bluuebunny/crossref_metadata_2025 huggingface dataset:
Inter-laboratory comparisons of low-frequency sound transmission: II. Narrow-band measurements and computer simulations
Authors: Warnock A. C. C. , Vorländer M.
Published: October 2005

Sound transmission through nominally identical 1.5×1.25-m steel plates was measured in two laboratories; NRC, Canada and PTB, Braunschweig in Germany. This sound paper presents results from a more detailed examination of the behavior of the sound fields at low frequencies in the laboratories. The long-term aim of the work is to understand reasons for poor reproducibility of low-frequency sound reduction measurements in laboratories. Narrow-band sound transmission measurements were made between the two pairs of rooms at PTB and NRC. In each case, the same procedure was used; loudspeakers were fed with a pseudorandom sequence and the impulse response was calculated using a Hadamard transform. The two sound transmission suites were also simulated using FEM and BEM programs. Comparisons between the measured and calculated results will be presented and discussed.
Hot topics in underwater acoustics
Authors: Baggeroer Arthur B.
Published: October 2005

There have been two major changes that have modulated the temperature of topics in underwater, or ocean, acoustics since the last ‘‘hot topics’’ session. First, close coupling among the acoustics, the ocean environment and its processes, numerical models, and the signal processing continues to lead to new methods for learning about the ocean and to improved performance of acoustic systems. Second, in response to the changing demands upon future sonars, there has been much more attention to both active systems and shallow water environments. Several ‘‘hot’’ (at least warm) topics will be discussed: adaptive focusing systems including phase conjugation, self-cohering arrays, and matched-field processing/tomography; global acoustics and ocean climate monitoring; high resolution bathymetric mapping; reverberation; seismoacoustics of interface waves; shallow water acoustics; ambient noise and acoustic daylight; and high data rate acoustic telemetry. (The order is not an indication of relative temperature.)
Detection of buried landmines by imaging with surface waves
Authors: Krumhansl Peter A. , Watters Bill G. , Sachs David A.
Published: October 2005

A technique has been developed to search an area of soil for buried landmines from a remote position. A two-dimensional synthetic aperture array of seismic sources and receivers is laid down adjacent to the search area. Broadband seismic sources generate Rayleigh surface waves that illuminate a search area out to a radius of 6 m and a depth of about 0.5 m. An array of vertical geophones receives backscattered signals that are recorded digitally. Unconsolidated soils have high rates of attenuation so an array with up to 21-dB of gain is used. A delay-and-sum near-field beamformer computes a 60×80 pixel image of the region’s scattering strength. The search area image displays the location and character of landmine echoes along with clutter. A large amount of field data has been collected at several sights. The mine echoes have been detected at ranges up to 5 m (Pd=0.8). Landmines have been distinguished from rocks and holes, and false alarms due to system artifacts are being reduced. [Work supported by U.S. Army BRDEC.]
Reverberation imaging of large scale under ice keel distribution
Authors: Yang T. C. , Yates T.
Published: October 2005

Low-frequency reverberation data received on a large aperture planar array of hydrophones are used to estimate the under-ice scattering strength over a basin wide area. The result is interpreted as a large scale under-ice keel distribution which, unlike the ice surface ridge distribution, has not been measured over a wide area. The reverberation data were collected during the CEAREX 89 experiment using explosive sources. Scatterer localization was performed for each time segment. The range-bearing ambiguity distributions at depth near the surface was range gated according to estimated two-way travel times, and combined to form the ambiguity surface for a large area. Ice keel distribution is obtained by removing the two-way transmission loss to and from the surface scatterers. This image is compared with that obtained using conventional beamforming techniques.
A comparison of voice analysis systems for perturbation measurement
Authors: Bielamowicz Steven , Kreiman Jody , Gerratt Bruce R. , Dauer Marc S. , Berke Gerald S.
Published: October 2005

Dysphonic voices are commonly analyzed using automated digital voice analysis software. However, reliability and validity of acoustic measures obtained from these programs has been questioned, especially in the assessment of dysphonic voices. This study evaluated the agreement among various commercially available speech analysis programs and a handmarked voice analysis system. Sustained vowels of 25 male and 25 female speakers with mild to severe dysphonia were digitized and jitter, shimmer, and harmonics-to-noise ratio were analyzed using CSpeech, Computerized Speech Laboratory (CSL), and SoundScope. The effect of dysphonic severity on the measures provided by these four programs was also assessed. The clinical utility and theoretical limitations of automated, perturbation-based measures will be discussed, especially with regard to the indeterminant nature of F0 in some types of dyhsphonia.
Nasometric evaluation of velopharyngeal function in nonliterate subjects
Authors: MacKay Ian R. A. , Kummer Ann W.
Published: October 2005

The Kay Elemetrics nasometer measures nasalance, a parameter of speech that reflects the proportion of total acoustic energy that is emitted nasally, making it possible to infer velopharyngeal (VP) function noninvasively. Nasometric evaluation is potentially widely applicable in the clinical assessment of suspected VF impairment. For clinical use, a patient’s mean nasalance on a passage of known phonetic composition must be compared to age-appropriate population norms. Most potential clinical subjects are young; many are preliterate. Passages for which norms have been established (Zoo, Rainbow, NasalSentences) are syntactically, semantically, and lexically complex, phonetically heterogeneous, phonologically mature, and long. Individual child subjects’ nasalance scores, if obtained at all, are therefore likely to be contaminated by artifacts created through hesitation noises, filled pauses, phonetic deviance from normed target, age differences, and measurement errors induced by coaching procedures. Differences in phonetic content between normed and actual utterances are almost inevitable; they lead to uninterpretable results. This study reports a technique for obtaining clinically useful nasalance scores from young, preliterate subjects, even those evidencing phonological deficits or noncompliant behavior. Large-n norms for preschool and primary children are presented.
Developmental phonological impairment: An acoustic description of improved production
Authors: Wilcox Kim A. , Morris Sherrill R. , Siren Kathleen A.
Published: October 2005

Although misarticulation of speech is one of the most common communication problems of young children, there is little available information concerning the phonetic form of young children’s errors. This paper reports on a longitudinal analysis of the acoustic properties of speech samples from two phonologically impaired children. Both children were enrolled in remediation programs that focused on the correct production of stops and fricatives. Bimonthly samples were taken from each child over a period of several months coinciding with significant improvement in perceived phonetic accuracy. Both durational and spectral aspects of the children’s speech were monitored throughout the period. The relationships between changes in specific acoustic properties and correct perception as well as interspeaker differences are discussed.
Spatial attenuation of bending waves in the infinite plates coupled by a viscous damping layer
Authors: Kang Jongmin , Akay Adnan
Published: October 2005

Plate vibrations can be reduced by a viscous damping layer between a primary excited plate and a secondary plate, of which frequency responses are considered by Ingard and Akay [J. Vib., Struct. Rel. Design 108, 178–184 (1987)]. For a free vibration, complex wave numbers are determined from a dispersion relation, where the imaginary part is related with the attenuation due to the damping layer. The steady state responses both in the plates and fluid layer are calculated when the primary plate is under a time harmonic line-driven force. Energy and power flow of a complex wave number are also considered. The complex wave number in a vibrating plate increases as the thickness of the damping layer decreases, such that the attenuation is greater and the period in space is shorter, and the waves in a damping layer become unstable. For a given thickness of a damping layer, as the exciting frequency is higher, the damping effects are weaker, since the boundary layer thickness becomes thinner. When a secondary plate of a same material is attached to attenuate the vibration of a primary plate, the secondary plate must be thicker than the primary plate to achieve an efficient vibration reduction. The bending waves in the primary plate are attenuated very fast, and become identical with the bending waves in the secondary plate at far field.
An analytic model for the vibrations of rectangular shells of variable curvature and thickness
Authors: Okajima Masahiko , Burroughs Courtney B.
Published: October 2005

A flexible and powerful model is developed for analyzing the vibration of a rectangular platform shell whose curvature and thickness are arbitrary. The shape of the shell can have almost any conceivable representation, since the curvature and thickness are represented by bicubic polynomials of the centerline arc length. The vibration model includes the effects of shear deformation, rotary inertia, and centerline extension. The equations of motion are solved by an alternative form of the Rayleigh–Ritz method. The resulting integral formulas for the stiffness and mass matrix elements are evaluated by a set of simple computer routines that do symbolic manipulations of algebra and calculus. Predictions of the natural frequency for the several shell geometries are compared to published data, with good agreement. A parameter study shows the dependence of the resonance frequencies and mode shapes on the curvature and the thickness of the shell.
Thin elastic spherical shells: the nonaxisymmetric motion
Authors: Ho Jin-Meng
Published: October 2005

This paper treats the nonaxisymmetric motion of a thin elastic spherical shell; it is motivated by the problem of a finite cylindrical shell with hemispheric shell endcaps. Here, the spherical shell is subject to intrinsic azimuthal deflection, as opposed to the well-documented case where the vibration is rendered axisymmetric by the special choice of coordinates. The kinematics of deformation is discussed, based on the thin shell assumption referred to in the literature as the Kirchhoff hypothesis. This leads to the expressions of the total kinetic and potential energies and external work in terms of the displacements of the middle shell surface; application of Hamilton’s principle then yields the desired dynamical equations of nonaxisymmetric motion. It is found, as two special cases, that the spherical shell undergoing free vibrations supports shear waves, in addition to compressional and flexural waves; but that for fluid loading, the former decouples from the acoustic wave while the latter observe the same dispersion relations as in the axisymmetry case.
Measurement of the real and imaginary piezoelectric, elastic, and dielectric constants for dispersive piezoelectric transducer materials
Authors: Sherrit Stewart , Wiederick Harvey D. , Mukherjee Binu K.
Published: October 2005

The recent past has seen the introduction of many new types of piezoelectric materials with relatively high dissipation and low mechanical Q (PVDF, ceramic–polymer composites). In order for designers to predict the performance of these materials in transducers, the imaginary components of the dielectric, elastic, and piezoelectric constants need to be known. This is typically done by analyzing the electrical impedance spectra and applying the methods described in the IEEE standard on piezoelectricity [IEEE Std. 176-1987] to calculate the relevant material constants. This paper describes new methods of analysis that expand on the IEEE standard and allow the experimenter to analyze materials with low mechanical Q and substantial piezoelectric loss factors. The paper also describes a technique to determine dispersion in the material constants from the experimental impedance or admittance spectra of the materials. [Work supported by DREA, DND-Canada.]
Anomalies in the neural tonotopic-synchrony pattern as the basis for the segregation of tones
Authors: Hartmann William Morris
Published: October 2005

It is possible to envision a comprehensive model for the segregation and integration of tones based upon synchrony and asynchrony of neural excitation patterns. Evidence for this model comes from experiments on mistuned harmonic matching, simultaneous and sequential octave tuning, and FM incoherence detection with harmonic and inharmonic tones. Such a model has the conceptual advantage of unifying temporal effects and mistuning effects upon segregation. A central remaining question in the formulation of this model is the role of tonotopic analysis. There is, in fact, tonal segregation attributable entirely to tonotopic oddity. More than that, there are tonotopic effects on the processing of synchrony anomalies. These can be seen in mistuned harmonic detection experiments with neighboring harmonics removed, or with added constant remote inharmonic confuser, or with several mistuned harmonics that are themselves either mutually synchronous or asynchronous. Such experiments have suggested a tuned-autocorrelator model with a bandwidth of about two critical bands. Tonotopically based synchrony models are, in turn, challenged by experiments on cross-channel interaction where excitation at intervening tonotopic sites has been deliberately squelched. [Work supported by the NIDCD, DC 00181.]
The effect of amplitude comodulation on extracting sentences from noise: Evidence from a variety of contexts
Authors: Carrell Thomas D.
Published: October 2005

While signal-to-noise ratios range from about 50–90 dB in laboratory experiments, measurements of speech levels in most natural environments show much poorer listening conditions. For example, Teder [Hear. Instrum. 11, 32–33 (1990)] measured signal-to-noise ratios ranged from a high of 13 dB in a carpeted office to low of 1 dB in a 1986 Chevy Nova traveling at 55 mph. These numbers indicate an immense difference between speech signals presented to listeners in laboratory experiments as opposed to the real-world environment. Although speech intelligibility has been well studied in noise, there has been little study of the acoustic characteristics of speech that allow the message to be separated from the background noise. One characteristic of voiced speech that shows great promise in this regard is amplitude comodulation. In the present research, amplitude comodulated tone-analog sentences [Carrell and Opie, Percept. Psychophys. 52, 437–445 (1989)] were presented with simultaneous white noise and multispeaker babble at 0-, 5-, and 10-dB signal-to-noise ratios. It was found that the beneficial effect of amplitude comodulation was greater at the lower signal-to-noise ratios.
Elastography: Technical considerations and preliminary clinical results
Authors: Ophir Jonathan , Cespedes Ignacio , Ponnekanti Hari , Maklad Nabil
Published: October 2005

The elastography technique is based on computing localized strain levels in tissue, which are produced in response to a small axial compression, and which are detected by subjecting pre- and post-compression radiofrequency a-line pairs to cross-correlation analysis. Additionally, the absolute stress field generated by the compressor is calculated from theory and from acoustic measurement of the applied stress. The local Young’s moduli are estimated from the local axial stresses and strains, with reasonable sensitivity and resolution. Theoretical considerations and simulations were used to investigate the mechanical, acoustical, and signal processing tradeoffs which are encountered, and some of these have been studied experimentally in tissue mimicking phantoms and in tissues invitro and invivo. Some of the interesting results to date include improved signal-to-noise ratio in elasticity images (elastograms) as compared to sonograms, the possibility of imaging elasticity in certain acoustically shadowed areas, and the ability to observe certain structures that are invisible on sonograms. Several image artifacts have also been identified.
A nonlinear filter bank model for the auditory periphery
Authors: Taliwal Vikas , Carney Laurel H.
Published: October 2005

The intrinsically nonlinear character of auditory processing has long been the bane of linear models for the auditory periphery. A previous computational model [Carney, J. Acoust. Soc. Am. 93, 401–417 (1993)] for single auditory nerve fibers contained a feedback mechanism to vary the bandwidth of a narrow-band gammatone filter as a function of sound pressure level. That model simulated the compressive nonlinearity, including aspects of temporal and average discharge rate characteristics of low-frequency auditory nerve fiber responses. The proposed model extends the previous work; its architecture is motivated by the most recent empirical evidence on outer hair cell (OHC) physiology. The nonlinear narrow-band gammatone filter is replaced with a broad second-order bandpass filter [G. von Békésy, J. Acoust. Soc. Am. 21, 245–254 (1949)] inside a feedback loop. The feedback path consists of a nonlinearity representing OHC transduction, followed by a lowpass filter for the cell membrane, and finally a nonlinearity representing OHC motility. A bank of such models allows representation of spatio-temporal discharge patterns across populations of auditory nerve fibers. [Work supported by The Whitaker Foundation and NIDCD.]
Wave theory modeling of bi-static bottom reverberation in a stratified ocean
Authors: Schmidt Henrik , LePage Kevin , Fan Huaiyu
Published: October 2005

Recent results by Lepage and Schmidt [J. Acoust. Soc. Am. 92, 2467–2468 (A) (1992)] have shown that broadband representations of rough surface scattering scenarios may be obtained for layered acoustic-elastic media by using a computationally efficient, hybrid perturbation/wave-number integration approach. These results are quite general for source characteristics and geometry but up until now the scattered field has only been obtained in the proximity of the scattering patch. Using a formulation similar to the one used by Schmidt and Glattetre for horizontal source arrays in a stratified ocean [J. Acoust. Soc. Am. 78, 2105–2114 (1985)], the two-dimensional Fourier representations of the scattering source strengths can be transformed into a cylindrical representation in terms of a Fourier series of Hankel transforms. The fact that the number of terms in the series is limited by the finite size of the scattering patch, and the fact that the kernels of the Hankel transforms are determined from a single, linear system of equations with multiple right-hand sides, makes this approach extremely efficient for simulation of long range bi-static reverberation. The seismoacoustic bottom reverberation in deep water is investigated for relevant bi-static scenarios, and the importance of elastic properties and the roughness characteristics is investigated. [Work supported by ONR.]
Design of a feature-based speech recognizer aiming at integration of auditory processing, signal modeling, and phonological structure of speech
Authors: Deng Li
Published: October 2005

The conventional design of speech recognizers tends to treat the ‘‘front end’’ (signal representation of speech) and the ‘‘back end’’ (lexical representation plus signal modeling and pattern matching) as separate modules. In the integrated framework being developed, signal representation is regarded as a process of ‘‘constrained optimization’’ with the objective function determined by the phonological structure (feature) of speech and by statistical representation of its acoustic/auditory correlates. The constraints are based on the significant properties known to be employed by the human auditory system. A preliminary version of a speech recognizer incorporating the above ideas will be presented where bundles of overlapping articulatory features are used as the basis for describing the phonological structure of speech. Several multi-valued features are assigned uniquely to each quasi-phonemic unit with ‘‘minimal’’ redundancy and ‘‘maximal’’ separability. Major contextual variations in speech are modeled as a natural result of overlapping the ‘‘intrinsic’’ values of one or more of these features across adjacent phonemic units. Knowledge from speech production and speech perception are utilized to limit the allowable feature overlaps. Linkage of this feature-based lexical representation to speech recognition is achieved by establishing a one-to-one mapping from a feature-overlap pattern to a directed graph where each node represents a unique composition of the features and is characterized by a time-series model. Given the explicit feature specification for each node in the overall speech space, a general set of acoustic/auditory measurements can be assigned specifically into the individual nodes based on the understanding of the acoustic/auditory correlates to the features.
A computational auditory model for real-world sounds of useful duration
Authors: Patterson Roy D. , Holdsworth John , Allerhand Michael
Published: October 2005

A psychoacoustic model of auditory processing has been developed to summarize peripheral processing and provide a convenient auditory simulator for research on real-world sounds like music and speech. Most of the processing is devoted to simulating the operation of the cochlea in a fairly traditional way, that is, with a bank of auditory filters and a bank of neural transduction units. The remainder is devoted to two novel processes: First, a form of quantized temporal integration introduced to account for the stablity of the auditory images produced by periodic sounds. Second, a spiral pitch processor that operates on the auditory image and measures the loudness, pitch, and strength of voicing in speech. The system is modular and offers displays of the auditory representation of the sound at each processing stage. Standard workstations process sentence length sounds promptly with larger databases processed overnight. The system is currently being used to assess vocal agitation in samples of normal and emotional speech.
Differential synchronization rates of eighth nerve and midbrain fibers to AM tones and AM noise in bullfrogs (Rana Catesbeiana)
Authors: Boatright-Horowitz S. , Simmons Andrea Megala
Published: October 2005

The American bullfrog (Ranacatesbeiana) provides an excellent model for neuroethological studies in pitch perception. It is particularly useful in the development of an auditory model of temporal coding because of its sensitivity to periodicities in complex sounds. Using a dorsal surgical approach, recordings were made of the neural synchronization responses of 8th cranial nerve fibers to AM tones and AM noise in the frequency range of 200 to 2500 Hz at different modulation depths, followed by single- and multi-unit recording in the midbrain (torus semicircularis) to the same stimuli. Analysis of synchronization rates of peripheral and central auditory sites elucidates the differences in neural temporal representation of the waveform periodicity for subjects ranging from recently post-metamorphic froglets to fully mature adults.
A comparison of octave-band noise masking patterns obtained from normal-hearing and hearing-impaired listeners
Authors: Rankovic Christine M. , Zurek Patrick M.
Published: October 2005

In cases where spread of masking plays a role, interfering noise is more detrimental to speech reception for hearing-impaired than for normal-hearing listeners [e.g., Rankovic etal., J. Acoust. Soc. Am. 90, 2319 (A) (1991)]. To examine such effects, masking patterns for octave-band noises collected from 5 normal-hearing and 6 hearing-impaired subjects were compared. Maskers were centered on 0.5, 1.0, and 2.0 kHz and varied in overall level from 70 to 95 dB SPL in 5-dB steps and masked thresholds were measured with 1/3-octave resolution. The hearing-impaired subjects’ masking patterns were compared with the averaged patterns of the normal-hearing subjects and the following were found: (1) a low-frequency spread-of-masking (for both normal and impaired listeners) that is roughly constant for the masker levels used here; (2) generally shallower slopes on the high-frequency side of masking patterns for impaired listeners; and (3) for some impaired listeners, substantially greater masking within the masker band. These results will be discussed in relation to the design of hearing aids that modify the frequency-gain characteristic with the goal of reducing upward spread of masking, and will be compared with the masking-pattern equations for impaired listeners proposed by Ludvigsen [C. Ludvigsen, J. Acoust. Soc. Am. 78, 1271–1280 (1985)]. [Work supported by NIH.]
Processing advantages for sequential pure tones related by small integer frequency ratios
Authors: Schellenberg E. Glenn , Trehub Sandra E.
Published: October 2005

The effect of frequency ratio complexity on the discrimination of changes to sequential tonal patterns was examined. Patterns consisted of two alternating pure tones (ABABA). Subjects heard a repeating background pattern (the standard pattern) presented in transposition (same frequency ratios between tones, different absolute frequencies), and were asked to identify when a contrasting pattern (different frequency ratios, different absolute frequencies) was substituted. Changes were significantly easier to identify when the component tones of the background pattern were related by small integer frequency ratios (3:2 or 4:3) and those of the contrasting pattern were related by more complex ratios (45:32) than when the situation was reversed. The effect did not extend to cases in which the relative differences in ratio complexity were reduced (3:2 vs 8:5 or 4:3 vs 5:4). A multiple regression analysis of the combined data sets showed that frequency ratio complexity of component tones in both the standard (background) and contrasting patterns made independent contributions in predicting these results. These findings cannot be explained by notions such as critical bandwidth. Moreover, the present test procedure may be a more sensitive measure of effects of tonal consonance and dissonance than others previously used.
A comparison of maskers on spatially separated competing messages
Authors: Ericson Mark A.
Published: October 2005

The intelligibility of simultaneous speech signals from pairs of talkers was improved with spatial separation of talkers using synthetic means. The simultaneous speech signals of the talkers, male versus male, female versus female, and male versus female, were separated by 0, 22, 44, 90, 134, and 180 deg. A simple left–right (180-deg) signal separation condition was also measured. Four listeners responded to both diotic and spatially separated presentations over headphones. The listeners were randomly prompted by a call sign to respond to one of the two talkers, providing an intelligibility baseline of 0 dB signal-to-noise ratio for each test phrase. Speech maskers used were either (1) pink noise or (2) a speech babble presented over headphones or, (3) pink noise presented by loudspeakers. In general, the female talkers were the least intelligible and the male versus female pair were the most intelligible. Spatial separations of 90 deg, or more, provided up to a 25% increase in intelligibility.
Development of efficient methods to reduce the noise level of dishwashers
Authors: Öztürk Cüneyt , Eksert Şemsettin
Published: October 2005

The aim of these studies was to keep the machine within the 50-dBA range to be competitive within the market. In order to achieve the ultimate goal of noise reduction, measurement methodology evolved on the basis of four steps. Source identification studies have led one to consider that the tub of the machine was driven to act as a loudspeaker because of permanent splashes of the sprayed waters and transmitted vibration of the motor housing, which was located over the tub. Studies have been focused around the elimination of high-frequency water noises and torsional noises of the motor that were dominant around the line frequency and double-line frequency and had a tendency to coincide with the natural frequency of the tub. Achievement of the proposed noise levels has led to studies of new treatment methods to keep the machine within the ranges of acceptable noise quality.
Intensity correlation and the approach to localization
Authors: Genack Azriel Z. , Garcia Narciso , Li Jiang Hong
Published: October 2005

Because the conductance is the prime physical property of interest for electronics and also the universal scaling parameter of the electronic localization transition, considerable attention has focused upon the scaling of conductance. For classical waves, however, the localization transition can be followed not only by the scaling of the average of local or global quantities such as the intensity, transmission, or conductance, but also in a broad array of distributions and correlation functions, in which the proximity to the localization threshold is revealed, even in samples of a fixed size. Quantitative agreement is obtained between microwave measurements of spectral and spatial correlation in samples of randomly positioned polystyrene spheres and Langevin and macroscopic matrix calculations. The degree of correlation is shown to be the inverse of the dimensionless conductance even in the presence of absorption. The intensity distribution in this sample is also given in terms of the dimensionless conductance. Thus the approach to localization is revealed in the statistical character of propagation. The role of dielectric sphere resonances and the breakdown of the diffusion model is metallic mixtures will also be discussed. [Work supported by the NSF and the Petroleum Research Fund of the ACS.]
Influence of sound-speed fluctuations and medium geometry on wave localization
Authors: Chandra Kavitha , Thompson Charles
Published: October 2005

The influence of spatial geometry and material composition on acoustic radiation is considered. Numerical methods are presented that compute the scattered wave field for wavelengths between the Rayleigh scattering and geometrical optics regimes. The transition from extended to localized modes and their dependence on the wave number, average sound-speed fluctuations, and volume fraction of the scatterers is demonstrated. It is shown that the sound-speed contrast must exceed a minimum value for the localized modes to exist. A spatially varying eigenfunction decomposition of the intensity field is carried out to demonstrate this localization effect.
Classical sound waves as a coherent superposition of phonons
Authors: Marston Philip L.
Published: October 2005

It is generally recognized that single mode classical light waves can be represented as a particular superposition of photon occupation number states [R. J. Glauber, Phys. Rev. 131, 2766–2788 (1963)]. The analogous superposition of phonons is examined for a chain of equal masses coupled only through nearest-neighbor harmonic potentials. This relates phonons to classical normal modes. While the resulting coherent phonon state may be implicit in the work of others, it illustrates the quantum limitations on the normal mode amplitude ξ. The expectation value <ξ≳ oscillates harmonically but the oscillating wave packet has a quantum spread of order (ℏ/ωM)1/2, where M is the mass of the chain. This magnitude agrees with estimates by others on the quantum limitation on the detection of classical vibrations. [Work supported by ONR.]
Integrated mathematical model of the ear. I. Free-field pressure to basilar membrane displacements
Authors: Kalb Joel
Published: October 2005

In order to provide insight into the processes operative in the ear, especially at high sound pressure levels, an integrated mathematical model of the ear has been produced. The model’s electroacoustic elements are conformal with the strucure of the ear, which promotes physical insight. For maximum utility the model is menued to allow parameter changes by the user. Mathematically, the model is equations of motion formulated as a system of coupled ordinary differential equations, which allow both linear and nonlinear claculations in the time domain. The ‘‘Q’’ of the basilar membrane is not constant and the range is selectable. The systems are linear, except at very high SPLs (130+dB) where the stapes becomes nonlinear. Input to the model is any 4096-point free-field pressure or pressure at the ear drum. Outputs are standardly numerical files of stapes displacements and basilar membrane displacements at any number of evenly spaced user-selected places. As a final output the model makes a ‘‘movie’’ of the basilar membrane displacements coordinated with the pressure history, which shows the effect of each part of the waveform.
A mathematical model of hair cell transduction
Authors: Krol Stefan , Cheesman Margaret F. , Jamieson Donald G.
Published: October 2005

A mathematical model is described for mechano-electro-chemical transduction in hair cells. The model relates the displacement of stereocilia to the intensity of firing of fibers attached to each hair cell through a cascade of four stages. The gatingstage relates hair bundle displacement to the change in conductivity of the hair cell membrane. It is described by a mechanical version of the Hodgkin–Huxley model. The electricstage relates the change in conductivity to the receptor potential through a hair cell electrical network of the Davis type. The calciumkineticsstage relates free calcium ion (Ca2+) concentration in hair cells to the receptor potential. It is assumed there are two states of calcium ions: free and bound (by buffers). The synaptictransmissionstage relates free calcium concentration to the intensity of firing as described by the Hill equation. Using relevant parameters, the model simulates the behavior of low- and high-spontaneous firing rate fibers, and is being implemented as a component of a complete cochlear model. [Work supported by NSERC, URIF, and Unitron.]
Effect of onset asynchrony and mistuning on the lateralization of a pure tone embedded in a harmonic complex
Authors: Hill Nicholas I. , Darwin C. J.
Published: October 2005

The effect of onset asynchrony and mistuning on the binaural processing of multi-tone stimuli was investigated using a paradigm derived from that of Trahiotis and Stern [C. Trahiotis and R. M. Stern, J. Acoust. Soc. Am. 86, 1285–1293 (1989)]. A tonal complex comprising harmonics 2 to 8 of 100 Hz and presented with an IDT of 1.5 ms gave rise to a single image lateralized towards the ear receiving the leading signal. However, when the central 500-Hz component was delayed by 40 ms relative to the flanking tones, it was heard out as a separate tone shifted towards the opposite side of the head. Similar effects were observed when the 500-Hz component was mistuned from the flanking complex, with shifts of ±3% being sufficient for the mistuned component to be lateralized in the vicinity of the mid-line. The results demonstrate that both onset asynchrony and mistuning influence which frequency components IDT information is integrated across. [Work supported by UK SERC and MRC.]
Acoustic design of the new Princess of Wales Theatre
Authors: O’Keefe John P. M.
Published: October 2005

The acoustic design of the new 2000-seat Princess of Wales Theatre in Toronto is based loosely on the neighboring Royal Alexandra Theatre. The new theatre is a traditional double balcony, horseshoe-shaped room, augmented by a modern interior design. Abstract sculptures by artist Frank Stella provide acoustic diffusion on the balcony facia. On the back walls, diffusion is provided by specially designed primitive root diffusors. The theatre has a volume of 10 500 m3, it is 29 m wide and the furthest seat is 30 m from the stage. Most materials in the theatre are either massive or stiff, to encourage acoustic warmth. The natural frequency of the balconies is approximately 6 Hz, higher than normal rhythmic motion. At the Royal Alexandra the natural frequency is half this and the balconies are easily set into motion by patrons during rock musicals. A hybrid computer modeling routine combining the method of images and particle tracing was used to assist in the design. Measurements in the new theatre will be presented and will be compared to the Royal Alexandra and other similar venues.
Water depth and drive voltage dependence of the acoustic parameters of a barrel-stave flextensional projector
Authors: Jones Dennis F. , Moffett Mark B.
Published: October 2005

A low-frequency barrel-stave flextensional projector for sonar and general underwater acoustics applications has been built at the Defence Research Establishment Atlantic in Dartmouth, Nova Scotia. The projector was calibrated at the Seneca Lake sonar test facility at Dresden, NY, as a joint research venture with the Naval Undersea Warfare Center, New London, Connecticut. The transmitting voltage response (TVR), mechanical quality factor (Qm), electrical admittance, and electroacoustic efficiency (ηea) were measured for driving voltages up to 5.0 kVrms at four depths: 30, 61, 91, and 123 m. At 5.0 kVrms, the resonance frequency (f0) increased from 780 to 840 Hz, Qm decreased from 4.4 to 3.3, and ηea decreased from 87% to 71%, as the depth was increased from 30 to 123 m. The change in each acoustic parameter, averaged over the four depths of interest, was −10 Hz/kVrms for f0, +0.4 dB/kVrms for the TVR at resonance, and +0.1/kVrms for Qm, as the driving voltage was increased from 0.1 to 5.0 kVrms. The dependence of the parameters on depth and driving voltage are discussed in terms of the interactions between the rubber boot and the staves. [Work sponsored in part by the U.S. Office of Naval Research.]
Preliminary bistatic and monostatic scattering results from a steep basin feature in the Tyrrhenian Sea
Authors: Preston J. R.
Published: October 2005

A feature scattering experiment was conducted by SACLANTCEN off the island of Palmarola in the Tyrrhenian Sea in March 1991. Estimates of this feature scattering are presented as a function of range, source type, and source depth. Area water depths ranged from 200 to greater than 3800 m. The receivers were a horizontal array of 64 elements spaced at 0.5, 1, and 2 m and a vertical array with 32 elements and the same spacings. Source depths varied from 90 to 1800 m and receiver depths ranged from 90 to 150 m. Depth charges were used as sources, as were low-frequency cw pulses and linear FM pulses of various pulse durations and bandwidths. Basin wide received reverberation levels and scattering strength values are also presented as functions of the estimated scatterer position on area bathymetry maps. Comparisons of shot and pulse data reverberation levels are presented. Estimates of monostatic bottom scattering strengths versus grazing angle are given using generic sonar model (GSM), PAREQ, and KRAKEN to interpret the data. Finally, comparisons of measured reverberation and modeled reverberation are presented.
Broadband bottom scattering measurements in shallow and deep water
Authors: McConnell Steven O. , McCown John H.
Published: October 2005

Measurements using broadband signals with bandwidths up to 5 kHz were made in shallow and deep water off San Diego. At the shallow (180–500 m) location 1- to 6-kHz coded signals were used for gathering simultaneous forward loss and backscattering data at grazing angles between 10° and 40°. Time resolutions as small as 0.25 ms were achieved and from the forward loss measurements these high resolution data clearly revealed a medium scale (∼102 m) patchiness in the surficial sediment type alternating between sand and silt. The deep (1800-m) water measurements were taken at a deep sea drilling project site using a combination of 1- to 5-kHz coded pulses and 0.05- to 2 kHz-bandpassed SUS charges. Fine scale subbottom layering with typical thicknesses of 1–10 m down to 130 m were delineated using these broadband source signals. The coded pulses yielded a better definition of this layered structure in the upper 40 m, but were limited in depth of penetration because of increased attenuation at higher frequencies. [Work supported by ONR-AEAS.]
Limitations of the operator expansion method
Authors: Kaczkowski Peter J. , Thorsos Eric I.
Published: October 2005

Preliminary studies of the operator expansion method applied to scattering from rough surfaces satisfying the Dirichlet boundary condition [P. J. Kaczkowski and E. I. Thorsos, J. Acoust. Soc. Am. 90, 2258 (A) (1991)] have indicated that this relatively new method [D. M. Milder, J. Acoust. Soc. Am. 89, 529–541 (1991)] has a broad range of validity. For moderate rms surface slopes, the method is accurate over almost all scattering angles, and represents a vast improvement over the Kirchhoff approximation and small perturbation methods. Further study of the operator expansion method has led to new insights that establish a link between the formal validity of the method and the validity of the Rayleigh hypothesis. While the Rayleigh hypothesis appears to place a strict limit on the operator expansion, numerical examples will be presented that illustrate that the accuracy of the scattering cross section computed by the operator expansion method degrades only gradually as the rms slope is increased beyond that limit. For scattering from surfaces rough in one dimension, the accuracy of the operator expansion solution is established through comparison with the solution to an integral equation. Studies of the convergence of the terms in the operator expansion series indicate how the convergence rate can be used to infer the accuracy of the solution at any given order. This property will be useful when applying the operator expansion method to scattering from surfaces rough in two dimensions, for which exact solutions are still very costly. [Work supported by ONR.]
Modeling of frequency broadening for sea surface reverberation
Authors: Thorsos Eric I.
Published: October 2005

Even at low frequencies (100–1000 Hz) backscattering levels rise above rough interface scattering levels at higher sea states, most likely due to scattering from bubble clouds near the surface. Because the bubble clouds are convected in the orbital motion of the surface waves, frequency broadening will occur for backscattering of narrow-band signals. However, the moving rough surface leads to another effect. A scatterer below the moving surface is ensonified by the total field: incident plus the surface scattered field. Because the total field vanishes on the surface, the main scattering contribution comes from several meters below the rough surface at low frequencies. The magnitude of this total field will fluctuate with time as the surface waves move by the scatterer. Therefore, even if the scatterer is stationary the scattered field will have some frequency broadening, and this will be combined with the Doppler broadening due the orbital motion for a scatterer free to move. The possible importance of rough surface effects on frequency broadening has been examined using numerical simulations with a one-dimensional surface model. [Work supported by ONR.]
Frequency and angle spreading for scattering from a rough ocean bottom
Authors: McCammon Diana F. , Thompson William
Published: October 2005

An analysis has been performed of the sound scattered from a Gaussian random rough ocean bottom when radiated from a time-harmonic point source and received by an omnidirectional receiver positioned at the same deep depth. Both source and receiver are moving, at low Mach number, in a plane parallel to the ocean’s surface, with arbitrary independent velocities. The problem is idealized and analyzed as a linear system with stochastically varying components, viz., the propagation distances because of the reflections from the random rough bottom. An expression is developed for the power spectral density of the received signal as a function of the source amplitude function. This expression describes the dependence of the frequency shift of the received signal upon the source and receiver speeds and upon the azimuthal angles, grazing angles, and ranges from source to arbitrary scattering facet of the rough bottom to receiver. [Work supported by ONR/AEAS Program.]
Measurements informing the design process: Experiences in occupied hall analysis
Authors: Kirkegaard Dana L.
Published: October 2005

In a performing arts facility, many design decisions take into account the influence that audience and performers will have in modifying the acoustics of the unoccupied or sparsely occupied hall. When correlating subjective experience to objective measures, it is very important to assess whether the phenomena being studied are dependent upon the presence of performers and/or audience, and to structure objective measurements accordingly. The impact of occupancy varies widely, and is dependent upon the location of important reflective surfaces. The musicians, music stands, and audience members can be obstacles to the direct sound and wall reflections. This impacts ensemble conditions onstage [Kirkegaard etal., ‘‘Concert Acoustics: The Performers’ Perspective,’’ J. Acoust. Soc. Am. Suppl. 1 84, S20 (1988)] as well as issues of clarity, imaging, and envelopment in the audience. In some notable cases, the character of the fixed absorption—seating predominantly—changes the spectrum and spatial quality of the reverberation with occupancy. Comparisons of occupied/unoccupied data will be used to illustrate the dependence of the early echo structure and reverberation upon occupancy and its relationship to the design process.
Phonetics of Jemez vowels
Authors: Bell Alan , Heins Rebecca
Published: October 2005

This paper presents a spectral and durational analysis of the vowels of Jemez, a Kiowa–Tanoan language spoken northwest of Albuquerque. The vowel system consists of six short vowels /i e æ ɑ o (barred eye)/ and six corresponding long vowels. For each long and short vowel, except /e/ and /ee/, there is a corresponding nasal vowel. The principal data for the analysis consists of repetitions of words containing each vowel pronounced by a single speaker in isolation and in sentences. Some data from another speaker and from other word contexts is also used. The vowels /e o (barred eye)/ are realized at the same heights, substantially closer to /i/ than to /æ ɑ /. The vowels are monophthongs, except for /e/ and /ee/, which have rising offglides. Long and short vowels do not differ significantly in quality. Nasal vowels are higher than corresponding oral vowels, contrary to cross-linguistic tendencies. Vowels are raised after the labialized consonants /Φw kw w/ and the palatalized consonants /(sh) kj kjh kj’ j/, but differences between the two contexts suggest that separate processes are involved. [Supported in part by a UROP grant from the University of Colorado.]