bluuebunny/crossref_metadata_2025 huggingface dataset:
Sound Absorption and Velocity in CO2/D2O Mixtures
Authors: Shields F. Douglas
Published: November 2005

Sound absorption and velocity measurements have been made in CO2/D2O mixtures at 300, 400, and 500°K. The results show that D2O is from one-third to one-fifth as efficient as H2O in de-exciting the bending mode vibration of CO2 in a molecular collision. The collision efficiency of D2O for de-exciting CO2 decreases with temperature at an even greater rate than does that of H2O. The large difference between D2O and H2O invalidates the chemical affinity explanation of effect of H2O and CO2. An approximate semi-classical calculation of the transition probability indicates that it is possible to attribute the relaxation to an interchange between the vibration of the CO2 and the rotation of the H2O or D2O.
Determination of Attenuation Constants for Air in Tubes by Standing Wave Measurements
Authors: Beech W. L. , Sanders J. V.
Published: November 2005

Attenuation constants were precisely measured for air, at ambient conditions, contained in a rigid-walled tube. Standing waves were excited by a piston with the fundamental having a frequency of 93.8 Hz and a bandwidth of 1.12 Hz. Attenuation constants were determined both by the conventional technique of measuring the frequency difference between the half-power points on the resonance curve (Method A), and by measuring the microphone and accelerometer output voltages at resonance (Method B). The experimental results to the 40th harmonic were compared with the Rayleigh-Kirchoff theory that predicts a f12 dependence. Both methods yield a frequency dependence of f0.54±0.3. The attenuation at the fundamental frequency was (1.03±0.03)×10−2 m−1 by Method A and (1.10±0.04)×1002 m−1 by Method B, approximately 10% and 15% higher than the theoretical value for a smooth tube without end losses. Method B which does not require accurate frequency determinations, has not been previously reported.
Pseudospeech Synthesis and the Phonette
Authors: Truby H. M.
Published: November 2005

Direct programming intimacy, spanning 17 consecutive years, with, respectively, the Haskins Labs PB-2 and Octopus, the Swedish Royal Institute of Technology Ove I, LEA, Lucia, progressively developmental stages of Ove II, etc., and the IBM San Jose Terminal Analog Synthesizer, (both Mark I: manual patterns, and Mark II: computer-stored, diphone-nucleus nuclei) has led the author of this paper to consider strongly the term “speech” as applied to the products of electromechanical “synthesis” operations. The linguistics (sic) implications of the contrivance “pseudospeech” to these products seem highly apt to this investigator, who at one time proposed the acronym TAPS for the IBM device (and thus: Terminal Analog Pseudospeech Synthesizer) and presented a paper before the Xth Annual National Conference on Linguistics entitled, “A Phonetic Macro-matrix for Pseudo-speech Synthesis.” The relevance of this iconoclastic, but perhaps useful, consideration to questions of listener judgment(s) and other psychological-testing procedure(s) is discussed, both in its own light and in light of a variable segmental unit, the phonette, proposed as a part of the Acta Radiol Logica Monograph Acoustico-Cineradiographic Analysis Considerations (Truby, 1959), a 227-page publication including 1100 sound spectrograms of American-English word utterances, each with correlated oscillogram, over-all-intensity record, pitch curve, and duplex oscillogram. Synthesis and speech-transmission analysis have much to offer future communication research, provided they are not delimited by misdefinition and equivocal evaluation criteria.
Control Rule of Voice Source to Improve the Naturalness of Synthetic Speech
Authors: Nakayama Takeshi , Ichikawa Akira , Nakata Kazuo
Published: November 2005

Though it is rather difficult to define the naturalness of speech clearly separated from its articulation, we assume we can roughly do so. Naturalness, in this sense, still means many aspects of speech. Some of them are very important in the practical application of synthetic speech, since it is very hard to grasp a whole meaning of synthetic speech quickly, if the speech was not provided with good naturalness. The objectives of the research is to find out the way to improve the naturalness of synthetic speech, through the control of its voice source characteristics. Firstly, analysis has been made on the voice source characteristics, especially on pitch frequency and intensity envelop of glottal waves. Secondly, rules has been derived from the data with several assumptions for the simplification. Thirdly, synthesis was made according to the rules and listening test was performed. The results tell us that some aspects of naturalness, which are mostly derived from syntax of the sentence, are improved by the relatively simple rule, but emotional state and voice quality are not so easily communicated to the listeners by synthetic speech. Further details of the analysis, synthesis, and results of listening test will be presented at the meeting.
Comparison of Sonar Equation and Decision Theory Approaches to Passive Detection
Authors: Stocklin Philip L.
Published: November 2005

The sonar equation for passive detection, usually expressed in decibel form, equates recognition differential (NRD) to target, propagation and sonar system power measures and is the basis for recognition differential (NRD) figure of merit and signal excess performance prediction methods. If the problem of detection performance prediction is formulated using decision theory, detectability index d is the major performance measure. Comparison of the two approaches yields (a) a quantitative measure of NRD in terms of d, bandwidth, processing time, and type of processing; (b) lack of a finite optimum bandwidth for detection, in general, (c) inherent difficulty of the decibel approach in finding theoretical detection performance over a very broad bandwidth, (d) means and the extent to which detection performance prediction can be factored with operational requirements versus design factors.
Matched-Filter Processing of Hydrophone Arrays
Authors: Flanagan J. L. , Landgraf L. , MacLean D. J.
Published: November 2005

Multipath transmission between a sound source and a simple beamforming array degrades the gain of the array. Matched-filter processing is one means for combating multipath distortion and for maintaining array gain (Parvulescu). In addition, matched-filter processing produces a volume focusing of the source (Schroeder). That is, where the simple beam former locates the source only in bearing the matched filter bounds the source in three dimensions. Simple relations for array gain and for received signal-to-noise ratios are derived for the matched filter. Undersea signals are recorded from five hydrophones for source ranges out to 100 miles. The signals are digitalized and processed by transversal matched filters simulated on an IBM 7094 computer. Measurements are made of array gain, and rough estimates are made of the focal volume size. Calculated and measured performance of the matched-filter array are in satisfactory agreement and suggest potential improvement in detection capability over the simple beam former. The improvement in gain is found to be on the order of the number of significant multipaths.
Effect of Spatially Uncorrelated Noise on the Maximum Array Gain Processor
Authors: Cron Benjamin F. , Becker Clair J.
Published: November 2005

Several authors have shown that large array gains may be obtained by weighting individual elements with the optimum amplitude and phase factors. It is known that spatially uncorrelated noise, α, such as electronic noise, will decrease this maximum array gain. The purpose of this study is to obtain a quantitative value for this loss. Vertical, linear, equally spaced arrays from two to 10 elements are analyzed for both an isotropic and a surface generated noise field. Calculations on each array with elements spaced from one eighth to one wavelength have been made showing: (1) array gain as a function of the direction of “look” for several values of α, (2) array gain versus α for various spacing intervals, and (3) array gain versus the number of elements for given values of α. The loss of array gain increases as the number of elements increases for a given α. However, for the worst case of 10 elements spaced one-eighth wavelength apart, α could be 20 dB below the ambient noise level and still give much better results than conventional processing.
Value of Memory in Sequential Detection
Authors: Roberts R. A. , Mullis C. T.
Published: November 2005

In detection models, one usually assumes the detection device can retain any function to any degree of precision necessary to optimize the performance of the detector. Under some conditions, it may be necessary to limit the soft memory of the detector for reasons of size, expense, etc. The problem of optimizing the detection performance of a sequential detector with a limited soft memory is investigated. For the sequential detection problem under study, the optimum full memory detector must store in soft memory two variables—one deterministic and one random. The random variable L gives the cause probabilities at each stage of observation. The limited memory detector is permitted only an m-bit register to store the random variable L. Limited numerical results indicate that a 3-bit register gives performance close to the full memory detector. [This work supported by NSF grant.]
Estimation of Periodic Signals in Noise
Authors: Kincaid Thomas G. , Scudder Henry J.
Published: November 2005

Two methods for the estimation of a periodic signal in additive noise are presented. Both assume a finite time sample of the signal plus noise is available with a large signal-to-noise ratio. Both minimize the mean-square error between the estimate and the sample. In the first method, estimates for the period of the signal and the complex amplitudes of its harmonics are derived. In the second method, estimates for the period of the signal and the waveform of one period are derived. Assuming white noise, the expected values and variances of the period estimates are derived. The estimates for the period are found to be the same by both methods. The estimate is unbiased and has a variance inversely proportional to both the signal-to-noise ratio and the cube of the number of periods in the sample. The expected values of the waveform estimates are derived, and the estimates are found to be biased. [This work was supported in part by the U. S. Office of Naval Research.]
Measurement of the Spectral Density of Ocean Reverberation
Authors: Westneat Arthur S.
Published: November 2005

An experiment is described that provides measured estimates of the spectral density of reverberation under typical ocean conditions with a spectral dynamic range in excess of 30 dB. Measurements were made with a precisely controlled narrow-band pulse at 15 kHz on a platform moving at various speeds between 0 and 15 knots, both across and with the wind, and in deep as well as shallow water under two sea conditions. A 10° array was employed that was alternately pointed at 90° and 0° relative to ships heading. Tape recordings of the reverberation echoes were analyzed through digital comb filters, a digital Fourier transform, and a fast Fourier transform program, to verify observed results and to obtain the widest available dynamic range compatible with cost of reduction. Tape flutter spectral components, which were found to obscure the reverberation spectra, were removed by controlled digital sampling. The effects of range on spectral width are examined by sliding the sampling window through the echo period. Comparisons are made of spectra with calculated beam pattern effects, and with assumptions of a normal distribution of scatterer velocities.
Ultrasonic Encephalography
Authors: Grossman Charles
Published: November 2005

A review of clinical applications of diagnostic ultrasound, in conjunction with EEG, will be presented.
Sonographic Interpretation—Pitfalls and Breakthroughs
Authors: von Micsky Lajos I.
Published: November 2005

Contrary to the impression conveyed by recent publications, the problems arising in diagnositc ultrasonics are not primarily of a technical nature. The difficulty now lies in deciphering the vast amount of information recorded on the sonograms and in elucidating the tissue's structural characteristics responsible for the echo pattern obtained. Since relatively little is known and understood of the physical mechanisms attending the propagation of high-frequency acoustic waves in biological materials, the first step toward intelligent interpretation is to explore new theoretical and experimental avenues for gaining insight into the sources of tissue echoes. The use of morphologic interpretive criteria alone has been rendered grossly inadequate by the well-known fact that a number of different conditions can produce sonographic patterns that appear nearly identical on visual inspection. The various methods of data processing practiced in our laboratory are discussed in detail, emphasizing a general tendency twoard some form of quantification. New techniques involving color-translating isodensitracing, ultrasonic holography, quantitative evaluation of compound scan sonograms, and automatic pattern recognition are mentioned.
Investigation on Electronic Image Conversion in Pulsed Operation
Authors: Pohlman R. , Radig G. , Schätzer E.
Published: November 2005

The two possible methods of the electronic ultrasonic image conversion—the CW or impulse-reflex technique—are confronted and compared. For short distances, an unequivocal superiority of the impulse-reflex-technique results. The low coverage at high frequencies proves to be hindering, which mainly depends on the damping in the transmission channel and by this on the frequency, but furthermore, also on the shape of the object that is to be imaged. At equal number of image elements, the diameter of the plate must increase at lower frequencies. Therefore, two possibilities to increase the mechanical solidity were investigated. By this it follows that at equal solidity, a shell construction allows a diameter that is larger by factor of 20. The materials usable for such a construction were tested concerning their application in the ultrasonic image conversion technique, and results are reported. The second part deals with the application of the impulse-reflex technique, The charge image on the transducer plate produced by an impulse can be scanned only partly during the short period of an impulse. Therefore, the application of a sampling method is necessary. The electronic arrangement for this method is described. The limits of the technique are specified.
Sensitivity Predictions for Ultrasonic Image Tubes
Authors: Turner William R.
Published: November 2005

The sensitivity of the electronically scanned ultrasonic image tube is assessed in terms of its potential development as well as the existing state of the art. The piezoelectric conversion element is treated not only as an open-circuit potential source, but also as an energy converter with storage capability. Low- and high-conductance modes of transferring the electronic image signal to the output circuit through secondary emission are contrasted, and the effective use of output coupling networks described for the high-conductance mode. Noise sources are identified and evaluated as to their relative importance in current tube designs, and also as to the steps that might be taken to reduce noise significantly. By a summary chart relating the equivalent noise intensity to the video bandwidth, published sensitivities for existing tubes are compared and referenced to potential sensitivities that might be achieved during further image tube development.
Reference Waves in Synthesized Acoustical Holograms
Authors: Metherell A. F. , El-Sum H. M. A.
Published: November 2005

The reference wave necessary for recording a hologram of an object irradiated with acoustical waves A. Metherell and H. El-Sum, Appl. Phys. Letters (July 1967)] can be provided externally by appropriately controlling the phase between two coherent signals, the one that derives the sound source, and the other which is used as a reference by summing it electronically with the signal diffracted from the object. The shape of the wavefront of the reference wave and the angle it makes with the object wave are determined by the phase shift between the two waves on the recording plane. This in turn depends on the wavelength, the recording technique (continuous or sampled [A. Metherell, H. El-Sum, J. Dreher, and L. Larmore, Appl. Phys. Letters 10, 277 (1967); J. Acoust. Soc. Am. (Oct. 1967), the type of the sought hologram (narrow or wide angle, Fourier, Fresnel, etc.), and the final optical reconstruction. These and other factors affecting the choice and control of the reference beam will be discussed. Experimental results of acoustical holograms taken with various sound frequencies (9–21 kHz) will be presented.
Comparison of Three Methods of Rating Floors for Impact Noise
Authors: Mariner T. , Spalding G. R.
Published: November 2005

About 200 floors were examined in the laboratory using as sources the ISO tapping machine and female walkers wearing hard high heels and prejudged to be consistent vigorous walkers. Data were reduced to impact noise rating (INR), for tapping machine noise [see T. J. Schultz, J. Acoust. Soc. Am. 36, 729 (1964)]; and, for walking noise, to loudness [see T. Mariner and H. W. W. Hehmann, J. Acoust. Soc. Am. 41, 206 (1967)], and to a detectability rating [see B. G. Watters, paper L3]. While loudness and detectability rating for these tests correlate generally within the estimated experimental error (±10% loudness) involved in the walking tests, there are larger discrepancies for some of the louder floors that subjective judgment had classed as “more detectable than loud” before detectability had been calculated. We conclude (1) that detectability rating is more significant than loudness rating and (2) that the INR is inadequately correlated with suppression of walking noise, whether related to loudness of footfall noise or to detectability of footfall noise.
Statistical Analysis of Sound Absorption by Audience
Authors: Geetha K. V. , Ramakrishna B. S.
Published: November 2005

It is proposed that the sound absorption coefficients of acoustic materials, in general, be considered as random variables since their values depend upon the sound fields in which they are measured. This viewpoint is particularly appropriate for audience absorption since clothing, seating, etc. vary randomly. On this assumption, it is possible to decide between the classical hypothesis that the audience absorption is proportional to their number and Beranek's hypothesis that audience absorption is proportional to the occupied area, by analyzing the variance. A two-way classification of the total absorption of a number of halls is made with seating density and seating area as the row and column variables, respectively. The absorption of the hall in the ith row and jth column is written as aij = μ + ri + cj + εij, where μ is the mean of all entries, and ri and cj are the row and column effects, respectively. The εij's represent contributions from other sources and interactions. Tests for the hypotheses ri = 0 and cj = 0 indicate that audience absorption varies significantly with seating area but not with seating density, supporting Beranek's hypothesis.
Improved Automatic Decay-Rate Meter
Authors: Presti A. J.
Published: November 2005

The original design of the automatic decay-rate meter [J. Acoust. Soc. Am. 40, 1267 (A) (1966)] has enabled us to measure the sound decay rate in a room easily and successfully, and has also enabled us to gain more insight into the operation of this device. This paper will review some of the design concepts and introduce au improved version designed to further reduce setup time and ambiguities.
Sabine Absorption Coefficients of Aluminized Rubber
Authors: Case Richard W. , Vahlkamp Eugene W. , Kinsler Lawrence E.
Published: November 2005

Since 1930, the work of Eyring and others has indicated that the effective Sabine absorption coefficient of highly absorbing materials is not given by αi, the randomly incident energy absorption coefficient, but is instead given by −ln(1 − αi). This indicates that for αi>0.63, the Sabine coefficient should be greater than 1.0. A search of the literature provides many measured values of 0.99 for the Sabine coefficient but rather surprisingly only one or two measured values in excess of 1.0. This paper reports on reverberation measurements made at frequencies from 10 to 100 kc/sec in water contained in a small tank completely lined with either flat or cone structured aluminized butyl rubber. The maximum value measured for the Sabine coefficient was 2.56 which corresponds to αi = 0.923. In carrying out these experiments, decay rates in excess of 25 000 dB/sec were measured through use of a Memoscope. Information as to the advantages of using a Memoscope in making reverberation measurements will be presented.
Causality in Sound Scattering from Elastic Cylinders
Authors: Überall H. , Uginčius P.
Published: November 2005

We have investigated the causality aspects of a plane acoustical wave being incident on an elastic cylinder, and producing circumferential waves on the cylinder surface. The phase and group velocities of the latter were obtained by performing a Watson transformation on the normal mode series and searching for the zeroes of the denominator in the complex plane. An incident wave packet was constructed by a Laplace transform; then the speeds of the head of the wave Ci can be found by closing the contour to the right. This procedure also furnishes the paths of propagation of the pulse during the scattering process: One finds that the waves enter and leave the cylinder surface towards the outside at critical angles ϑi given by sinϑi = c/Ci, towards the inside at ϑli,t given by sinϑi = cl,t/Ci, where c is the sound speed in the surrounding medium, and cl,t are the longitudinal and transverse speeds. Two types of circumferential waves are obtained; Rayleigh type, with ci>c, and Franz type, with Ci≅c.
Radiation from a Spherical Array Enclosed by a Concentric Spherical Shell
Authors: Douglass R. E. , Jay B. E. , Moyer W. C.
Published: November 2005

Farfield beam patterns and mutual acoustic impedances have been computed for circular pistons mounted in a spherical baffle that is enclosed by an elastic spherical shell. For the beam pattern computation, the pistons are arranged in a rectangular array and phased to a plane to direct a narrow beam. The effect of enclosing the array by the shell is investigated by comparing with the no-shell results. It is seen that the shell does not change the main lobe of the beam pattern, but that the side lobe level is raised. The interaction coefficient between element pairs is given as a continuous function of element spacing, with zero spacing corresponding to the self-impedance. While addition of the dome does not change the basic shape of these curves, which are decaying oscillatory function, the shell-baffle spacing is seen to have a strong effect on the magnitudes of the interaction coefficients.
Binaural Hearing in Cat and Man
Authors: Diamond Irving T.
Published: November 2005

Cats were trained to respond in a double-grill box to a change in a binaural pattern of tones produced by alternately stimulating one and then the opposite ear. Tests showed that the cats did not, in fact, perceive a single sequence to which each ear contributed its share, but instead waited for a frequency change to occur in one ear. Ablation of auditory cortex contralateral to the side of the attentive ear resulted in an amnesia, while ablation of the auditory cortex ipsilateral to the attentive side had no effect upon the learned habit. The question of how the engram is isolated to one hemisphere was explored by further studies in which the corpus callosum was sectioned. The results suggest that the engram is kept out of the ipsilateral hemisphere by an active suppression originating in the contralateral hemisphere. In the course of these experiments, it was observed that the rate of clicks that alternate from side to side was underestimated when compared to a train of clicks presented monaurally. A subsequent experiment by Axelrod with college students as subjects showed precisely the degree of underestimation. [Work supported by Grant from N. I. M. H.]
Binaural Effects in Psychoacoustic Research
Authors: Green David M.
Published: November 2005

A review of the psychoacoustic research on sound localization and the role of phase and amplitude differences between the two ears is presented. The precedence effect and the steady-state cues for localization are related. A survey of the work on masking level differences (MLD's) as well as two prominent theoretical accounts of this phenomena are discussed. [Research supported in part by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education and Welfare.]
Estimation and Detection: A Unified Approach I
Authors: Cox Henry
Published: November 2005

The thesis of this paper is that a variety of results in optimum detection and estimation can be most easily comprehended if one first examines in detail some very simple but general problems and fully understands the assumptions, solutions, and interrelationships for these simple problems. The relationships among a variety of seemingly diverse, complicated problems may then be clearly seen since the first step in obtaining a solution is usually to transform the problem by some technique into one of the simple problems. The transformation step is frequently of such mathematical complexity that the basic strategy is effectively camouflaged. After examining the simple general problems, various applications, including optimum arrays, are discussed.
Null Steering as a Realizable Process and Its Relationship to Optimum Beamforming
Authors: Anderson Victor C.
Published: November 2005

A real-time digital processor is described that is designed to reject plane-wave interference from an operator-controlled direction, prior to normal beamforming. Both hardware and an analysis are discussed. The process is compared with the corresponding optimum process, indicating the similarities and differences that occur.
The Adaptive Likelihood Ratio Detector
Authors: Birdsall Theodore G.
Published: November 2005

A search for a theory of optimum adaptive detectors leads instead to a theory of adaptive realizations for optimum (likelihood ratio) detectors. The virtue of adaptation is not in achieving breakthroughs in performance. The real role of adaptation is that certain levels of performance that are achievable by both adaptive and nonadaptive detectors may be achievable with cheaper or smaller equipments if they are adaptive. The paper ends with a short discussion of implementation of the design rules furnished by likelihood-ratio theory.
Industry Noise
Authors: Morse Kenneth M.
Published: November 2005

The definition of noise as “unwanted sound” is purposely devoid of technical language owing to the wide spectrum of possible effects upon humans that are both physiological and psychological. The former is largely objective and the latter subjective. While there are a considerable number of published efforts to establish criteria on hearing-damage risk, such “numbers” are widely debated upon the basis of lack of valid supporting data. In the area of annoyance, efforts to establish criteria are on even more untenable grounds. Attempts to equate degrees of annoyance are most difficult and highly complex. An effort to attach numbers to annoyance is faced not only with emotional and sociological factors but also with the fact that there are wide differences in human susceptibility and adaptability to noise. This paper discusses the major efforts that have been made to evaluate annoyance from industrial noise, zoning laws with performance standards, the rôle of transportation noise in such standards, and the views of the author on the usefulness of such data.
Air Conditioner Equipment
Authors: Meling A. E.
Published: November 2005

Although early residential air conditioners were usually water-cooled, air-cooled versions, which may result in complaints if not properly controlled, quickly became by far the dominant type. The first efforts to control such noise by means of ordinances took place about 1958. These efforts continued on a quite sporadic basis until the summer of 1966 when they mushroomed in such widely separated suburbs as Coral Gables (Miami), Fla., Beverly Hills (Los Angeles), Calif., Irvington (New York), N.Y., and even Etobicoke (Toronto), Ontario. Since sound tends to be confusing to people who are not experts in acoustics, it is not surprising that these noise ordinances vary from effective to unenforceable. To fill an obvious need in this regard, ARI made a study of the factors that should be taken into account by communities considering such ordinances. The resulting “model ordinance” is designed to control noise that will be a nuisance to most people and is practical to enforce in the field. The ARI ordinance is not a panacea for this problem. The real solution will require a coordinated blend of good equipment, proper installation practices, and realistic controls.
The Noise Receiver, the Citizen
Authors: Baron Robert Alex
Published: November 2005

Urban man, immersed in everyday noise, receives little benefit from the science and technology of acoustics. He is low man in the noise source-transmission path-receiver system. Yet there is extensive know-how for noise control in industry and aerospace. In contrast, urban man continues to suffer, unabated and magnified, the same disabling noises of two generations ago. Today in addition, his environment is blighted by the inadequately muffled noises of aviation. Uniform guidelines are needed. Faced with this indisputable evidence of neglect, urban man must become responsible for his own protection. Citizens for a Quieter City has been formed to create an awareness of the need for the control of city noises and of the means available for noise control. It has a formal structure and draws upon a wide spectrum of experience and support, including that of humanist scientists and technologists. It is concluded that a knowledgeable citizen's noise abatement organization is a necessity. CQC has already proven productive, and extensive planning for the future is underway. A quieter everyday environment is possible, reasonable—and long overdue.
Ultrasonic Coupling Loss
Authors: Ghering Walter L.
Published: November 2005

Ultrasonic coupling losses are found to be a significant component of the experimentally observed loss in measurements of small, high Q specimens. An investigation of the characteristics of this coupling loss showed that it is mainly a dynamic viscous-type loss or a surface friction loss. Viscous losses due to shear components of the vibration are found to be important for “longitudinally” vibrating disks. An analysis of the Aggarwal solution for the disk shows the shear component of the energy to be of the same order of magnitude as the longitudinal component. Experimental data show the loss due to free films, films loaded with 12 and 14 wavelength samples, and the coupling loss in optical contact. A variation of the technique used to investigate coupling losses appears to have promise for dynamic viscosity measurements as a function of frequency. [This work was supported by Air Force Grant.]
Acoustic Emission from Metal Caused by Changes in Applied Stress
Authors: Mitchell Larry , Kerawalla J. N. , Frederick J. R.
Published: November 2005

When the stress level on a metal specimen is increased or decreased, it is possible to observe bursts of noise by the use of a sensitive contact microphone. At stress levels within the elastic range, the emission observed during the removal of the stress is usually at least two orders of magnitude greater than when it is being applied. When the applied load is removed, there is no emission until the stress has decreased by an amount Δs from the maximum load. The magnitude of the emission is dependent upon the strain rate and on the metallurgical and stress history of the specimen. [Work supported in part by the National Science Foundation.]
Bechmann's Number for an Inverted Mesa Structure
Authors: Bleustein J. L.
Published: November 2005

If the ratio of the length of the electrode strip to the thickness of a partially electroded infinite crystal plate is kept below a certain critical value, Bechmann's number, then, for the crystal vibrating at frequencies in the neighborhood of its fundamental thickness-shear frequency, the current through the crystal will be unaffected by the anharmonic overtones of the thickness-shear motion. The concept of the inverted mesa structure (a crystal with an electrode and an insulating film) can be employed to design crystals with large values of Bechmann's number without increasing the electrical resistance of the electrode. In this paper, by means of a special approximate theory, an explicit formula for the Bechmann's number of an inverted mesa structure, in terms of the dimensions and the material properties of the insulating film the electrode and the crystal, is obtained.
Sound Generation by a Dusty Gas
Authors: Crighton D. G.
Published: November 2005

When a finite region of fluid is in turbulent motion, the stresses in the fluid generate sound waves in the surrounding fluid in the same manner as a suitable distribution of acoustic quadrupoles occupying the trubulent region. If the turbulent fluid also contains many small dust particles, the viscous drag force between the dust and gas will also cause generation of sound, but in the manner of a distribution of dipoles. At sufficiently low Mach numbers, the dipole-generated sound must dominate the radiation from the turbulence, and it is shown that this will be true for Mach numbers less than f, the mean dust mass concentration ratio. [Research carried out under the Bureau of Ships and General Hydromechanics Research Program, administered by the David Taylor Model Basin, under contract.]
Light Scattering from Thermally Excited Surface Waves
Authors: Katyl Robert H. , Ingard Uno
Published: November 2005

We report results of a spectral analysis of light scattered by a liquid surface. These results are consistent with the assumption that thermally excited surface waves are responsible for the scattering, and the phenomenon may be regarded as the surface-wave analogue of ordinary Brillouin scattering in the bulk of a fluid. [This work was supported principally by the U. S. Navy Office of Naval Research under Contract and in part by the Joint Services Electronics Program; additional support was received (by R. H. K.) through a National Science Foundation Graduate Fellowship.]
Free-Field Localization of Acoustic-Images
Authors: Toole F. E.
Published: November 2005

Experiments in free-field localization where head movements are restricted have revealed that complex in-head and external localizations frequently occur. The in-head localization may be total (including all of the sound) or partial, in which case part of the sound is localized somewhere in the space around the listener. The externalized sound may be localized correctly in the direction of the loudspeaker, or with the same degree of sidedness but with front-back reversal, or at both correct and reversed locations simultaneously. The factors giving rise to localization judgments in each of these categories are not immediately obvious, and the situation is complicated by intersubject differences. It is possible, however, to observe systematic changes in localization as a function of certain signal parameters such as frequency and bandwidth. These trends may provide clues to the nature of the auditory mechanism underlying front-back discrimination.
On Central Masking and a Time Constant of the Auditory System
Authors: Zwislocki J. J. , Newman R. A.
Published: November 2005

Previous experiments performed at 1 kHz have been extended to 2 and 0.25 kHz. The new results together with the preceding ones lead to the following conclusions. The effect of central masking (as measured in terms of threshold shift) is maximum at the time of masker onset. The maximum increases with sound intensity, but remains frequency independent when the loudness level in the critical band under investigation is kept constant. Provided the latter is true, the maximum does not depend on spectral characteristics, i. e., whether the masker is a pure tone, narrow-band, or wide-band, or wide-band noise. The threshold shift decays exponentially as the time delay from the masker onset is increased; it reaches an asymptote at about 250 msec. The time constant of the decay, on the order of 50 msec, appears to be independent of stimulus parameters. It may be considered a a system,s constant. The same time constant may be derived from various neurophysiological recordings.
Binaural Unmasking and Frequency Discrimination
Authors: Robertson Ronald M. , Goldstein David P.
Published: November 2005

Frequency difference limens (DL's) were determined for three observers employing a 300 Hz target signal for NOSO, NOSπ, and NmSm at three sensations levels (SL's) above masked threshold (5, 10, and 15 dB) and two masker levels (20- and 59-dB spectrum level). The size of the frequency difference limen in noise is dependent upon the sensation level at which it is measured, the interaural phase of the target signal and the level of the noise. The difference limen is significantly larger when measured at low sensation levels under high-level noise when the target signal is 180° out of phase. This effect diminishes at higher sensation levels or when noise level is reduced, and does not appear when the signal is in phase or when a monaural noise-signal configuration is used. Masker level has no effect on the size of the DL for NOSO or NmSm but a differential effect was seen for NOSπ at 5 and 10 dB SL under the higher masker level where larger DL's were observed as compared to the lower masker level. Theses results are predictable from previous findings in regard to the band width employed by the auditory system under conditions where masking level differences (MLD's) are observed.
Psychophyiscal Reality of the Distinctive Features of Phonology
Authors: Klatt Dennis H.
Published: November 2005

Confusions in short-term memory between English CV nonsense syllables are a form of psychophysical data relevant to phonology. A binary distinctive feature is used to divide a stimulus ensemble of phones into two sets. Confusions between phones within a set should be more likely than confusions between phones belonging to opposite sets, otherwise the distinctive feature does not define a categorical perceptual boundary for speakers of the language. Optimal binary features based exclusively on this criterion have been derived, using the 23 consonant confusion matrix data of Wickelgren [J. Acoust. Sec. Am. 39, 388 (1966)]. These optimal features are closely related to the binary distinctive features of phonology.
Machine Recognition of Speech
Authors: Martin T. B. , Zadell H. J. , Cox R. B. , Herscher M. B.
Published: November 2005

This paper summarizes the status of a continuing research program concerned with the recognition of phonemes in both isolated and continuous speech. The acoustic analysis technique employs analog-threshold logic to abstract features that provide the basis for the recognition decisions. These feature-abstraction networks have been organized in a hierarchy of processing levels, ranging from the recognition of broad classes of sounds to decisions on a phoneme-by-phoneme level. As part of this program, a detailed comparison has been made of the characteristics of phonemes in continuous speech as contrasted with well-articulated discrete speech. The development of a continuous speech recognition capability makes possible the realization of several specific applications. Among these are spoken ZIP-code recognition systems that will improve the efficiency of parcel-sorting operation. In this application, it is necessary to recognize continuous strings of digits in a very high-noise background. A speech communications system is also being developed utilizing a speech recognition system at one end of a communications link, a narrow bandwidth channel transmitting the recognition results, and a speech synthesizer at the receiver.
Rules for Word Stress Analysis: for Conversion of Print to Synthetic Speech
Authors: Gaitenby Jane H.
Published: November 2005

Successful conversion of graphemes to English allophones depends on correct assignment of syllable stress (word accent). In turn, stress reflects morphological and syntactic patterns that are intrinsic to the language. Although written English lacks obvious prosodic markers on the word level, its spelling generally represents phonetic realities if stress is not overlooked. (Printed words are also conveniently framed by space.) An important truism is that normal printed texts closely follow spoken grammatical routines. With these facts made operational, and coupled to a modest storage of letter sequences (with appropriate syllables treated as stable stress elements), a fair degree of prosodic contour prediction is attainable. In this paper, preliminary rules for deriving stress information from a printed input are exemplified. The usefulness of these rules in a program for basic intonation in a synthetic speech output is demonstrated. [This research on reading machines for the blind was made under contract to the Research and Development Division of the Prosthetic and Sensory Aids Service, Veterans Administration, New York.]
Syntactical versus Temporal Cues for Speaker Switching in Natural Dialogue
Authors: Gerstman Louis J. , Feldstein Stanley , Jaffe Joseph
Published: November 2005

Intercomparison of two data domains permits an assessment of the relative importance of pauses and syntax as determinants of speaker switching in spontaneous dialogue. The pause and switching data derive from the output of the automatic vocal transaction analyzer, which samples the presence and absence of each participant's speech every 300 msec. The syntactic data derive from boundary markings (points of linguistically permissible phrase endings) on 10 642 words of text transcribed from four 15-min dialogues. Synchronization of both data bases revealed that switching occurs nine times more often after pauses than after nonpauses, and 21 times more often after boundaries than after nonboundaries. The two effects are nonadditive, since the co-occurrence of both cues makes switching 42 times more likely than the co-occurrence of neither. When in conflict, the synthetic cue outweighs the pause cue, since switching occurs 2.6 times more often after a nonpausal boundary than after a nonboundary word followed by a pause. [Research supported by grants from the National Institute of Mental Health.]
The Reflectivity of Two Bottom Areas as Measured by Total Energy Reflection Coefficients
Authors: Menotti Francis R.
Published: November 2005

In a paper presented at the 72nd meeting of the Acoustical Society of America, the author discussed the high variability in the peak amplitude bottom reflection coefficients obtained using pulsed CW signals over an abyssal plain area. These results led to an investigation into the use of a reflected-to-incident energy ratio as a more suitable description of bottom reflectivity. Ratios between the integral-square values of the bottom-reflected and direct-path signal envelopes were computed for 100 msec pulsed CW and 250-msec linear frequency modulated (LFM) signals. The frequencies were 1080 and 3700 Hz for the CW; the LFM bands were centered on these frequencies. Results indicate that the integral-square ratios, which are essentially energy ratios, are as variable as the peak reflection coefficients. The variability, expressed as the interval bounded by the mean plus and minus one sigma, is higher for the 3700-Hz data. For both frequencies and signal types, this variability often exceeds 4 dB over survey areas only a few miles in extent.
Coherence of Ocean Bottom Reflected Acoustic Pulses
Authors: Santaniello Salvatore R.
Published: November 2005

Experiments have been conducted at abyssal plain locations in the Atlantic Ocean with linear frequency modulated pulses 250 msec in length. The frequencies were 1100 Hz ±50 Hz) and 3700 Hz (±300 Hz). Nonoverlapping direct and bottom-reflected instantaneous signals received at two vertically spaced (1100 ft. apart) hydrophones were polarity correlated. Cross-correlations were also obtained (1) between a group of consecutive reflected arrivals at one hydrophone using one arrival as replica and (2) between arrivals at the two hydrophones. These temporal and spatial coherence measurements resulted in mean peak correlation values >0.5 as a function of grazing angle and frequency. At one location, 50 consecutive reflected pulses were consistent in their modulation characteristics and were analyzed for different time-bandwidth products. The higher-frequency 600-Hz bandwidth data resulted in a lower mean peak correlation value because of the multipaths within the reflected pulses caused by the fine grain structure of the bottom. A reduced bandwidth (300 Hz) resulted in a larger spread in peak correlation values, but these values had a greater average and produced less complicated correlation functions. By use of spectral analysis, these stationary reflected pulses have also provided a means for inferring the apparent acoustic complex structure of ocean bottoms.
Ocean Surface Reverberation Mechanisms and Their Laboratory Simulation
Authors: Hayre H. S.
Published: November 2005

Ocean surface roughness is generated by a combination of gravity and wind driven waves. These water/air interface perturbations are directly related to water motion just below this interface. This circular motion of the water may extend down to a depth of up to approximately two times the trough to crest measure of such waves. The ocean reverberation analyses to date have employed an interface description in the form of wave height measurements taken at a point and/or its associated spectrum, with very reasonable results. The experimental reverberation data has not been fully exploited to determine the significance of the said underlying water motion as the major contributor to the acoustic signal intensity scattered into the water body. It is this aspect that is investigated both theoretically with a model of the moving surface as well as the water mass underneath it, and experimentally in a laboratory tank with controlled and repeatable conditions using 1 Mc/sec carrier pulse of widths 4–6 μsec. The water motion was simulated by forced flow of water just underneath the air/water intersurface. The position of a small specular reflecting test plate was varied vertically between the transmit-receive transducer and the air/water interface in order to identify and separate subsurface volume and water/air interface reverberations. Various mechanisms generating the frequency spread of the acoustic signal incident on the surface are also discussed. [This work is sponsored by the Office of Naval Research, under Contract.]