations. Values which are considered practical are suggested for the parameters of certain of the systems which are discussed. [ABSTRACT FROM AUTHOR]

This paper is concerned with the technique of temperature measurement in living tissue during irradiation by high intensity ultrasound. The interpretation of data obtained by the use of thermocouples is presented. The specific biological object used in this study is the spinal cord of rat exposed by laminectomy. This particular preparation serves to illustrate the relative importance of the heat conduction process in contributing to the temperature change as a function of the proximity of the imbedded thermocouple to bone and the time elapsed after initiation of the exposure. The ultrasonic frequency used in these studies was 980 kc. The sound intensities incident on the cord were between 60 and 80 watts/cm2. The experimental results presented in the paper are used to obtain values for the acoustic absorption coefficient of the tissue of the spinal cord. The range of values obtained for the intensity absorption coefficient per centimeter from measurements made on six adult rats at various positions in the spinal cord is 0.19 to 0.23 if the heat capacity of the tissue at constant pressure is 1.00 calorie/cm3. [ABSTRACT FROM AUTHOR]

In a previous paper by Fletcher and Galt [J. Acoust. Soc. Am. 22, 89 (1950)] a method was described for measuring experimentally and also for calculating the interpretation aspect of the perception of speech. The listeners were considered to have normal hearing. In the present paper the same principles are applied to persons having abnormal hearing. [ABSTRACT FROM AUTHOR]

Equations showing the relation between the volume, V, of an auditorium and its optimum reverberation time, T0, were published independently by MacNair and Lifschitz. MacNair's equation was derived from the following basic assumptions: 0T1 (logρ)dt = a const., E = const., where ρ=instantaneous value of the energy density of sound during decay,T1=time of decay to minimum audibility,E=rate of supply of energy during the steady state condition. This paper shows that an equation, relating T0 and V, can be deduced which more nearly fits all the empirical facts by basing the derivation on the following assumptions: 0T1 ρ · dt = a const., E = GVn, where G=a constant,n=a constant which should be less than unity. The resulting equation for n = 2/3 is T0 = 0.212 V1/6. This is in agreement with the empirical data and with the equation derived by Maxfield and Albersheim from acoustic 'liveness' considerations. The psychologists and physiologists studying the mechanism of hearing should be interested in these results, as they have a bearing on the manner in which the ear integrates the sound being perceived. [ABSTRACT FROM AUTHOR]

A peculiar problem in communication arises when a talker is wearing an oxygen mask or a gas mask, in that both react on the vocal mechanism and distort the voice at its source. Thus, the loss of intelligibility when a gas mask is worn is much greater than would be predicted from the amount of muffling, and, even when the oxygen mask contains a microphone, the talker's enunciation is not, in general, clear. The reaction on the voice is in part mechanical, by constraining the facial muscles and obstructing the flow of the breath, and in part acoustical, by adding a new cavity onto the vocal system so that the talker has less control over the character of the sound. The requirements for good intelligibility during the use of such enclosures have been discussed in some detail in a previous paper (see reference 1). The present paper concerns itself with an experimental analysis of the distortion produced by some small enclosures, and an evaluation of present theories of vowel production by comparing their predictions with the experimental results. Such a comparison is probably as severe a test of the theory of vowels as can be devised. In general predictions from the present state of the theory of vowels give a useful qualitative picture of the nature of distortion by small enclosures, but are not in quantitative agreement with experiment. A criticism is given of the assumptions involved in the present theory, and some suggestions are made toward the future improvement of our knowledge of speech. [ABSTRACT FROM AUTHOR]

Dedicated to the late O. M. Corbino in 1939, this institute lost, during the war, its original building and most of its facilities, which included newly constructed reverberation and free-field rooms for large-scale acoustics research. Most of the comprehensive acoustics library was salvaged, together with some pieces of equipment. Operations were renewed in 1945 in a portion of the Italian National Research Council building at Piazzale delle Scienze, Rome. The group numbers about ten research scientists, some of whom are members of the staff of the University of Rome, and about ten service personnel. The program features mainly ultrasonics, vibration studies of solids, and acoustic instrumentation. The ultrasonics program is characterized by the exploitation of light diffraction methods for measurement. In some recent developments, the usually employed standing waves between a quartz crystal and a reflector have been replaced by a pair of oppositely directed parallel beams of progressive waves from two quartz plates driven at the same frequency by a common source. The new device is free from the high precision requirements for parallelism and operates continuously over a fairly wide range of frequencies without mechanical adjustment. Ultrasonic velocity and absorption in several liquids and liquid mixtures are being studied from 1 to 10 megacycles, as a function of temperature. Velocity is now determined by measurement of wave-lengths in a progressive beam which is illuminated stroboscopically by the two-crystal cell described above. For absorption measurements, a monochromatic light line is passed through a single progressive ultrasonic beam and masked to allow a single-order diffraction line to fall on a photo-cell. The measured light intensity is proportional (within certain limits which can be checked) to the ultrasonic intensity which can then be measured as a function of distance to determine absorption. Dynamic properties of wood and metal are being studied by vibrating small samples and measuring the elastic and damping coefficients from resonant behavior. The basic tool is a condenser which drives the sample by electrostatic force and which also frequency modulates a high frequency carrier to provide a measure of vibration amplitude. The output is presented oscillographically to display force and displacement on the two axes of the scope. Samples are suspended on fine stretched wires and driven in transverse or longitudinal modes of vibration. These simple and effective means for studying internal damping and elasticity as dependent upon composition and temperature should prove useful in solid-state physics studies. Instrumentation studies include tube resonance methods of acoustic impedance measurement, frequency dividers, and multipliers for stable sound and ultrasonic sources, earphone testing, and microphone calibration. The I.N.E.A.C. has issued some eighty reports and papers, which have appeared in Ricerca Scientifica, Alta Frequenza, Atti dell 'Accademia Nazionale dei Lincei, Journal of the Acoustical Society of America, and other journals. A Bibliography, annotated with abstracts or summaries of several of the papers, is included in this report. [ABSTRACT FROM AUTHOR]

Studies on rigid acoustical tiles and soft blankets are described in this paper. It is shown that two waves travel through the material-one primarily airborne and the other primarily structure-borne. From a knowledge of the density of the sample, the volume coefficients of elasticity of the air and of the skeleton of the material, the porosity, the air flow resistance, the inter-fiber frictional resistance, and the structure factor, the propagation constants of each of these waves can be calculated. The experimental results indicate that the theory is useful in calculating the performance of the flexible, airplane type of blankets over the entire audible frequency range. For rigid tiles, however, the theory appears to fail at frequencies above 1000 c.p.s. if the flow resistance is high, and it fails at all frequencies for materials with low flow resistance. Experiment shows that the condensations and rarefactions of the gas in blankets take place isothermally at low frequencies and adiabatically at high. The transfer from one state to the other occurs gradually in the 100 to 2000 c.p.s. region. A more complete theory is required to explain the effects of thermodynamic and viscous losses on the propagation constant of rigid materials. [ABSTRACT FROM AUTHOR]

This paper presents data on the properties of a very simple, low power underwater noise generator-a wire heated by a heavy electric current. The dependence of the sound generated upon frequency, input power, wire size, material, and wire history has been determined. The sound has a very broad frequency distribution. For small wires a large part of the sound is supersonic. About one part in a million of the input electrical energy appears as sound. With increasing electric power the sound power passes through a broad maximum. This paper can also be considered as a study of cavitation noise, the cavities being produced by heat rather than by reduced pressure. Thus a new approach to the problem of cavitation noise is provided. As a study in heat flow, this report provides quantitative data on the acoustical concomitants of boiling. [ABSTRACT FROM AUTHOR]

The problem of the flexural vibration of prismatic bars neglecting the rotatory and lateral inertia is treated in various texts on sound and vibrations. The effect of neglecting these two terms introduces no appreciable error when the cross section of the bar is small in comparison to its length. For bars of large cross section the error introduced in neglecting these terms is sufficient to warrant attention. In his text on sound Rayleigh offers an approximate solution introducing a correction term for the rotatory inertia, under certain boundary conditions. In a more recent paper Mason gives an exact solution for the frequency of vibration, where the rotatory and lateral inertia are taken into account. The disadvantage of this solution lies in the fact that his Eq. (14) for the eigenvalues of the frequency is extremely complicated, thereby throwing up a barrier to further analysis. Also no mention is made by previous investigators of the effect of the rotatory and lateral inertia on the node positions or the shape of the deflection curve. It is the purpose of this paper to present a simplified exact solution and to determine the effect of the two terms mentioned on the position of the nodes and the relative amplitude of vibration. Curves applicable to the solution of any type of constant cross section are included. [ABSTRACT FROM AUTHOR]

The laboratory facilities and apparatus described in an earlier paper were used to study the normal intensity and frequency limits of audition for bone conduction. The condition of the observer's head to give greatest acuity for pure tones, and the optimal total force of application and area of the vibrator button were found to be essentially the same as for speech sounds. Acuity was found to vary with the position of application of the vibrator; for example, the maximum variation with position of the 1000-cycle threshold was 18 db. A threshold for open canals was determined for the frequency range 80-2000 cycles, without interference from stray air radiation (18 normal observers). Above 2000 cycles air radiation interfered with open canal tests to such an extent that a special technique was devised to obviate its effects. The occluded threshold curve, for a single normal individual, lay below his open canal curve over the range 80-2000 cycles, and also at 10,000 cycles. The usable intensity range for open canals was tentatively determined; it is a maximum of 80-90 db at 1000-2000 cycles. The total audible frequency range for open canals was found to be at least 25-17,000 cycles. [ABSTRACT FROM AUTHOR]

Most of the previous theoretical work on acoustic filtration has dealt with idealized infinite structures. The present paper is a theoretical study of finite filters such as are used in practice. Considering an acoustic structure with air as the medium with main line impedance Z and with n branch impedances Zb (pure reactances) equally spaced at intervals 2l, it develops that one can express the power transmission ratio for the structure in the simple form Pr = 1[big_slash_(use_in_display_math)]1 + Z2/4|Zb|2·sin2 nW/sin2 W, (1) where cos W=cos 2kl+iZ/2Zb·sin 2kl, (2) the familiar parameter of the transmission theory of filtration (reference 2). The plot of Pr in (1) as a function of frequency shows the presence of transmission and attenuation bands which approach those of the corresponding ideal infinite case as n becomes large compared with unity. Comparison of (1) with the actual transmission measurements of Stewart (reference 2, pp. 170, 175) shows satisfactory agreement. The phase change which occurs between successive sections in a filter is also computed and it is shown that unlike the situation in the infinite case the phase change is a function of the section. However, at relatively high frequencies and for large n this approximates to the total phase change along the structure divided by n. Comparison with such experimental results as are at present available yields reasonably satisfactory agreement. [ABSTRACT FROM AUTHOR]

This paper considers theoretically the propagation of compressional waves in a structure consisting of an infinite series of alternating layers of two different media which may be either fluid or solid. It is shown that such a structure acts as a low-pass acoustic filter. A number of special cases are computed and it is found that the cut-off frequency depends essentially on the section length and the relative acoustic impedance of the media. The problem is shown to be mathematically quite analogous to that of the propagation of acoustic waves in air through an infinite tube containing alternate constrictions and expansions. Moreover the loaded solid filter considered in a previous paper by Lindsay and White proves to be a limiting case of the non-homogeneous medium filter of the present article. [ABSTRACT FROM AUTHOR]

In a previous paper (Greenwood, 1972a), the measurement of masking by bands of noise of external origin led to determinations of signal/masker ratio that are applied in the present paper to the task of estimating combination band levels. Estimates of the levels of combination bands, given by the expression (n + 1)fl - nfh, were made by using the maximum masked threshold, read from a masking pattern produced by a given band, to calculate the denominator of the previously obtained signal-to-masker ratio. The shapes of the masking patterns and the estimates of level lead to the following conclusions: (a) Comparison of the masking effects of combination bands and bands of external origin further demonstrates that to assume that combination components, once generated, are not equivalent to external stimuli in ultimate loci and subsequent effects in the cochlea would require complex ad hoc explanations to account for the indistinguishable masking effects produced by the two kinds of bands. (b) Combination bands generated by mixtures of line and continuous spectra vary in level as functions of stimulus parameters in ways very similar to the variation in the level of combination tones produced by tonal primaries, as measured by cancellation techniques (Zwicker, 1955, 1968; Goldstein, 1967). (c) The present data extend the previously reported empirical functional relations, in that the level of the band 2fl>-fh is (i) a less sensitive function of primary frequency separation at higher primary levels and (ii) a more nearly constant percentage of primary level at wider primary separations. (d) The generation of combination components in essentially the same way, whether they are produced by line, continuous, or mixed spectra, should advance the task of calculating empirically the amplitude characteristics of the combination spectra produced by complex primary spectra. [ABSTRACT FROM AUTHOR]

In this paper we describe a novel method of probing a sound field in three dimensions with a focused light beam. In our method, the spatial-temporal modulation impressed upon the light by the sound is extracted by the use of either polarization sensitive elements or spatial filters placed in front of a photodiode. The technique is inherently capable of high-resolution sampling because, as is shown, phase and amplitude of the resulting rf current are indicative of the complex sound pressure in a narrow region around the focus of the light beam. This is in contrast to earlier methods using a narrow collimated light beam which only give an indication of sound-pressure amplitude and phase integrated over the entire width of the sound field traversed by the light beam. The first part of the paper analyzes the mode of operation and discusses sensitivity and resolution in a heuristic manner. The second part provides experimental results for various frequencies and sound media. The third part treats the rigorous theory. [ABSTRACT FROM AUTHOR]

The present paper compares four methods for measuring the speech-quality parameter preference. The scales of the isopreference method, the category judgment method, the relative preference method, and the absolute preference judgment method (a proposed modification of the category judgment method) are related to a 'preference unit' scale. Capabilities and performance of the methods are discussed and illustrated by evaluating a set of test signals with different types of degradation containing a subset of clearly discriminable signals. The paper tries to show how far preference results gained with one method allow prediction of corresponding results in terms of another method. Because of the quantitative limitations of subjective tests and especially since the four methods use different approaches and have different application ranges, it is not unexpected that the preference unit scale has been found to be more of scientific rather than of practical engineering interest. Listeners have been found capable of discriminating reliably, even without reference or anchor signals, more than the five quality steps provided by the category judgment method, and somehow also by the relative preference method. The proposed absolute preference judgment method recognizes this finding and, therefore, yields much better agreement with the isopreference method than the two other methods, which are apparently too strongly quantized. [ABSTRACT FROM AUTHOR]

The effect of a stochastic ocean bottom on underwater acoustic propagation is examined in two previous papers by the authors [J. Acoust. Soc. Amer 43, 1395-1403 (1968); 44, 1103-1114 (1968)]. In those investigations, the first and second moments of the random acoustic intensity are determined for various source and receiving-point geometries. In a more recent study by the authors [J. Stat. Phys. 2, 279-289 (1970)], the amplitude and decibel amplitude, as well as the intensity, of a random acoustic field are examined. There, each of the three measures of acoustic strength is shown to differ from the others in the analytic properties of its mean value and standard deviation. Therefore, in the present paper, the random-bottom problem of the two earlier studies is reexamined. In particular, the first and second moments of the total-field amplitude and decibel amplitude are studied under certain restrictions and are compared with those of the intensity. Furthermore, the first and second moments of the total-field phase are treated. [ABSTRACT FROM AUTHOR]

A set of short sketches is presented, giving an overview, unobscured by mathematical detail, of the literature on transient fields of acoustic radiators. Related papers are grouped together and interrelationships between results emphasized. [ABSTRACT FROM AUTHOR]

The propagation of acoustic waves in stochastic media is a problem of fundamental importance in the study of the stability of such media. This paper represents a first attempt to construct a full Born series for the expectation of the potential function. Keller's second-order results are obtained as a special case. An example, with no particular application in mind other than to establish a bound on the region of absolute convergence, is used to illustrate the theory. Higher-order moments of the solution, as well as other examples, are best left as the subjects of other papers. [ABSTRACT FROM AUTHOR]

A sonar system may incorporate blanket to cover its transducer system in an attempt to achieve a better signal-to-noise ratio. The blanket is intended to displace the external pressure field away from the baffle-the surface in which the transducer system is flush mounted. In this paper, the propagation of pressure waves in the blanket material is assumed to have fluidlike properties. The analysis of the influence of the baffle-blanket system on the performance of the sonar system is carried out in spectral space and is expressed in terms of the filtering action of the former system. Of particular concern are the effects associated with changes in the speed of sound in the material of which the blanket is cast. [ABSTRACT FROM AUTHOR]

In recent years, the question of noise generated by rolling-element bearings has been given considerable attention. That a certain irreducible 'minimum' noise is created by a properly functioning bearing has been pointed out in earlier work. Acceptable roller-bearing noise levels above this minimum are regarded in this paper as being, of necessity, set by subjective standards. The paper addresses itself first to the validity or consistency of certain subjective evaluations of bearing noise made by a group of observers in representative circumstances. Next, the question is examined as to what quantitative objective measurements are to be made in order to reflect accurately the character of the subjective evaluations. Finally, correlations between objective and subjective data are shown to be good. A representative method is thus defined for providing objective criteria that reflect subjective appraisal in this type of problem. [ABSTRACT FROM AUTHOR]

In an earlier paper dealing with dispersion of waves in composite rods, it was noted that the dispersive properties of one rod were quite different from those of another with different properties. This observation prompted the speculation that the dispersive properties of a composite rod could be controlled through a choice of the geometric and material parameters of the rod. In this paper, we show how the dispersive properties can be controlled; that is, we show the influence of each of the parameters on the dispersive characteristics of a rod. Our previous study had led us to suppose that if we were sufficiently adroit, we could choose the rod parameters so that the resulting composite rod would be nondispersive. Our study here shows that this is impossible and that a rod will always be dispersive, at least if it has a traction-free surface. We show that, with a very restricted, theoretical exception, the least dispersive composite rod is the degenerate one: the one-material rod. [ABSTRACT FROM AUTHOR]