bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaural correlation sensitivity
Authors: Culling John F. , Spurchise Matthew , Colburn H. Steven
Published: July 2002

Sensitivity to differences in interaural correlation was measured as a function of reference interaural correlation and frequency (250 to 1500 Hz) for narrow-band-noise stimuli (1.3 ERBs wide) and for the same stimuli spectrally fringed by a broadband correlated noise. d′ was measured for two-interval discriminations between fixed pairs of correlation values, and these measurements were used to generate cumulative d′ versus correlation curves for each stimulus frequency and type. The perceptual cue reported by subjects was perceived as intracranial breadth for narrow-band stimuli (wider image for lower correlation) and loudness of a whistling sound heard at the frequency of the decorrelated band for the fringed stimuli (louder for lower correlation). At low correlations, sensitivity was greater for fringed than for narrow-band stimuli at all frequencies, but at higher correlations, sensitivity was often greater for narrow-band stimuli. For fringed stimuli, cumulative sensitivity was greater at low frequencies than at high frequencies, but listeners produced varied patterns for narrow-band stimuli. The forms of cumulative d′ curves as a function of frequency were interpolated using an eight-parameter fitted function. Such functions may be used to predict listeners’ perceptions of stimuli that vary across frequency in interaural correlation. [Work supported by MRC and NIDCD Grant No. DC00100.]
Detection of Doppler-like signals
Authors: Ericson Mark A. , Feth Lawrence L.
Published: July 2002

Moving sounds induce a Doppler shift of frequency in direct proportion to a sound source’s velocity. Concurrent with the frequency change is a change in intensity related to the source’s velocity and distance from the listener. These simultaneous changes in frequency and intensity may be audible for any moving sound source. Jorasz and Dooley [Arch. Acoust. 21, 149–157 (1996)] modeled the physical effects of constant velocity motion on a sound source’s frequency and intensity as observed at a single point in space. Three linear trajectories of a sound source were simulated over headphones for different minimal distances between the moving sound source and observer. These minimal distances were 1, 10, and 100 m. An adaptive tracking procedure was used to determine detection thresholds for velocity induced changes in frequency and intensity. Intensity and frequency were varied independently as well as together. A series of experiments was conducted to test a perceptual model of these Doppler effects.
Modeling the vibration behavior of an induction motor
Authors: Wang Chong , Lai Joseph C. S.
Published: July 2002

With the advent of power electronics, variable speed induction motors are finding increased use in industries because of their low cost and savings in energy usage. However, the acoustic noise emitted by the motor increases due to switching harmonics introduced by the electronic inverters. Consequently, the vibro-acoustic behavior of the motor structure has attracted more attention. In this paper, considerations given to modeling the vibration behavior of a 2.2-kW induction motor will be discussed. By comparing the calculated natural frequencies and the mode shapes with the results obtained from experimental modal testing, the effects of the teeth of the stator, windings, outer casing, slots, endshields, and support on the overall vibration behavior are analyzed. The results show that when modeling the vibration behavior of a motor structure, the laminated stator should be treated as an orthotropic structure, and the teeth of the stator could be neglected. As the outer casing, endshields, and the support all affect the vibration properties of the whole structure, these substructures should be incorporated in the model to improve the accuracy.
Integration of acoustic cues in Spanish voiced stops
Authors: Feijóo Sergio , Fernández Santiago , Balsa Ramón
Published: July 2002

In Spanish, voiced stops in initial position usually show the presence of a voice bar before the release burst. In this study, the perception of word-initial voiced stops when the voice bar is removed is examined. Nine men and nine women pronounced 15 Spanish words in which the initial consonant was /b/, /d/, or /g/ in combination with the vowels /a/, /e/, /i/, /o/, /u/. Seventeen subjects with normal hearing heard the stops in two conditions: (1) whole voice bar + 102.4 ms of signal from burst onset; (2) 102.4 ms from burst onset. In condition (2), tokens were perceived as the correct stop, as its voiceless counterpart, or as an ambiguous signal. Removing the voice bar caused 37% of /b/ tokens to be classified as /p/; 41% of /d/s to be classified as /t/s ; and 19% of /g/s to be classified as /k/s. The change in voicing characteristics was significantly more marked for women. The results indicate that the integration of the voice bar with the burst and the vowel plays a relevant role in the perception of voicing in voiced stops, especially in women’s speech, smoothing the dynamic frequency characteristics of burst and vowel.
Timing effects on successive alveolar consonants in Swedish
Authors: Bannert Robert , Czigler Peter E.
Published: July 2002

The duration of a consonant is potentially affected by various factors related to the phonetic nature of the segment and its phonetic environment. The present study addresses the concurrent effects of prominence, syllable structure, and manner of articulation in intervocalic /s/+alveolar consonant /t, n, l/, and alveolar consonant+/s/ clusters in Swedish. Six real words, imbedded in a carrier sentence, were repeated five times with, and five times without, focal accent by ten native speakers of standard Swedish. Results show that the duration of a cluster, and the duration of its constituent consonants, are longer with focal accent than without focal accent. Consonant clusters with /s/ as the first member do not differ in duration from consonant clusters with /s/ as the second member. Clusters containing an alveolar stop are shorter than clusters with an alveolar nasal or alveolar liquid. The duration of /s/ is always longer than the duration of any adjacent alveolar stop, nasal or liquid. A number of interactions was found between prominence, cluster structure, and manner of articulation, indicating clear differences between the patterns of cluster internal timing for the investigated cluster pairs. These differences will be presented, compared with data on American English, and discussed.
The perception of place of articulation in three coronal nasal contrasts
Authors: Harnsberger James D.
Published: July 2002

Place of articulation contrasts which undergo perceptual assimilation are often difficult to discriminate if absent in a listener’s native language, as demonstrated by American English (AE) listeners with Hindi dental-retroflex stops [Polka (1991)] and Salish velar-uvular ejectives [Werker and Tees (1984)]. To see if this pattern generalizes to other manners of articulation, nasal contrasts (dental-alveolar, dental-retroflex, alveolar-retroflex) from three languages (Malayalam, Marathi, and Oriya), varying in talker, syllabic position, and vowel context, were presented to speakers of Malayalam, Marathi, and Oriya (control groups), and Bengali, AE, Tamil, and Punjabi in two tests: AXB discrimination, and identification with goodness ratings. AE and Bengali were chosen because both possess a single relevant perceptual category for these stimuli, an alveolar nasal. Tamil and Punjabi were selected for their two nasal categories, dental and retroflex. Of the contrasts tested, Malayalam dental-alveolar was the most challenging, with all non-native groups performing at-chance on the AXB test. The discriminability of the other contrasts proved to be highly dependent on the particular talker, syllable position, or vowel context, with performance ranging from at-chance to 98.4%. An acoustic analysis of the stimuli will also be provided.
Vowel perception by formant variation
Authors: Yang Byunggon
Published: July 2002

The acoustic parameters of six Korean vowels produced by a healthy male subject with normal hearing were analyzed to synthesize the six vowels by a formant synthesis method. The f0, amplitude envelopes, and the first six formant values were elaborately matched to the those of the original vowels. Then, F1 and F2 values of the synthesis file were modified by 50 Hz over and under the original values but not interfering with adjacent formants. F3 varied 500 Hz over and under the original values by 100 Hz to obtain 270 stimuli. Twenty male and female subjects in a quiet room listened to the original vowel followed by the corresponding synthesized one 0.5 s later and judged whether they sounded qualitatively ‘‘similar’’ or ‘‘different.’’ From the experiment, it was found that male subjects responded ‘‘similar’’ within the range of variance by an average of 163 Hz for F1, 415 Hz for F2; and 843 Hz for F3. Female subjects showed 40-Hz higher range than males. The ranges supported the nonlinearity of the human auditory scale in the speech sound. This suggests that the validity of exact formant frequency measurement varies according to frequency levels.
In-plane bistatic calculations of sub-bottom volume reverberation in shallow water
Authors: Ellis Dale D. , Hines Paul C.
Published: July 2002

A shallow-water reverberation model based on normal modes and ray-mode analogies has been previously developed [J. Acoust. Soc. Am. 97, 2804–2814 (1995)]. It was first developed for boundary scattering and recently extended to handle volume reverberation in both the water and sub-bottom. The volume scattering is formulated in terms of an empirical plane-wave scattering function, which depends on depth but which can also depend on the incident and scattered angles. Our first approximation for the volume reverberation is to choose the scattering to be isotropic, but to get a better approximation based on physical parameters, the in-plane bistatic scattering function of Hines is used [J. Acoust. Soc. Am. 99, 836–844 (1996)]. In this paper, calculations of shallow-water reverberation are made with the Hines scattering function used as input to the normal-mode model. Results are compared with reverberation assuming isotropic scattering in the bottom, as well as with reverberation due to bottom interface scattering using Lambert’s rule.
Analysis of laboratory measurements of sound propagating into an unconsolidated water-saturated porous media
Authors: Simpson Harry J. , Houston Brian H.
Published: July 2002

A series of measurements in the NRL shallow-water laboratory have been conducted to understand the propagation of sound into and within an unconsolidated water-saturated porous medium. The initial set of measurements was taken to quantify sound penetration as a function of incident angle and interface roughness and to identify the types of waves generated within the water-saturated sandy bottom. These investigations included two-dimensional synthetic array measurements for both a smoothed and a roughened interface. Additionally, above interface and buried source, one-dimensional synthetic array measurements were taken to investigate specifically the types of compressional waves generated within the sandy bottom. To complete the physical characterization of the wave speeds propagating in the bottom, measurements of the shear wave speeds have been made. These measurements provide a large data base for analysis to understand the physics of this sandy bottom, which consists of a 3.0-m-deep bed of a manufactured 212-μm mean diameter sand. Analysis of these measurements using Biot models and other fluid models is presented. In addition, analysis of enhanced sound penetration at shallow grazing angles due to a roughened interface is discussed. [Work supported by ONR.]
Perceptual magnet effect in corner vowels
Authors: Fox Robert Allen , Carahaly Lynn
Published: July 2002

In previous studies of speech perception, Kuhl and colleagues have provided evidence that the category goodness of a vowel influences the perception of that particular vowel—the perceptual magnet effect. These data indicate that listeners demonstrate poor discrimination of vowel tokens when they are close to the prototype vowel but good discrimination when the vowel is close to a nonprototypic vowel. However, data will be provided from experiments conducted in this laboratory using an MDS paradigm on the /i/–/ɪ/ distinction that indicate this effect is eliminated or severely curtailed when all tokens are good exemplars of the /i/ category (>75%) and the nonprototypic exemplars are not near a phoneme boundary. In addition, given the almost exclusive reliance in the literature on the /i/–/ɪ/ vowel pair, additional data will be provided on the magnet effect in the /u/–/ɲ/ and /ʌ/–/ɑ/. Similar to /i/, extreme tokens of both /ɑ/ and /u/ that are distant from the prototype, but not in the direction of another vowel category (and thus near a phoneme boundary). The results will be discussed in terms of whether the effect is linguistic (phonetic) or auditory in nature.
Perceived vowel quantity in Swedish: Effects of postvocalic voicing
Authors: Behne Dawn M. , Czigler Peter E. , Sullivan Kirk P. H.
Published: July 2002

Swedish is described as having a distinction between phonologically long and short vowels. This distinction is realized primarily through the duration of the vowels, but in some cases also through resonance characteristics of the vowels. In Swedish, like many languages, vowel duration is also longer preceding a voiced postvocalic consonant than a voiceless one. This study examines the weight of vowel duration and the first and second formant frequencies F1–F2 frequencies when distinguishing phonologically long and short vowel before a voiceless consonant (experiment 1) and before a voiced consonant (experiment 2). For three pairs of Swedish vowels ([i:]-[ɪ], [o:]-[ɔ], [ɑ:]-[a]) 100 /kVt/ (experiment 1) and 100 /kVd/ (experiment 2) words were resynthesized having ten degrees of vowel duration and ten degrees of F1 and F2 adjustment. In both experiments listeners decided whether presented words contained a phonologically long or short vowel. Reaction times were also recorded. Results show that vowel duration is a more dominant cue than the first and second formant for distinguishing phonologically long and short vowels. However, for [ɑ:] and [a] the perceptual influence of vowel duration and spectral attributes appears to be more complex. These findings are discussed for vowels preceding postvocalic voiceless and voiced consonants.
Linear thermoacoustic instability in the time domain
Authors: Karpov S. , Prosperetti A.
Published: July 2002

An approximate time-domain description of the development of the thermoacoustic instability in gas-filled tubes is developed by exploiting the difference between the instability time scale and the period of standing waves. The perturbation results compare very favorably with the exact frequency-domain theory of Rott. The perturbation results are further simplified by introducing a short-stack approximation which is numerically much simpler and only slightly less accurate. An approximate expression for the critical temperature gradient accounting for viscous effects and other design features is also derived. In addition to the fundamental mode of a tube closed at both ends, the theory includes higher modes as well as open-end boundary conditions.
Finite element modeling of lead magnesium niobate electrostrictive materials: Static analysis
Authors: Debus Jean-Claude , Dubus Bertrand , Coutte Jocelyne
Published: July 2002

New lead magnesium niobate (PMN) ceramics, which can generate large strains at moderate electric fields, are good candidates for future actuators or sonar projectors. In this paper, two finite element models are proposed to describe static analysis of electrostrictive materials. Both models include quadratic dependence of strain with electrical displacement, assume constant temperature, and exclude hysteresis. One of the models includes the saturation of the polarization. The theoretical formulation is justified by the method of the weighted residuals. The numerical implementation is presented. The validation is performed by comparing numerical results with measurements for a PMN bar subjected to mechanical prestress and dc electric field.
Reduced models in the medium-frequency range for general external structural-acoustic systems
Authors: Soize Christian
Published: July 2002

This paper presents a theoretical approach for constructing a reduced model in the medium-frequency range in the area of structural acoustics for a general three-dimensional dissipative structure made of an anisotropic, inhomogeneous, viscoelastic bounded medium coupled with an external acoustic fluid. All the results presented can be used if the structure is made of beams, plates, and shells. The boundary value problem in the frequency domain and its variational formulation are presented. For a fixed medium-frequency band, an energy operator related to the structural-acoustic system is introduced. This operator is symmetric positive definite and has a countable set of positive eigenvalues. Its dominant eigensubspace allows a reduced model to be constructed using the Ritz–Galerkin method. A finite dimension approximation of the three-dimensional continuous case is presented and an effective construction of the dominant subspace using the subspace iteration method is developed. As an example, the reduced model is used for constructing the time-stationary random response of the structural-acoustic system submitted to a random wall pressure field. Finally, the theory is validated for a finite length circular cylindrical shell coupled with several dashpots and springs and immersed in a gas (air) and in a liquid (water).
The role of auditory filters in comodulation masking release (CMR)
Authors: Buss Emily , Hall Joseph W.
Published: July 2002

Comodulation masking release (CMR) is the detection advantage conferred by coherence of amplitude modulation across masker frequency. This phenomenon has typically been described in terms of across-frequency comparisons or in terms of cueing, where analysis of the output of an auditory filter in the region of the signal is aided by the outputs of independent auditory filters. An alternative approach is to assume a broad initial predetection filter, one which encompasses frequencies generally thought to fall into disparate auditory filters. These two basic approaches are compared. Stimuli consisted of comodulated maskers, spaced in frequency at one of three fixed intervals, with fine structure that either produced strong envelope beats in the summed waveform or did not. The signal was a pure tone of random starting phase. For the smallest masker frequency spacing detection of a high-frequency signal seemed to be improved in the presence of envelope beats, while detection of a low-frequency signal seemed to be degraded by envelope beats. These results are discussed in terms of the number of maskers assumed to sum in an auditory filter and the relative availability of within- and between-channel cues. This explanation is consistent with an initial stage of auditory filtering and is fundamentally inconsistent with a broad initial filter. Results for larger masker frequency spacings showed this trend less reliably, a finding that was further explored via data from a modulation discrimination task.
A method for forward and inverse solutions of a three-dimensional model of the cochlea
Authors: de Boer Egbert
Published: July 2002

In this Letter a method is described for computing the response of a linear three-dimensional classical model of the cochlea. The method can be applied when the geometry of the model lends itself to separation of variables, for instance, when the model has the shape of a homogeneous rectangular block or box. The method is an improvement over previously published computation methods, because it handles forward and retrograde traveling waves symmetrically, and it can be used for forward as well as inverse solutions. Furthermore, the method can be extended to a time-domain solution.
On the problem of source identification from far-field observations in hysteretic materials
Authors: Kadish Abraham
Published: July 2002

Propagation resulting from finite pulselength stresses applied at one end of a hysteretic material is analyzed using a propagation model containing a double modulus, or two-signal-speed, approximation of the stress-strain relation. The local signal speed is determined at any instant by both the value of stress and the sign of its time derivative (i.e., time-local history). It is shown that far-field waveforms do not determine unique source profiles. The propagation mechanism responsible for the ambiguity in source identification is common to broad classes of both local and global hysteretic stress-strain operators. Consequently, one may expect that it is typical of hysteretic materials that remote sources are not uniquely determined by observed waveforms.
Vibration analysis of line-coupled structures using a coupling load decomposition technique
Authors: Hatam M. , Cheng L. , Rancourt D.
Published: July 2002

A new substructuring technique is proposed to perform vibration analysis of line-coupled structures. In dividing the whole structure into a master structure and several auxiliary structures, a variational formulation is used to model the master structure, enabling one to introduce the effects of all auxiliary structures by using their compliance characteristics at several observation points along the junction. Continuous functions of the compliance are obtained via a regression analysis. Given the problem of using the compliance inverse to attain a straightforward formulation, a “Coupling Load Decomposition” technique is proposed since a direct formulation using the compliance inverse is not feasible. By decomposing the interactive load between substructures, relations with displacement decomposition of the master structure can be found. This new formulation permits the direct use of the compliance of the junction, which may be obtained analytically, numerically, or experimentally. Numerical examples using both calculated and experimentally measured compliance data are given. Simulation results are also compared to those obtained experimentally, showing good agreement in low- and medium-frequency ranges.
Spatial heterogeneity of acoustic bottom backscattering model parameters and predicted results
Authors: Briggs Kevin B.
Published: July 2002

Sediment geoacoustic and roughness measurements were made during a mine burial experiment in the North Sea in November 1997. The experiment site was a sand ridge (20.5–32-m water depth) influenced by strong tidal currents and wave action. Stereo photographs indicated that the sediment roughness was characterized by cross-rippled fine sand that transitioned to straight- and sinuous-rippled mixtures of fine quartz sand and mollusk shell fragments. Box core samples were subsampled with core tubes from which measurements of sediment compressional wave velocity and attenuation, density, and grain size distribution were made. Values for sediment velocity ratio, density ratio, slope of the roughness power spectrum, roughness spectral strength, and other measured and calculated parameters were used as input parameters for the composite roughness model to predict bottom backscattering strengths from various regions within the experiment site. Horizontal and vertical variability in sediment properties is high relative to other shallow sites under the influence of strong hydrodynamic forcing. There is a marked interdependence among sediment geoacoustic properties, water depth and bottom roughness features. The influence of hydrodynamic conditions and sediment type on the acoustic model predictions is demonstrated by the spatial variability in predicted scattering of high-frequency sound from the site.
Boundary condition sensitivity for hybrid SEA/FEA modeling
Authors: Tracey Brian H. , Manning Jerome E.
Published: July 2002

Hybrid SEA/FEA techniques offer the promise of improved noise and vibration predictions for midfrequency problems. One of the outstanding issues in hybrid modeling is how best to use FEA estimates of midfrequency response. Perturbation theory and Monte Carlo simulations of simple plates are used to study the sensitivity of FEA estimates to uncertainty in boundary conditions. For low modal overlap, the main effect of random boundary conditions is to cause shifts in mode frequencies. Sensitivity to these perturbations can be reduced through appropriate frequency averaging. For intermediate or high modal overlap, perturbations of mode shapes are shown to have a more significant effect on prediction accuracy. Mode shape perturbations cause phase errors to accumulate away from the drive point, leading to high sensitivity for FEA transfer accelerance predictions. Numerical results also indicate a decay of the coherent response similar to that predicted by Rybak for inhomogeneous plates.
Modeling the subglottal space for American English /r/
Authors: Espy-Wilson Carol Y. , Boyce Suzanne E. , Jackson Michel T. T. , Alwan Abeer , Narayanan Shrikanth
Published: July 2002

One challenge in modeling the acoustics of American English /r/ is the fact that F3 may vary from 1300–2000 Hz in different contexts, even in the same speaker. Previous models have accounted for F3 lowering to the upper portion of this range, but have not accounted for the lower F3 range. In previous work, acoustical models of /r/ were tested utilizing the Maeda computer model (Maeda, 1982) and vocal tract dimensions for /r/ derived from MRI studies of two American English speakers. It was concluded that the F3 range exhibited by the speakers could be modeled successfully only by including the sublingual space. In the study presented here, two methods were examined for incorporating the sublingual space, (i) as an extra cavity resonator, and (ii) as an increment to the length and volume of the front 190 cavity. Using a recently developed adaptation of the Maeda model that incorporates a side branch from the front cavity, theoretical projections were compared against model results with and without the sublingual space resonator. It was concluded that an adequately low F3 can be generated using either method of incorporation, as long as certain conditions apply.
Evolution of the secular organ performance space: An historical overview
Authors: Clayton Dan
Published: July 2002

The earliest organ was the 3rd century (BC) Greek ‘‘hydraulis,’’ a machine of wind-blown pipes which evolved through Roman and Byzantine eras into a musical instrument, by the 13th century becoming the exclusive domain of the church. The organ remained largely in the church through the 17th century, by which time it had matured into the sophisticated instrument we know today. By the 18th century the organ was being used outside the church, first in royal salons and music rooms. The Hanover Square rooms, complete with a small pipe organ, opened in 1775 and for the next century was London’s principal concert hall. The English ‘‘town hall’’ tradition of organ and choral music began in the mid-19th century, spreading rapidly throughout Britain, and eventually to other countries, most notably Australia and the U.S. Most of the ‘‘great’’ concert halls of the late 19th and early 20th centuries (Amsterdam, Boston, Leipzig, Vienna, etc.) included significant organs. The 20th century has seen the widest variety of organ styles and rooms, including sumptuous private residences, massive outdoor exhibition amphitheatres, and extravagant theatre organs. Expansion of higher education beginning in the 1950s brought many important university installations, most recently culminating in highly specalized ‘‘pure’’ organ performance rooms.
From reverberation chamber to movable ceiling: Organ builder meets acoustician and architect through artistic and scientific cooperation in concert-hall organ projects
Authors: Klais Philipp
Published: July 2002

A successful concert-hall organ holds a commanding musical presence. As a solo instrument the organ must be flexible and comprehensive, and when playing with full symphony orchestra the organ’s great power and impact allow it to stand in stark tonal and dynamic contrast to the orchestra. Every concert-hall organ project poses a different set of design challenges and requires a unique solution—the most successful of these are when the organ builder is involved from the early project design stages. Klais Orgelbau has designed and built pipe organs for many international concert halls including those in Kyoto, Japan; Athens, Greece; Krakau, Poland; Munich, Germany; and Cologne, Germany. Five current and upcoming major projects include concert hall instruments in Kuala Lumpur, Malaysia; Bochum, Germany; Birmingham, UK; Halle, Germany; and Singapore. The considerable experience gained from this wide variety of projects will be reviewed. Project examples include such special acoustic features as stage canopies and reverberation chambers (Birmingham and Singapore) and a movable ceiling (Kuala Lumpur). The author will discuss the results of collaborations with acousticians and architects as well as those projects where the organ builder could only respond and react to planning and design decisions already in place.
Environmental constraints on sound transmission by humpback whales
Authors: Mercado Eduardo , Frazer L. Neil
Published: July 2002

Singing humpback whales in Hawaii produce a variety of sounds at high source levels (ca. 185 dB re: 1 μPa), in water 15–500 m deep. The utility of these sounds is limited by their detectability and discriminability (which is a function of their acoustic features and the channel through which they are transmitted). To investigate how shallow water propagation might constrain humpback whales use of sound, simulations were run to calculate optimum frequencies for environments frequented by singers [here optimum frequency is the f that maximizes maxzrI(zr,f), where I is intensity, and zr is receiver depth]. Simulations were performed using ORCA, an acoustic propagation model for multilayered acousto-elastic ocean environments based on normal mode theory [Westwood et al., J. Acoust. Soc. Am. 100, 3631–3645 (1996)]. The frequency band tested was 20–4000 Hz; the sub-bottom was taken to be a 50-m-thick sandy/silty layer with gradient, above a basalt half-space. Water depth, source depth and thermocline axis depth were varied across simulations. Source depth was found to be a major determinant of which frequencies propagated the farthest. Optimal frequencies decreased as source depth increased; they were typically above 500 Hz for source depths of 30 m or less. Humpbacks could affect transmission range (by factors of 2 to 3) by adjusting their position and sounds in response to environmental factors.
Thin, low-frequency, high-displacement actuator panels
Authors: Tressler James F. , Howarth Thomas R. , Bucaro Joseph A.
Published: July 2002

The Naval Research Laboratory has recently developed a thin, lightweight, high-displacement, low-frequency actuator panel. The 4-in.×4-in.×0.25-in.-thick panels consist of cymbal-type flextensional actuator subelements placed mechanically and electrically in parallel between two stiff cover plates. Two different panel designs have been considered: one to operate in the frequency band of 100 Hz to 1 kHz, the other to operate between 1 and 10 kHz. Each of the panels was evaluated for its normal displacement using laser Doppler vibrometry (LDV) techniques over both decade bands. For the low-frequency cymbal panel driven at its resonance frequency of 444 Hz, a displacement of 2.5-μm for a 1-V drive has been observed. At this frequency, the cymbal drivers can be driven at higher drive levels for larger displacements if desired. An advanced, higher displacement design utilizes copper-electroplated, graphite-epoxy cover plates. Preliminary data indicate that even higher displacements can be achieved with this design. Applications to both acoustic source generation and structural control technologies will be discussed. [This research is supported by the Office of Naval Research, Code 321SS.]
Sonic boom propagation through turbulence: A geometric acoustics and a KZK approach
Authors: Lipkens Bart , Blanc-Benon Philippe , Dallois Laurent , Hamilton Mark , Blackstock David T.
Published: July 2002

Sonic boom propagation is strongly affected by atmospheric turbulence. It has been shown that turbulence affects the perceived loudness of sonic booms, mainly by changing its peak pressure and rise time. The models reported here describe the nonlinear propagation of sound through turbulence. The turbulence is modeled as a set of individual realizations of a random temperature or velocity field. In the first model, linear geometric acoustics is used to trace rays through each realization of the turbulent field. A nonlinear transport equation is then derived along each eigenray connecting the source and receiver. The transport equation is solved by a Pestorius algorithm. In the second model, the KZK equation is modified to account for the effect of a random temperature field and it is then solved numerically. Results show that, on average, turbulence decreases the mean peak pressure and increases the rise time. Nonlinear distortion is less when turbulence is present than without it. The geometric acoustics results indicated that the effects of random vectorial fields are stronger than those of random temperature fields. The location of the caustics and the deformation of the wavefront are also presented. [Work supported by a grant from NASA.]
Field experience in assessing open plan office acoustical privacy
Authors: Berry Lincoln B. , Foulkes Timothy J.
Published: July 2002

Experience continues to show that the significant factors affecting open office plan speech privacy include available masking (background), sound barrier height and absorption, distance between sound source and receiver, ceiling sound absorption, furniture layout, speech effort of occupants, etc. These factors are adequately quantified by currently available metrics, and methods for predicting speech privacy prove to be practical, easy to use, and quite accurate. Case studies of open plan offices will be presented including available systems and approaches for electronic sound masking in both large and small office configurations.
Seabed sediment property inversions and verifications
Authors: Yamamoto Tokuo
Published: July 2002

The acoustic wave propagation model used in inversion is a key to sediment properties inverted from acoustic data. Geoacoustic models (Biot, Squirt Flow, BISQ, Super-k, Gassmann, Wood models) are all reviewed in light of their applicability to seabed sediment inversions. The simplest sediment model is desirable for a given inversion from inverse calculation standpoint. Depending on sediment type and acoustic frequencies, an optimal model is determined. The second key is the acoustic measurement method whose data is used in inversion. The third key to inversions is the availability of reliable ground truth data from established measurement methods. Two examples of shallow-water sediment inversions are shown to demonstrate these points. The first example is imaging the permeability–porosity structure of limestone seabed from cross-well tomography (1–12 kHz) measurements based on the Super-k model as compared with pumping tests, downhole neutron, gamma ray, and acoustic tests, and cores. The second example is inversions of measured (5–15 kHz) acoustic backscatter data for density, sound speed, attenuation, and their spectra based on a Woods sediment model. Crosswell tomography is used to compare with the inversion results. [Work supported by ONR.]
Standing waves in an electromagnetically driven conducting wire
Authors: Sabatier James M. , Drewrey Jessica
Published: July 2002

An elastic cord or slinky is often used to demonstrate various wave phenomena including the nodes and antinodes in standing waves. In this talk the drive force results from the interaction of an electric current in a pretensioned conducting wire and an applied orthogonal magnetic field. If the electric current is sufficiently increased, the wire will glow brightly at the nodes. Due to convective air cooling, the antinodes will be dark. As the wire heats, it elongates, reducing the tension and lowering the resonate frequency. Since this demonstration is typically accomplished using a Variac, the tension in the wire must be adjusted as the wire elongates. Here, a power oscillator will be used to allow for a variable drive frequency.
Noise labels—Satisfying many users
Authors: Pope J.
Published: July 2002

In order to be successful, noise labels must provide information that is useable by many different groups (consumers, buyers, manufacturers, etc.). (In this paper, the term ‘‘noise label’’ refers to acoustical information that is provided by a manufacturer or supplier to purchasers or users of products; the information may be presented as a label physically applied to the product, as a ‘‘tag’’ attached to the product, in the products specification sheet, in the products users manual, or possibly in a ‘‘catalog’’ of data on several different products.) The noise label should provide information that permits the purchaser and user to determine the products suitability or compatibility with the environment in which the product will be used. The information in the noise labels for all products should be similar in format and content to enable users both to understand the metrics contained in the label and to make informed decisions based in part upon the information contained in the label. This paper discusses these issues and others that must be resolved in the development of a noise labeling standard by ANSI S12 working group 38 and for its successful implementation.
Fiber optic interferometric sensor for ultrasound
Authors: Beadle Brad , Jarzynski Jacek
Published: July 2002

A fiber optic interferometric sensor, designed to detect tangential surface strains in the frequency range ∼200 kHz to 1 MHz, is described. The sensor is configured with a large number of segments of the fiber bonded to a thin plastic or metal base plate. The base plate can then be attached with a shear wave couplant to the solid sample of interest and the fiber sensor can be used to detect, in this sample, ultrasonic waves with a tangential surface displacement component. The sensor forms one arm of a Mach–Zehnder interferometer and the sensor sensitivity is proportional to the number of fiber segments bonded to the base plate. The fiber segments bonded to the base plate are of equal length and the maximum response of the sensor is at the frequency for which the bonded segment length is one-half of the tangential component of ultrasonic wavelength. The sensor is directional, with maximum response in the direction broadside to the bonded segment array. Measurements of the sensor performance are presented and compared with a theoretical model. [This work is supported by the ONR M-URI program.]
Direct and inverse problems of linear resonant ultrasound spectroscopy
Authors: Lebedev Andrey V. , Soustova Irina A. , Ostrovsky Lev A. , Johnson Paul A.
Published: July 2002

The model approach of linear resonance ultrasound spectroscopy (LRUS) is described: obtaining the elastic moduli and Q values from resonance spectral measurements at frequencies ranging from several kHz to tens of kHz on complex solids such as rock. In the direct (forward) problem, LRUS is based on the variational principle, that of determining the eigenvalues from resonance spectral peaks of samples (complex in the general case). By minimizing the difference between the measured and calculated resonant modes for a given geometry of the sample, the linear properties of the sample (inverse problem) can be determined. The method was tested by comparing theoretical and experimental results obtained by Demarest [H. Demarest, J. Acoust. Soc. Am. 49, 768–775 (1971)] and data obtained from experiments carried out in IAP RAS on rectangular bricks at audio frequencies. Comparison of measured and calculated data showed that the difference may be as low as 0.6%. [This work is supported by the United States Industry Coalition, with the U.S. DOE, Contract No. W-7405-ENG-36, through the University of California.]
Sound movement: The dynamics of interaural amplitude and phase modulation processing are different
Authors: Witton Caroline , Rees Adrian , Rao B. Vishwanatha , Griffiths Timothy D. , Green Gary G. R.
Published: July 2002

Listeners use two binaural cues when detecting motion of a sound in the horizontal plane; interaural amplitude and phase modulation (IAM and IPM). It has been suggested that IAM is converted into the same neural code as IPM, in which case the dynamics of IAM and IPM processing should be the same. To test this hypothesis, three subjects participated in 2-AFC psychophysical experiments. Thresholds were measured for detection and modulation-direction discrimination of linear IAM and IPM of a 500 Hz tone, for ramp durations between 20 and 1000 ms. At durations between 200 and 1000 ms detection thresholds for both cues remained constant. IAM sensitivity decreased in a biphasic manner at durations below 200 ms, whereas IPM sensitivity remained constant until much shorter durations (60 ms). This suggests that IAM detection has a longer integration period than IPM detection. Discrimination thresholds for IAM were 3 to 4 times smaller than detection thresholds (mean ratio 0.29, s.d.=0.04, n=3). IPM discrimination thresholds were similar to IPM detection thresholds (mean ratio 0.81, s.d.=0.05, n=3). These results demonstrate that the dynamics of IAM and IPM processing are not the same, and the hypothesis is rejected.
Visual influences on auditory distance perception
Authors: Brown Julie M. , Anderson Krista L. , Fowler Carol A. , Carello Claudia
Published: July 2002

Much of the work on sound localization has focused on sound sources in the horizontal plane. This study looks at the auditory perception of distance using a reaching task [L. D. Rosenblum, A. P. Wuestefeld, and K. L. Anderson, Ecological Psych. 8, 1–24 (1996)]. In this task, blindfolded participants judged the reachability of a rattle based on a straight right arm reach. In order to investigate visual influences on auditory distance perception, in another condition, participants judged the reachability of an ‘‘auditory’’ rattle while simultaneously viewing a ‘‘visual’’ rattle that did not produce sound. The ‘‘visual’’ rattle was placed 8 cm in front of the ‘‘auditory’’ rattle or 8 cm behind it. Compared to an auditory alone condition, participants were more likely to judge that the rattle was within reach when the visual stimulus was closer to the participant than the auditory stimulus. These results show that vision influences the perception of sound source distance.
Homogenization of fluid-loaded plates over the full frequency range for efficient calculation of structural acoustic behavior
Authors: Bliss Donald B. , Franzoni Linda P.
Published: July 2002

A homogenization method for complex structures, applicable over the entire frequency range, has been developed. This approach has application to naval structures, e.g., ribbed shells, and to aerospace structures, e.g., panel-frame fuselages. The homogenization method utilizes a local/global decomposition facilitated by adding and subtracting canceling smooth forces. The global problem has an infinite-order structural operator, and periodic discontinuities are replaced by an equivalent distributed suspension with slowly varying properties. The global problem can be solved very efficiently since all rapidly varying scales have been removed. The local problem, which provides transfer function information for the global problem, is solved separately and independently, except for amplitude information from the global problem. Once formulated for a specific structure, the self-contained global problem is solved first, and the local solution can be reconstructed afterwards. The application of this approach to structural waves on fluid-loaded plates is described. The analytical reformulation embodied in this homogenization method allows the global problem to be solved at lower resolution than the length of flexural waves on the original structure. Furthermore, the effects of fluid radiation can be transferred to the global problem. [Work sponsored by ONR.]
Acoustic harmonic radiation from long thin bodies of revolution via generalized internal source density method
Authors: Stepanishen Peter R.
Published: July 2002

A previously developed generalized internal source density method [P. R. Stepanishen, J. Acoust. Soc. Am. 102, 1955–1963 (1997)] is used to investigate acoustic harmonic radiation from circular cylinders with hemispherical end caps and normal velocity distributions corresponding to the lowest nonaxisymmetric (n=1) circumferential modes. A classical least squares approach leads to an inhomogeneous integral equation for the internal dipole line source distributions. Singular value decomposition methods are then used to determine the source distributions for the velocities of interest. The pressure and velocity fields in the fluid are readily obtained from line integrals of the dipole line source distribution. Numerical results are presented to illustrate the general characteristics of the source distributions and the near and far field radiation as a function of L/a (length/radius) and ka (normalized frequency) for various velocity distributions of interest.
Practical implementation of active noise control
Authors: Pan George J. , Brammer Anthony J.
Published: July 2002

Effective application of active noise control requires an understanding of acoustics, control theory, signal processing, and electronics. The physical mechanism of control may involve localized cancellation, modifying the impedance of an unwanted source, or the absorption or reflection of energy. Successful implementation relies on realistic modeling and robust design of the active noise control system. It also depends on precise realization of the control algorithms. Analog controllers offer the attraction of simplicity and speed, but cannot adapt to changes in the acoustic system. Nonparametric identification of the electroacoustic system, such as formed by the secondary source and error sensor, is essential. The causality condition for adaptive feedforward control of broadband noise introduces another challenge for applications to small acoustic devices, such as hearing protectors. Performance of localized active control also depends on the coherence between the signal that will be chosen to drive the controller and the noise at the cancellation point. This coherence function reflects the nature of the sound field and the passive acoustic system. The influence of these factors on active reduction will be discussed with reference to the performance of a digital ANR hearing protector.
Considerations in the design of ANR communication headsets
Authors: Gauger Daniel M. , Sapiejewski Roman S.
Published: July 2002

Active noise reduction integrated into communication headphones or headsets began to see use in high-noise military and commercial environments in the late 1980s. In a few applications ANR headphones have been quite successful; however, the technology has not seen the widespread use that was originally promised. Based on this experience, engineering challenges facing the designer as well as factors contributing to the success or failure of the technology in various applications to date will be discussed. Opportunities for improvement in new designs will also be examined.