bluuebunny/crossref_metadata_2025 huggingface dataset:
Auditory Function in Atherosclerotic Rabbits
Authors: Voots Richard J. , Lawrence Richard
Published: November 2005

Atherosclerosis was induced in a population of rabbits by feeding a high-cholesterol diet for a period of six months. A control group from the same colony was maintanied on an identical diet without the cholesterol. Observations of auditory function were made on five diet animals and four control animals by means of acute round window electrode implants. The action potential response to a standard acoustic click and microphonic sensitivity response curves for gradated 1-sec tone bursts at frequencies from 125 Hz to 15 kHz were recorded from all animals. The AP responses for the diet animals are consistently lower than for the control animals by 10–20 dB. On the other hand, the microphonic responses indicate no obvious differences between the two groups except at 2 kHz, where the diet animals appear to be in the order of 20 dB more sensitive than the controls. The significance of this latter finding, however, is open to question. [This research supported in part by Public Health Service grants.]
Effect of Chloride Deficiency on Cochlear Potentials
Authors: Konishi Teruzo , Kelsey Elizabeth
Published: November 2005

The scala tympani or scala media in guinea pigs was perfused with Ringer-Locke's solution (in the case of the scala media, potassium-rich Ringer's solution) in which chloride was replaced with ferrocyanide, nitrate, glutamate, or acetate. Cochlear microphonics (CM), summating potential (SP), action potential (AP), and endocochlear potential (EP) were recorded from the basal turn before, during, and after the perfusion. Chloride lack in the endolymph did not alter the cochlear potentials, including EP, immediately. Perfusion of the scala tympani with acetate-Ringer's solution caused reversible depression of CM and temporary increase of AP followed by gradual depression. The dc polarization persisted even after chloride ions were removed from the perilymph by introduction of chloride-free solution into the scala tympani. The relationship between the cochlear potentials and the cochlear fluid is discussed. [Work supported by a grant from the National Institute of Neurological Diseases and Blindness, National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]
Effect of Solid Boundaries on Aerodynamic Sound
Authors: Meecham W. C.
Published: November 2005

The theory of aerodynamic sound from turbulence near solid boundaries is re-examined. For nearly incompressible flows, it is shown that the surface integrals, believed to be the source of relatively strong surface sound, may, in fact, merely give the reflecting and diffracting effect of the surface on volume-generated sound. The apparently much larger acoustic effect of hydrodynamic pressure variations may be largely spurious. These characteristics are shown to follow from the use of a simple identity involving the incompressible pressure, which is defined. The present form of the result of this work gives Ribner's source term (known to be equivalent to Lighthill's) for the volume sound. Thus, the total amount of radiated sound can be estimated in the usual way to be proportional to Mach number to the eighth power. There is the usual complication caused by the dependence of the relative turbulence intensity on Mach number. In many boundary-layer applications, the effect of the surface is merely to multiply the intensity of such sound by four. Of course it is true that small objects placed in a uniform flow can generate relatively large velocity fluctuations and cause relatively large amounts of sound to be radiated by the volume sources. It also seems likely that volume sources near small objects will radiate a dipole pattern, though with a Mach number dependence the same as that of volume sources. This is in agreement with experimental observations. [Work was partly done at the Lockheed Palo Alto Research Laboratories; it has been partially supported by ONR].
Sound Radiated by an Elastic Plate Excited by Boundary Layer Turbulence
Authors: Feit David
Published: November 2005

The problem of sound radiation by an elastic plate excited by turbulent boundary-layer pressures is investigated. In determining the velocity response, the area of the plate is assumed to be effectively infinite. To provide a more accurate description of the plate motion in the high-frequency range, the Timoshenko-Mindlin thick plate equation of motion is used. Describing the boundary layer pressure field by a narrow-band cross-correlation function proposed by White [J. Acoust. Soc. Am. 40, 1354–1362 (1966)], an expression for the spectral density of the mean-square farfield pressure is obtained. For frequencies above coincidence, the directivity pattern of the mean-square farfield pressure displays two relative maxima. The angles at which the pattern displays its maxima are distinctly different from those that are predicted using classical plate theory. [Work supported by Naval Ship Systems Command, General Hydromechanics Research Program, administered by the Naval Ship Research and Development Center.]
Response of a Transducer System to Turbulent Boundary Layer Pressure Field
Authors: Maidanik G. , Jorgensen D. W.
Published: November 2005

A system of flush-mounted pressure transducers can be considered as a spatial and a spectral filter. The filtering properties of systems consisting of a single transducer, two transducers, and three transducers were previously treated by the authors. [73rd Meeting of the Acoustical Society of America, 21 April 1967, New York, Abstract N/EF8]. This treatment was conducted in {x,ω} space. In this paper, the same problem is analyzed; however, the analysis here is conducted and illustrated in {k,ω} space, the Fourier conjugate of the real physical {x,t} space. It is argued that defining the filtering properties of the transducer systems in {k,ω} space offers certain conceptual advantages. This is particularly relevant when one considers the response of the transducer systems to pressure fields that are stationary, both spatially and temporally. The variations in the filtering properties of these systems as functions of the sizes and the sensitivities of the individual transducers and the separations between the centers of the transducers are discussed. It is shown that by properly adjusting the sizes, the sensitivities and the separations, substantial variations in the normalized response of the systems to the pressure field in a turbulent boundary layer can be achieved.
Some Effects of Surface Roughness on Turbulent Boundary-Layer Wall-Pressure Fluctuations in Incompressible Pipe Flow
Authors: Schloemer Howard H. , Recine Emilio C.
Published: November 2005

Spectral density, magnitude of the normalized longitudinal and lateral cross-spectral density functions, and convection velocity ratios of wall-pressure fluctuations were measured for smooth and rough surfaces. These measurements were made with small flush-mounted transducers in a 3.5-in.-i.d. pipe air flow facility with centerline velocities ranging from 140 to 238 ft/sec. Two different grades of roughness were used: a coarse, closely packed silica sand grain surface with an average height of 0.088 in., and a finer-grained surface of No. 60 grit commercial sand paper. The effect of increasing grain size was to increase the nondimensional spectral density throughout the frequency band measured and to substantially lower the convection velocity ratio when compared with smooth-wall data. The longitudinal and lateral decay of a particular eddy was more rapid for the rough wall. Experimental evidence indicated that the longitudinal cross-spectral density was more sensitive than the spectral density to surface conditions.
Experimental Study of the Velocity-Dependent Damping of a Turbulence-Induced Vibrating System
Authors: McCormick Michael E. , Ripley Thomas C.
Published: November 2005

This paper presents the results of a recent experimental study of the damping characteristics of boundary-layer-induced vibrations of a thin metal ribbon. One side of the metal ribbon was subjected to a turbulent boundary layer in a subsonic wind tunnel. The displacement of the ribbon was measured by a capacitance probe. (The spectral content of the probe's output was analyzed using a wave analyzer.) Each frequency component was then scrutinized to determine its damping characteristics; that is, the −3 dB-down points about each center band/or modal frequency were observed to increase significantly with velocity. This increased damping is attributed primarily to the surface shear stress caused by the fluid on the ribbon. These results can significantly affect the radiated sound from turbulence-induced vibrating surfaces.
Propagation of Shear Ultrasonic Waves below the Relaxation Frequency in Molten Glasses—Highly Sensitive Phase-Lock Detection System
Authors: Macedo P. B. , Simmons J. H.
Published: November 2005

The pulse operation of the high-temperature ultrasonic interferometer using transmission of shear waves will be described. A feature that made this work possible was the use of a lock-in amplifier in the video circuit, which suppressed the noise level by 25 dB. Sample data will be shown where both the velocity and absorption are independently measured with an absorption per wavelength of 4.9 Np.
Volume Viscosity of Liquid Antimony
Authors: Smirnow J. R. , Jarzynski J.
Published: November 2005

Liquid antimony exhibits many of the anomalous properties of water. For example, its density increases on melting, and its compressibility shows a minimum as a function of temperature. As a further study of its properties, the absorption of ultrasound was measured in molten antimony at temperatures up to 900°C. The measured absorption is found to be higher than the absorption due to shear viscosity and thermal conductivity alone. The ratio volume/shear viscosity calculated from the excess absorption is 4.2. The significance of this result is discussed in relation to other properties and the structure of liquid antimony. [Work supported by a grant from the National Science Foundation.]
Effect of Pressure on the Volume Viscosity of Water
Authors: Davis C. M. , Jarzynski J. , Fermi S.
Published: November 2005

Measurements of ultrasonic absorption α/f2 in water have been made over a range of temperatures from 0° to 80°C and at pressures from atmospheric up to 1000 kg/cm2. From the measured values of α/f2, the volume viscosity ηv has been calculated and found to exhibit a maximum versus pressure at all temperatures. [Work was supported by a grant from the Office of Saline Water, Department of the Interior.]
Molecular Mechanisms Contributing to Ultrasonic Absorption by Tissues
Authors: Edmonds Peter D. , Wang Richard Y. C. , Hussey Matthew , Brower Ronald W.
Published: November 2005

The interpretation of data presented by ultrasonic visualization techniques may be expected to benefit from an understanding of the mechanisms of the predominant contributions to the total ultrasonic absorption coefficients of tissues. Since aqueous solutions of hemoglobin have been most extensively investigated, analyses of specific molecular mechanisms have been undertaken with relation to the structure of this macromolecule and its environment. The contributions that could arise from reactions occurring at the charged side chains of residues of arginine, lysine, aspartic acid, and glutamic acid were considered since these residues occupy positions with highest frequency of occurrence at the hydrophilic exterior of the hemoglobin molecule. On the assumption of a structural mechanism, a family of possible single relaxation curves was calculated from which one member could be selected with knowledge of an experimental value of relaxation time. We conclude that basic side chains make significant contributions, which are larger than those of acidic side chains. [Work supported by a grant from the National Institutes of General Medical Sciences.]
Spectrographic Analyses of English Consonants
Authors: Takefuta Yukio
Published: November 2005

The purpose of this study was (1) to analyze the English consonants spectrographically and (2) to calculate the relative contribution of each acoustic correlate to the distinction of one articulatory feature from another. Three male speakers of General American dialect recorded 24 English consonants five times in intervocalic positions of five different vowels, /a, e, i, o, u/. Three types of spectrographic display were made for all consonants: sonagram, section, and amplitude display. Quantitative measures were made for each of three aspects of acoustic analysis (intensity, duration, and frequency spectrum). The acoustic features were interpreted in relation to the articulatory features of manner or place of articulation. Each correlate was also considered as a possible distinctive feature or an acoustic signal of the consonants, and the magnitude of this signal was a measure of its strength. The index of signal detectability was calculated to quantify the relative contribution of the acoustic features.
Real-Time Colored Display of Sound Spectrogram
Authors: Nakano Yasuaki , Nakayama Takeshi , Koshikawa Tsuneji , Miura Tanetoshi
Published: November 2005

If signal spectrograms are displayed in real time, so-called brightness modulation display is used in general. Because of the limited dynamic range of brightness modulation of CRT, details of the spectrum are lost very often. In order to overcome such defects and be able to observe instantaneous spectrum patterns more clearly and easily, we constructed new display apparatus in which effective use of visual function is considered. In this system, instantaneous spectrum amplitude is quantized in 11 levels with the step of 4 dB, and each amplitude level is converted to predetermined hue resembled to contour map. Furthermore, these colored instantaneous spectrograms are memorized in sky-sign like fashion in a certain time interval. As the results of displaying various acoustic signals, it is confirmed that color display of this type is more useful than monochromatic display for the visual discrimination of the characteristics corresponding to each signal differences.
Spectrum Analysis of Various Asian Dialects
Authors: Campanella S. Joseph , Klopfenstein R. C.
Published: November 2005

It was the objective of the study reported here to analyze a variety of Asian dialects for the purpose of discovering spectrum distribution differences that may be correlated to the dialects. The dialects subjected to the analysis were North (10), Central (10), and South (10) Vietnamese; Cantonese (5), Mandarin (5), and Fukienese (4) Chinese; Cambodian (15) and the highland tribal dialects of Jari (3), Bahnar (3), Sedang (3), Rade (3), Cham (3), Koho (3), and Hre (11). The number of individuals sampled in each dialect is shown by the digit in the parentheses. Confidence in the results should be rated accordingly. All samples were taken from male talkers. Spectrum analysis was performed by means of a 31-channel 1/3-oct band filter bank over the frequency range from 20 to 20 000 Hz, scanned at a rate of 60 Hz. The speech source data were collected on high-quality portable tape recorders and these, after appropriate editing to remove unwanted background, were played into the 1/3-oct band spectrum analyzer. The spectra were then digitized and transferred to an IBM 1410 computer for analysis for mean spectrum distribution for each dialect. Voiced and unvoiced events were segmented into separate groups and separate spectra for each of these classes thereby obtained. For the summary analysis, all spectrum scans of the voiced type and unvoiced type were individually averaged to produce an average voiced event spectrum and an average unvoiced event spectrum for each dialect. A tally of the number of spectra for each excitation class for each dialect also permitted the estimation of the ratio of voiced to unvoiced excitation that is characteristic of each dialect. The summary analysis showed that, generally, the voiced event mean spectrum differed only in minor detail as a function of dialect. The same was found true of the unvoiced event mean spectrum. The most variable parameter appeared to be the percentage of time occupied by voiced excitation. This parameter varied from 76% for Mandarin-Chinese to 90% for Cambodian, Jari, and Hre. [Dr. Campanella was employed at Melpar, Inc. at the time of performance of the study reported in this paper. The work was performed under Contract Booze-Allen Corp. subcontract 5-66-1]
Coarticulation and the Locus Theory
Authors: Delattre Pierre
Published: November 2005

The effects of coarticulation on formant transitions do not “… necessitate a re-evaluation of the locus theory…” [S. E. G. Ohman, J. Acoust. Soc. Am. 39, 151 (1966)]. In fact, no acoustic data on human speech behavior could be used to alter this theory since it is essentially based, not on the production of human speech, but on the perception of controlled acoustic variables by human brains. The locus concept simply describes the direction and extent that the second- and third-formant transitions of a consonant must take in order to contribute to the perception of place of articulation. It does not claim that the specifications of formant transitions defined by the locus are observed by all human speakers under all conditions. Earth speakers are only human. But it does assume that when, in human speech, a transition does not point to the appropriate locus, that transition does not contribute to the perception of the appropriate place of articulation. Tables of VCV coarticulation will be examined to find how the perception of place of articulation is possible when the interference of coarticulation prevents a transition from pointing to the appropriate locus. It will be shown that in every such case, other cues substitute for the locus cue.
Digital Formant Synthesizer for Speech Synthesis Studies
Authors: Rabiner Lawrence R.
Published: November 2005

Recent work on speech synthesis by rule has led to the development and evalation of a novel digital formant synthesizer. The synthesizer was simulated on a computer at a 20-kHz sampling frequency. Among the novel points are an excitation source for the unvoiced component of voiced fricatives; a voicebar for the stop gap period of voiced stops; a novel source filter providing the voiced excitation for the synthesizer and the elimination of the higher pole correction network for voiced sounds by exploiting the properties of sampled data systems. A comparison (in terms of the frequency response for vowels) between digital and analog synthesizers will be made. A brief discussion of the advantages and disadvantages of cascade and parallel synthesizers will be presented. Examples of synthetic speech will be presented.
Control Rule of Vocal-Tract Configuration
Authors: Ichikawa Akira , Nakano Yasuaki , Nakata Kazuo
Published: November 2005

Objectives of the research is to find out a simple but an effective rule for the control of vocal-tract configuration in the synthesis of speech. One of the following two alternatives is often selected as the control rule: (1) independent linear interpolation, (2) mathematical descriptions with several parameters. The former has an advantage of simplicity but also has suffered from over simplified deformation. The latter is hardly applicable to consonant. The proposed processes are as follows: (1) Define three key points for each target configuration; they are maximum area points of front and back cavity V1, V2, and maximal constriction point P between these two. (2) Trace the trajectory of these key points between two target configurations in a certain time fashion. (3) Calculate the temporal change of each section by the interpolation from starting target value to ending target value with considering a restriction due to the pass of V1, V2, and P point. The proposed rule has two advantages: (1) applicable to any target configurations including consonants, (2) the restrictions avoid the results from over-simplified deformations. Some of the result will be shown with aids of our vocal tract pattern display.
The “Voiceprint” Mystique
Authors: Vanderslice Ralph , Ladefoged Peter
Published: November 2005

Proponents of the use of so-called “voiceprints” for identifying criminals have succeeded in hoodwinking the press, the public, and the law with claims of infallibility that have never been supported by valid scientific tests. The reported experiments comprised matching from sample—subjects compared test “voiceprints” (segments from wideband spectrograms) with examples known to include the same speaker—whereas law enforcement cases entail absolute judgment of whether a known and unknown voice are the same or different. There is no evidence that anyone can do this. Our experiments, with only three subjects, show that: (1) the same speaker, saying the same words on different occasions without any attempt to disguise his vioce, may produce spectrograms which differ greatly; (2) different speakers, whose voices do not even sound alike, may produce substantially identical spectrograms. As with phrenology a century earlier, “voiceprint” proponents dismiss all counter evidence as irrelevant because the experiments have not been done by initiates. But our data show that the use of “voiceprints” for criminal identification may lead to serious miscarriages of justice.
Space-Time Structure of Likelihood Ratio Sonar Receiving Systems
Authors: Bartram James F.
Published: November 2005

The conventional way of designing a SONAR receiving system is to subdivide the design task into at least two major parts: the array and the receiver proper (the transmitter of an active SONAR system is beyond the scope of this paper). The array processes in space; that is, it combines suitable delayed space samples of the acoustical field, resulting in a voltage output that is a function of time. The receiver proper processes in time; that is, it makes use of the input time function over a finite observation time, yielding at the end the decision of the required type. The present paper investigates the factors involved in the synthesis of a best signal processing system spanning the whole domain from ocean to decision. Having formed a suitable space-time sampling plan, one can write the requisite likelihood ratio, which prescribes the best signal processing operations. In general, these operations will consist of inextricably mixed space and time processing. The question then suggests itself: What are the necessary and sufficient conditions for separation of the likelihood ratio system into space processing followed by time processing, or vice versa? This subject is treated in this paper.
Optimum Threshold Detection with Adaptive Beamforming in a Class of Non-Gaussian Signal and Noise Fields
Authors: Middleton David
Published: November 2005

The threshold (i.e., weak input signal) structures for the optimum binary detection of general signals in a broad class of non-Gaussian noise fields are determined for a variety of situations that include both adaptive and preformed beams. The nonnormal noise fields represent various types of process with slowly fluctuating intensities, e.g., “fading”. They are derived from the multivariate X2-gauss distribution and include as important special cases the multivariante and multiple Lapace densities. For the important case of independent sampling of the background noise (multiple Laplace density), the optimum threshold structure requires in various orders: ideal limiting (“superclipping”), squaring, beamforming, and integration of the input. Several examples involving independent space and/or time sampling of the input signals are operationally diagrammed, and the general approach is shown to yield DIMUS structures as special cases. Superclipping occurs in all instances, basically because of the non-Gaussian falloff of the tails of the amplitude distribution of the noise.
Analysis of Doppler Shift of Sonar Backscatter
Authors: Hartley Robert
Published: November 2005

A digital procedure for the analysis of Doppler shift of SONAR backscatter in presented along with examples from 4.5 and 14 kHz sonar signals. The reduced data are compared with the results of other researchers and existing theory. The digital program is run on a CDC 8090 with 4096 words of memory. The program makes use of a single sideband algorithm for heterodyning the digital data into the range of a fixed band of simulated digital resonant filters. Outputs of the simulated filters are typed in symbolic form with each symbol representing an increment of 3 dB. There are 12 possible symbols giving a system dynamic range of 36 dB. The method employed eliminates the effects of wow and flutter from the original analog recordings and produces a variable width spectrum about the transmit frequency.
Ultrasonic Stereotaxis
Authors: Gordon Douglas
Published: November 2005

Ultrasonic visualization of human tissues has aimed at obtaining information simultaneously from a number of different depths from the surface. In consequence, only weakly focused transducers have been employed. In stereotaxic surgery when the highest possible accuracy is essential in three dimensions, it is preferable to sacrifice all other considerations to reducing the size of the focus to the minimum and to move the transducer bodily so that the focus scans a single plane of the body which can be in any of the three anatomical axes. As echoes are obtained from what is virtually a point source, the effect of the angulation of the surface is much less important than when plane waves are used. Using conventional gating circuits, it is possible to select only those echo pulses that occur exactly at the focus. These are recorded automatically on electrosensitive paper, either directly or with enlarged scale, by use of a pantograph. The problems involved in obtaining short well-damped pulses for diagnosis and high acoustic power continuously for destructive purposes from the same transducer have been overcome by employing high harmonics for diagnosis and a spherically ground ceramic bowl with no added damping. In actual laboratory experiments on cats, it has been possible to localize the major blood vessels to 0.1 mm three dimensionally and to distinguish between the surface of the hemisphere and the roof of the lateral ventricle only 5 mm below.
Ultrasonography in Ophthalmology
Authors: Baum Gilbert
Published: November 2005

This paper is a historical review of the use of ultrasound in ophthalmology. The paper will review its earliest therapeutic applications, the use of A and B Mode for diagnostic purposes, the localization of intraocular and intraocal foreign bodies by both the A and B Mode techniques, ultrasonic measurement of eyesize, and the use of intense focused ultrasound for the production of focal chorioretinal lesions. The present state of these applications will also be discussed.
Ultrasound Cardiogram in Clinical and Physiological Studies
Authors: Joyner Claude , Pyle Richard , Gruber John
Published: November 2005

Ultrasound cardiograms have been obtained from over 3000 subjects over the past 6 yr. The accuracy of this method for the assessment of mitral valve disease, as described in earlier reports, has been confirmed in this large patient study. This method of external, safe study has been found to equal cardiac catherization in accuracy when judged by findings at operation. Equally reliable evaluation of tricuspid valve disease has been obtained, and actually found superior to catherization in preoperative assessment. Valve substance, pliability, and mobility can be determined from the ultrasound records. The prediction of valve characteristics determining whether replacement of a valve with a prosthesis is needed, has been quite accurate. This preoperative information is not obtained from catherization studies. The behavior of the mitral valve, accounting for the opening snap in mitral stenosis, and the Austin-Flint murmur of aortic regurgitation, have been defined by simultaneous record of direct video display of the mitral valve ultrasound with the phonocardiogram. The use of the mitral ultrasound as a reference for analysis of sound records will be presented. The ultrasound method of determining pericardial fluid has been confirmed as valid but subject to record error and misinterpretation. The ultrasound cardiogram is 100% accurate in prediction of mitral valve sizes and valve leaflet character. The accuracy in determination of pericardial fluid is less reliable.
Diagnostic Application of Pulse Echo Ultrasound to the Abdomen
Authors: Holmes Joseph H.
Published: November 2005

Present studies indicate that ultrasonic pulse echo compound scanning techniques are of value in demonstrating intra-abdominal pathology and thus may prove to be a valuable diagnostic aid in a wide variety of diseases. Equipment used employs either contact scanning or water-path scanning. The liver, kidney, and spleen all transmit sound well and thus can be readily outlined to determine size and position. In the liver, which transmits sound well, abnormal echo patterns are observed with such lesions as cirrhosis, tumor, abscess, chloecystitis, congestion, and hepatitis. Renal cysts and tumor give abnormal echo patterns. The ultrasonic technique has had greatest diagnostic application on examining abdominal masses. Fluid filled structures like the stomach and the bladder are outlined readily by ultrasound, and it is possible to delineate structural distortion, pressure from adjacent structures, and to estimate the amount of fluid present. The pancreatic area, abdominal aorta, and vena cava can be visualized in some patients with appropriate use of time-varied gain and depth control. Ultrasonic controls that must be used to obtain proper visualization will be discussed.
Acousto Optics and Their Application to Ultrasonic Visualization
Authors: Jones H. W.
Published: November 2005

This contribution reviews the present position of acousto-optics in relation to ultrasonic visualization. The basic principles relating to matching, reflection, and refraction are briefly reviewed. Detailed consideration is given to the problem of matching at the front face of an image convertor. The attenuation in liquids and solids is considered and related to the diffraction effects that arise in lenses and mirrors. The results of calculation of the relative importance of diffraction and geometric aberrations in lenses and mirrors accounting for absorption and mode conversion effects are given. The use of zone plates and other artifices to improve performance is discussed. Finally, the problems of ultrasonic illumination are considered in relation to reflection and transmission modes of operation.
Control of Air Distribution Noise in Critical Auditoriums
Authors: Hoover R. M.
Published: November 2005

To achieve low background noise levels in critical air-conditioned auditoriums, such as concert halls, it is essential to control the noise generated by air flow through air outlets and in terminal distribution ducts. In this paper, the air distribution systems of several auditoriums, and the corresponding background noise levels, are examined to help define appropriate noise-control measures for the design of silent air distribution systems. In addition to the evaluation of several existing air distribution systems, laboratory noise data on various types of air outlets are presented and related to field results.
Application of Random Walk to Reverberant Room Acoustics
Authors: Lubman David
Published: November 2005

In a reverberant room driven with a steady high-frequency tone, it has been reported that values of squared sound pressure are distributed through space according to the chi-square distribution of two dimensions. Under what circumstances is this distribution to be expected, and what is the physical significance of two statistical dimensions? We gain insights, and some answers, by casting the problem into the form of a random walk in two (sic) dimensions, wherein the reverberant field is viewed as the sum of interfering, travelling waves of the dirving-tone frequency. The chi-square distribution is shown to be a limiting case for many waves under broad conditions. With few waves, the problem is more complex. Useful and revealing results are found by examining special cases for which the orderly transition to the limit can be observed.
Improved Rotating Diffuser for Reverberation Chambers
Authors: Lawler Edward D.
Published: November 2005

An experiment was conducted with a rotating diffuser consisting of several acoustically reflective panels in the form of a truncated cone to determine if it would give more efficient diffusion of a reverberant room's modal patterns than a typical flat-panel rotating vane. The diffuser construction was such that deviations from the purely conical shape could be made to determine the effect of changes in shape on the degree of diffusion. Since the amount of diffusion in most low-frequency regions varies with the location of the rotating vane within the room, it was also considered to be possible that a spatial traverse of the vane would result in a space-averaged diffusion and more uniform over-all modal response. To determine the effect of such a spatial traverse, the drive mechanism of the conical diffuser was modified so that the vane's axis of rotation simultaneously traversed an asynchronous orbit. It was found that the orbital-rotating conical diffuser gave a significant flattening of the room's low-frequency modal response and was much superior to the rotating flat diffuser.
Excessive Reverberation Time for Organs?
Authors: Fitzroy Dariel
Published: November 2005

Whether or not organists and organ builders are demanding excessively reverberant environment is posed as a problem for consideration. The point is brought up that too long reverberation periods could result in an undesirable coloring of what is heard.
Scattering by Coated Prolate Spheroids
Authors: Yeh C.
Published: November 2005

Most previous theoretical analyses [See W. P. Mason, Ed., Physical Acoustics (Academic Press Inc., New York, 1964)] were carried out with the assumption that the scattering object was either an elastic sphere, an elastic cylinder, or a rigid spheroid. Because of the importance of the penetrable spheroid problem with regard to the scattering by nonspherical bodies, the task of solving this problem was carried out recently [presented at the 73rd Meeting of the Acoustical Society of America in New York during April 1967 by C. Yeh]. The purpose of the present presentation is to consider the problem of the scattering by a coated prolate spheroid. A rigid prolate spheroid coated with a sheath of acoustic material characterized by (ρ1,c1) is assumed to be immersed in a acoustic medium characterized by (ρ0,c0). ρ and c are, respectively, the density and the sound speed of the medium. Emphasis will be placed upon the presentation and interpretation of the numerical results in the resonance region. [Work supported by the Office of Naval Research.]
Luneburg Lens and Wave Theory
Authors: Boyles C. Allan
Published: November 2005

The wave theory for an underwater Luneburg lens is discussed in terms of a generalized wave equation, which differs from the ordinary wave equation in that it contains a term involving the gradient of the material density of the lens. We then consider the special case where, to a first approximation, the density of the lens has a constant value equal to that of water. This case is of some importance since it corresponds to the compliant tubing lens built and tested by W. J. Toulis [J. Acoust. Soc. Am. 35, 286 (1963)]. For this special case, we determine the analytic solution of the wave equation when the lens is being irradiated by plane waves, and then present the results of a numerical evaluation of that solution. In particular, we calculate the acoustic pressure field along the axis of the lens and the pressure receiving patterns. These results give us the gain and beamwidths for the range 1 ⩽ k0a ⩽ 30 (k0 the wavenumber in water, a the radius of the lens).
Time-Domain Analysis of Broad-Band Refraction and Diffraction
Authors: Wright H. A.
Published: November 2005

The refraction and diffraction of short-duration transients is analyzed by means of the Kirchhoff integral. A solution for acoustic refraction is obtained which expresses the disturbance on the axis of a spherical liquid lens (diffraction plate) in terms of: the lens (plate) parameters, the lens (plate)-to-observation point distance, and the source-emitted disturbance. It is shown that at distances small compared to the image distance, the disturbance on axis will be predominantly that emitted by the source; that the disturbance in the vicinity of the image point will be functionally the derivative of the source-emitted disturbance; and that at distances large compared to the image distance, the disturbance will be predominantly the inverse of that emitted by the source. Experimentally observed pressure-time records resulting from refraction and diffraction of short-duration electrodeless spark pulses are described that confirm the analytical results.
Simultaneous Variation of Frequency and Angle in Acoustic Studies
Authors: Barss W. M.
Published: November 2005

The effect of submerged objects on a beam of sound in water is strongly dependent on both the frequency of the sound and the angle of incidence at the interface. Instead of measuring the intensity of transmitted or scattered sound at one frequency, while the angle is varied, and then repeating the process at each of a series of discrete frequencies, it is more convenient to sweep both variables simultaneously at appropriate rates. Typically, the frequency is swept uniformly through a range, e.g., from 0.8 to 1.0 MHz, every 10 sec, while the angle changes continuously by 1°. Since the acoustic signal is generated as short bursts, with a repetition rate of 10 sec−1, the measurements for one quadrant of angular variation may be represented as a regular two-dimensional array of 9000 intensities, like a slightly skewed television picture. The angular distribution of the scattered sound may be treated similarly. The signal from the acoustic detector is heterodyned with a swept reference frequency in order to permit narrow-band amplification.
Model Studies on an Array of Interacting Piston Radiators
Authors: Gruber George J.
Published: November 2005

The mutual radiation impedance has been studied as a function of separation distance, element phasing, and shading using a model array of circular piston projectors radiating into a pool at 18 kHz. The elements are acoustically small (ka = 0.72) and of the high Q-type (Q = 120), mounted in an effectively infinite, rigid baffle. The sound generators consist of slender rods driven into their fundamental resonance mode by ceramic tubes, conveniently provided with vibration pickups for the measurements of the head velocities. The direct mechanoacoustical methods, in contrast to previous electroacoustical techniques, used to determine the absolute values of both the real and the reactive parts of the acoustical coupling coefficients, the induced pressure- and amplitude-distributions over the array, and the phase shifts needed at the electrical terminals of the vibrating pistons for maximum radiated power, are discussed. Reported network computations based on known equivalent mechanical circuit representations and iterative-type field solutions for interacting active-passive and active-active elements are both in agreement with the experimental data. [Work supported by the National Science Foundation, Engineering Division, and the U. S. Office of Naval Research, Acoustics Programs.]
Initial Value Problems for Acoustic-Gravity Waves
Authors: Pierce Allan D.
Published: November 2005

Small-amplitude acoustic-gravity waves are governed by the linearized equations of hydrodynamics with gravity included and with the ambient atmosphere in hydrostatic equilibrium. The analog of Green's theorem for these equations is derived and applied to the formulation of the initial value problem solution. Although five different types of point sources must be considered in general, it is shown that one Green's function suffices if the ambient atmosphere is isothermal and at rest. The transient solution for waves from a spherical source initially motionless and with ambient density, but at higher than ambient pressure, is derived in terms of an integral over frequency and volume. The integral is evaluated near times of first arrivals and approximately evaluated at other cases of interest using the saddle point approximation. Numerical techniques are discussed and applied to the calculation of typical waveforms. At early times the results agree with the N-wave profile derived by Baker and Copson for a spherical wave in a homogeneous medium without gravity. The effect of gravity is to add a long period oscillatory tail to the waveforms.
Electrophysiological Studies of Binaural Hearing
Authors: Goldberg Jay M.
Published: November 2005

Attention is focused on the superior olivary complex. Of the nuclei of the complex, the medial superior olive (MSO) is unique in that most of its neurons are affected by stimulation of either ear. Three-quarters of the binaural MSO neurons—EE cells—receive a predominantly excitatory input from both ears. The remainder—EI cells—are activated by stimulation of one ear and inhibited by stimulation of the other ear. The response of MSO neurons to dichotic stimuli is reviewed and compared with the behavior of cells in other nuclei. Response to clicks: EI cells are sensitive to interaural time and intensity differences and show time-intensity trading. EE cells respond to binaural clicks, usually in an occlusive manner. Response to tones: EE cells are sensitive to the average intensity of dichotically presented tones and are relatively insensitive to interaural intensity differences. EI cells may be insensitive to average intensity, but quite sensitive to interaural intensity differences. Both EE and EI cells respond to interaural phase differences; such cells discharge in a phase-locked manner to low-frequency sinusoids. [Work supported by National Institutes of Health grant.]
Adaptive Nonparametric Detection
Authors: Groginsky Herbert L.
Published: November 2005

The aim of an adaptive detector is to vary the characteristics of the device so that nearly optimal sensitivity is obtained among classes of signals from targets or noises perturbing the measurements. The objective is to reduce the losses inherent in using Bayes average statistics to describe the signals and noise. In order to obtain this functional independence, two sensors are used, only one of which can contain the signal. The technique then is to choose a processing system that is inherently distribution free (nonparametric) and vary the available free parameters of the processor in accordance with the system inputs, to bring the sensitivity of the detector to nearly that which could be obtained if the statistics of both the signal and noise were known. It can be shown that if an optimal nonparametric detector exists it must be of the rank-order type. For weak signals, the optimum detector uses linear processing of the rankings. In the adaptive detector described in this paper, the linear processor coefficients are varied intermittently in accordance with the results of each successive detection test. Theoretical calculations verified by computer simulation indicate that this type of device has a definitive lower threshold so that no detection can occur at all with signals below the threshold, while for signals above threshold, essentially perfect detection can take place given sufficient data.
Surface Transportation. III
Authors: Thiessen G. J.
Published: November 2005

As technology advances, the level of noise in our everyday environment appears to increase. Among the factors contributing to this in the traffic field are the increased horsepower used in vehicles, the reduction in weight of engines, the higher compression ratios, and the increased use (especially in buses and trucks) of diesel engines. Legislative control has so far been somewhat timid and lacking the followthrough of enforcement. Noise-control technology has been applied only sporadically, so that the range of noise commonly encountered in any octave band for standard-size passenger cars is more than 10 dB. For heavy trucks, it is even greater. Motorcycles at full throttle, almost regardless of speed, exceed the noise of tractor trailors crusing at 60 mph. Stationary baffles have been successfully used, especially for trains. Rubber tires have also been found practical in subways and urban trains. Proper highway location, design, and noise zoning are further means toward a quieter community.
Twist Overtones of Thickness-Shear and Flexure in AT-Cut Quartz Plates with Partial Electrodes
Authors: Lee P. C. Y. , Spencer W. J.
Published: November 2005

The equations developed by Mindlin and Spencer for twist overtones of thickness-shear and flexure have been applied to AT-cut quartz plates with partial electrodes. The frequency and displacements for resonances near the fundamental thickness-shear mode have been calculated. These results are compared with measured resonances and the mode shapes determined by x-ray diffraction topography.
Out-of-Plane Motion of a Stretched String under Forced Vibration
Authors: Oplinger D. W.
Published: November 2005

This paper treats the nonlinear phenomenon of out-of-plane motion that may develop under certain conditions in a stretched string subjected to planar forced vibrations. As in a previous paper dealing with the case of in-plane motion [J. Acoust. Soc. Am. (Dec. 1960)], the lack of inertial effects for longitudinal deformations occuring during transverse vibrations leads to tension levels that are uniform along the string but varying in time, and separable solutions are seen to result. In the course of the discussion, the out-of-plane motion is analyzed in terms of stability diagrams of Mathieu's equation, and results provide an interpretation of two types of out-plane motion, a “jump rope” mode (out of plane component 90° out of phase with in-plane component) and a “warped plane” mode (out of plane component in phase) which have been observed in experiments involving a slotted end constraint on the string. In the oral presentation, a motion picture sequence illustrating the characteristics of transverse vibration in an actual vibrating string will be presented.
Detection and Localization: Analysis of an Ideal Observer
Authors: Hershman Ramon L. , Lichtenstein M.
Published: November 2005

We extend the theory of signal detectability to a problem in detection and localization (DAL). On each trial, at most one of k observation intervals contains a signal, and the observer indicates either “no signal present” or “the signal is in interval j” (1⩽j⩽k). To maximize correct decisions, the ideal DAL observer is realized by the sequential application (in either order) of YES-NO aid Forced-Choice (FC) decision rules. The theory predicts a higher percent correct on signal trials than on NO-signal trials. Quite independently, the observer has an apparent decision “bias” for saying “signal.” Ideal DAL and FC receivers are compared.