bluuebunny/crossref_metadata_2025 huggingface dataset:
Articulatory activity and aerodynamic variation during voiceless consonant production
Authors: Koenig Laura L. , Löfqvist Anders , Gracco Vincent L. , McGowan Richard S.
Published: October 2005

The production of voiceless consonants is associated with changes in oral air pressure which reflect the time course and coordination of the requisite laryngeal and supralaryngeal articulations. The present experiments were conducted in order to characterize more precisely the relationships among glottal and supraglottal activities and the resulting aerodynamic changes in the vocal tract. In the first experiment, simultaneous recordings were made of glottal articulation (obtained via transillumination), two-dimensional lip and jaw movements, and air pressure variation during the production of voiceless labial consonants. In the second experiment, two-dimensional motion of the jaw and multiple points on the tongue were obtained along with air pressure during the production of voiceless lingual consonants. Analysis focused on the time-varying changes in the pressure waveform and the accompanying articulatory motion. The data suggest that the overall time course of pressure variation depends largely on the timing of the laryngeal devoicing gesture. However, details in the pressure waveforms showed a close correspondence to the time course of supraglottal articulations. Taken together, results suggest that laryngeal and supralaryngeal timing is highly constrained, and that different articulators contribute uniquely to producing pressure variations within the vocal tract. [Work supported by NIH.]
Three acoustically predictable factors underlying vowel tongue shapes
Authors: Nix David A. , Papcun George J.
Published: October 2005

To obtain a low-dimensional, speaker-independent parameterization of vowel tongue shapes, the three-mode factor analysis procedure PARAFAC [Harshman etal., 693–707 (1977)] was applied to x-ray microbeam tongue measurements of ten English vowels spoken by two male and two female subjects in seven different /CVC/ contexts. PARAFAC reliably extracts three speaker-independent, nonorthogonal factors. The resulting speaker-independent factor coefficients cluster by vowel in three-dimensional articulatory space. In two-dimensional projections, they qualitatively reflect the traditional vowel quality chart. A multi-layer perception (neural network) independently corroborates this solution: these tongue shape coefficients are significantly more predictable from the corresponding acoustics than coefficients from either the nonorthogonal two-factor solution or the orthogonally constrained three-factor solution. These three factors also correspond qualitatively to the three nonorthogonal factors extracted from Icelandic x-ray film vowel data [Jackson, 124–143 (1988)]. Thus the current English solution contradicts Jackson’s distinction (based on Harshman etal.’s two-factor English vowel solution) between language-independent and language-specific vowel articulation primes. This low-dimensional, potentially cross-linguistic representation could benefit speech recognition, coding, or synthesis applications in which an acoustically correlated vowel tongue shape parameterization is required.
Texas highway noise barriers—The good, the bad, and the ugly
Authors: Busch-Vishniac Ilene , Ho Steve , Peron Ron , McNerney Michael
Published: October 2005

Until recently, Texas has managed to avoid extensive use of highway noise barriers for roadway noise mitigation in residential areas. In recognition of the growing noise problem, particularly in the urban areas of Texas, the Texas Department of Transportation (TxDOT) is supporting a 3-year project aimed at producing a highway barrier design guide. In addition to acoustical performance, the design guide will consider issues such as barrier support and aesthetics. This talk will review the barrier project, concentrating on the first phase of the work which has been to document and evaluate the existing barriers in Texas. [Work supported by TxDOT.]
Sonic boom as possible mechanism of the low-frequency hum
Authors: Krylov Victor V.
Published: October 2005

The problem of disturbing low-frequency noise, also called low-frequency hum, has been known for at least two decades. However, in many aspects the nature of low-frequency hum still remains a mystery (see, e.g., ‘‘The Independent’’ of 22 June 1994). It may be possible that in some cases the sources of this hum are underground gas or petrol pipes where turbulent flows of gas or liquid generate sound waves of high amplitude propagating in a pipeline as in a waveguide. The velocities of sound C0 inside the pipes (450 m/s for methane) sometimes may be higher than the velocities of Rayleigh surface waves CR in the ground at the frequencies of interest (5–50 Hz). Typical values of CR are 300–600 m/s. If so, i.e., if C0≳CR, then ground Rayleigh waves might be effectively generated by sound wave propagating inside the pipes, the mechanism of generation being similar to that of a sonic boom from supersonic jets. Preliminary calculations show that central frequencies of generated Rayleigh wave ground vibration spectra depend on depth of the pipe and are in the low-frequency range. The amplitudes of generated ground vibration velocity due to sound waves propagating in gas pipes buried at a depth of 2 m can be around 70 dB (relative to 10−9 m/s). This may be enough to annoy some people both because of direct impact of vibrations and due to generated structure-borne noise.
Application of computational fluid dynamics (CFD) to automobile wind noise source minimization
Authors: Hseuh Keng D. , Abhyankar Sanjay , Addala Sanjeeva , Kamat Anant , Wu Chun , Haffey Mike P.
Published: October 2005

Wind noise is becoming a critical comfort requirement to customers due to greatly reduced powertrain and road noise, particularly at high-speed driving conditions. The physical phenomenon generally can be categorized into: sources (A-pillar vortex and mirror wake) and path (door/window weatherstrip leakage). Two different vehicle greenhouse geometries that produce attached- and vortex-flow, respectively, were used in this A-pillar vortex minimization case study to correlate the CFD predicted A-pillar vortex size and sideglass pressure distribution (Cp) with measurements from wind tunnel testing. A-pillar vortex and pressure distribution have been shown to be key factors affecting wind noise excitation on sideglass and shape-induced aerodynamic suction force on door/window (which is required in designing door/weatherstrip to prevent aspiration leaks through weatherstrip under high-speed condition), respectively. Results demonstrate that the CFD can successfully predict the effects of geometry changes on A-pillar vortex size and Cp within ≳80% accuracy under various speeds/yaw angles. This study confirms that CFD can be applied with confidence as an upfront engineering tool to optimize vehicle greenhouse geometry for minimum wind noise excitation in a cost and time effective manner.
Numerical and analytical investigation of unsteady lift and sound due to airfoil-wake interaction
Authors: Moran Paul R. , Thompson Donald E. , Swanson David
Published: October 2005

The passage of an airfoil through a wake is a dominant source of noise in low Mach number flows. In order to examine this phenomenon, two prediction schemes were used. The first was a thin airfoil analysis used to predict the unsteady lift response to sinusoidal transverse and longitudinal gusts [H. Naumann and H. Yeh, ASME J. Eng. Power 12, 1–10]. The strengths of these gusts are determined from the Fourier coefficients of the wake profiles. The sound was then determined from the unsteady force using a concentrated force radiation mechanism [N. Curle, Proc. R. Soc. London Ser. A 231, 451–460 (1955)]. The second method used an incompressible Navier–Stokes equation to predict the mean flow and unsteady pressure due to the passage of the wake past an airfoil. The resulting sound was then determined with a Kirchhoff solver. The pressure and sound results from both of these methods were compared with experimental data. [H. Fujita and L. S. G. Kovásznay, AIAA J. 12, 1216–1221 (1974).]
Sound due to flow through a nozzle with time-dependent throat area
Authors: Moran Paul R. , Swanson David
Published: October 2005

An unsteady compressible Euler code was developed for flow through a nozzle. Method of characteristic boundary conditions were used to permit the unsteady pressure to be nonzero downstream of the exit boundary. The flow is perturbed by modulating the cross-sectional area in the midsection of the nozzle. The far-field unsteady pressure was determined for both steady and unsteady inlet velocities and compared to experimental results.
An experimental and computational study of fundamental reactive silencers in the induction system of firing spark-ignition engines
Authors: Selamet A. , Novak J. M.
Published: October 2005

The present study investigates the performance of fundamental reactive silencers such as expansion chambers and Helmholtz resonators in the presence of both high-amplitude pressure waves and oscillating fluid flow. The silencers are installed in the induction system of a Ford 3.0-Liter V6 Vulcan engine in a dynamometer test facility. The experiments with the firing engine have been conducted with speeds ranging from 1000 to 5500 rpm. Measurements including the mean flow rate, the temperatures, and the absolute dynamic pressures of the induction air before and after the silencer with fast-response, piezoresistive transducers facilitate the calculation of acoustic and flow performance of these elements. A nonlinear computational fluid dynamics method is then employed in the time domain for the prediction of noise reduction and insertion loss characteristics of these silencers. The study is concluded with comparisons of these predictions to the experimental results from the engine dynamometer facility.
Surface acoustic wave investigation of phase transitions in YBa2Cu3O7−δ films
Authors: Feller J. , Hucho C. , Gaffney R. , McKenna M. J. , Sarma B. K. , Levy M.
Published: October 2005

Pulsed surface acoustic waves (SAW’s) at 165 MHz are used to study the superconducting transition and an apparent structural phase transition in films of YBa2Cu3O7−δ (YBCO). The structural phase transition occurs in the temperature range 200–230 K and is evidenced by large changes in SAW attenuation and velocity. Small changes are also seen at the superconducting transition temperature. These changes are markedly different when a conventional conductor (e.g., copper) is brought into close proximity to the YBCO film. The results of this investigation are in agreement with the hypothesis that YBCO is piezoelectric below the 200 K transition. [This work was supported by the Office of Naval Research, with C. Hucho supported by Deutsche Forschungsgemeinschaft.]
Acoustic microscopy and dispersion of leaky Rayleigh waves on randomly rough surfaces: A theoretical study
Authors: Pecorari Claudio , Briggs G. A. D.
Published: October 2005

A theoretical investigation of the dispersion of leaky Rayleigh waves propagating along one-dimensional, rough, fluid–solid interfaces was carried out by simulating the measurement process of a line-focus acoustic microscope. The interface profiles were described in terms of their rms, also known as the roughness of the profile, autocorrelation length, and autocorrelation function. Theoretical V(z) curves were obtained and analyzed to yield values of the phase velocity of the Rayleigh waves. The reflectivity of the interfaces was calculated by using a second-order perturbation approach in the profile roughness. The dependence of the Rayleigh wave velocity on the profile and material parameters was examined. Significant variations of the phase velocity were found for values of the roughness which are small compared to the shortest of the wavelengths involved in the scattering. Similarly, the dispersion relations showed considerable sensitivity to changes in mechanical properties typical of materials of engineering interest. In the low-frequency range, on the other hand, simulations illustrated the dispersion of Rayleigh waves to be rather insensitive to the spectral content of the profile. [Work performed within the LINK Project on Characterization of Surface and Sub-Surface Damage.]
Acoustic scattering from finite length cylinder bounded by two spherical endcaps
Authors: Carnet J. , Dujardin J. , Décultot D. , Maze G.
Published: October 2005

The acoustic scattering from finite cylindrical objects endcapped by two hemispheres is studied. To explain the experimental resonance spectra when the object is parallelly insonified to the axis, a condition of phase matching is written on the meridian circumference. To apply this condition, it is necessary to know the phase velocity of surface waves along the different parts of the object. To verify this hypothesis, resonance identifications are realized. The identification diagrams are not easy to interpret. The lobe number is not equal to the antinode number, and these lobes do not have the same amplitude. An integral method will permit the knowledge of the acoustic pressure in the far field if the profile of the vibration state along the meridian line is sinusoidal. A good agreement is obtained between the theoretical and experimental studies. To confirm this hypothesis, a finite element method is developed. A 2-D problem is considered. A meridian plane and the water around the object is meshed. A sinusoid burst with several periods insonifies the object. The vibration amplitude of the surface of the object is determined in every way. The results confirm the hypothesis used in the integral method and allows the validation of the phase-matching condition. a)In memory to J. Carnet deceased in June 1994.
Acoustic scattering from a circular cylindrical shell excited by a short pulse in oblique incidence: Helical waves
Authors: Maze G. , Conoir J. M. , Léon F. , Décultot D.
Published: October 2005

The theoretical and experimental spectra, obtained from an infinite pipe insonified with a plane wave in oblique incidence, show resonances which are related to three types of helical waves: the circumferential waves (Ai or Si waves), the transversal guided waves (Ti waves), and the Scholte wave (A wave). The resonances of the Scholte wave are detected in a frequency window and their frequency slowly increases when the incidence angle increases, whereas the ones of the other waves increase towards infinity when the incidence angle tends towards the transversal critical angle. At oblique incidence, the experimental results obtained with the MIIR show resonances which are related to the helical waves S0, T0, T1, and A. This method uses a long pulse with many sinusoid periods, a steady state takes place in a part of the infinite shell. In this presentation, the excitation is a short pulse and the scattered echoes are detected when the helical wave emission is in front of the receiver. Between each echo, the helical wave has covered one step of the helix (L=2πa/cos γ, a is the outer radius of cylinder, γ is the angle of the helix). This method allows us to calculate the group velocity of the helical waves.
Observation of seismic wave propagation in particulate composite material with various inclusion sizes and concentrations
Authors: Nakagawa Seiji , Cook Neville G. W. , Nihei K. T. , Myer L. R.
Published: October 2005

Two-phase particulate composite samples with inclusions of varying size and concentration were made with cement and sand or pebbles. The velocities of P-wave (60-kHz) and S-wave (150-kHz) pulses and the attenuation of S-wave pulses were examined. The results of the tests suggested that the velocities were consistent with the results of effective media models which were inclusion size independent. However, the frequency-dependent attenuation of the S wave was strongly affected by the size of the inclusions. For inclusions sized on the order of 1/10 of the wavelength, the waves showed decreasing attenuation with increasing concentration, while for the sizes of about 1/4 and 1/1 of the wavelength, the waves showed maximum attenuation at volumetric concentrations of about 30% and 70%, respectively. Many aspects of the observed wave behavior for moderate concentrations were similar to numerical simulations of 1-D wave propagation in a layered media, where the matrix and inclusions were represented by alternating layers with different seismic properties and stochastically varied thicknesses. [Work supported by NSF.]
Reciprocity-type relations for waves in a moving inhomogeneous fluid
Authors: Godin Oleg A.
Published: October 2005

The reciprocity principle is known to be invalid for acoustic waves in a moving fluid due to differences in up- and down-flow wave propagation velocities. A variation of the reciprocity principle, a flow reversal theorem (FRT), which states symmetry of some field quantity with respect to interchange of the source and receiver positions and the simultaneous reversal of flow, was considered by many authors during the last four decades. It was proven under that or other specific assumptions about fluid parameters and/or flow velocity space dependence or in a framework of some asymptotic representations of the acoustic field. A simple but rather general proof of the FRT will be presented which is valid for sound as well as acoustic-gravity waves in an arbitrary three-dimensional inhomogeneous moving fluid with time-independent parameters provided divergence of the flow velocity is zero. The fluid may be unbounded or have pressure-release, rigid, or impedance boundaries. The key point in the approach is the choice of a set of dependent variables in hydrodynamic equations for describing the wave field. An implication of the FRT on wave action conservation for cw sound in moving fluid is considered. Some possible FRT applications are indicated. [Work supported by NRC.]
Measurements of Biot type I and type II waves in an air-filled packing of sand
Authors: Hickey Craig J. , Sabatier James M.
Published: October 2005

The interpretation of acoustic and seismic measurements in porous materials are usually carried out using the Biot theory. This theory predicts the existence of two P waves (referred to here as type I and type II) and one S wave. The type I P wave is predicted to have small dispersion and attenuation. The type II P wave is predicted to be dispersive and highly attenuating. An experiment is carried out whereby air borne sound is incident upon an air-filled packing of sand. For such a configuration, a large proportion of the transmitted energy is partitioned to the type II P wave. However, due to the high attenuation of the type II P wave this energy should decay rapidly near the surface. Measurements using a probe microphone apparatus, in-situ microphones, and in-situ geophones are obtained in the frequency range of 500–3000 Hz. The in-situ microphones and geophones extend to a depth of 40 cm below the surface in an attempt to detect the Type I P wave. Attenuation and phase velocity of the air-filled packing of sand is determined as a function of depth from these measurements. [Work supported by USDA.]
Simulation of wave propagation through an inhomogeneous turbulent medium with the aid of an integral formulation
Authors: Kaneko Hirobumi
Published: October 2005

A propagation simulation algorithm is described whereby, at the beginning of step n, the pressure associated with a progressive wave is specified as a function of time and lateral position along a planar surface, x=xn. The algorithm for step n yields the pressure as a function of time and lateral position at x=xn+1. The basic mathematical formulation employs an integral equation that predicts the waveforms at arbitrary positions to the right of the first surface. The medium between the point and the surface, x=xn, is turbulent. The integral over the surface involves the Green’s function for a point source in the actual medium. Although the exact Green’s function is extremely difficult to compute, it is argued that a good approximation for moderate step sizes, ‖xn−1−xn‖, results if the Green’s function is taken to be that which results from a ray-acoustics approximation. Moreover, because the first caustic for a point source Green’s function is not encountered for a distance considerably longer than the distance between successive caustics for a nominally parallel group of rays within a ray tube, the difficulties of explicitly taking caustics into account is circumvented with this algorithm.
Functional organization and reorganization of primary auditory cortex
Authors: Schreiner Christoph E.
Published: October 2005

Neurons in primary auditory cortex (AI) of cats and monkeys have a wide range of functional properties that are related to the coding of basic attributes of simple and complex signals. In particular, cortical neurons have been found to be sensitive to the bandwidth of the signal, the spectral energy distribution of broadband stimuli, the overall intensity of the signal, and the temporal sequence of signal elements, in addition to their frequency selectivity and sound localization sensitivity. These response properties appear to be nonuniformly distributed across AI and, thus, create spatially and functionally distinct subregions that may constitute parallel auditory processing streams. Studies with behaviorally trained animals suggest that these functional cortical organizations are not fixed but can undergo changes. This representational plasticity results in more detailed representations of portions of the animal’s acoustic environment that have high behavioral relevance. An understanding of the creation, relationships, and interconnections of these different coding properties is essential for the comprehension of the neural code of communication sounds such as speech. [Work supported by the Office of Naval Research, the Human Frontier Science Project, and the Coleman Fund.]
Representation of the acoustic spectrum in the primary auditory cortex
Authors: Shamma Shihab A.
Published: October 2005

A fundamental goal in auditory cortical physiology has been to understand how the spectral profile is represented in the firing rate of cortical cells. Recent experimental findings shed light on two basic properties of this representation in AI: (1) Responses to sounds with broadband spectra (such as speech and most environmental sounds) superimpose linearly. Thus if a complex arbitrary spectral profile is viewed as composed of elementary spectral profiles, then AI responses to such a profile can be reconstructed from the sum of the responses to these simpler elementary profiles. This seems to be true both for stationary and dynamic spectra. (2) AI units are rather selective to the spectral and temporal parameters of the acoustic profile. Specifically, when tested with elementary spectral profiles that are sinusoidally shaped against the logarithmic frequency axis (or so called rippled spectra), and that slide against this axis at various velocities, AI units are found to be tuned around different ripple densities, ripple phases, and ripple velocities. The above two findings suggest that AI performs a Fourier-like analysis of the spectral profile into a composite of weighted sinusoidally shaped spectra (ripples). Such an analysis is analogous to that of visual scenes found in the primary visual cortex (VI).
Processing of complex sounds in rhesus monkey auditory cortex
Authors: Rauschecker Josef P.
Published: October 2005

Several auditory fields surrounding primary auditory cortex (AI) have been described in the rhesus monkey. Most recently, three areas have been identified in the so-called auditory belt region on the lateral surface of the superior temporal gyrus [Rauschecker etal., Science (1995) (in press)]. Functional identification of these lateral areas (AL, ML, and CL) was based on single unit responses to bandpassed noise (BPN) bursts, which constitute a class of superior stimuli for neurons in this region. Best center frequency (BFc) of the BPN bursts varies systematically along a rostro-caudal axis, revealing three cochleotopic maps. Neurons in the lateral areas also display tuning to a ‘‘best bandwidth’’ of the noise bursts, which varies along a medio-lateral axis, orthogonal to the BFc axis. Digitized vocalizations from the rhesus monkeys’ own repertoire were finally used for presentation during single-unit recording. In many instances, neurons responded even better to the monkey calls than to noise bursts or other synthetic stimuli. It appears that the lateral belt areas of macaque auditory cortex could form an important step in the preprocessing of species-specific communication sounds, somewhat equivalent to superior temporal areas in humans that have been implicated in phonological processing.
Elevation sensitivity in the cat’s thalamo-cortical auditory system: Role of monaural spectral and binaural disparity cues
Authors: Imig Thomas J. , Poirier Pierre , Samson Frank K.
Published: October 2005

High-frequency neurons in auditory cortex (AI) and medial geniculate (MGB) of anesthetized cats are differentially sensitive to monaural and binaural directional cues present in broad-band noise. Binaural directional (BD) cells depend upon binaural stimuli for azimuth sensitivity, whereas monoaural directional (MD) cells are sensitive to the direction of monaural stimuli. In the MGB, neurons’ spatial receptive fields (SRFs) were obtained using noise bursts presented throughout the frontal hemifield and sound pressure levels that varied over an 80-dB range. BD cells were broadly tuned to elevation. Those that received excitatory input from one ear and exhibited binaural inhibition or mixed interactions had SRFs that extended throughout one lateral hemifield. Predominantly binaural cells exhibited strong binaural facilitation and had SRFs that formed a vertical band in front of the head. MD cells’ SRFs varied considerably, some were focal areas restricted in azimuth and elevation. Others consisted of multiple areas that in some cases showed level-dependent changes in location. The elevation sensitivity of MD cells was nearly identical under monaural and binaural conditions showing that it derived from monaural spectral cues. AI units showed similar response properties. [Work supported by NIDCD.]
Transmission of turbulent boundary layer pressures through thin and thick shells
Authors: Cole Jack
Published: October 2005

Turbulent flow along a structural boundary acts as a source of noise to the interior space. Characteristics of the transmitted noise are determined not only by the turbulent flow field but also by the transmission characteristics of the bounding structure. In low-speed flow applications, the spatial scale of the turbulence can be smaller than the structural wall thickness. Under this circumstance, thickness effects are important in modeling the wall transmissibility. These effects are examined using the elasticity solution for the axisymmetric response of cylindrical shells. Results are presented for steel-like and rubber-like wall materials and compared with results from thin shell theory.
Frequency domain assessment of the doubly asymptotic approximation
Authors: Ginsberg Jerry H.
Published: October 2005

The most widely implemented technique for modeling fluid–structure interaction effects associated with shock response is the doubly asymptotic approximation (DAA), which has been developed in a variety of versions. Analytical validations of this method have thus far only been performed for spherical and infinitely long cylindrical shells. The present work uses Nicholas-Vuillierme’s derivation [NumericalTechniquesinAcousticRadiation, edited by R. J. Bernhard and R. F. Keltie (ASME-NCA, Vol. 6, 7–13 1989)] of the frequency-domain version of DAA as the basis for examining the accuracy and limitations of DAA for a slender hemi-capped cylindrical shell. The basic concept is to use DAA to determine the wet surface impedance matrix relating surface pressure and velocity variables, whose values are compared to those obtained from the surface variational principle (SVP) using the same set of basis functions. After such comparison is made, the alternative wet surface impedances are used to predict the structural response of the hemi-capped cylindrical shell to a ring force. Assessments for frequencies in the range ka<10 for a shell whose length to diameter ratio is L/2a=6 indicate that DAA fails to recognize effects associated with transition from supersonic to subsonic structural waves. The implications of this shortcoming for structural response are discussed. [Work supported by the Office of Naval Research, Code 1222.]
An approximation to the local acoustic impedance of a cylindrical shell with hemispherical endcaps
Authors: Utschig Michael J. , Achenbach Jan D. , Igusa Takeru
Published: October 2005

A method has been developed to approximate the local radiation impedance of a cylindrical shell with hemispherical endcaps. This approximation greatly reduces the effort required to calculate the acoustic impedance as compared to an approach using a variational method. The approximate method uses the exact acoustic impedances of several separable geometric shapes to approximate the acoustic impedance of a complex structure that is a composite of those shapes. The shell is broken into three components: two hemispheres and a finite cylinder. These components are parts of regions that are separable in an orthogonal coordinate system. It is assumed that the acoustic impedance of the components is the same as the acoustic impedance calculated exactly for the separable shapes. Furthermore, it is assumed that the local acoustic impedance of the original complex shape is the same as that of corresponding points on the simple components. The accuracy is improved when the interaction between neighboring components is considered. The acoustic impedance and surface pressure generated by a load applied in the center of the complex shape is compared with that calculated using a variational formulation.
The acoustical background for elastic shells of nonspherical objects
Authors: Werby M. F. , Sidorovskaia N. A.
Published: October 2005

The acoustical background for elastic shells which allows one to isolate elastic shell resonance’s was first presented at an ASA conference in 1989 for spherical shells. A formulation has been developed that is based on the T-matrix method general for nonspherical shells. An outline of the formulation is presented and it’s use in isolating resonance’s for elastic spheroidal shells is presented. [Work sponsored by NRL and the Office of Naval Research.]
Sound spectra from air-driven American organ reeds
Authors: Cottingham James P. , Colson Ben L. , Wilson Scott T. , Quigley Keelyn W.
Published: October 2005

The ‘‘American’’ reed organ is distinguished from the ‘‘European’’ harmonium by the use of a partial vacuum to draw air past the free reeds rather than the use of a pressure bellows to drive compressed air through them. A sample of reeds from three instruments has been studied in the laboratory using a specially constructed windchest. Spectral analyses of near field sound produced by air-driven reed vibrations were obtained. Measurements were made of the variation with pressure of the frequency and amplitude of the fundamental as well as the spectral components. Relationships between certain aspects of reed design and the spectrum of the resulting sound can be compared with some ‘‘conventional wisdom’’ found in the literature on the instrument. Results are also compared with spectra obtained when these reeds are played in the instruments and with averaged sound spectra from the instruments. It is found that the frequency remains essentially constant over a very wide pressure range, and that the sound spectrum from a given reed, although modified somewhat by its surroundings in the actual instrument, is recognizably the main determinant of the sound spectrum radiated from the instrument.
Discrimination of musical chord components
Authors: Acker Barbara E. , Pastore Richard E.
Published: October 2005

The current study uses an accuracy version of the Garner paradigm to evaluate the nature of the roles played by the E and G frequencies in the perception of root position C major triads. Triads differed in the E and/or G frequencies, relative to an equal-tempered triad (prototype, or P set) or an out-of-tune triad (nonprototype, or NP set). Thus, the P stimuli were more representative of major chords than the NP stimuli. Significant redundancy gains and interference effects were found for both frequencies in both contexts, thus demonstrating the components to be integral, as might be expected for tuning based upon intervals. The amount of redundancy gain found was dependent on the type of correlation, with the negatively correlated stimuli experiencing a greater redundancy gain than the positively correlated stimuli. Finally, better overall discrimination was found in the P context, thus replicating previous work [Acker, Pastore, and Hall, Percept. & Psychophys. (in press)] showing that a prototype functions as a perceptual anchor. In addition, major chord prototypes appear to be located in the physiologically motivated area of just temperament, as opposed to the more experientially defined area of equal temperament. [Work supported by AFOSR.]
Modeling urban noise pollution as an architectural acoustics problem
Authors: Miller Gregory A. , Raichel Daniel R.
Published: October 2005

The problem of urban noise pollution can almost be considered as an architectural acoustics problem. City blocks are treated in a manner mathematically analogous to the acoustics of rooms. Six New York city blocks were selected—chosen for their varying geometries, materials, and traffic patterns—and measurements of Leq were taken during one-hour periods using a type 1 sound level meter. This is an experiment in progress with even more data to be accumulated for further refinement of the theory. The sound levels produced by various sources in these blocks are found by measuring average traffic flow, pedestrian traffic, etc. Predicative noise level equations (based on the sound level from a point source) are being generated on the basis of the physical characteristics of each block, and will be reconciled with experimental data to formulate characteristic equations that should accurately predict the sound pressure levels which observers are subjected to. It is anticipated that the alteration of the absorption coefficients of the structures lining the blocks will constitute the major factor within the reconciliation. The results of this experiment can in time be used to encourage wiser materials choices and more careful planning in future urban development.
Noise barriers with random edge profiles
Authors: Ho Steve , Busch-Vishniac Ilene J. , Blackstock David T.
Published: October 2005

In normal design the top edge of a noise barrier is straight. As a result, noise diffracted from the barrier edge seems to come from a string of highly correlated point sources, that is, a straight line source. The coherence of the diffracted sound therefore limits the effectiveness of the barrier. One way to spoil the coherence of the diffracted sound, and thus increase the barrier’s insertion loss, is to vary the barrier height by making the top edge irregular instead of straight. The radiations from the point sources at the edge then are not well correlated. We have conducted preliminary experiments using physical scale models with random edge profiles. The spacing between height transitions and the height variation maxima are scaled to the wavelength at which the sound source (a spark) has a peak in its spectrum. Results to date show significant improvement (3–8 dB) for a barrier with a random edge profile compared to one of the same average height with a straight edge. [Work supported by TxDOT.]
Global durational patterns in spontaneous speech
Authors: O’Shaughnessy Douglas
Published: October 2005

Most analysis of speech examines carefully read texts. Natural spontaneous speech differs in several ways, having interruptions and large changes in speaking rate. The acoustic phenomena studied here concern the global speaking rate of spontaneous speech, how it varies for both fluent and disfluent speech. Such a model should find application in automatic speech synthesis and recognition. There is a tendency for speakers to adopt a specific articulation rate in fluent speech, especially for brief monosyllabic function words; stressed content words show greater variability, especially in prepausal situations. The greatest variability, however, occurs in disfluent speech, which have extremes in slow and fast speech. A large amount of the variability among word durations can be accounted for by: the number of phonemes per word, whether it is a function word or a content word, and whether the word forms part of a common sequence of words. Words at the start of a syntactic unit tended to be shorter than those at the end of the unit. The first time a content word was introduced into a discourse, it was stressed; repeated occurrences of such a word in the ensuing discourse had shortened durations. [Work supported by NSERC-Canada.]
Demarcating prosodic groups with articulation
Authors: Fougeron Cecile , Keating Patricia A.
Published: October 2005

It is hypothesized that phrasal position affects articulation, and that what looks like overall declination of articulatory displacement could arise from local enhancements or reductions at particular phrasal positions. To test this hypothesis, linguopalatal contact was measured for both the consonant /n/ and the vowel /o/ in reiterant speech. Utterances were based on arithmetic statements like ‘‘(1+1)×(1+1)’’ [reiterant ‘‘(no no no) no (no no no)’’], where stress and phrasing were varied by choice of numerals and location of parentheses. For the one speaker analyzed, there was no overall downtrend in contact of /n/ through any sentence type when all syllables—stressed, word-initial, or phrase-initial—were compared. Instead, word-, phrase-, and sentence-initial /n/’s have cumulatively more contact than medial and final ones. It is proposed that greater initial contact contributes to marking prosodic boundaries by enhancing the consonant–vowel contrast. Also enhancing the CV contrast is the more open position for phrase-final /o/’s. As a result, final edges of domains are marked by a greater articulatory distance from final /n/ to /o/, and initial edges of domains are marked by a greater articulatory distance from final /o/ to initial /n/.
Intelligibility of Arab’s production of English intonation
Authors: Mitleb Fares
Published: October 2005

This paper was intended to test the intelligibility of English intonation spoken by Arabs learning English as a foreign language. Two native British speakers heard English sentences produced by two native British speakers and six Arabs to decide whether a sentence is said with a falling or rising tune. Findings indicated that most Arabs confused the two English tunes to a significant level. They showed insensitivity to the two intonation patterns, a situation that might have resulted from the priority given to the teaching of segmental units of the target language. Therefore, the question of priority to at least the incorporation of intonational information and other suprasegmentals in the teaching process right from the outset is reconsidered. [Research supported by Yarmouk University.]
Acoustic phonetic characteristics of internal open juncture by Mexican Spanish readers
Authors: Karn Helen E. , Yeni-Komshian Grace H.
Published: October 2005

Internal open juncture refers to a set of two or more phrases which contain the same sequence of phonemes, but differ in their prosody, meaning, and orthography. In this study, ten adult native speakers of Mexican Spanish read three sets of phrases. Each set of phrases contained two words and three syllables with the sequence 〈la〉♯〈sa〉, 〈las〉♯〈a〉, and 〈las〉♯〈sa〉, as in the phrases lasabes ‘‘you know it,’’ lasaves ‘‘the birds,’’ and lassabes ‘‘you know them.’’ The phrases were read both in isolation and embedded in sentences (initial, medial, and final positions). Acoustic phonetic measurements were made of: (1) the duration of pauses (when present) between the first orthographic word and the second, (2) the duration of 〈s〉 and 〈ss〉, and (3) the average duration, fundamental frequency, and amplitude of the first syllable versus the second. Preliminary results suggest that internal open juncture in Mexican Spanish is more salient in phrases read in isolation than embedded in sentence contexts and that pause duration is the most consistent indicator of internal open juncture.
Bottom backscattering strengths at low grazing angles using adaptive beamforming
Authors: Ogden Peter M. , Erskine Fred T.
Published: October 2005

Bottom backscattering strengths have been measured between 70 and 1000 Hz using broadband, omnidirectional SUS charges as sources and a horizontal line array as a receiver in the Critical Sea Test (CST) series of at-sea tests. When conventional beamforming is used to form beams in this geometry, bottom fathometer returns often contaminate the backscattering results for grazing angles below about 30 deg. The use of an adaptive beamformer (ABF) combined with examination of near-endfire beams allows scattering strengths to be reliably determined down to considerably lower grazing angles in many cases, over the entire range of frequencies measured. The ABF technique and its parameters and limitations will be discussed briefly. Examples of low-grazing-angle backscattering-strengths results will be shown for a variety of sites visited during various CST tests. [Work supported by ONR.]
Shallow water bottom scattering strength at low frequencies
Authors: Cable Peter G. , Steele Mike , O’Connor James
Published: October 2005

Determinations of acoustic scattering strength for sand bottoms have been made at several shallow water sites under downward refracting sound propagation conditions in the frequency band 50 Hz to 1 kHz. The measurements have been made using explosive sources detonated at mid-water depth and received on two collocated, bottom-mounted hydrophone line arrays, with one array in vertical and the other in horizontal orientation. The major focus of this work has been the variation of scattering strength with frequency and with bottom grazing angle. For the scattering strength measurements, the presence of multipaths in shallow water prevents a direct path scattering geometry from being used at low frequencies and, consequently, scattering strength must be extracted from the full reverberation field. Two techniques for obtaining scattering strength integrated over grazing angle and for using the vertical array to examine the angular dependence of the scattering strength will be described. The results will be compared with other determinations of scattering strength for shallow water sand bottoms and will be discussed in terms of the role of scattering from structure within the bottom sediment.
Preliminary comparisons between bistatic reverberation from an ocean ridge and wavelength-scale geomorphology
Authors: Makris Nicholas C. , Avelino Lilimar , Menis Richard
Published: October 2005

Bistatic reverberation measured from a highly lineated ridge in the mid-Atlantic during the ARSRP Main Acoustics Experiment of 1993 was compared with bottom slope orientation determined from 200-m resolution Hydrosweep bathymetry in a previous abstract [Makris etal., 3329(A) (1994)]. It was found that prominent returns register with extended scarps facing the source and receiving array. These scarps typically extend for lengths greater than 1 km and have widths that are less than 1 km. However, the hydrosweep bathymetry is not of sufficient resolution to determine the fine-scale geomorphology of the scarps, and leads to slope estimates (20° to 30°) that are a severe underestimate. Fine-scale bathymetry of 5-m resolution recently obtained for the same ridge shows that the scarps returning prominent reverberation generally contain cliff faces with slopes between 60° to 90°. However, the separation between these cliff faces is typically less than the roughly 500-m cross-range resolution of the towed-array imaging system. An attempt is made to resolve individual cliff faces with remote returns measured at 1/2 CZ by exploiting the much higher range resolution of the towed-array imaging system (which approaches roughly 10 m) and examining differently oriented bistatic measurements of the same sites.
Backscatter from midfrequency (325–1375 Hz) LFM signals at the Mid-Atlantic ridge
Authors: Preston J. R.
Published: October 2005

In July 1993 SACLANTCEN participated in an experiment for the Acoustic Reverberation Special Research Program (ARSRP). The primary objective was to take high-resolution measurements to shed light on the detailed physical processes dominating the low-frequency scattering from rough topographic features and from deep sediment pond areas. A very detailed set of monostatic and bistatic scattering experiments were conducted (using lower frequencies from 200–375 Hz) just west of the Mid-Atlantic Ridge near 26 °N and 47 °W. New results are presented which show higher frequency monostatic scattering from selected bathymetric features using LFM signals. The receivers were horizontal arrays of 128 elements spaced at 0.5, 1, and 2 m. Source/receiver depths were ≊130 and 450 m, respectively. Received reverberation levels are presented as functions of the estimated scatterer position on area bathymetry maps. Inferences for monostatic bottom scattering mechanisms are given using two-way FEPE parabolic equation propagation models from Collins to interpret the data. Some comparisons of measured and modeled reverberation are also presented.
Pulse length dependence in the CST bottom reverberation measurements
Authors: Reilly Sean M. , Christian Raymond J. , Chester John B. , Vaccaro Mark J.
Published: October 2005

The Critical Sea Test (CST) is an empirical Navy program which collects low-frequency (100–1000 Hz) environmental acoustics measurements in order to provide a diverse, high-quality database for sonar performance prediction. During the course of its experiments in direct path bottom reverberation, CST has observed frequency, grazing angle, and waveform behaviors which differ significantly from those assumed in commonly available bottomscattering strength models. For empirical programs, deviations from standard models are significant because they limit the ability to extrapolate survey measurements into sonar performance scenarios. The most controversial aspect of the coherent source experiments has been the observation of a pulse length dependence in the scattering strength measurements beyond the linear term normally associated with ensonified area. This paper discusses CST’s bottomscattering strength measurement technique and summarizes the pulse length ‘‘anomaly’’ results for a variety of geographic areas. Because these results run counter to standard modeling assumptions, this paper will also discuss the data quality procedures used to reach these conclusions. [Work supported by SPAWAR.]
Preliminary study of the semi-empirical geoacoustic (SEGA) model for bottom reverberation
Authors: Reilly Sean M.
Published: October 2005

Standard bottom reverberation models such as Lambert’s rule and perturbation theory assume that scattering from the rough water/bottom interface is the dominant mechanism at all sonar frequencies. However, direct path bottomscattering strength measurements by the Critical Sea Test (CST) program in the 100- to 1000-Hz frequency range suggest that volume scattering from within the sediments may be the dominant reverberation mechanism in many applications. The CST program has been actively investigating a number of new bottom reverberation models which include scattering from within the sediments [Mourad etal., APL/UW Tech. Rep. No. 9107 (1991); Holland etal., 3247(A) (1994)]. Using a combination of elements from these prior techniques, the Semi-Empirical Geoacoustic (SEGA) model for bottom reverberation is used to extrapolate geoacoustic survey measurements into general-purpose reverberation predictions. This presentation summarizes the results of a preliminary 3-month study which explored the viability of this new model using direct path bottom reverberation measurements from CST-5. [Work supported by SPAWAR.]