bluuebunny/crossref_metadata_2025 huggingface dataset:
Doppler measurement of the motion of a physical pendulum
Authors: Ngabonziza Jean Paul , Frederickson Carl
Published: September 2012

The Doppler shift of a reflected acoustic signal has been used to characterize the motion of a physical pendulum. The pendulum is covered with a rough surface to provide specular reflection at any angle. Comparison between theoretical and measured spectrograms will be presented. The measurement dependence on the frequency of the source signal will be explored. Source frequencies will be in the audible range. The system is being evaluated for use with a double physical pendulum modeling the motion of a human leg.
Investigation of helmet-to-helmet collisions in football: Experiments using a mechanical lumped element coupled harmonic oscillator model structure for the skull, fluid, and brain mass
Authors: Miller Duncan M. , Korman Murray S.
Published: September 2012

The study of extreme helmet to helmet football collisions may lead to future precautions to prevent serious head injuries. First, (a) oscillations of the helmet alone (much like a tuning fork) are investigated. Then (b) a thin walled 1/16 inch thick 2 inch tall by 6 inch diameter polycarbonate hoop is used to model the skull (in the n = 2 mode). Next, (c) the hoop is filled with a light weight polyurethane foam to model fluid in the structure. Then (d) a solid brass cylindrical 1 Kg weight is inserted in a carved out slot in the foam. The hoop-foam-brass weight structure is studied in transient vibration. Finally (e) the “skull”, “fluid”, “brain mass” structure is set in the helmet and cushioned with extraneous foam. A second identical helmet on a pendulum is released with some angular momentum and collides with the helmet (fitted with the structure (e)) that is suspended vertically by its own pendulum cord - initially at rest. In laboratory collision studies three single axis accelerometers are placed on (1) the helmet at rest, (2) the hoop and (3) the end of the cylindrical mass, in an effort to rudimentary model the vibration of the model brain mass.
Design characterization and testing of a custom air horn
Authors: Ward Frederick J. , Slaton William
Published: September 2012

Construction and testing of an air horn can provide educational insight into how certain design decisions can influence resulting acoustic properties. Using readily available materials such as pvc pipe and tin sheeting, one can construct an air horn capable of producing sound waves in the 100+ decibel range and frequencies between 150 and 400 Hz. Upon completion of a prototype, many experimental opportunities are available. The degradation of sound intensity over a distance can be tested by use of a sound level meter. Due to the unidirectional behavior of the sound waves from the horn, samples from different distances and angles from the source can provide more understanding of how sound propagates as a wave in an open environment, as opposed to it being a simple directional wave. Upon completion of the testing, changes to the initial construction design can be implemented to investigate the relationship between the new model’s performance and the prototype’s. The air horn provides many opportunities for experimentation and testing. For example, frequencies and sound intensity can be altered by making design adjustments such as: diaphragm size, diaphragm material, housing material, bell size, nozzle length, etc. With a better understanding of the inner workings of these sound sources, one could use this design as a blueprint to expand the concept to either much larger or much lower frequency ranges which have applications in many different fields of study.
Objective and subjective differences between adjacent seats in a multipurpose hall
Authors: Dick Michael J. , Daly Jenna M. , Vigeant Michelle C.
Published: September 2012

The purpose of this study was to evaluate differences between adjacent seats in terms of objective measures and subjective perception based on measurements and recordings taken in a mid-sized multipurpose hall. The work is based on the hypothesis that minimal differences should be found between nearby seats. Measurements were taken in three groups of nine adjacent seats. The differences between seats were analyzed in terms of the number of just noticeable differences (JNDs), using 1 dB for strength (G), 5% for early decay time (EDT) and 1 dB for clarity index (C80). The average differences between adjacent seats within a given group were approximately 2.5 JNDs for G, 4 JNDs for EDT and 2.5 JNDs for C80, which implies that these differences might be audible. However, these differences may be within measurement error. Differences in late lateral energy level (GLL), a measure of listener envelopment (LEV), were all less than 1 dB. A total of 35 test subjects were presented binaural recordings from two seat groups and were asked to evaluate LEV and acoustical quality. In general, subjects did not perceive differences between the recordings as hypothesized, with the exception of two cases where differences in LEV were statistically significant.
Sound radiated from vibrating trumpet bells and its share in the overall radiated sound of that instrument
Authors: Kausel Wilfried , Chatziioannou Vasileios , Moore Thomas R.
Published: September 2012

Dallas Blues, published in 1912 by Hart A. Wand, is often considered to be the first published blues song. In this work the trumpet is the lead voice, and this is still often the case in blues music. Indeed, it is difficult to overstate the importance of this instrument to the development of the genre. Recent research indicates that bell vibrations with circular symmetry, such as breathing modes and axial length oscillations (i.e., piston-like vibrations of the bell or rim), have the potential to affect the input impedance and pressure transfer function of the trumpet. This in turn can significantly affect the sound. Structural and acoustical finite element simulations of an axisymmetric trumpet bell show that the sound level radiated from the vibrating walls is of the same order of magnitude as the sound level radiated by the air column in a wide frequency band around the structural resonances. Since these axial structural resonances have a much wider bandwidth than elliptic modes, it is not necessary that air resonances exactly match structural resonances in order to produce a significant effect. The contribution of axial bell vibrations to the sound of the instrument is shown to be consistent with these simulations.
Full-scale rocket motor acoustic tests and comparisons with models: Revisiting the empirical curves
Authors: James Michael M. , Salton Alexandria R. , Gee Kent L.
Published: September 2012

Development of the next-generation space flight vehicles has prompted a renewed focus on rocket sound source characterization and near-field propagation modeling. Improved measurements of the noise near the rocket plume are critical for direct determination of the noise environment. They are also crucial in providing inputs to empirical models and in validating computational aeroacoustics models. NASA’s SP 8072 acoustic load prediction model is a widely used method for predicting liftoff acoustics. SP-8072 implements two Distributed Source Methods (DSM-1 and DSM-2), which predict the loading as the sum of the radiated field from each source distributed along the plume. The prediction model depends largely on empirical curve fits computed from historical data to determine the source power and frequency content at distances along the plume. Preliminary results from measurements of a static horizontal firing of Alliant Techsystems Orion 50S XLG performed in Promontory, UT are analyzed with respect to the historical data that drives the SP-8072 prediction model.
Prediction of nonlinear propagation of noise from a solid rocket motor
Authors: Muhlestein Michael B. , Gee Kent L. , Thomas Derek C. , Neilsen Tracianne B.
Published: September 2012

The extreme sound pressure levels radiated from rocket motors are such that nonlinear propagation effects can be significant. Here, free-field nonlinear propagation has been modeled for noise produced by a GEM-60 solid rocket motor. Measured waveforms were used as inputs into a numerical model based on the generalized Burgers equation. In both temporal and frequency domains the nonlinear predictions are significantly closer to the measured signals than free-field, linear predictions. In the temporal domain, shock coalescence and a transition from the weak-shock regime of propagation to the beginning of the old-age regime are clearly observed in both the nonlinear prediction and the measured data. These phenomena are completely missing in the linear prediction. In the frequency domain, continual transfer of energy upward in the spectrum reduces attenuation of high-frequency components when compared to predictions from the linear model. Various comparisons are made as a function of input distance for two different radiating angles from the rocket plume; these comparisons illustrate the importance of including nonlinear effects in rocket noise propagation modeling.
Modeling of photoacoustic Raman spectroscopy with dissipation
Authors: Chambers David , Carter Chance
Published: September 2012

Photoacoustic Raman spectroscopy (PARS) is a technique used to identify chemical species mixed in a gas or liquid based on their pattern of vibrational energy levels. Raman spectroscopy differs from the more familiar absorption spectroscopy by using a nonlinear two-photon process that can be more sensitive to small differences in vibrational energy levels. Thus it can detect defect sites in solid-state optical materials, or low concentrations of chemical species in gases. The Raman scattering process generates acoustic pulses that can be detected with a microphone. In this talk we present an overview of PARS and present an updated model that includes dissipation for the production of acoustic pulses from the energy deposited in the medium during the Raman scattering process. We also show some preliminary measurements of the process for Raman conversion in hydrogen. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Actuating micro devices with acoustic white noise
Authors: Esquivel-Sirvent Raul
Published: September 2012

We present a theoretical calculation of the actuation of a model micro system, such as a microelectromechanical system (MEMS), by the acoustic pressure of white noise. This is a classical analog of the Casimir effect, thus the name Casimir acoustic pressure. Unlike the quantum case, the acoustic Casimir pressure can be attractive or repulsive depending on the frequency bandwidth of the acoustic noise. As a case study, a one-degree-of-freedom simple-lumped system in an acoustic resonant cavity is considered. By properly selecting the frequency bandwidth of the acoustic field, the acoustic pressure can be tuned to increase the stability in existing microswitch systems by selectively changing the sign of the force. The acoustic intensity and frequency bandwidth are introduced as two additional control parameters in capacitive micorswitches. Applications of this concept in microfluidics will be also discussed.
Perceptual weights for loudness reflect central spectral processing
Authors: Joshi Suyash N. , Jesteadt Walt
Published: September 2012

Weighting patterns for loudness obtained using the reverse correlation method are thought to reveal the relative contributions of different frequency regions to total loudness, the equivalent of specific loudness. Current models of loudness assume that specific loudness is determined by peripheral processes such as compression and masking. Here we test this hypothesis using 20-tone harmonic complexes (200Hz f0, 200 to 4000Hz, 250 ms, 65 dB/Component) added in opposite phase relationships (Schroeder positive and negative). Due to the varying degree of envelope modulations, these time-reversed harmonic complexes have been shown to produce different outputs at the basilar membrane and different amounts of forward and simultaneous masking. The perceptual weights for loudness did not differ for these two complexes. To determine whether the level rove introduced to obtain weights had changed the fundamental differences in the stimuli, a similar level rove (±8 dB) was introduced on each component of Schroeder positive and negative forward maskers. The Schroder negative maskers continued to be more effective. These results suggest that perceptual weights for loudness are not completely determined by peripheral processes and reflect a central frequency weighting template. [Work supported by NIH R01 DC011806 and P30 DC004662.]
Using optimization for acoustic cloak design
Authors: Cai Liang-Wu , Bao Chunyan
Published: September 2012

Many of the acoustic cloak designs are based on the acoustic analogy of transformation optics. This process dictates some major challenges when realizing such cloaks: the materials are very otherworldly. One of the most significant obstacles, the mass-anisotropy, has been removed by using two isotropic acoustic materials to create an equivalent anisotropy. In this presentation, optimization is used as a tool for designing acoustic cloaks such that materials can be feasibly fabricated using naturally occurring materials. The initial designs are based on Cummer-Schurig prescription for acoustic cloak, rendered in a layered structure, and using the anisotropic-isotropic equivalency. The first is using unconstrained optimization to demonstrate that material singularity is not a requirement for perfect cloaking. The optimization is able to fine-tune material properties in the initial design to achieve perfect cloaking within a limited frequency range. The second work is using multi-objective optimization to expand the range of the frequency range in which the cloaking remains effective. The third are is to use constrained optimization to limit the material properties to ranges that are naturally available. Lastly, different optimization techniques are combined to design acoustic cloaks that are made of mixtures of conventional isotropic solid and fluid (acoustic) materials.
Consonant-f0 interaction under predictable voicing: f0 lowering due to phonetic factors
Authors: Dutta Indranil , George Jasmine M. , Paul Minu S.
Published: September 2012

We report on consonant-f0 interactions in Malayalam. Crosslinguistically, voicing lowers f0 in the following vowel (House and Fairbanks 1953, Hombert 1978, Clements 2002, Moreton 2006). While this lowering has been attributed to physiological and phonetic factors (Stevens 1998, Atkinson 1978, and Honda 2004), Ohde (1984), Svantesson and House (2006), and Keating (1984) have argued that f0 lowering serves to maintain a phonological contrast between voiced and voiceless segments. Voicing in Malayalam is predictable; voiceless stops appear initially, and voiced intervocalically. We report on data from 6 native speakers. 3 repetitions of each word in a frame sentence were recorded. Since Malayalam words only appear with voiceless initial stops, we contrast these with nasals from corresponding places of articulation. We examine time-normalized f0 perturbation due to voicing in Malayalam for all places of articulation for both initial and medial contexts. Our findings lend support to the physiological and phonetic account of f0 lowering. Malayalam exhibits a pattern of f0 lowering following voicing and raising during the production of voiceless segments. In spite of Malayalam voicing being predictable, the f0 perturbation in the following vowel follows the cross-linguistic pattern of lowering following voiced segments. This finding dove-tails with the results from earlier studies that take physiological factors to be responsible for the lowering of f0 following voiced segments.
Acoustic correlates of breathy voice in Marathi sonorants
Authors: Berkson Kelly
Published: September 2012

Breathy voiced sonorants occur in fewer than 1% of the languages indexed in the UCLA Phonological Segment Inventory Database. Acoustic analysis of these sounds remains sparse, and our understanding of the acoustic correlates of breathy voice in sonorants is incomplete. The current study presents data from Marathi, an Indo-Aryan language which boasts a number of breathy voiced sonorants. Ten native speakers (five male, five female) were recorded producing Marathi words embedded in a carrier sentence. Tokens included plain and breathy voiced nasals, laterals, rhotics, and approximants before the vowel [a]. Measures reported for consonants and subsequent vowels include duration, F0, Cepstral Peak Prominence (CPP), and corrected H1-H2*, H1-A1*, H1-A2*, and H1-A3* values. As expected, breathy sounds have lower CPP values than modal sounds, and larger positive values for the remaining spectral measures. The spectral effect of breathiness extends from the beginning of the consonant through the end of the vowel. While some breathy voiced sounds contain a salient breathy interval that is highly visible in the waveform and spectrogram, others don’t, and in its absence the spectral differences between breathy and modal sounds are greatly increased.
Acoustic correlates of vowel intelligibility in clear and conversational speech for young normal-hearing and elderly hearing-impaired listeners
Authors: Ferguson Sarah H. , Quene Hugo
Published: September 2012

Previous reports on the relationship between clear speech acoustic changes and the clear speech intelligibility benefit for vowels have used an “extreme groups” design, comparing talkers who produced a large clear speech benefit to talkers who produced little or no clear speech benefit. In Ferguson and Kewley-Port (2007), 12 talkers from the Ferguson Clear Speech Database (Ferguson, 2004) were assigned to groups based on the vowel identification performance of young normal-hearing listeners, while Ferguson (2010) chose 20 talkers based on the performance of elderly hearing-impaired listeners. The present investigation is employing mixed-effects models to examine relationships among acoustic and perceptual data obtained for vowels produced by all 41 talkers of the Ferguson database. Acoustic data for the 1640 vowel tokens (41 talkers X 10 vowels X 2 tokens X two speaking styles) include vowel duration, vowel space, and several different measures of dynamic formant movement. Perceptual data consist of vowel intelligibility in noise as reflected by the performance of young normal-hearing and elderly hearing-impaired listeners. Analyses will explore the relative importance of the various clear speech acoustic changes to the clear speech vowel intelligibility effect as well as the degree to which this relationship varies between the two listener groups.
An acoustic analysis of lexical stress in Uyghur
Authors: Yakup Mahire
Published: September 2012

In this study, the accent pattern in Uyghur, a Turkic language, was investigated. Two experiments provide a detailed phonetic analysis in order to determine the acoustic cues to stress in Uyghur. In Experiment 1, six disyllabic minimal pairs (e.g., A-cha, a-CHA), contrasting in location of stress, were produced by five native Uyghur speakers with three repetitions in a fixed sentence context. In order to generalize the results from the small set of minimal pairs in the first experiment, Experiment 2 examined the initial syllable of disyllabic nouns that contrasted in first-syllable stress (e.g., DA-ka, da-LA) while syllabic structure (CV versus CVC) was also manipulated. In both experiments, average fundamental frequency, duration, and average intensity were collected in the vowels in accented and unaccented syllables. The results from both experiments showed that there were significant differences in duration and intensity between stressed and unstressed syllables, with the intensity differences moderated by syllable structure. No differences were found in fundamental frequency. While previous studies have classified Uyghur as a pitch-accent and a stress-accent language, the present acoustic data suggest that native speakers make no use of pitch cues to signal stress in Uyghur.
Video recordings of L1 and L2 jaw movement: Effect of syllable onset on jaw opening during syllable nucleus
Authors: Abe Yusuke , Wilson Ian L. , Erickson Donna
Published: September 2012

Video is a convenient, inexpensive method of recording data for jaw movement during speech. However, when using markers attached to the chin, it is possible that the data will not represent actual mandible motion, because of the skin stretching over the mandible - especially true for labial consonants. In this study, we made video recordings of L1 and L2 speakers of English saying 5 trials of 34 sentences each, and we automatically measured the distance between paper markers attached to the chin and glasses. We compared jaw opening during syllable nucleus for syllables with and without labial onsets, for L1 and L2 English speakers of various proficiencies. Although speakers must stretch the lower lip upwards for a labial constriction, preliminary results show that there are no statistically significant differences for any speaker’s jaw opening during the nucleus of non-labial- versus labial-onset syllables. There is also very little intra-subject variation in the metrical structure (as measured by jaw opening) for a given sentence across trials. However, across-trial variability in the time between jaw movement peaks is a lot less for L1 than for L2, presumably because these L2 speakers have not yet mastered the metrical structure of English.
Tracking calling depths and movements of North Atlantic right whales using multipath localization
Authors: Valtierra Robert D. , VanParijs Sofie M. , Holt R. G. , Cholewiak Danielle M.
Published: September 2012

The track and calling depths of a North Atlantic right whale (NARW) recorded by 10 bottom-mounted Autonomous Acoustic Recording Units (ARUs) in the Stellwagen Bank National Marine Sanctuary was determined using the Direct Reflected Time Difference of Arrival (DRTD) localization method. An autocorrelation technique was used to extract direct-reflected time difference of arrival information from recorded NARW up-calls containing several overlapping multipath signal arrivals. The method’s feasibility was tested using data from play back transmissions to localize an acoustic transducer at a known depth and location. The method was then used to track an hour of movements and depths of a single NARW using periodic up-calls for localization purposes.
Bidirectional equalization for underwater acoustic communications
Authors: Song Hee-Chun
Published: September 2012

The bi-directional decision feedback equalizer (BiDFE) that combines the outputs of a conventional DFE and backward DFE can improve the performance of the conventional DFE by up to 1-2 dB based on simulations. In this paper, the BiDFE concept is extended to multi-channel time reversal communications involving a DFE as a post-processor. Experimental data collected in shallow water (10-20 kHz) show that the performance can be enhanced by 0.4-1.8 dB in terms of output SNR. In particular, a larger improvement (e.g., 1.8 dB) is achieved for time-varying channels where the channel diversity in opposite directions is more profound.
Acoustical Society of America Silver Medal in Physical Acoustics
Authors: Prosperetti Andrea
Published: September 2012

The Silver Medal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.
Underwater radiated noise and impact assessment of marine piling operations during offshore windfarm construction
Authors: Lepper Paul A. , Robinson Stephen P. , Theobald Pete D.
Published: September 2012

In UK waters numerous large scale offshore wind farm developments have been constructed typically using large hollow steel mono-pile foundations with pile diameters varying from a few meters to greater than 6 m diameter and lengths 60-80 m. Piles may be driven 20-30 m into the seabed in water depths from a few meters to greater than 30 m. Typically percussive piling construction operations are used with many thousands of individual strikes over periods of several hours resulting in repetitive high amplitude impulsive sound within the water column that has potential for impact on marine life. Data is presented for in-situ measurements made during installation a range of mono-pile diameters used on offshore windfarms. Full piling sequences were recorded at fixed ranges using fixed autonomous data loggers and sampled range dependent boat based measurements. Simultaneous recordings at multiple ranges varying from 10’s meters to 10’s km were made. Data is analyzed in terms of received levels, spectral and temporal components. Using range dependent propagation loss modeling equivalent mono-pole source levels are estimated. Level dependence on range, hammer energy, etc. are discussed. A Monte Carlo approach is used to obtain total cumulative exposure (SEL) risk for single foundation to whole windfarm construction scenarios.
Modeling underwater impact pile driving noise in shallow, inhomogeneous channels
Authors: Laws Nathan D. , Zurk Lisa , Schecklman Scott , Siderius Martin
Published: September 2012

The broadband synthesis of a parabolic equation (PE) propagation model for shallow water acoustic propagation in inhomogeneous channels is presented to account for the noise produced by impact pile driving. The PE model utilizes sediment information obtained from boring measurements and detailed bathymetry to model range dependent propagation in the Columbia River between Portland, OR and Vancouver, WA. The impact pile driving source is modeled in two ways: first, as a reverberating impulse source that emits Mach-wave radiation [Reinhall, Dahl, J. Acoust. Soc. Am. 130, 1209 (2011)]; and second, with a structural acoustic finite-difference time-domain (FDTD) model [Shahab, Woolfe, and Hastings, J. Acoust. Soc. Am. 130, 2558 (2011)]. Model results using both source models are shown to be in good agreement with acoustic measurements of test pile operations in the Columbia River at multiple locations from 10 to 800 meters from the pile driving source. Implications for noise levels in river systems with varying bottom sediment characteristics are presented and discussed. [This research is supported with funding from the Oregon Department of Transportation.]
Effect of inter-element apodization on passive cavitation images
Authors: Haworth Kevin J. , Mast T. D. , Radhakrishnan Kirthi , Holland Christy K.
Published: September 2012

Acoustic cavitation has been correlated with a variety of ultrasound-mediated bioeffects. Recently developed passive cavitation imaging methods provide spatially resolved maps of cavitation activity with good azimuthal resolution but poor axial resolution. Here, inter-element apodization is investigated as a means of improving image quality. Cavitation was induced from echogenic liposomes in a flow phantom exposed to 6 MHz Doppler ultrasound (Philips HDI-5000). The resulting acoustic emissions were passively recorded on 64 elements of a linear array (L8-3 transducer, Zonare z.one ultra scanner). Amplitude scaling of each waveform by its root-mean-square value improved axial resolution at the expense of creating an ‘X-shaped’ artifact. Cosine amplitude apodization of the received waveforms across the array and centered about the azimuthal location of the beamformed image pixel was found to reduce grating lobe artifacts. Numerical time reversal of the received waveforms, using the Fresnel approximation for the acoustic field of each array element, resulted in an effective apodization due to element directivity and also reducing grating lobe artifacts. Applying apodization may be an effective means of increasing passive image quality for certain cavitation distributions, which will be discussed. [Supported in part by NIH grants F32HL104916, R01HL074002, R21EB008483, R01HL059586, and R01NS047603.]
Scattering by bubbles at frequencies well below resonance
Authors: Culver R. L. , Smith Robert W. , McElhone Dale I.
Published: September 2012

We are interested in acoustic scattering by bubble clouds in water at frequencies and densities such that the acoustic wavelength is large relative to the average distance between bubbles and large relative to that corresponding to the bubble resonance frequency. At high frequency and moderate bubble density, bubble scattered intensity is proportional to N (the number density of the bubbles, m4), which corresponds to incoherent scattering. Effective medium theory has been shown to predict predominantly incoherent scattering at high frequencies, but coherent scattering (scattered intensity proportional to N2) at lower frequencies. An incoherent scattering assumption at low frequencies can substantially under predict the intensity of the scattered signal. Coherent (low frequency) scattering from bubble assemblages has also been explained in terms of collective shape, but this approach does not provide a means of predicting the temporal extent of the scattered signal in low frequency regimes. The literature apparently does not provide precise guidance as to when and how bubble scattering transitions from incoherent to coherent scattering in response to increasing wavelength, and the relationship between the acoustic wavelength and average bubble separation. Modeling and a tank experiment are underway that we hope will provide some answers to this question.
Low-frequency measurement of encapsulated bubble compressibility
Authors: Schoen Scott J. , Ilinskii Yurii A. , Zabolotskaya Evgenia A. , Hamilton Mark F.
Published: September 2012

Interest in measuring underground water flow has motivated synthesis of encapsulated microbubbles for use as contrast agents. The large acoustic attenuation in earth prohibits use of the high frequencies required to exploit resonant scattering. Instead, contrast enhancement must rely on the reduction of acoustic impedance due to higher compressibility of the microbubbles. Bubble compressibility is measured at the kilohertz frequencies of interest using a resonance tube filled with water and observing the change in tube resonance frequency due to the presence of bubbles for different void fractions [Wilson and Dunton, J. Acoust. Soc. Am. 125, 1951 (2009)]. Buoyancy makes it difficult to maintain a uniform distribution of bubbles throughout the tube in order to relate sound speed to resonance frequency. Therefore, the bubbles were restrained with acoustically transparent barriers to form discrete layers within the water column. A model was developed to investigate the effect on the tube resonance frequency due to different spatial distributions of the bubble layers, and the predictions were compared with measurements. Good agreement with the known compressibility of air was obtained experimentally with only three or four layers. [Work supported by Advanced Energy Consortium.]
Application of inversion techniques for bubble size spectra from attenuation measurements in lab-generated bubble distributions
Authors: McElhone Dale I. , Smith Robert W. , Culver R. Lee
Published: September 2012

The size distribution of a bubble population can be estimated from measurements of the frequency-dependent attenuation through the bubble cloud. These attenuation values are the inputs to an inversion method that makes use of a resonant bubble approximation wherein it is assumed that only resonant bubbles contribute to the attenuation at a given frequency, e.g., Caruthers et al., [JASA (1999)]. H. Czerski has shown that power law bubble distributions proportional to (radius)x, where x≤-2, have few enough large bubbles for resonant bubble inversion methods to yield accurate results. In this paper, the Caruthers and Czerski inversion methods are both verified with synthetic data and applied to acoustic measurements in a fresh water tank using lab-generated bubble distributions. Work sponsored by the Office of Naval Research, Code 321US.
Investigating the fidelity of a pseudo-analytical solution of a rib-stiffened, layered plate structure subjected to high frequency acoustic loading
Authors: Teferra Kirubel , Cipolla Jeffrey
Published: September 2012

There is a need for a fast and reliable tool to assist in the analysis, design, and optimization of submarine and UUV coatings due to high frequency incident acoustic pressure loading. An existing pseudo-analytical, frequency domain solution for wave propagation in coated, ribbed, three-dimensional elastic layered plates excited by acoustic plane waves provides fast solutions for high frequency excitations. Weidlinger Associates, Inc. (WAI) is developing an analysis software tool which integrates this solution methodology while adding some technical improvements to the formulation. The solution methodology, which is found to be numerically unstable under certain conditions, contains a fundamental ansatz regarding the set of excited wave forms expressed through a particular wave number expansion in the direction of periodicity. Evidence is presented to show that the numerical instability is due to the specific choice of the wave number basis used in the solution. In order to provide a remedy while retaining the positive aspects of the solution methodology, WAI is implementing a pre-processing step to determine the optimal wave number basis: the set of admissible propagating (and attenuating) waves are predetermined via an eigenvalue analysis and then substituted into the wave number basis in computing the pseudo-analytical solution.
Damping of flexural vibrations in plates containing ensembles of tapered indentations of power-law profile
Authors: Bowyer Elizabeth P. , O'Boy Daniel , Krylov Victor V.
Published: September 2012

In this work, we report experimental results on damping flexural vibrations in rectangular plates containing tapered indentations (pits) of power-law profile, the centres of which are covered by a small amount of absorbing material. In the case of quadratic or higher-order profiles, such indentations materialise two-dimensional acoustic ‘black holes’ for flexural waves. Initially, the effects of single pits have been investigated. It has been found that, in order to increase the damping efficiency of power-law profiled indentations, their absorption cross-sections should be enlarged by drilling a central hole of sufficiently large size (14 mm), while keeping the edges sharp. Such pits, being in fact curved power-law wedges, result in substantially increased damping. The next and the major part of this investigation involved using multiple indentations in the same rectangular plates to increase damping. Plates with combinations from two to six equal indentations have been investigated. The results show that, when multiple indentations are used, the associated damping increases substantially with the increase of a number of indentations. For the plate with 6 indentations, the resulting damping becomes comparable if not greater than that achieved by a wedge of power-law profile.
Identifying highly rhythmic stretches of speech with envelope-driven resonance analysis
Authors: Tilsen Sam
Published: September 2012

This paper proposes envelope-driven resonance analysis as a technique for characterizing rhythmicity in speech, emphasizing the degree to which a brief stretch of speech creates a rhythmic expectancy. Most approaches to characterizing the rhythm of speech have utilized measurements derived from the durations of linguistically relevant units such as feet, syllables, or vocalic/consonantal intervals. Recently, alternative approaches have been developed which are based upon the amplitude envelope of the speech waveform after the waveform has been filtered to emphasize low-frequency oscillations associated with alternations between vowels and consonants. These approaches include spectral analysis and empirical mode decomposition of the envelope. The method explored here is resonance analysis, which utilizes a bank of resonators that differ in their characteristic resonant frequencies. The resonators are 2nd order dynamical systems analogous to driven, damped springs. The powers of the resonator amplitudes are analyzed during and subsequent to excitation by a speech amplitude envelope. The power and frequency distribution of the resonant response is used to identify highly rhythmic stretches of speech and characterize their spectral properties.
Analysis of rhythm performance strategies on the Indian tabla as a function of tempo
Authors: Singh Punita G.
Published: September 2012

In north Indian classical music, the range of tempi can extend from the ultra-slow ‘vilambit’ at less than a beat every 5 seconds to the super-fast ‘drut’ at over 10 beats per second. To hold a rhythm at these speeds and generate a perceptible metrical structure, performers routinely alter playing strategies that derive from neurophysiological and psychoacoustical considerations. At slow speeds, theoretically silent intervals are in practice punctuated by filler sounds to maintain perceptual connectivity. At high speeds, an interesting phenomenon is observed as compound sounds or ‘bols’ segregate into their simpler components, forming auditory streams of acoustically similar sounds. Compound bols such as ‘dha’ break up into the tonal ‘ta’ and the noisy ‘ghe’, with the sequence of rapidly recurring ‘ghe’ sounds forming a noise band that could potentially mask tonal accent markers. To avoid this, performers routinely drop out the ‘ghe’ sounds at high speeds at metrically unimportant points in the sequence, while retaining them at points that would mark accents. These playing strategies are useful in providing mental and physical relief to performers in maintenance of a steady rhythm across such a vast range of tempi while also preserving the rhythmic integrity of the music for listeners.
Classroom acoustics 2012: Recent developments, current issues, and field reports
Authors: Lubman David , Sutherland Louis C.
Published: September 2012

This introductory paper provides an overview of the papers in this session. It showcases important findings of the UK’s Essex Study by David Canning & Adrian James (2012) which confirms large listening benefits for reducing reverberation times (RT) to 0.4 sec or less. The Essex study also found a marked drop in LA90 for occupied classrooms when RT was halved. This introductory paper also briefly reviews the Acoustical Society of America’s initial actions leading to development of the influential ANSI standards on classroom acoustics (S12.60 - 2010/Parts1 and 2), and subsequent outreach actions, including publication of Classroom Acoustics booklets. (Two new booklets, one aimed at Educators and the other aimed at Architects, are being prepared for publication.) Also reviewed is the ongoing struggle to incorporate meaningful noise and reverberation time criteria into design guidelines for the California Collaborative for High Performance Schools, Los Angeles Unified School District, and LEED for Schools. Finally, it shows that noise transients occurring during classroom noise measurements can make quiet classrooms seem misleadingly noisy.
Effectiveness of steady versus varied-color/varied-pattern visual tasks during acquisition of late auditory evoked potentials
Authors: Marx Charles G. , Goshorn Edward L.
Published: September 2012

Instructions for late auditory evoked potential (LAEP) testing include a need for the subject to remain alert (not go to sleep). Previous studies show an inverse relationship between alertness level and waveform morphology. Thus, a need exists to maintain alertness during LAEP testing. If not maintained, a wide range of alertness, and thus waveform morphology, may exist from one run to the next. Therefore, if alertness level is not controlled, any variations in waveform morphology may be due to variations in alertness rather than auditory system integrity. Previous investigators have implemented visual tasks consisting of still or action images in an attempt to maintain alertness. In these visual tasks, a subject is typically instructed to attend to a video screen during LAEP testing. This project investigated the effectiveness of two visual task screens: unvaried blue with no pattern, versus varied colors-patterns occurring in 1-3 second random intervals. LAEPs were gathered on twenty-five young adult subjects who were instructed to attend to a video display of one of the screens during LAEP testing. Six replicates were obtained for each screen in counter-balanced order. Results showed no significant (p>.05) differences in mean P1 or P2 latency or amplitude for the two screens.
Temporal weighting for interaural time differences in low-frequency pure tones
Authors: Diedesch Anna C. , Bibee Jacqueline M. , Stecker G. Christopher
Published: September 2012

In contrast to envelope-based interaural time differences (ITD) at high frequencies, where sound onsets play a dominant role, the reliability and salience fine-structure ITD at low frequency (<1500 Hz) suggests uniform sensitivity to information across periods of an ongoing stimulus waveform. Several past studies, however, have demonstrated low-frequency ITD thresholds to improve sub-optimally with increasing sound duration [e.g. Houtgast & Plomp 1968, JASA 44:807-12], suggesting that the initial periods of a brief tone play a greater role in ITD processing than do later periods. Here, we measured the temporal profile of ITD sensitivity in pure tones ranging from 250-1000 Hz. Sounds were presented with ITD that either remained fixed over the sound duration (condition RR) or progressed linearly to eliminate the ITD cue from either the beginning (condition 0R) or end (R0) of the sound. Durations varied from 40-640 ms, including 20 ms ramps applied diotically to minimize envelope cues. ITD detection thresholds demonstrated (a) suboptimal improvement with duration and (b) greater sensitivity to ITD available early (R0) rather than late (0R) in the stimulus, a pattern nearly identical to that observed for high-frequency envelope ITD. [Supported by NIH R01 DC011548.]
How talker-adaptation helps listeners recognize reduced word-forms
Authors: Poellmann Katja , McQueen James M. , Mitterer Holger
Published: September 2012

Two eye-tracking experiments tested whether native listeners can adapt to reductions in casual Dutch speech. Listeners were exposed to segmental ([b] > [m]), syllabic (full-vowel-deletion), or no reductions. In a subsequent test phase, all three listener groups were tested on how efficiently they could recognize both types of reduced words. In the first Experiment's exposure phase, the (un)reduced target words were predictable. The segmental reductions were completely consistent (i.e., involved the same input sequences). Learning about them was found to be pattern-specific and generalized in the test phase to new reduced /b/-words. The syllabic reductions were not consistent (i.e., involved variable input sequences). Learning about them was weak and not pattern-specific. Experiment 2 examined effects of word repetition and predictability. The (un-)reduced test words appeared in the exposure phase and were not predictable. There was no evidence of learning for the segmental reductions, probably because they were not predictable during exposure. But there was word-specific learning for the vowel-deleted words. The results suggest that learning about reductions is pattern-specific and generalizes to new words if the input is consistent and predictable. With variable input, there is more likely to be adaptation to a general speaking style and word-specific learning.
Lexical representation of perceptually difficult second-language words
Authors: Broersma Mirjam
Published: September 2012

This study investigates the lexical representation of second-language words that contain difficult to distinguish phonemes. Dutch and English listeners' perception of partially onset-overlapping word pairs like DAFFOdil-DEFIcit and minimal pairs like flash-flesh, was assessed with two cross-modal priming experiments, examining two stages of lexical processing: activation of intended and mismatching lexical representations (Exp.1) and competition between those lexical representations (Exp.2). Exp.1 shows that truncated primes like daffo- and defi- activated lexical representations of mismatching words (either deficit or daffodil) more for L2 than L1 listeners. Exp.2 shows that for minimal pairs, matching primes (prime: flash, target: FLASH) facilitated recognition of visual targets for L1 and L2 listeners alike, whereas mismatching primes (flesh, FLASH) inhibited recognition consistently for L1 listeners but only in a minority of cases for L2 listeners; in most cases, for them, primes facilitated recognition of both words equally strongly. Importantly, all listeners experienced a combination of facilitation and inhibition (and all items sometimes caused facilitation and sometimes inhibition). These results suggest that for all participants, some of the minimal pairs were represented with separate, native-like lexical representations, whereas other pairs were stored as homophones. The nature of the L2 lexical representations thus varied strongly even within listeners.
Depth discrimination using waveguide invariance
Authors: Turgut Altan , Fialkowski Laurie T.
Published: September 2012

Waveguide invariant theory is used to analyze the acoustic striation patterns generated by a moving surface vessel and a towed broadband (350-600 Hz) source during two field experiments (TAVEX08, AWIEX09) conducted in the East China Sea and New Jersey Shelf. Results from the East China Sea site indicated that slopes of striation patterns are different when the source is below the thermocline and receivers are below and above the thermocline. However, slopes are the same when the source (surface vessel) is above the thermocline and receivers are below and above the thermocline. In addition, results from the New Jersey Shelf site indicated that slopes of striation patterns are different when two co-located sources (tow-ship and towed source) are placed below and above the thermocline, and received on a single hydrophone below the thermocline. Results are explained by the dominance of reflecting and refracting modes for sources being above or below the thermocline during summer profile conditions. [Work supported by the Office of Naval Research.]
Acoustic cavitation localization in reverberant environments
Authors: Anderson Samuel J. , Perlitz Daniel A. , Bonness William K. , Capone Dean E.
Published: September 2012

Cavitation detection and localization techniques generally require visual access to the fluid field, multiple high-speed cameras, and appropriate illumination to locate cavitation. This can be costly and is not always suitable for all test environments, particularly when the bubble diameter is small or duration is short. Acoustic detection and localization of cavitation can be more robust and more easily implemented, without requiring visual access to the site in question. This research utilizes the distinct acoustic signature of cavitation events to both detect and localize cavitation during experimental water tunnel testing. Using 22 hydrophones and the processing techniques plane-wave beamforming and Matched-Field Processing (MFP), cavitation is accurately and quickly localized during testing in a 12” diameter water tunnel. Cavitation is induced using a Nd:YAG laser for precise control of bubble location and repeatability. Accounting for and overcoming the effects of reflections on acoustic localization in acoustically small environments is paramount in water tunnels, and the techniques employed to minimize error will be discussed.
Methods of discovering problem room modes
Authors: Bridgewater Ben
Published: September 2012

Determining the best course of action to eliminate problem room modes in the Kansas Public Radio Live Performance studio required a way of measuring room modes and determining the problem dimensions. This case study focuses on how the room modes where measured and the determination of the problem modes in the KPR studio.