bluuebunny/crossref_metadata_2025 huggingface dataset:
An exploratory study of community noise levels in the city of Lima.
Authors: Jiménez-Dianderas Carlos R. , Rivas-Tejeda Iván F.
Published: October 2005

Lima, the capitol city of Perú, a metropolis with more than 6 million people, has had in the last 30 years a sudden, explosive, and unsettled growth. Consequently, the city is always attacked by an endless number of noise sources. The nonacception of requirements for acoustic planning has caused noise producer activities to be mixed in with buildings requiring a quiet sonic environment. This study analyzes the main community noise sources and their levels: traffic and transportation noise, aircraft noise, and industrial noise. The noise pollution levels obtained, which were calculated through theoretical formulas and empirical methods, are plotted in noise maps of the metropolitan area of Lima. Unfortunately, in Peru there are no acoustical research centers or laboratories in acoustics; nor are there professional researchers in acoustics. The results of this research allowed comparison of the average levels calculated, around 88 dB in downtown, in regard to requested noise levels. The lack of legislation, acoustic research, and people’s knowledge about noise damage indicates the progressive increase in the noise levels, almost 1 dB per year, in the near future.
A proposal for a new Canadian regulation on noisy toys.
Authors: Leroux Tony D. , Laroche Chantal
Published: October 2005

The Canadian Federal Act prohibiting sale of hazardous products limits the sound level emitted by toys to 100 dB. The scientific literature shows that this criteria is not safe for children regarding the risk of acquiring hearing loss. Based on a safe limit of 75 dBA, more than 85% of the toys available on the Canadian market are not safe and may induce hearing loss and other adverse effects on the long term. There is evidence that this situation is probably the same or even worse in the United States. Toys emitting noise from an explosive source, which can be very harmful to hearing after one short exposure, are not covered by the Canadian Act. In fact, the actual Act authorizes the sale of hazardous noisy toys that may contribute to some extent in producing hearing loss in children. Two factors can explain the inefficiency of the Canadian Act: The actual limit for sound level is too permissive and the regulation does not include a precise and specific method for determining the sound level produced by a given toy. Based on a review of literature and previous studies done by the Groupe d’Acoustique de l’Université de Montréal, a new regulation and a measurement method have been proposed to Consumers and Corporate Affairs Canada in order to correct those deficiencies. The limit for sound level has been set to 75 dBA, a world-wide accepted safe limit, regardless of the exposure duration. Concerning the method of measurement, the Canadian Standard Association standard on noise emitted by small appliances [CSA Z107.71-M1981] has been proposed. This proposal will be discussed. A comparative review between the American and Canadian legislations on noisy toys will be presented. [Work done for the Quebec Consumers Association and granted by Consumers and Corporate Affairs Canada.]
Discrimination of redundant spectral-temporal cues. II. Level and duration effects.
Authors: Monahan Caroline B. , Espinoza-Varas Blas
Published: October 2005

The effectiveness of stimulus level and duration on listeners’ ability to attend to and discriminate redundant increments in frequency and duration of pure tones is studied. The stimuli comprised pairs (T1, T2) of 1500-Hz tone bursts separated by a 60-ms silent interval. Sensation level was either 66 dB SL for both tones, or one of the tones was attenuated 25 or 40 dB relative to the other 66-dB SL tone. Tone duration was either 80 ms for both bursts, or T2 was two or three times longer than the 80-ms T1 burst. In the same three-interval, 2AFC task described in the above paper, listeners discriminated a ‘‘standard’’ pair of tone bursts from a ‘‘comparison’’ pair containing increments in the duration of T1 and/or in the frequency of T2. Data were obtained for eight highly trained listeners with normal hearing sensitivity. In three listeners, better discrimination performance was obtained for the increment occurring in the louder or longer burst. In four other listeners, tone level and duration had little or no effect on discrimination of either kind of increment. One listener failed to discriminate both increments in practically all conditions. Another source of interindividual variability is the listener’s ability to shift attention from one kind of increment to the other. [Work supported by OCAST Grant HSO-005 and Presbyterian Health Foundation.]
Vibration and sound radiation of complex plates: A variational approach.
Authors: Berry Alain , Nicolas Jean
Published: October 2005

Current analytical methods for predicting the sound radiation from finite structures are usually incapable of handling complex boundary conditions along the contour of the structure or mechanical elements added on the surface of the structure, such as localized masses, localized stiffnesses, stiffeners. Yet, such parameters significantly affect the vibroacoustic behavior in practice and should be retained when evaluating practical means of passively reducing the structural radiation. An analytical method is proposed to study the vibrations and sound radiation of baffled rectangular plates showing the above elements of complexity. The method is based on a variational formulation of the invacuo structural vibrations, which allows energy contributions of different mechanical elements to be calculated independently. The selection of a set of Ritz trial functions compatible with the geometric boundary conditions brings the method amenable to computation of the displacement response as a solution of a linear system of equations, as well as of the radiated sound as a combination of simple Fourier transforms. The method is shown to combine reasonable times, versatility, and computation precision. Numerical results illustrate the effect of the boundary conditions of the plate, added mass, added stiffeners of complex shape. Comparisons with BEM calculations and with experiments are also presented.
The accuracy and computational efficiency of the method of wave superposition for the computation of acoustic fields.
Authors: Fahnline John B.
Published: October 2005

The method of wave superposition is a numerical method for calculating the radiation from arbitrarily shaped bodies. The main advantage of the method is that the accuracy of a superposition solution can be assessed by comparing the body’s specified normal surface velocity with that calculated using the method of wave superposition. While this method also suffers from the same nonuniqueness problems as other methods, this self-checking procedure will indicate if a particular solution is inaccurate, thus giving an effective way of alleviating the problem. The computing time and memory requirements depend on the size of the system of linear equations generated by the method of wave superposition. The size depends on the complexity of the surface velocity, the complexity of the structure’s shape, the required solution accuracy, and the frequency. A certain amount of computational effort is also required in order to check the accuracy of a superposition solution. An example will be solved using the method of superposition to illustrate the process.
Acoustic radiation and scattering from shells of revolution using finite element and boundary element methods.
Authors: Stepanishen Peter R.
Published: October 2005

The use of modal methods to determine acoustic transient and harmonic radiation and scattering from fluid loaded shells of revolution will be reviewed. Using such methods the velocity field of a fluid loaded shell is first expressed as an invacuo modal vector expansion where the modes are determined either analytically for simple structures or via finite element methods for more complex structures. Boundary element or other methods are subsequently used to evaluate mode-dependent acoustic radiation impedances and impulse responses which account for the coupling of the fluid. In contrast to the harmonic problem which results in sets of algebraic equations for the coefficients of the modal expansion, the transient problem results in sets of coupled time-dependent convolution integral equations for the time-dependent coefficients. Our experience in solving both two- and three-dimensional radiation and scattering problems using modal methods will be reviewed. Numerical results for a wide variety of two- and three-dimensional radiation and scattering problems will be presented. In particular results will be presented and discussed for cylindrical, spherical, and spheroidal shells.
A new formulation for the vibrations and sound radiation of fluid-loaded plates with elastic boundary conditions.
Authors: Berry Alain
Published: October 2005

This communication considers the dynamic response and acoustic radiation of baffled rectangular plates elastically restrained against deflection and rotation along the four edges, and exposed to a half-space of dense fluid. Classical methods using invacuo plate eigenfunctions to formulate the fluid/structure coupling are limited to the simply supported case and lead to considerable difficulty, both theoretical and numerical. The proposed method employs a variational formulation of the structural motion and a minimization process over a subspace of suitable displacement functions. The selection of simple polynomials to generate this subspace is shown to have many advantages: (i) It permits an analytic solution of both the resistive and reactive components of the plate’s radiation impedance; (ii) it furnishes a natural decomposition of the radiator in monopôles, dipoles, ..., 2n upôles; and (iii) it decreases the computation cost and increases the generality of the problem addressed, as compared to available methods. The details of the formulation will be exposed and preliminary results will be shown. [Work supported by the Defence Research Establishment Atlantic Contract OSC 90-00409-(011).]
Wave analysis of the forced vibration of a finite elastic shell in vacuum.
Authors: Borgiotti Giorgio V. , Rosen Erik M.
Published: October 2005

The vibrational response of a circular cylindrical shell of a finite length excited by a point force of arbitrary orientation is studied by using wave techniques and the state vector formalism. Because of the geometric symmetry both the point excitation and the resulting vibrational response can be decomposed into Fourier circumferential components. The forced vibration is expressed as a linear superposition of ‘‘waveguide modes’’ with different circumferential numbers both propagating and attenuating. State vector techniques are used to identify the ‘‘reflection matrices,’’ characterizing for each circumferential number the linear relationship between the complex amplitudes of the waves ‘‘ingoing’’ to and ‘‘outgoing’’ from the end terminations. The discontinuity condition at the point excitation provides the last set of equations needed for the complete identification of the vibrational response. The particular case of terminations consisting of rigid disks having mass and moving as rigid bodies is discussed in detail. Numerical results are presented. Because the approach is essentially analytical, the computational complexity is substantially reduced with respect to purely numerical methods, and largely independent of the cylinder length. [Work supported by Naval Research Laboratory.]
The interlingual identification of Spanish and English vowels.
Authors: Flege J. E. , Munro M. J. , Fox R. A.
Published: October 2005

Spanish/English bilinguals and English monolinguals (30 each) rated pairs of vowels separated by 1.2 s on a nine-point scale. The pairs consisted of two Spanish vowels (drawn from one of three tokens each of /i/, /e/, /a/), two English vowels (tokens of /i/, /i/, /ei/, /ε/, /æ/, /Λ/, /α/), or one Spanish and one English vowel. Both auditory and phonetic factors influenced the ratings. Native Spanish subjects judged pairs consisting of two Spanish vowels to be more dissimilar than the English subjects; conversely, the native English subjects judged pairs of English vowels to be more dissimilar than the Spanish subjects. As expected, both the Spanish and the English subjects judged pairs of vowels that were distant in an F1–F2 space to be more dissimilar than pairs of vowels that were closer together. The Spanish subjects seemed not to distinguish phonetically certain pairs of English vowels (e.g., (/i/–/i/, /α/–/Λ/)) and thus to have rated them as more similar than the English subjects. The study provided little evidence that the Spanish subjects−even those experienced in English−were developing phonetic categories for English /i/ or /æ/. It did provide evidence, however, that the Spanish subjects were learning to distinguish /ε/ from Spanish /e/ (which has an [ε] allophone). As expected, given the larger number of vowels in English than Spanish, the best MDS solution involved more dimensions for the English than the Spanish subjects (three versus two). Spanish subjects who pronounced English well gave greater weight to F1 formant movement than subjects who pronounced English poorly. They also judged pairs of English vowels to be more dissimilar than the nonproficient subjects, suggesting a possible auditory perceptual basis for individual differences in L2 speech learning ability. [Supported by NIH.]
Assessing accentedness in English vowels produced by native speakers of Arabic.
Authors: Munro Murray J. , Nearey Terrance M.
Published: October 2005

This study examines the relationship between the acoustic properties of non-native vowel productions and the extent to which native speakers perceive the vowels to be accented. Measurements were made of F1 and F2 frequencies, F1 and F2 movement, and duration in vowels produced in /bVt/ and /bVd/ contexts. Significant differences of some sort were observed between native and non-native groups on every vowel. A panel of native English judges rated a subset of the front vowel productions for accentedness. A multiple regression analysis was then used to explore the relationship between the acoustic properties and the listeners’ ratings. Clear relationships were found between some of the predictors (F1 frequency, formant movement, and duration) and the accentedness scores. The results of the measurement study and the regression analysis will be discussed with attention to individual differences among the speakers. [Work supported by SSHRC and NIH Grant No. DC00257.]
Identification of vowels produced by various talkers.
Authors: Nabelek Anna K. , Czyzewski Zbigniew
Published: October 2005

Differences in identification of vowels in degraded listening conditions, produced by various talkers, were investigated. Fifteen American monophthongs and diphthongs (vowels) were produced by six male talkers in a /b–t/ context. Each syllable was produced five times. The order of production of the 75 syllables was random. All vowels were highly identifiable in a quiet listening condition as assessed by two speech pathologists. Confusion matrices for the vowels degraded by either speech-spectrum noise (S/N=0 dB) or reverberation ( T=1.5 s) were collected with two groups composed of 20 normal-hearing and 20 hearing-impaired subjects. In each group, there were 100 responses for each vowel. Vowel identification scores depended on talkers, listening conditions, and type of subjects, indicating a relationship between production of the vowels and their vulnerability to degradations. Errors for selected vowels will be discussed. [Research supported by National Institute of Deafness and Other Communication Disorders.]
Dynamic specification of coarticulated German vowels.
Authors: Strange Winifred , Bohn Ocke-Schwen
Published: October 2005

To test the generality of the finding that American English (AE) vowels are specified by dynamic information defined over syllable onsets and offsets taken together, the perception of 14 Northern German vowels produced in /d–vowel–t/ syllables in a carrier sentence was examined. Separate groups of native German speakers were tested in four conditions: (1) silent-center syllables, in which vocalic nuclei were attenuated to silence, leaving syllable onsets and offsets in their appropriate temporal relationships; (2) fixed duration silent-center syllables, in which silent intervals were adjusted so that all syllables were the same duration; (3) initials, in which only syllable onsets remained; and (4) finals, in which only syllable offsets remained. Silent-center syllables were identified very well (90% correct). As predicted, performance on fixed duration silent-center syllables was significantly poorer (70%), although still better than on either initials (45%) or finals (49%). These data corroborate those reported previously for AE vowels and demonstrate the perceptual importance of dynamic spectral information. Acoustical analysis is under way to examine similarities and differences in the dynamic specification of German and AE vowels. [Work supported by NIDCD.]
Rate normalization is not necessary for the identification of coarticulated vowels.
Authors: Clarke William D. , Stack Janet W. , Evans Alba R. , Strange Winifred
Published: October 2005

Consonant–vowel–consonant syllables, excised from a carrier sentence produced at normal and rapid rates, were presented to subjects in a mixed rate condition (normal and rapid syllables presented in random order) and a blocked rate condition (normal and rapid syllables presented in separate subtests). In the mixed rate condition, subjects made errors in judgments of speakingrate on 25% of the trials (50%=chance). Errors were predictable from absolute syllable durations. Nevertheless, identification of the intended vowels in the mixed rate condition (by an independent group of subjects) was only slightly less accurate than in the blocked rate condition (93% vs 98% correct) and in a control condition in which the syllables were presented in the original sentences (98% correct vowel identification and 98% correct rate judgments). These results argue against the hypothesis that perceivers ‘‘normalize’’ for perceived differences in speaking rate prior to identifying coarticulated vowels. Acoustical analysis of this corpus revealed that ‘‘vowel-intrinsic spectral information’’ remained relatively unchanged across speaking rate and consonantal context, while vowel durations varied systematically with speaking rate. [Work supported by NIDCD.]
On the linear dependence of temperature structure and acoustic backscatter at the western edge of the Gulf Stream using optimal least-squares filtering.
Authors: Jech J. Michael , Clay C. S. , Stanton T. K.
Published: October 2005

A quantitative approach, Wiener optimal least-squares filtering, was used to determine the linear correlation between physical and biological structure along the western edge of the Gulf Stream. Temperature, vertical temperature gradient, and diurnal effects on the vertical distribution of biological sound scatterers in the top 200 m of Gulf Stream frontal regions were studied. Coordinated temperature and 70- and 120-kHz acoustic backscatter data were obtained 105 km northeast of Cape Hatteras along a transect perpendicular to the Gulf Stream front. The data show that temperature is a better predictor of 70- and 120-kHz scattering than is temperature gradient at the fine scale. Diurnal differences suggest biological influences can override temperature preferences by nekton and zooplankton. A universal filter is developed to determine a consistent temporal relationship between acoustic scatterers and temperature structure. Application of this technique is a unique means of quantitatively determining relationships of acoustic scatterers to physical structure in the ocean.
Integrating noise control engineering into the design process.
Authors: Brittain Frank H.
Published: October 2005

There are challenging technical issues and uncertainties in designing a power plant to meet the noise level criteria. Noise level criteria must be established, which include regulations and criteria established during permitting. Noise levels must be predicted and controls selected and procured. While this is often challenging, it is the easy part of the job. The difficult part of the job is ensuring the controls selected are practical and integrating them into the design of the plant. The noise controls must be cost effective and maintainable as well as having an acceptable total cost, life expectancy, and impact on the operation of the plant. Many noise control engineers are not familiar with power plants−design or operation−and how to interface with the design team. While this paper briefly reviews how noise controls are selected and procured, the primary emphasis is on practicality, interfacing with the design team, and integrating noise controls into the design. Probably the key elements are planning and working directly with the project team. Typical problem areas and how to avoid them are discussed.
Specifying acoustical performance of turbine exhaust mufflers.
Authors: Keith Reginald H.
Published: October 2005

In response to surging demand for increased electrical power, utilities and independent power producers are evaluating and installing large numbers of gas turbine driven generators. Often these are sited close to existing developments and have to meet stringent environmental guidelines. The primary noise source of gas turbine generators is generated by the power turbine and radiated from the exhaust stack. Most often this is controlled by use of a muffler and/or heat steam recovery boiler (HRSG). Due to the increasingly restrictive noise requirements and the desire for accountability, there is greater need to specify and evaluate the installed performance of gas turbine exhaust mufflers. The most appropriate performance specification, for the evaluation of mufflers, is ‘‘insertion loss’’ despite the difficulties that currently exist with its measurement and determination.
Nonlinear distortion of surface waves in an isotropic solid.
Authors: Zabolotskaya E. A.
Published: October 2005

The process of nonlinear propagation and distortion of Rayleigh waves in an isotropic solid is investigated theoretically. A set of coupled equations for the harmonic amplitudes is derived by means of Hamiltonian formalism. A time domain evolution equation is also derived for the disturbance on the surface of the solid. Numerical results for plane and circular Rayleigh waves are presented for an initially monochromatic wave that propagates in steel. It is shown that the horizontal component of the particle velocity wave forms a shock profile, while the vertical component forms a pulse. Finally, the governing equations are generalized to include diffracting nonlinear Rayleigh wave beams. a)On leave from the General Physics Institute, USSR Academy of Sciences, 38 Vavilov Street, 117942 Moscow, USSR.
Choked-jet edge-tone experiments, Continued.
Authors: Powell Alan , Lin Dan
Published: October 2005

Edge tones occur continuously from somewhat below choking, at pressure ratio R=1.89, to somewhat above R=4.1, for a 17.7-×3.7-mm nozzle and 8° wedge. In marked contrast to the classical edge tone, the behavior is complex with varying characteristics. For 2.22≤R≤2.43 and edge-to-nozzle distance 2≤h/δ≤17 distance (δ=3.7 mm) many scattered edge tones occur. Around R=2.50 with 3.1≤h/δ≤20, two prominent frequency bands occur, the dominant tone switching back and forth; one band is near screech frequency. This band alone predominates for 2.56≤R≤3.04, and is alone for 3.18≤R≤4.0. Nine stages occur, with 2≤N≤10 and p=0.33 (N+p is the number of cycles in the feedback loop). The jet instability convection speed varies between 0.4UFE and 0.55UFE (UFE is the fully expanded jet velocity), averaging 0.47UFE. Schlieren photographs show that for R<2.36 and 2.9≤ h/δ≤3.4, the jet instability mode and the associated sound fields are symmetric. [Work supported by Texas Advanced Research Program.]
The effect of intensity increments on decrement detection.
Authors: Sheft Stanley , Yost William A.
Published: October 2005

A previous study [S. Sheft and W. A. Yost, J. Acoust. Soc. Am. 89, 1913(A) (1991)] indicated that decrement detection thresholds are affected by sudden level changes unrelated to the decrement. The present study measured the time course of the effect of an intensity increment (pedestal) on decrement detection with wideband noise. In one set of conditions, the increment followed the decrement with the temporal separation between the decrement offset and the increment onset varying between 0–80 ms. In another set, the decrement occurred within the pedestal with the decrement onset 0–160 ms from the pedestal onset. Increment size ranged from 3–12 dB. Compared to thresholds obtained without the increment, the effect of the increment depended on the temporal separation between both the stimulus and pedestal onsets and the decrement onset. With brief separations, performance improved across all increment levels. Consistent with interference due to the neural onset response, the introduction of a silent gap before the pedestal eliminated the beneficial effect of the increment. However, the effect of the increment extended out to 160 ms, past possible involvement of the neural onset response and short-term adaptation. [Work supported by NIDCD and AFOSR.]
Spectral-shape discrimination as a function of stimulus duration.
Authors: Dai Huanping , Green David M.
Published: October 2005

Thresholds for discriminating changes in the spectral shape of complex tones (profile analysis) were measured as a function of stimulus duration. The observer discriminated a standard spectrum, in which all components were equal in level, from a standard-plus-signal spectrum, in which the level of some components was altered. The overall level of the stimulus was randomized over a 20-dB range across presentations. An adaptive, maximum-likelihood procedure was used to measure the threshold (signal-to-standard ratio for 94% correct) in a two-alternative, forced-choice task. The results from five observers show that, for complexes composed of closely spaced components, the threshold decreases by 10 to 20 dB as duration is increased from 10 to 100 ms and remains constant as duration is further increased to 1000 ms. For a complex composed of widely spaced components, however, the threshold is nearly constant as duration is changed from 10 to 1000 ms. While some of these results are consistent with the idea that the critical band is wider at stimulus onset, other data are inconsistent with this view. [Work supported by NIH and AFOSR.]
The relation between auditory grouping and comodulation masking release.
Authors: Grose J. H. , Hall J. W.
Published: October 2005

The feature of coherent amplitude modulation across frequency, which gives rise to the phenomenon of comodulation masking release (CMR), is also considered to be a cue for auditory grouping. This commonality raises the question of whether it is a prerequisite for CMR that the correlated noise bands comprising the masker be grouped together. The present study measured signal threshold in the presence of correlated bands of noise under conditions designed to discourage the fusion of the noise bands. In the first set of conditions, the onset/offset synchrony between the noise band centered on the signal and the comodulating flanking bands was manipulated. The results indicated that the CMR measured when the on-signal band and flanking bands were gated synchronously was largely eliminated with onset/offset asynchronies of 50–100 ms (on-signal band beginning before and ending after the flanking bands). In the second set of conditions, signal threshold in the on-signal band was measured in the presence of a single flanking band, either with or without a background harmonic complex that included in its harmonic series the center frequency of the flanking band, but not the on-signal band. No consistent effect of harmonicity was observed. [Work supported by AFOSR.]
Inferring bottom roughness from multi-narrow beam sonar amplitude statistics.
Authors: Tyce Robert , Talukdar Kushal
Published: October 2005

This paper describes recent attempts to reconcile acoustic backscatter theory with sonar backscatter measurement obtained using a sea beam multi-narrow beam sonar system with special amplitude data acquisition hardware. A backscatter model developed for data from this sonar based on the Helmholtz–Kirchhoff formulation of scattering theory is described, where the seafloor is considered to be an irregular surface described by rms roughness and by correlation distances in the lateral dimensions. Estimation techniques were developed to determine parameters such as roughness from an optimal fit of model parameters to scattering strength versus angle measurements derived from the sonar returns. Attempts to match the model to actual measurements were very successful, but only after adapting the model for subbottom scattering. Examination of probability density functions for peak echo statistics was also undertaken, with encouraging results for seafloor roughness estimation.
Microtopographical roughness of oscillatory ripple fields.
Authors: Briggs Kevin B.
Published: October 2005

Large-scale bottom topography measurements are being made with a number of sonar mapping systems, yet little is known of the small-scale relief of the seafloor. High-resolution roughness height measurements of the seafloor have been made using stereo photogrammetry. Roughness power spectra are generated from closely spaced height measurements in order to develop a valid stochastic model for fine-scale seafloor topography and, ultimately, to predict high-frequency acoustic scattering from the seafloor. The anisotropy inherent in an oscillatory ripple field gives a peculiar signature to the power-law decay of the roughness spectrum. Roughness power spectra are presented for the crest to crest and along-strike directions at four shallow-water sites. Comparisons of periodograms derived from storm-generated ripples off the Pacific, Atlantic, and Gulf of Mexico coasts show a strong dependence on grain size. Grain size constrains the possible ripple morphologies through grain-to-grain interactions characteristic of silt, fine sand, or coarse sand. Predictably, values of correlation length estimated from the spectra for the two orientations examined in the ripple fields are indicative of sediment type.
Bottom roughness of the Mid-Atlantic Ridge flank observed in SeaMARC II sidescan sonar and sea beam multibeam bathymetry.
Authors: Tucholke Brian E. , Reed Thomas B. , Lin Jian
Published: October 2005

Existing sea beam bathymetry along the Mid-Atlantic Ridge (MAR) axis, and SeaMARC II sidescan-sonar images along Kane Fracture Zone, have been analyzed to characterize patterns of bottom roughness that may be expected in the ONR acoustic reverberation corridor. Fault patterns along the MAR axis were determined in slope maps calculated from gridded beam-point data, and along Kane Fracture Zone they were mapped from sidescan-sonar images geometrically corrected for seafloor depth variations. Faults occur primarily in three orientations within well-defined provinces. MAR-parallel faults are restricted to the interior of MAR spreading segments, dip toward the spreading axis, and commonly have large throw (≳100’s m) and steep dips (up to 50°). Smaller, oblique to curvilinear faults occur at boundaries between spreading segments. MAR-orthogonal faults are restricted to fracture-valley crust generated in the large-offset Kane Transform Zone. Hummocky volcanic edifices and volcanic cones appear intermittently within spreading segments.
Active reverberation time control: A sound intensity based approach.
Authors: Stanzial Domenico , Pedrielli Francesco
Published: October 2005

The control of reverberation time is certainly one of the outstanding problems in Architectural Acoustics. Besides the classical techniques, some control techniques using electroacoustical devices for artificial reverberation are available today. Commonly, these devices merely supply the ‘‘reverberation’’ to an enclosed space so as to simulate the sound queue phenomenon instead of actually controlling the proper reverberation time of the room in such a way to make it longer, but in this case, even shorter. This paper presents an intensity-based approach to the reverberation time control using the total transfer function of the acoustic system constituted by the room and by the control device itself. As the energy transfer function of an enclosed space is simply related to the reverberation time [D. Stanzial, J. Acoust. Soc. Am. Suppl. 1 88, S185 (1990)], an alternative criterion for the local active control of the reverberating acoustic field is readily obtained.
A proposal for audibility weighted acoustic measures−Parts I and II.
Authors: Griesinger David
Published: October 2005

Part I: Current acoustic measures such as reverb time (RT), clarity (C80), early decay time (EDT), gain (G), and early lateral fraction (LF or ELF) attempt to describe the musical acoustics of halls. However, the predictive value of these measures is considerably less than desired, with halls that measure the same sounding very different and vice versa. A set of psychoacoustic experiments will be presented that enumerates the audibility of reflected energy as a function of direction, time, and frequency. Data from these experiments indicate that it is useful to separate reflected energy into a lateral component and a medial component. The lateral component is perceived with greater sensitivity than the medial component, and tends to dominate both the sense of reverberance and spatiality. The medial component is found to be a more effective masker of both musical clarity and speech clarity than the lateral component. These data will be used to develop a proposal for a set of acoustic measures that uses weighted sums of the medial and lateral energy to more accurately reflect the perceived reverberance of halls. Measured data from a few halls will be presented.
On the performance of the overlap-correlator synthetic-aperture technique
Authors: Edelson Geoffrey S. , Sullivan Edmund J.
Published: October 2005

The overlap-correlator technique of passive synthetic-aperture array processing [S. Stergiopoulos and E. J. Sullivan, J. Acoust. Soc. Am. 86, 158–171 (1989)] is investigated. This method of providing an effective aperture greater than that of the physical array utilizes phase correction factors that are calculated by correlating overlapping space samples of the acoustic signal from successive measurements of the moving towed array. Given the criterion of minimizing the effect of the signal-to-noise ratio (SNR) on the phase correction factor error while achieving a fixed effective aperture length, the optimal overlap in number of hydrophones between these two successive measurements is derived. The conditions under which the calculated phase correction factor is equivalent to that of the desired phase correction factor are also studied.
A model of the sound generated by breaking waves
Authors: Loewen M. R. , Melville W. K.
Published: October 2005

The sound produced from a single bubble, oscillating at its breathing mode frequency, and the bubble size distribution are used to model the sound produced by breaking waves. The data of Medwin and Daniel [J. Acoust. Soc. Am. 88, 408–412 (1990)] is used to evaluate the performance of the model. The model generates a damped sinusoidal pulse for every bubble formed, as calculated from the bubble size distribution. If the range from the receiver to the breaker is known then the only unknown parameters are ε, the initial fractional amplitude of the bubble oscillation, and L, the dipole moment arm. It is found that if the product ε×L is independent of the bubble radius the model reproduces the shape and magnitude of their measured sound spectrum accurately. The success of this simple model implies that the inverse problem (calculation of the bubble size distribution from the sound power spectrum) may be solved without the need to explicitly identify individual bubble pulses in the acoustic time series.
A rotating ultrasonic waveguide for studying acoustic radiation forces on particles
Authors: Whitworth Glenn , Nyborg Wesley L.
Published: October 2005

An apparatus was designed to allow a suspension of biological cells to be subjected to a well-defined, 160-kHz standing ultrasonic field while being viewed through a stereo microscope. Cell positions were recorded either photographically or by means of a video camera. The chamber cavity, which has a square cross section and pressure-release walls, acts as a single-mode acoustic waveguide. The well-defined single-mode field is achieved through use of a special design involving air-filled chamber windows. Aqueous metrizamide solution is used to fill the ultrasonic chamber because it has a unique combination of properties, including low viscosity, low osmolarity, and high density. The chamber rotates about its axis (whose inclination can be varied) producing the centripetal force necessary to contain the buoyant cells in the axial region. Observations were made on stroboscopically illuminated suspensions both of latex microspheres and of red blood cells. The particles formed groups at half-wavelength intervals along the rotation axis near positions of acoustic pressure–amplitude minima. The position and shape of these groupings are explained by a scalar-potential theory for noninteracting particles that considers gravitational, rotational, and acoustic radiation forces on the particles.
A new ray-tracing algorithm for arbitrary inhomogeneous and moving media, including caustics
Authors: Boone Marinus M. , Vermaas Edward A.
Published: October 2005

In this paper, a new ray-tracing algorithm is presented that can handle arbitrary temperature and wind profiles in horizontal and vertical directions. This is accomplished by following a ray tube instead of a ray path. The algorithm is a direct finite difference implementation of the ray-tracing equations for arbitrary temperature and wind profiles. A computer model has been made, based on this algorithm. Special attention is given to the shortcomings of ray theory in the case of caustics, which are compensated for by appropriate phase and amplitude corrections of the computed ray tubes. The method is well suited to study the effect of locally heated areas on the sound propagation, as occurring on for instance petrochemical plants. Numerical experiments show that the proposed ray-tracing method and the relatively expensive, but accurate, wave field extrapolation method agree very well in many cases.
Reflection of incident pressure waves by ribbed panels
Authors: Maidanik G. , Dickey J.
Published: October 2005

The definitions of the reflection coefficients, in the absence of ribs and due to ribs, of an incident pressure wave on a plane at the surface of a ribbed fluid-loaded panel are defined, examined, and computed. The incident pressure wave is described by a plane wave and by a collimated beam. The results of representative computations are displayed. Through these displays, some aspects of the influence on the reflection coefficients caused by changes in the parameters that describe the ribbed panel, the fluid loading, and the incidence are investigated. These aspects include wave-number aliasings and symmetries in some of the terms and factors that compose the expressions for the reflection coefficients; the wave number of concern lies across the ribs. Aliasings are present, however, only when the separations between adjacent ribs are conditioned to be equal. Moreover, in some of these aliased terms and factors, symmetry is present only when the incidence obeys specific conditions. Disturbing these conditions tends to spoil the aliasing and/or the symmetries in these terms and factors. It is shown, however, that the aliasing and symmetry properties are invariant to changes in the parameters that describe the ribbed panel and/or the fluid loading to which it is subjected. The role that the phenomenon of pass and stop bands (bands in reference to the frequency domain) plays in the reflection properties of ribbed fluid-loaded panels is of particular interest here. It is illustrated that in the frequency ranges of pass bands, diffraction orders and aliasings tend to fade, and in the frequency ranges of stop bands they are enhanced. Fluid loading subdues the pass and stop bands; however, even substantial fluid loading does not eliminate these bands. Finally, the relationship between the reflection coefficients defined on the surface of the panel and on a control surface placed in the farfield is formulated and discussed.
Transient wave response of the violin body revisited
Authors: Molin Nils-Erik , Wåhlin Anders O. , Jansson Erik V.
Published: October 2005

In this investigation, the dispersive, transient wave propagation field of the top plate of a complete violin excited by a mechanically induced pulse at the top of the bridge is presented. A similar investigation has previously been made for excitation parallel with the top plate and is now completed with excitation perpendicular to the plate. From presented interferograms, it is seen that the top plate initially deforms in a nonsymmetric two-pole with centers at the two bridge feet. Shortly thereafter the two poles (valleys) are joined into one, but after 0.30 ms the displacement is still nonsymmetric with maximum motion at the bridge foot closest to the excitation point. From the measurements it can be concluded that for excitation parallel with the top plate, the plate between the f-holes acts mainly as a dipole, but with excitation perpendicular the same part acts mainly as a monopole. Thus the excitation of the top plate when playing the violin depends on the angle of the bow in relation to the top plate and should influence the tone character.
Vibrations of pyroelectric plates
Authors: Paul H. S. , Raman G. V.
Published: October 2005

Symmetric and antisymmetric wave propagations in a pyroelectric plate of crystal class 2 are considered. The frequency equations are derived when the surfaces of the plate are traction free and completely coated with electrodes that are shorted and thermally insulated. The frequency equations are also deduced for crystal classes 2 mm and 6 mm. Numerical work has been carried out for piezoelectric polyvinylidene fluoride belonging to the 2-mm class as heat conduction coefficients and specific heat capacity are small compared to other material constants of polyvinylidene fluoride. Barium titanate ceramic is considered for numerical calculation to illustrate the effect of pyroelectricity. Results are tabulated and the dispersion curves are also given.
Acoustic intensity measurement in the presence of mean flow with application to noise measurements in a wind tunnel
Authors: Comparin Robert J.
Published: October 2005

Wind tunnels are frequently used in the experimental study of moving sound sources. Although a number of techniques are currently used to determine the radiation characteristics of a sound source in a wind tunnel, they are usually limited by a lack of explicit directional information and/or a requirement that measurements be made in a free field. The multiple microphone acoustic intensity technique provides explicit directional information and can be used to measure sound fields in the near field of a source and, therefore, represents a possible alternative to the current measurement techniques used in wind tunnels. The formulations currently used to measure acoustic intensity are limited to either zero flow or plane waves in a one-dimensional mean flow. A new formulation has been developed that extends the method to the case of a spherically spreading wave in a uniform one-dimensional flow. Using an analytical simulation, the intensity distributions for a monopole and dipole source are studied. Initial results suggest that the formulation is suitable for the analysis of compact sources. Although a more detailed study will be required to develop a practical measurement tool, this study provides additional insight into the problem of intensity measurement in the presence of mean flow.
Aging and consonant errors in reverberation and noise
Authors: Helfer Karen S. , Huntley Ruth A.
Published: October 2005

Identification accuracy and error patterns on the City University of New York (CUNY) Nonsense Syllable Test were examined for three groups of subjects (young normal-hearing, older hearing-impaired, and older with minimal hearing loss) listening binaurally in four conditions (quiet, noise, reverberation, and reverberation plus noise). Percent-correct performance was analyzed for stimuli aggregated by place and manner categories, and error patterns were examined via analysis of variance and correlational procedures. Results suggested that some of the difficulty experienced by the older subjects was related to amount of hearing loss, but a portion of the data could not be explained by elevated auditory thresholds. Confusion patterns also varied across listening conditions, especially for the nasal and semivowel stimuli.
Phase relations of jaw and tongue tip movements in the production of VCV utterances
Authors: Nittrouer Susan
Published: October 2005

A previous study by Nittrouer et al. [J. Acoust. Soc. Am. 84, 1653–1661 (1988)] found that the spatiotemporal relations between jaw and upper lip movements for speech were affected not only by the segmental structure of the utterance, but by stress pattern and rate of production, as well. Specifically, the angle on the vowel-to-vowel jaw cycle phase plane at which the upper lip began moving toward closure for an intervocalic consonant varied systematically and discretely with changes in vowel-cycle duration. The development of the x-ray microbeam has permitted the observation of these effects for gestures involving articulators other than the lips and jaw. In the present study, the onset of tongue tip movement for an intervocalic consonant was represented as an angle on the jaw cycle phase plane for vowel–consonant–vowel utterances. Although the tongue tip exhibited greater variability in its movement onset than the upper lip had, the relative phasing of tongue tip movement onset was also found to vary with jaw vowel-cycle duration: Any manipulation that shortened the jaw vowel cycle also served to reduce the phase angle at which the tongue tip began movement. This relation was not found to be continuous in nature, but rather a main effect of phonetic and nonphonetic factors.