bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffraction impulse response of rectangular transducers
Authors: San Emeterio Jose Luis , Ullate Luis G.
Published: October 2005

A closed-form expression for the impulse velocity potential of rectangular pistonlike transducers, without any far field or paraxial approximation, is presented. The classical time-domain impulse response approach is used considering free-field, rigid baffle, and pressure release boundary conditions. Previous approaches to the rigid baffled rectangular piston require the use of superposition methods in order to find a general solution numerically. These must add or subtract, according to the field point location, the analytical expressions that were derived only for specific field points or geometrical regions. In this paper the complexity introduced by the geometrical discontinuities of rectangular apertures is analyzed. A new compacting methodology is proposed and applied to obtain a general solution for the impulse response. This new solution provides the value of the impulse response directly in the time domain, without requiring superposition methods. In addition, a closed-form solution for the pressure impulse response is also presented. This can be useful for physical insight and a qualitative analysis of transient and continuous wave pressure fields. Also included is a description of the temporal behavior of the impulse velocity potential and the pressure impulse response for field points in different regions. The proposed solution allows an efficient and accurate computation of pressure fields under realistic excitations. Several examples illustrate the use of this new solution in the computation of transient pressure waveforms, when wideband and relatively narrow-band excitation pulses are used. Three-dimensional plots of the peak amplitude of the transient pressure near field are presented, and certain characteristics are analyzed using the pressure impulse response.
Method for identification of the vibrational modes of a rectangular parallelepiped
Authors: Stekel Andrés , Sarrao John L. , Bell Thomas M. , Lei Ming , Leisure Robert G. , Visscher William M. , Migliori Albert
Published: October 2005

An experimental method has been developed for identifying the vibrational modes of a rectangular parallelepiped solid, based on the study of its vertex motion. This method is an important enhancement of the resonant ultrasound spectroscopy technique for determination of elastic constants. The method was tested by identifying the modes of a sample of amorphous Ni80P20. The experimental setup developed to identify the modes is also useful in finding all the resonance frequencies of a solid. This technique is used on a single crystal of YbAs to illustrate the recovery of missed modes and the improvement in accuracy of the elastic constant determination.
Computer-assisted tracking simulation (CATS)
Authors: Dempsey James J. , Levitt Harry , Josephson Judith , Porrazzo Josephine
Published: October 2005

The tracking technique involves a sender reading consecutive segments from a story and a receiver attempting to repeat each segment verbatim. The reliability and validity of the tracking procedure have been criticized based upon uncontrolled variables such as sender, receiver, and text characteristics. To address these problems, a computer-assisted interactive tracking simulation (CATS) system has been developed in which story segments are presented to the receiver via a video laser disc system and repair strategies are implemented through a computer program.
Phonetic prototypes: Influence of place of articulation and speaking rate on the internal structure of voicing categories
Authors: Volaitis Lydia E. , Miller Joanne L.
Published: October 2005

In this investigation, the effects of context on the perception of voicing contrasts specified by voice-onset-time (VOT) in syllable-initial stop consonants were examined. In an earlier paper [J. L. Miller and L. E. Volaitis, Percept. Psychophys. 46, 505–512 (1989)], it was reported that the listener’s adjustment for one contextual variable, speaking rate, was not confined to the region of the phonetic category boundary, but extended throughout the phonetic category. The current investigation examines whether this type of perceptual remapping also occurs for another contextual variable, the place of articulation of the syllable-initial consonant. In a preliminary experiment that involved acoustic measurement of natural speech, it was confirmed that as place of articulation moves from labial to velar, VOT increases, and it was established that this occurs across a range of speaking rates (syllable durations). In the main experiments, which focused on the voiceless category, it was found that this acoustic change was reflected in perception not only as a shift in the location of the voiced–voiceless category boundary, but also a change in both the specific range of stimuli identified as members of the voiceless category and the set of stimuli judged to be the best exemplars, or prototypes, of the category. These findings extend earlier research by showing that a change in place of articulation, like a change in speaking rate, systematically alters the internal perceptual structure of voicing categories.
A cognitive influence on the loudness of tones that change continuously in level
Authors: Schlauch Robert S.
Published: October 2005

The loudness of tones that change continuously in level over time was studied using magnitude estimation and a delayed loudness-balance procedure. In the magnitude estimation task, subjects estimated the loudness of continuous and intermittent 1000-Hz tones that either increased or decreased continuously in level over roughly 3 min. Two stimulus ranges were used: 30 to 70 and 50 to 90 dB SPL. For the low-level conditions, the results are essentially identical to those of Canévet and Scharf [J. Acoust. Soc. Am. 88, 2136–2142 (1990)], who ran similar conditions. Tones that increased in level changed in loudness as a function of SPL at a slower rate than tones that decreased in level. For the high-level conditions, the same result was obtained, but the magnitude of the difference among conditions is smaller. A delayed loudness-matching procedure was used to measure the physical magnitude corresponding to loudness differences among a subset of the conditions. Judged equal-loudness levels showed a sharp decline in loudness for conditions with tones that decreased continuously in level, but the magnitude of the reduction was less than that interpolated from magnitude estimates for identical stimuli. The source of the difference is unclear. To explore the role of cognitive influences, subjects’ attention was diverted by a video word-identification task during the period of adaptation. For this task, the loudness decline was reduced for loudness balances and magnitude estimations compared to conditions where attention was concentrated on the adapting stimulus. In another magnitude-estimation task, the loudness decline for monaural stimulation was found to occur only in the ‘‘adapted’’ ear. In aggregate, these findings lend additional support to the notion that the effect is a sensory phenomenon, with a substantial portion mediated by a central mechanism.
Dynamic frequency change among stimulus components: Effects of coherence on detectability
Authors: Cohen Marion F. , Chen Xiaofen
Published: October 2005

Experiments were performed to determine the effect of coherent dynamic frequency change among stimulus components on detection of one of those components. Detectability of a frequency glide signal, centered at 660 Hz, was measured in the presence of two additional frequency glides centered at 220 and 440 Hz. Results show that the signal is most difficult to detect when it is changing coherently with the other stimulus components, and that detectability gradually improves as the frequency change among stimulus components becomes less coherent. A control experiment indicated that detectability of the signal is influenced somewhat by the average spectral distance between the signal and the other stimulus components. In order to separate the effects of dynamic frequency change from those of altering harmonic relationships, the experiment was repeated with stimulus components not harmonically related. Results are similar in pattern, though with somewhat smaller shifts. A final experiment was performed to determine if the observed shifts in detectability might be due to changes in the maximum spectral distance between signal and masker when their frequencies are changing incoherently. Results of this experiment indicate that detectability improves when frequency change of signal and masker is not coherent, even when maximum spectral distance does not change. These data indicate the likelihood that the auditory system is able to use coherent dynamic frequency change among stimulus components.
Piano string excitation. VI: Nonlinear modeling
Authors: Hall Donald E.
Published: October 2005

Accurate modeling of the piano string–hammer interaction requires that the nonlinearity of the force-displacement relation for the hammer be recognized and included. Two models that accomplish this with numerical integration are described, and sample results are presented. The first model is valid for a perfectly flexible string, where nondispersive traveling waves can be conveniently followed with a digital delay line. The second model uses standing waves instead to describe the vibrations of a stiff string, with the stiffness itself justifying truncation of what would otherwise be a poorly converging normal-mode summation. Predictions with these models give significantly better agreement with data than did previous calculations with completely linear models.
Monostatic shadowing of homogeneous fractal profiles
Authors: Goff John A.
Published: October 2005

The effect of shadowing on the probability density of illuminated slopes is investigated for a class of homogeneous fractal profiles. Unlike smoother surfaces, the shadowing of slopes for a fractual surface will depend strongly on the horizontal scale over which slopes are determined. Under the approach taken, the analytic solution is difficult to solve, if not intractable. However, this approach gives rise to an approximate form to the solution that is dependent on a single parameter α. It is found that for a large range in surface morphology an α can always be found that yields a satisfactory fit to numerical solutions of the shadowing problem. An analytic form for α is proposed whose coefficients, dependent on morphological parameters and the grazing angle, are determined by an inversion of empirical fits to the numerical solution. This analytic form successfully predicts α to within 18% of its numerically determined value, which is likely accurate enough for most acoustic backscatter applications.
The effect of large-scale atmospheric inhomogeneities on acoustic propagation
Authors: Noble John M. , Bass Henry E. , Raspet Richard
Published: October 2005

A large-scale wind-driven turbulence model is put forth to account for long-term (1–5 min) phase variations observed in outdoor sound propagation experiments. The long-term variations experimentally observed cannot be explained by small-scale turbulence. Fourier analysis of phase variations show outer scales of 200 m and greater, which correspond to turbulence in the energy-containing subrange. This size suggests organized atmospheric structures that may be as large as the planetary boundary layer. These structures may be elongated longitudinal vortex pairs roughly aligned with the mean wind. Because the size of the vortex pair is large compared to the scale of the experiment, the effect of the vortex pair on the acoustic field can be modeled as a time-dependent sound-speed profile. The roll vortices provide results with the same trends and variations in phase observed experimentally, but other structures present in the atmosphere might yield similar agreement with data.
Leaky axisymmetric modes in infinite clad rods. II
Authors: Drescher-Krasicka Eva , Simmons John A.
Published: October 2005

When a guided ultrasonic interface wave travels along the interface between two materials, acoustic energy is radiated from each point on the interface, producing a displacement field at the outer surface of the material. We show how this unique feature of guided interface waves may be used for metal–metal and metal–ceramic interface studies. The propagation parameters of these waves were measured and several of these modes were used to obtain direct acoustic images of the interfaces between two solids.
Axisymmetric wave propagation in fluid-loaded cylindrical shells. I: Theory
Authors: Sinha Bikash K. , Plona Thomas J. , Kostek Sergio , Chang Shu-Kong
Published: October 2005

An analysis is carried out of axisymmetric waves propagating along fluid-loaded cylindrical shells within the framework of linear elasticity and classical perfect-slip boundary conditions at the solid–fluid interface. Numerical solutions are obtained for various axisymmetric eigenmodes for a cylindrical shell in vacuum; a cylindrical shell surrounded by a liquid of infinite radial extent; a hypothetical liquid column with both the stress-free and displacement-free boundary conditions; a cylindrical shell with a liquid core; and a cylindrical shell immersed in an infinite liquid. Numerical results are obtained for both the radiating (leaky) and nonradiating eigenmodes of the system by a careful search of the complex eigenfrequencies of the associated boundary value problem. In particular, attenuation of leaky modes due to radiation of energy into the surrounding medium is expressed in terms of the imaginary part of the eigenfrequency. Computational results are presented for the dispersion curves as well as the displacement and stress amplitude component distributions along the radial direction for various propagating modes of the system. Practical benefits from such analyses are discussed.
Axisymmetric wave propagation in fluid-loaded cylindrical shells. II: Theory versus experiment
Authors: Plona Thomas J. , Sinha Bikash K. , Kostek Sergio , Chang Shu-Kong
Published: October 2005

The axisymmetric wave propagation along fluid-loaded cylindrical shells (excluding torsional modes) has been investigated both theoretically and experimentally. For a steel cylindrical shell with a fixed ratio of inner to outer radius, four different fluid configurations are considered: water inside and outside the steel shell, air inside and outside; water inside and air outside; and air inside and water outside. Calculations of the transient pressure response for the case of an axisymmetric ring source and a point receiver are made as a function of source–receiver separation. Experimentally, a PZT ring source and ring receiver are placed around a steel cylindrical shell with an outer radius of 9.53 mm and an inner radius of 7.94 mm. Waveforms are recorded for multiple source–receiver hydrophone spacings in the frequency band 50–240 kHz. Using a Prony’s method, the complex wave number for each of the modes in the system are derived from both the theoretical and experimental waveforms. These axisymmetric modes are grouped into three categories: steel modes, noncutoff fluid modes, and cutoff fluid modes. Excellent agreement is obtained between theory and experiment.
Comments on ‘‘Single-phase drive of a circular ultrasonic motor’’ [J. Acoust. Soc. Am. 9
, 1723–1728 (1991)]
Authors: Ceperley Peter H.
Published: October 2005

Additional references are cited for single-phase, single-point excitation of rotating wave modes.
Reply to ‘‘Comments on ‘Single-phase drive of a circular ultrasonic motor’ ’’[J. Acoust. Soc. Am. 9
2, 1167 (1992)]
Authors: Kurosawa Minoru , Ueha Sadayuki
Published: October 2005

Supplemental background is referenced for single source excitation of mode rotation in an elastic vibrator and an electromagnetic antenna.
The measurement of ultrasonic shear wave properties in electrorheological fluids
Authors: Bellin Jack. L. , Holsinger Roy , Chow Andrea W.
Published: October 2005

Electrorheological (ER) fluid systems acquire reversible solid-like material properties upon the influence of a strong electric field. Prior efforts to study ER system properties acoustically have employed compressional waves. In this work, three ER systems have been studied by means of an ultrasonic shear wave reflectometry technique. In each case, a moderate to substantial increase in the shear wave velocity, storage modulus, and loss modulus was observed at the ER transition at 3 MHz. These results are interpreted in light of limited dynamic shear data at lower frequencies found in the literature, recent theoretical calculations, and direct observations using optical microscopy.
Investigation of the mechanisms of low-frequency wind noise generation outdoors
Authors: Morgan Scott , Raspet Richard
Published: October 2005

Simultaneous measurement of wind noise and the instantaneous wind speed were performed for bare and screened microphones outdoors. Analysis of these measurements demonstrates that the dominant source of pressure fluctuations at the microphone outdoors is the intrinsic turbulence in the flow. This is in contrast to the results of measurements performed in low-turbulence environments by Hosier and Donavan [Natl. Bur. Stand. Rpt. NBSIR79-1599 (Jan. 1979)] and by Strasberg [J. Acoust. Soc. Am. 83, 544–548 (1988)]. For low-turbulence conditions the fluctuating wake of the screen is the dominant noise source. This finding has important implications for windscreen design for outdoor measurements since the principles described by Hosier and Donavan apply only to low-turbulence conditions.
Acoustics of snare drums
Authors: Rossing Thomas D. , Bork Ingolf , Zhao Huan , Fystrom Dell O.
Published: October 2005

Modes of vibration, of a snare drum, as observed by holographic interferometry, impulsive modal analysis, and scanning with accelerometers, are related to vibrations of the drum heads, the shell, and the support stand. A simple two-mass model correctly describes the lowest modes of vibration, but at the higher frequencies the drum heads vibrate more or less independently. Each mode of vibration radiates sound in a characteristic pattern which may have dipole, quadrupole, and higher multipole components. The snares move in a complex way, being in contact with the snare head during part of its cycle but losing contact at a later time and returning to strike the head.
Excitation of thin beams using asymmetric piezoelectric actuators
Authors: Gibbs Gary P. , Fuller Chris R.
Published: October 2005

In this paper, an approximate analytical model is developed for the excitation of a thin beam by a single piezoelectric actuator bonded to the surface of the beam. The premise of this work is to investigate the excitation of beams by piezoelectric actuators on a more fundamental level than present work, and then use the asymmetric model to predict a wave response, rather than a modal response, on more complicated structure/actuator systems. It is determined that the single surface mounted piezoelectric actuator simultaneously excites both flexural and extensional motion in beams whose relative amplitudes are functions of beam/actuator geometry and properties. The model is then applied to the excitation of an infinite beam by two colocated arbitrarily driven actuators. It is shown that this configuration can produce any desired combination of flexural and extensional waves in beams by varying the degree of asymmetry between the actuators.
Deriving the equations of motion for porous isotropic media
Authors: Pride Steven R. , Gangi Anthony F. , Morgan F. Dale
Published: October 2005

The equations of motion and stress/strain relations for the linear dynamics of a two-phase, fluid/solid, isotropic, porous material have been derived by a direct volume averaging of the equations of motion and stress/strain relations known to apply in each phase. The equations thus obtained are shown to be consistent with Biot’s equations of motion and stress/strain relations; however, the effective fluid density in the equation of relative flow has an unambiguous definition in terms of the tractions acting on the pore walls. The stress/strain relations of the theory correspond to ‘‘quasistatic’’ stressing (i.e., inertial effects are ignored). It is demonstrated that using such quasistatic stress/strain relations in the equations of motion is justified whenever the wavelengths are greater than a length characteristic of the averaging volume size.
An exact solution for the one-dimensional elastic wave equation in layered media
Authors: Tenenbaum Roberto A. , Zindeluk Moysés
Published: October 2005

A new approach to the direct scattering problem in one-dimensional inhomogeneous bodies is presented. A general formulation considering density, wave speed, and cross section variation is introduced and a compact form for the wave equation in the characteristic plane, with a generalized acoustical impedance profile as a parameter, is established with the aid of a nonsingular variable transformation. The wave propagation pattern in layered (or discretized continuous) media is then examined and an exact algebraic solution for the reflected wave is obtained. The resulting formula is adequate to an arbitrary input pulse, furnishing a quick computation of all multiple reflection contributions to the final echo.
Anisotropy of ultrasonic velocity and elastic properties in normal human myocardium
Authors: Verdonk Edward D. , Wickline Samuel A. , Miller James G.
Published: October 2005

Measurements of ultrasonic quasilongitudinal velocity were made in the muscle fiber plane of excised human myocardium. Multiple adjacent planes across the left ventricular wall were interrogated to assess the transmural dependence of velocity. For each measurement plane, data were obtained in 2-deg increments through the full 360 deg relative to the myofibers. An approximate 1.3% magnitude of anisotropy was observed with maximum velocity along the muscle fibers and minimum velocity perpendicular to the muscle fibers. The known transmural shift in myofiber orientation was evidenced in the anisotropy of velocity as angular shifts between plots obtained from adjacent transmural planes within the same specimen. Measured values of velocity and density were used to estimate the effective C33 and C11 elastic constants of a thin layer of normal myocardium.
20-Hz pulses and other vocalizations of fin whales, B
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s, in the Gulf of California, Mexico
Authors: Thompson Paul O. , Findley Lloyd T. , Vidal Omar
Published: October 2005

Low-frequency vocalizations were recorded from fin whales, Balaenoptera physalus, in the Gulf of California, Mexico, during three cruises. In March 1985, recorded 20-Hz pulses were in sequences of regular 9-s interpulse intervals. In August 1987, nearly all were in sequences of doublets with alternating 5- and 18-s interpulse intervals. No 20-Hz pulse sequences of any kind were detected in February 1987. The typical pulse modulated from 42 to 20 Hz and its median duration was 0.7 s (1985 data). Most other fin whale sounds were also short tonal pulses averaging 82, 56, and 68 Hz, respectively, for the three cruises; 89% were modulated in frequency, mostly downward. Compared to Atlantic and Pacific Ocean regions, Gulf of California 20-Hz pulses were unique in terms of frequency modulation, interpulse sound levels, and temporal patterns. Fin whales in the Gulf may represent a regional stock revealed by their sound characteristics, a phenomenon previously shown for humpback whales, birds, and fish. Regional differences in fin whale sounds were found in comparisons of Atlantic and Pacific locations.
Structural design of hidden Markov model speech recognizer using multivalued phonetic features: Comparison with segmental speech units
Authors: Deng L. , Erler K.
Published: October 2005

A novel approach to speech recognition, on the basis of a multidimensional, multivalued phonetic-feature description of speech signals, is presented and evaluated. The hidden Markov model (HMM) framework is used to provide the recognition algorithm, which assumes that the underlying Markov chain tracks the temporal evolution of the features. It is shown that this approach can naturally accommodate such coarticulatory effects as feature spreading and formant transition in the functionality of the recognizer, and can provide a high degree of acoustic data sharing that makes effective use of training data. Use of phonetic features as the basic speech units creates a framework where the Markov model’s state topology in the recognizer can be designed with guidance of detailed speech knowledge. Details of such a design for a stop consonant–vowel vocabulary are described. Experimental results on the task of speaker-dependent stop consonant discrimination, evaluated from speech data from a total of ten male and five female speakers, demonstrate effectiveness of this feature-based recognizer. Over the 15 speakers, the error rates were shown to be reduced by 23%, 37%, 42%, and 38%, respectively, compared with the conventional HMM-based recognition methods using words, phonemes, allophones, and microsegments as the primary speech units.
Effect of multiple speechlike maskers on binaural speech recognition in normal and impaired hearing
Authors: Bronkhorst A. W. , Plomp R.
Published: October 2005

Speech-reception thresholds (SRT) were measured for 17 normal-hearing and 17 hearing-impaired listeners in conditions simulating free-field situations with between one and six interfering talkers. The stimuli, speech and noise with identical long-term average spectra, were recorded with a KEMAR manikin in an anechoic room and presented to the subjects through headphones. The noise was modulated using the envelope fluctuations of the speech. Several conditions were simulated with the speaker always in front of the listener and the maskers either also in front, or positioned in a symmetrical or asymmetrical configuration around the listener. Results show that the hearing impaired have significantly poorer performance than the normal hearing in all conditions. The mean SRT differences between the groups range from 4.2–10 dB. It appears that the modulations in the masker act as an important cue for the normal-hearing listeners, who experience up to 5-dB release from masking, while being hardly beneficial for the hearing impaired listeners. The gain occurring when maskers are moved from the frontal position to positions around the listener varies from 1.5 to 8 dB for the normal hearing, and from 1 to 6.5 dB for the hearing impaired. It depends strongly on the number of maskers and their positions, but less on hearing impairment. The difference between the SRTs for binaural and best-ear listening (the ‘‘cocktail party effect’’) is approximately 3 dB in all conditions for both the normal-hearing and the hearing-impaired listeners.
Neural network models of sound localization based on directional filtering by the pinna
Authors: Neti Chalapathy , Young Eric D. , Schneider Michael H.
Published: October 2005

Three-layer neural-network functions were developed to transform spectral representations of pinna-filtered stimuli at the input to a space-mapped representation of sound-source direction at the output. The inputs are modeled after transfer functions of the external ear of the cat; the output is modeled on the spatial sensitivity of superior colliculus neurons. Network solutions are obtained by backpropagation and by a method that enforces uniform task distribution in the hidden layer of the model. Solutions are characterized using bandlimited inputs to study the relative strength of potential sound localization cues in various frequency regions. This analysis suggests that the frequency region containing the first spectral notch (5–18 kHz) provides the best localization cues. Response properties of model neurons were studied using input patterns modeled after auditory nerve response profiles to pure tones at various frequencies and sound levels. The response properties of hidden layer model neurons resemble cochlear nucleus types III and IV and their composites. Neurons in both hidden and output layers show the properties of spectral notch detectors. Although neural networks have limitations as models of real neural systems, the results illustrate how they can provide insight into the computation of complex transformations in the nervous system.
Analysis of dynamic behavior of human middle ear using a finite-element method
Authors: Wada Hiroshi , Metoki Tetsuro , Kobayashi Toshimitsu
Published: October 2005

Applying the general-purpose finite-element package program (ISAP), a three-dimensional finite-element method (FEM) model of a human right middle ear, which included ossicles, was made and the mechanical properties and boundary conditions of the middle ear were determined by a comparison between the numerical results obtained from the FEM analysis and the measurement results of the fresh cadavers, normal subjects and patients, which were obtained by our developed sweep frequency middle ear analyzer (MEA). The ‘‘Elastic’’ boundary condition consisting of linear and torsional springs at the eardrum attachments to the annular ligament was more appropriate for the actual condition than ‘‘fully clamped’’ one. Rotational axis of the ossicular chain was assumed to be a fixed straight line from the anterior process of the malleus to the short process of the incus, and a load of the ossicular chain and cochlea was simplified to be expressed by the stiffness of the cochlea. Vibration patterns of the eardrum and ossicles at the first resonance frequency, obtained under these assumptions, were in agreement with the experimental results obtained by means of time-averaged holography and by using a video measuring system, except for the relatively large displacements at the tympanic ring.
Soviet aeroacoustics—A short review
Authors: Powell Alan
Published: October 2005

A short review of Soviet aeroacoustic literature is presented, covering moving sources and media, aerodynamically generated sound (including vortex acoustics, transition radiation and shock wave interaction), noise of turbulent jets, the screech of supersonic jets, flow resonance of impinging supersonic jets, boundary layer noise, and some aspects of turbomachinery noise. Not included are supersonic boom, physical resonators and flow excited cavities, cavitation, structural aeroacoustics other than for simple boundary layer walls, acoustically induced structural fatigue, and scattering (other than by vortices).
On the development and control of caustics in shear flows over elastic surfaces
Authors: Abrahams I. David , Kriegsmann Gregory A. , Reiss Edward L.
Published: October 2005

The propagation of acoustic waves from a high-frequency line source in a shear layer flowing over an infinite elastic plate is considered. The fluid is inviscid and compressible. The Lagrange–Kirchhoff linear plate theory, including structural damping, is used to describe the small amplitude motions of the plate. The resulting problem is solved approximately by first obtaining the integral representation of the solution using Fourier transforms, and then obtaining asymptotic expansions of this expression for high-frequency sources, as we did previously for the shear flow over a rigid wall. An infinite sequence of caustics (localized noisy regions) are created, downstream of the source and adjacent to the elastic surface, by the refraction of rays from the source and their subsequent reflections from the plate. The acoustic fields on and off the caustics, and in the near and the far field, are obtained from the asymptotic solution. Because of the structural damping, large attenuation of the caustic sound field is obtained for special values of the plate and fluid parameters.
Experimental analysis of the scattering from the edge of a plate insonified by an external source
Authors: de Billy M.
Published: October 2005

The end section of a brass plate submerged in water is perpendicularly insonified by an acoustic wave generated in the fluid. The variations of the scattered signal are recorded in a plane perpendicular to the end of the plate and plotted versus the scattering angle. The angular diagrams point out first the reemission of symmetric leaky guided waves at particular angles according to the dispersion curves of the plate. Also, maxima are observed whose angular positions agree with theoretical calculations based on the diffraction by a slit as in optics. The influence of the sharpness on the polar diagrams is also investigated.
Transmission coefficient measurement and improved sublayer material property determination for thick underwater acoustic panels: A generalization and improvement of the ONION method
Authors: Piquette Jean C.
Published: October 2005

Modifications of the ONION panel-measurement method [J. C. Piquette, J. Acoust. Soc. Am. 85, 1029–1040 (1989)] that allow for simultaneous analysis of transmitted- and reflected-wave data are described. The revised algorithm determines more reliable values for the sound speed and loss of the material of each panel sublayer than does the algorithm that is based exclusively upon analysis of the reflected wave. Included in the revised method is a Taylor series expansion of the sound-speed function of each layer about the steady-state driving angular frequency. This Taylor series is similar to that used for the loss function in the original ONION method, and is introduced here to more accurately accommodate the frequency variation of the phase speed than does the frequency-independent model used previously. Descriptions of successful applications of the revised ONION method to experimental data are provided. The version of the ONION method described in this report has recently been adopted as the standard panel measurement method at the Underwater Sound Reference Detachment of the Naval Research Laboratory (NRL-USRD) in Orlando, FL for tests conducted in the 1- to 20-kHz frequency interval.
Coupling of plate waves at joints
Authors: Lu I-Tai , Bertoni Henry L. , Chen Han-Yang
Published: October 2005

For flat plates with infinite lateral extent, fundamental plate waves propagate independently without coupling. However, at a joint of two or more plate elements, these waves can couple together, and a wave incident from one element will excite other waves propagating away from the junction in each element. The propagation direction for incidence oblique to the junction, and the magnitude of each wave can be determined by the following boundary conditions: continuity of displacement at the joint, continuity of rotation about the axis of the joint, and vanishing net force and torque on the joint. These boundary conditions are derived from the approximation that the joint is massless, has rigid cross section, but offers no resistance to extension along or twisting about the axis of the joint, or to bending transverse to the axis. To satisfy the boundary conditions, it is necessary to account for the first cutoff flexural wave in addition to the three propagating waves in each plate. Numerical examples for various joints of one, two, and three plate segments are discussed. Coupling at a rib stiffened plate is also computed by treating the rib as a plate segment and accounting for the coupling between two neighboring joints. The wave coupling phenomena, distribution of power among the plate segments, and the power conservation property are examined in detail for large ranges of frequency and of the wave number along the joint, which is determined by the angle of incidence. Both propagating and evanescent waves in the direction transverse to the joint are considered. The power conservation error are examined and quantified to establish the range of validity of this approach.
Application of BEM (boundary element method)-based acoustic holography to radiation analysis of sound sources with arbitrarily shaped geometries
Authors: Bai Mingsian R.
Published: October 2005

A method employing holograms that conform with arbitrarily shaped sources has been developed for enhancing conventional near-field acoustic holography, which has been limited to sources with simple geometries, e.g., planar or cylindrical surfaces. Four holography transformation algorithms have been developed, based on acoustic holography theory and the boundary element method (BEM). Singular value decomposition (SVD) has been incorporated into the algorithms in order to alleviate the ill-posed nature frequently encountered in backward reconstruction of a field. A pulsating sphere, a cylinder with spherical endcaps, and a vibrating piston set in a rigid sphere have been adopted in a numerical simulation for verifying the algorithms. Satisfactory agreement has been achieved between the holographically transformed results and the analytical solutions.
Comments on ‘‘Unidirectional, second-order gradient microphone’’ [J. Acoust. Soc. Am. 8
6, 2063–2066 (1989)]
Authors: Korenbaum Vladimir I.
Published: October 2005

The possibility of considerable improvement of a second-order gradient microphone by means of minimizing sidelobes level is described. All results are generalized for orders higher than second order.
Discussion of transmitting directivity index for volumetric arrays
Authors: Bick E. Theodore
Published: October 2005

A new method for the direct calculation of the transmitting directivity index for volumetric arrays is derived. The calculation is based on the solution of the linear algebraic formulation using Pritchard’s approximation of the mutual acoustic impedance between radiators in an array [J. Acoust. Soc. Am. 32, 730 (1960)], and the assumptions of negligible scattering and simple sources. Comparison with the receiving array directivity index is discussed, and is shown to be consistent with the array reciprocity principle.
Vowel duration in Afrikaans: The influence of postvocalic consonant voicing and syllable structure
Authors: Wissing Daan
Published: October 2005

A production study was conducted to investigate the effect of vowel lengthening before voiced obstruents, and the possible influence that the openness versus closedness of syllables have on the temporal structure of vowels in some languages. The results revealed that vowels were significantly longer when followed by voiced consonants than voiceless consonants. Vowel duration did not, however, vary with syllable structure. However, vowels in open syllables followed by [+ voiced] consonants tended to be longer than when the following consonants were [− voiced]. These results are discussed in the context of current knowledge of other languages.
The sound distribution in a rectangular reverberation chamber
Authors: Zeng Li Jun
Published: October 2005

The spatial distribution of the sound intensity and the sound pressure in a rectangular chamber can be calculated by the geometrical ray acoustics method. The calculated results for a random point monopole sound source show that the spatial distribution of the sound intensity in a rectangular room roughly obeys the inverse-square law, and that the sound pressure contains an apparent reverberant part. These results are in very good agreement with experimental measurements. The reverberant part of the sound intensity is found to be nonzero, and the reverberant part of the sound pressure is not distributed evenly throughout the room. The fluctuation of the reverberant part of the sound field depends on factors such as the sound absorption of the room, the location of the measurement point, and the location of the sound source.
Diffraction of elastic P waves by four equal coaxial circular rigid strips
Authors: Sharma K. A. , Jain D. L.
Published: October 2005

The two-dimensional boundary value problem of diffraction of obliquely incident low-frequency elastic P waves by four equal coaxial circular rigid strips embedded in an infinite isotropic and homogeneous elastic medium is solved. Approximate expressions are derived for the far-field amplitudes and scattering cross section when the wavelengths are large compared to the radius of the circular strips.
An objective quality assessment method for bit-reduction coding of wideband speech
Authors: Hayashi Shinji , Kitawaki Nobuhiko
Published: October 2005

This paper proposes a new objective quality assessment method for bit-reduction coding of wideband speech taking into account the masking effect of quantizing noise. First, this paper analyzes the reliability and sensitivity of the speech quality assessment method, based on a paired-comparison test with a modulated noise reference signal, for the bit-reduction coding of high-quality wideband speech. Then, the perception of quantizing noise is studied using speech with noise synthesized similar to the quantizing noise. The detection of quantizing noise is found to be influenced by masking by the source signal. This leads to a new method of objectively estimating the quality of coding speech by multiple regression analysis. The factors for the estimation are segmental signal-to-noise ratio, spectrum envelope distance between source signal and quantizing noise, and the similarity of the noise power envelope to the source signal in the time domain. This estimation method is applied to the parameter optimization of wideband coding systems.
Sound-power collection by the auditory periphery of the Mongolian gerbil M
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s. I: Middle-ear input impedance
Authors: Ravicz Michael E. , Rosowski John J. , Voigt Herbert F.
Published: October 2005

This is the first paper of a series dealing with sound-power collection by the auditory periphery of the gerbil. The purpose of the series is to quantify the physiological action of the gerbil’s relatively large tympanic membrane and middle-ear air cavities. To this end the middle-ear input impedance ZT was measured at frequencies between 10 Hz and 18 kHz before and after manipulations of the middle-ear cavity. The frequency dependence of ZT is consistent with that of the middle-ear transfer function computed from extant data. Comparison of the impedance and transfer function suggests a middle-ear transformer ratio of 50 at frequencies below 1 kHz, substantially smaller than the anatomical value of 90 [Lay, J. Morph. 138, 41–120 (1972)]. Below 1 kHz the data suggest a low-frequency acoustic stiffness KT for the middle ear of 970 Pa/mm3 and a stiffness of the middle-ear cavity of 720 Pa/mm3 (middle-ear volume VMEC of 195 mm3); thus the middle-ear air spaces contribute about 70% of the acoustic stiffness of the auditory periphery. Manipulations of a middle-ear model suggest that decreases in VMEC lead to proportionate increases in KT but that further increases in middle-ear cavity volume produce only limited decreases in middle-ear stiffness. The data and the model point out that the real part of the middle-ear impedance at frequencies below 100 Hz is determined primarily by losses within the middle-ear cavity. The measured impedance is comparable in magnitude and frequency dependence to the impedance in several larger mammalian species commonly used in auditory research. A comparison of low-frequency stiffness and anatomical dimensions among several species suggests that the large middle-ear cavities in gerbil act to reduce the middle-ear stiffness at low frequencies. A description of sound-power collection by the gerbil ear requires a description of the function of the external ear.
Using acoustic distortion products to measure the cochlear amplifier gain on the basilar membrane
Authors: Allen J. B. , Fahey P. F.
Published: October 2005

Most models of the cochlea developed during the last decade have explained frequency selectivity and sensitivity of the cochlea at threshold by the use of power amplification of the acoustic wave on the basilar membrane. This power amplification has been referred to as the cochlear amplifier (CA). In this paper, a method to measure the cochlear amplifier gain as a function of position along the basilar membrane is derived from a simple model. Next, experimental evidence is presented that strongly restricts the properties of these proposed cochlear amplifier models. Specifically, it is shown that small signals generated by mechanical nonlinearities in the basilar membrane motion are not amplified during basilar membrane propagation, contrary to what would be expected from the cochlear amplifier hypotheses. This paper describes a method of measuring the cochlear power gain as a function of frequency and position, from the stapes to within 2 mm of the place corresponding to the frequency being measured. Experimental results in the cat indicate that the total gain of the cochlear amplifier, over the range of positions measured, must be less than 10 dB. The simplest interpretation of the experimental results is that there is no cochlear amplifier. The results suggest that the cochlea must achieve its frequency selectivity by some other means.
Least-squares time-delay estimation for transient signals in a multipath environment
Authors: Vaccaro R. J. , Ramalingam C. S. , Tufts D. W. , Field R. L.
Published: October 2005

The problem of estimating the arrival times of overlapping ocean-acoustic signals from a noisy received waveform that consists of scaled and delayed replicas of a deterministic transient signal is considered. It is assumed that the transmitted signal and the number of paths in the multipath environment are known, and an algorithm is developed that gives least-squares estimates of the amplitude and time delay of each path. A method is given to ensure that the global minimum of the error surface is found in spite of the existence of numerous local minima. The algorithm is then extended to the case in which the transmitted signal is not known precisely, but is assumed to belong to a parametric class of signals. The extended algorithm additionally obtains the parameters that characterize the transmitted signal. The algorithm is demonstrated on the class of signals consisting of gated sinusoids, using both simulated and experimental data.
Nonlinear analysis of cyclically correlated spectral spreading in modulated signals
Authors: Wilbur Jo Ellen , McDonald Robert J.
Published: October 2005

This paper examines the mapping from the Cohen class of bilinear time-evolutionary spectral estimators (TES) to a conjoint frequency-cycle frequency signal description for modulated acoustic signals. The transform mapping provides a cycle spectrum estimation that is used to identify cyclostationarity in modulated acoustic signals that often remains undetected in the one-dimensional time history and power spectral density (PSD). The Wigner distribution (WD) TES is derived as the case for which the PSD used in stationary analysis of acoustic signals is preserved in the Fourier transform mapping to a conjoint frequency–frequency correlation signal representation for modulated signals. Fourier transformation over temporal window centers of a pseudo-WD TES of modulated acoustic signals is shown to equate to the time-variant cyclic spectrum, defined for cyclostationary signals, evaluated along the center of a moving average estimate. A pseudo-WD TES based function mapping procedure for cycle frequency estimation of modulated acoustic signals is presented and applied to several modulated signal examples. These include the acoustic reflection from a periodically vibrating object, frequency hopped pulse trains, and bi-phase modulated continuous wave sonar signals. The function solution is shown to achieve cycle frequency estimation in −3-dB signal-to-noise.