bluuebunny/crossref_metadata_2025 huggingface dataset:
The open office privacy calculator: A value engineering tool for acoustic professionals
Authors: Kemp Jonathan , Bell Mark , Horrall Thomas
Published: October 2013

Open-plan spaces consistently challenge architects and acoustic consultants to achieve reasonable speech privacy and low inter-office distraction. This paper presents a computerized tool to optimize design decisions, maximizing speech privacy while minimizing design effort and implementation cost. Speech privacy can be estimated through real-time calculation of the Speech Privacy Index (SPI) at a grid of points in a given simulated open office plan. The Open Office Privacy Calculator graphically shows how much workers in that open office would be distracted by any single speaking person and the impact of office environmental parameters on the level of distraction. The tool provides a direct graphical link between design decisions, cost, and acoustic performance for partition height, ceiling height, ceiling type, and the addition of sound masking. Further, this tool introduces the Distraction Index (DI), a measure of how many adjacent office talkers that a given office worker can routinely be distracted by (SPI=70%). The combination SPI/DI Calculator allows acousticians and architects to make informed value judgments, choosing design elements which have the greatest impact on speech privacy. The Calculator has been validated with measured data and by comparison with other existing and accepted models for predicting SPI in office spaces.
Herman Medwin as observed by an interested bystander
Authors: Wright Wayne M.
Published: October 2013

Herman Medwin was a brilliant scientist, a complex individual, and a strong-willed advocate. Although his most significant scientific contributions were associated with acoustical oceanography, his professional creativity was not limited to this technical field. Hank’s graduate work at UCLA involved acoustic streaming in gases; in his early professional years he reported substantial work with intense sound waves in gases; he was an accomplished violinist; and his final published work involved auditorium acoustics. His contributions to the Acoustical Society of America were particularly noteworthy, from his initial service as a technical committee and Executive Council member through its presidency. His well-deserved recognition by ASA included award of the Silver Medal in Acoustical Oceanography and the Gold Medal. He spearheaded establishment of the Medwin Prize in Acoustical Oceanography, which is awarded annually by ASA to provide recognition to mid-career researchers in the field. Personal observations are given on some of these topics by an outsider (from AO), who was privileged to spend a year assisting with Hank’s research, and who closely followed his experiences with ASA through the formalities associated with creation of the prize given in his name.
High-frequency broadband (150–600 kHz) acoustic backscattering from oceanic microstructure and zooplankton in the presence of internal solitary waves
Authors: Lavery Andone C. , Chu Dezhang
Published: October 2013

As one of the founders of acoustical oceanography, Hank Medwin has directly or indirectly influenced the careers of many scientists. Throughout his illustrious and prolific career, Hank Medwin was passionate about using and developing acoustic techniques to study the ocean and, in particular, to study the physical processes of the ocean interior, a passion shared by the authors. In this spirit, the authors present highlights of an experiment in which a high-frequency broadband (150–600 kHz) acoustic backscattering system was used to investigate the scattering of sound from oceanic microstructure and zooplankton throughout the evolution, from generation to dissipation, of internal solitary waves. The broadband spectrum of the scattered returns is used to differentiate between regions in which the scattering is dominated by zooplankton versus microstructure. Interpretation of the measured scattering relies heavily on a fundamental understanding of scattering processes as well as on direct measurements of microstructure and biology.
Operator noise exposure reduction using coated conveyor chain flight bars
Authors: Smith Adam K. , Kovalchik Peter G. , Alcorn Lynn A.
Published: October 2013

Continuous miners are one of the fundamental machines used to cut, gather, and remove coal and noncoal minerals from underground room and pillar mining facilities. These machines are among mining equipment that generates the highest sound levels in an underground environment. The Mine Safety and Health Administration has determined that continuous mining machines rank first among all equipment in underground coal mining whose operators exceed 100% noise dosage. The conveying system is one of the principal noise sources on continuous mining machines, due to metal on metal impacts that occur between chain flights and the conveyor deck. A highly durable polyurethane coating has been developed by NIOSH for the chain flights to decrease noise generated by these impacts. A continuous mining machine retro-fitted with coated flight bars have achieved overall sound level reductions of 5–7 dB(A) in a laboratory setting (Kovalchik et al., 2004). This research describes the effectiveness of this engineering noise control in reducing the noise exposure of continuous mining machine operators in an underground environment. Results show that continuous mining machine operators receive a 3 dB(A) time-weighted average reduction over an 8-h period.
Global temporal characteristics of English clear and conversational speech
Authors: Smiljanic Rajka , Viau Josh , Bradlow Ann
Published: October 2013

This study investigated the effect of hyperarticulated, intelligibility-enhancing clear speech on global temporal characteristics in paragraph-length utterances. The results of sentence-in-noise listening tests showed a consistent clear speech intelligibility gain across the utterances indicating that the talkers successfully maintained clear speech articulatory modifications throughout the paragraphs. We then explored temporal properties of the speech signal in terms of the percentage and variability of vocalic and consonantal intervals (following Ramus et al., 1999). Consonantal and vocalic intervals were lengthened equally in clear speech: %V remained stable across speaking styles. Moreover, coefficients of variation for both consonantal and vocalic intervals remained stable across clear and conversational speech, suggesting that global temporal properties remain rather stable in the two speaking styles. There was also evidence of an increase in the number of prosodic phrases and of vocalic and consonantal intervals for clear speech. Longer durations of consonantal segments in combination with insertion/strengthening of short consonantal segments that were dropped or coarticulated in conversational speech were reflected in an increased consonantal standard deviation in clear speech. Overall, these results suggest that increased intelligibility of clear speech may be attributed to prosodic structure enhancement (increased phrasing and enhanced segmentability) and stable global temporal properties.
Does the production of speech necessarily rely on auditory feedback?
Authors: Byrne Stacie K. , Johnsrude Ingrid S. , Munhall Kevin G.
Published: October 2013

Talkers show sensitivity to a range of perturbations of auditory feedback (e.g., manipulation of vocal amplitude, fundamental frequency, formant frequency). When the auditory concomitants of speech (feedback) are perturbed, talkers compensate in order to preserve accurate productions. These effects demonstrate the role of sensory feedback in articulatory control and have been used to study the role of prediction in motor planning. In this study, 15 subjects spoke a monosyllable (‘head’) and the formants in their utterances were shifted in real time using a custom signal processing system and were fed back over headphones with an imperceptible delay. The first and second formants were altered so that the auditory feedback matched the subjects’ productions of ‘had’. Despite explicit instruction to ignore the feedback changes and maintain consistent production of ‘head’, subjects produced a robust compensation similar to the compensatory behavior shown by naive subjects. In general, subjects altered their vowel formant values in a direction opposite to the perturbation, as if to cancel its effects. These results suggest that compensation in the face of formant perturbation is automatic and obligatory. Results will be discussed in terms of the representations that guide speech motor control. Work supported by NIDCD and NSERC.
Robust ground vehicle classification using the modulation spectrogram
Authors: Oh Geok Lian
Published: October 2013

The performance of a vehicle classification system using acoustic emissions is affected by acoustic interferences such as wind noise. In this paper, we propose using the modulation spectrogam as features for classification. This is done by extraction of the temporal structure in the vehicular sounds that appear as amplitude modulations in the frequency band corresponding to the harmonic structure present in the vehicular sounds. The amplitude modulations are processed in subband channels following critical band frequency analysis. Our results of the visual displays of vehicle sounds produced with the modulation spectrogram are relatively stable in the presence of wind noise. This suggests that the use of the modulation representation is another method for improving the robustness of vehicle classification system. In the paper, we apply the suggested approach to classify between four classes of vehicles and obtain reasonably good classification rate even for data contaminated with interferences.
Single and multiple channel estimation using the time-updated recursive least squares algorithm
Authors: Li Weichang , Preisig James
Published: October 2013

A time-updated recursive least squares algorithm (TURLS) is presented, analyzed, and applied to the problem of estimating the time-varying impulse response in both single and multiple channel cases. The TURLS algorithm may be viewed as a least squares extension of the EM channel estimation algorithm [W. Li and J. C. Preisig, ICASSP, IV 313IV, 316 (2005)], in the sense that it jointly estimates the channel impulse response and its dynamic parameters by minimizing a least squares error instead of maximizing the likelihood function. Based on the intuition that the sequence of channel estimates contains information regarding the true channel dynamics, the algorithm estimates the parameters from the sequence of channel estimates. Analysis of the algorithm based on a first-order AR channel model shows that the resulting channel estimate is a second-order approximation whose poles converge as the parameter estimate improves. In addition, it is shown that with exponential weighting, the resulting parameter estimate may be biased at low SNR level. The algorithm is applied to experimental data and results with both single channel and multiple channels are demonstrated. [Work supported by ONR Ocean Acoustics.]
Estimating the state of a one-dimensional waveguide
Authors: Berdahl Edgar , Smith Julius
Published: October 2013

Methods for estimating the state of a one-dimensional waveguide are analyzed. The state is parameterized in terms of right-going and left-going traveling waves for applications in reflectometry and control. Traditional methods estimate the localized state at a single position in the waveguide. In many cases, the history of a simple estimator may serve as time-delayed or time-advanced estimates for the remainder of the waveguides state. The decomposition method estimates the traveling wave components at a point using integration and a spatial gradient approximation. The delay method, which involves implementing a single delay accurately, is shown to be equivalent to the causal Wiener filter least-squares optimal estimator. If sensors are spaced irregularly, then an optimization problem typical of beam forming applications may be solved to find an FIR filter-based localized estimator. On the other hand, when the estimator needs to estimate the entire waveguide state quickly, then either additional sensors or computation cycles are required. The Kalman filter requires much more computation in general, but with the help of a digital waveguide model, it can provide complete state estimates with less than one sample of delay using as few as one sensor. [Work supported by the Wallenberg Global Learning Network.]
Evolution of hearing specializations in teleost fishes
Authors: Braun Christopher B. , Brande Terry
Published: October 2013

Among teleost fishes, the spectacular diversity of body forms, ecotypes, and behavioral repertoires is matched by a tremendous diversity of hearing mechanisms and, presumably, auditory function. Morphological specializations with the potential to enhance hearing have arisen as many as 20 times within teleosts. These specializations range from modest modifications of the buoyancy-regulating gas bladder to wholesale reorganization of the rostral vertebral column and posterior neurocranium. Since many of these specializations involve vertebral elements and/or cranial modifications, it is possible to recognize enhanced hearing in fossil taxa. Other specializations, like the rostral swimbladder extensions of some holocentrids, appear to provide similar, but more modest, enhancements. In other cases, however, rostral swimbladder extensions may only increase the upper frequency limit (as in some scaeinids) or somehow underlie improved spectral resolution (in notopterids). The functions of these and many other specializations await more complete functional characterization. For instance, the number, linkages, and robustness of Weberian ossicles vary considerable within Otophysi, and it is clear that hearing abilities differ widely, too. How and why individual Weberian apparatus morphologies confer differences in hearing abilities remains a critical issue in studies of fish hearing.
The evolution of the mammalian middle ear
Authors: Rosowski John J.
Published: October 2013

The transition from water-to-land in vertebrate evolution precipitated physical differences between sound transmission in the new surround (air) and the water-filled inner ear. These physical differences led to the development of the vertebrate middle ear. The old idea that the middle ear first developed in amphibians, was refined in reptiles and birds, and was further refined in mammals has been contradicted by the available paleontologic evidence which clearly points to the independent development of the tympanic-ossicular middle ear in multiple vertebrate lines, including amphibians, reptiles, and mammals. Indeed, mammalian and reptilian evolutionary trees diverged over 300 million years ago at a time well before the development of either the reptilian or mammalian middle ear. The evidence on the evolutionary development of the mammalian middle ear will be reviewed and put in context of the development of the reptilian and bird middle ears. Attempts to describe the function of the early mammalian ear will also be made through comparisons with the function of ears of similar structure in living animals. The significant influence of the evolving inner ear will be a major point of discussion. [Work supported by the NIDCD.]
Searching among felids for evolution’s influences on middle ears
Authors: Peake William T. , Rosowski John J. , Peake Helen C.
Published: October 2013

The 36 cat species display moderate structural variations that may be adaptive, involving species ethology, size, and lineage. Measurements of skull dimensions, acoustic responses in live and cadaver ears, and auditory brain-stem responses in anesthetized specimens have been collected. Of special interest are interspecies variations in the acoustic properties of the felid middle-ear air space, which has two coupled cavities separated by a bony septum. The acoustic effect of the cavities is to decrease middle-ear response uniformly for low frequencies, and to produce a narrow-band reduction at a mid frequency determined by the cavities configuration. We address two issues: (1) The volume of the cavities increases with species size. A physics-based model shows that the cavity-related loss in low-frequency middle-ear transmission decreases from 10 dB for the smallest species to 1 dB in lions. Is this size-dependent variation adaptive? (2) The configuration of the cavities-dividing septum is unusual in eight species, all of which have relatively wide facial skulls and live in open habitats; as these species represent six of nine lineage groups, this constellation of habitat, skull, and ear features apparently evolved several times. Can we hypothesize a testabIe, adaptive mechanism? [Work supported by NIH and NSF.]
The molecular basis for auditory system evolution
Authors: Fritzsch Bernd , Feng Feng , Nichols David
Published: October 2013

Evolution of the auditory system requires coordinated changes in three interrelated systems: the ear, sensory neurons, and brainstem. The auditory periphery evolved by building on the capacity of vestibular hair cells to respond to mechanical stimulation, then segregating a distinct sensory patch dedicated to processing auditory information and evolving accessory structures. Auditory ganglion neurons share much of the molecular basis of their development with vestibular neurons and are, therefore, likely derived from vestibular neurons, possibly through the expression of specific genes such as the zinc finger protein Gata3. In mammals, Gata3 is selectively associated with spiral sensory neurons. Hair cells, sensory neurons, and central auditory nuclei development depends on only two bHLH genes, Atoh1 and Neurog1. Atoh1 null mutant mice never differentiate hair cells and show an almost complete loss of cochlear nuclei. In contrast, Neurog1 null mice form no sensory neurons. Overall, the ear hair cells, sensory neurons, and the brainstem auditory nuclei show molecular conservation of critical regulatory genes, embedded in an organ-specific molecular context which results in the modification of the developmental pathways governed by these conserved molecules to serve either hair cell or cochlear nucleus neuron differentiation in the case of Atoh1.
Binaural interaction in the medulla and midbrain of toadfish (Opsanus tau)
Authors: Fay Richard , Walton Peggy
Published: October 2013

Responses of cells in the toadfish medulla (descending octaval nucleus: DON) and midbrain (torus semicircularis: TS) were studied to investigate binaural interaction and processing. Normally, the two ears of fish cannot be stimulated independently. A method was developed to temporarily inactivate one ear by slightly displacing the saccular otolith on one side (tipping) to change its orientation in space and, therefore, alter the responsiveness of the hair cells. Brain cells were evaluated for directional characteristics and frequency response (1) before otolith tipping, (2) with the otolith tipped, and (3) post-tipping. For DON cells (n=14), contralateral saccular otolith tipping most often resulted in subtle effects consisting of an overall change in responsiveness (±spikes/sec); significant changes in the preferred direction were rare. In the TS (n=20), most cells exhibited changes in responsiveness and in directionality. These experiments demonstrate the existence of excitatory and inhibitory binaural interactions in the medulla and midbrain and show rather complex and unexpected binaural effects on the responsiveness and directional properties of auditory brain cells. [Work supported by the NIH/NIDCD.]
Proof that plane wave attenuation at low frequencies is proportional to square of frequency
Authors: Pierce Allan D. , Carey William M.
Published: October 2013

Several published and presented papers by Ingenito [1973], Zhou and Zhang [2005], and others have discussed the attenuation of sound in marine sediments at low frequencies, and another is shortly to appear [Holmes, Carey, Dediu, and Siegmann, JASA Express Letters, 2007], the latter reporting a nonlinear frequency dependence as ωn, where n=1.8±0.2; earlier literature gives results with non-integer values of n that are between 1 and 2. The present paper argues that the exponent should be exactly 2 in the limit of low frequencies, given that the sound speed is finite. Plane wave propagation in a general medium allows specific modes for which wavenumber k is a given function k(ω). Attention is given to those propagating modes where the real part of k is proportional to ω at low frequencies, so that the phase velocity approaches a finite value as the frequency goes to zero. For such circumstances, causality considerations require the imaginary part of k to have a low-frequency dependence that is as the square of frequency or weaker.
A time-frequency distribution-based approach for modal eigenvalue estimation in range-dependent shallow-water waveguides
Authors: Ballard Megan , Becker Kyle
Published: October 2013

In shallow water, geoacoustic properties of the seafloor can be inferred from estimates of modal eigenvalues. For range-dependent environments, horizontal wave numbers associated with propagating modes are sensitive to both changes in bathymetry and sediment properties. Assuming slow variations in the environment, range-dependent wave number estimates can be obtained using short-time Fourier transform (STFT) based approaches. Alternatively, range-dependent wave number estimation can be achieved using time-frequency distributions (TFDs). Traditionally, TFDs have been used for the analysis of signals containing multiple time-varying frequencies. In this work, these methods are applied to horizontal line array data in the spatial domain to reveal instantaneous changes of discrete horizontal wave numbers. In contrast to STFT-based approaches, which assume the environment be comprised of multiple, nearly range-independent segments, the time-frequency distribution approach allows for continuous variations of waveguide properties. Instantaneous wave numbers estimated by TFDs clearly reveal range dependence of the geoacoustic environment through a simple graphic representation. The discrete Wigner-Ville distribution was used for this work with smoothing employed to suppress artifacts caused by closely spaced wave numbers. The utility of using TFDs is demonstrated by application to several range-dependent environments. [Work supported by a NDSEG fellowship and ONR.]
Biological cell and bubble interactions and behavior in acoustic fields
Authors: Allen John S. , Zinin Pavel
Published: October 2013

For developing biomedical ultrasound applications such as drug delivery, a more comprehensive understanding of the interaction of an individual cell in an acoustic field with a cavitation bubble at close vicinity is needed. The underlying mechanisms of these phenomenons are not well understood since limited analytical theory exists on the governing mechanics of these interactions. A recent model [Zinin, Allen and Levin, Phys. Rev. E, 2005] for the natural oscillations of a biological cell in a high frequency acoustic field is extended to account for the cells response and deformation from a nearby oscillating bubble. The elastic properties of the cells membrane and viscous properties of the cytoplasma (internal fluid) and the surrounding fluid media are considered in this model. The cells mechanical response is dominated by the surface area modulus (dipole) or shear modulus (quadrupole). The induced stress on the cells membrane from a bubbles oscillation can be calculated and related to membrane transport behavior. For a preliminary study, the influence of linear radial bubble oscillations are examined in detail and potential extensions to the nonlinear regime are discussed. Also highlighted are the potential implications for applications involving bacteria and cancer cells.
Weakly nonlinear bubble pulsations in rigid tubes
Authors: Cui Jianying , Hamilton Mark F. , Wilson Preston S. , Zabolotskaya Evgenia A.
Published: October 2013

In a previous investigation [Cui et al., Proc. 17th ISNA, edited by Atchley et al. (AIP, New York, 2006), pp. 229–232], an analytical model was developed for the weakly nonlinear pulsation of a spherical bubble in a channel formed by two rigid parallel plates. The boundary conditions on the plates were satisfied by introducing an infinite line array of image bubbles. Here we extend this approach to rigid tubes having triangular, square, and hexagonal cross sections. The method of images can also be used for these three geometries because their cross sections tessellate two-dimensional space. Whereas the signals from the images can be summed analytically for a channel formed by parallel plates, numerical summation is required for the three tubes. Resonance curves for an acoustically driven bubble are presented for the response at the fundamental and second-harmonic frequencies as functions of effective tube diameter. The main result is that the resonance curves for all three cross-sectional geometries agree when normalized by the cross-sectional areas. Except when the bubble is within several bubble radii of a tube wall, the results are also nearly independent of the position of the bubble in the tube. [Work supported by ONR.]
Grating lobe reduction in transducer arrays through structural filtering of supercritical plates
Authors: Anderson Brian E. , Hughes W. Jack
Published: October 2013

The effect of placing a structural acoustic filter between water and the transducer elements of an array is investigated to help reduce undesirable grating lobes. A plate is mounted to transducer elements with a thin decoupling polyurethane layer between the transducers and the plate. The plate acts as a radiation/incidence angle filter to pass energy at angles near normal incidence, but suppress energy at large incidence angles. Grating lobe reduction is achieved at the expense of limiting the available steering of the main lobe. Within this steer angle limitation, the main lobe can be steered as normal while the grating lobe level is reduced by the plates angular filtering. The insertion of a plate structural filter provides an inexpensive and easily implemented approach to extend usable frequency bandwidth with reduced level grating lobes, without increasing the number of array elements. Even though some data matches theory well, a practical material has yet to be found that possesses optimal material properties. To the authors’ knowledge, this work represents the first attempt to advantageously utilize a plate to provide angular dependent sound transmission filtering above the plates critical frequency (the supercritical frequency region). [Work sponsored by ONR Code 333, Dr. David Drumheller.]
Analysis of a second order endfire line array using SYSNOISE
Authors: Burns Thomas
Published: October 2013

It can be shown canonically that two equal-amplitude dipoles configured linearly can be summed to yield a directivity index of 9 dB if the directional axes are pointed in 180 deg opposition, and the rear-facing dipole is delayed by the appropriate amount of time. For a 9 mm end-to-end aperture, the rear facing dipole should be delayed by 7.25 microsec before it is summed with the front-facing dipole in order to achieve the 9 dB. The purpose of this study is to compare the canonical results to those of SYSNOISE. The two dipoles are modeled within SYSNOISE as: 1) four monopoles, 2) four meshed spheres with ka1, and 3) a 9 mm by 1 mm meshed sheet of zero thickness. For each of these three cases, the amplitude and phase of the two dipoles is summed as described above, and the directivity pattern and directivity index is computed by integrating the responses from 614 field points located at equal 10 deg azimuth and elevation angles at 1 m radius from the line array origin. Although the four monopoles and four meshed spheres yielded excellent results at 1 kHz and 6.3 kHz, the results from the meshed sheet was degraded. Further analysis indicated that the phase computation from SYSNOISE was the culprit.
Fourier-operator methods for parametric array analysis: Theory versus Experiment
Authors: Woodsum Harvey , Hogan William
Published: October 2013

Fourier operator methods pertaining to nonlinear scattering of sound by sound, previously developed by the present authors [J. Acoust. Soc. Am. 95(5), part 2 (2PA14)], have been refined into computer codes, to allow prediction of parametric array performance over a wide range of circumstances, to include parametric array far field and near field, with linear medium attenuation as well as saturation effects fully accounted for. Experimental data sets have been obtained in the course of parametric source calibrations, which allow precise comparison with the new model, showing favorable comparisons in all cases.
The acoustic intensity and directivity of the modern concert harp was investigated
Authors: Panzer Elizabeth , Braasch Jonas
Published: October 2013

The acoustic intensity and directivity of the modern concert harp was investigated in two distinct scenarios. Previous studies [Bell and Firth, Acustica (1989); Gautier and Dauchez, Appl. Acoust. (2004)] have relied on mechanical excitation of the strings. Their findings identify two main sources for acoustic radiation, the soundboard and the soundbox holes, the second of which proved to be the dominant source in three frequency ranges. To gain better knowledge of the acoustics of the harp under natural playing conditions, new measurements were conducted in which harp players excited the instrument. One particular goal was to demonstrate the effect of the player on the sound radiation. The absorption and diffraction introduced by the performer diminished the relative importance of the radiation from the soundbox holes. A detailed description of the acoustic intensity field with and without the player is given. In addition, the acoustic profiles of a variety of extended techniques used in contemporary music were investigated. A complete timbral description of these techniques demonstrates the breadth of character the modern harp can produce.
Low-frequency wind noise reduction by spherical windscreens
Authors: Raspet Richard , Webster Jeremy , Yu Jiao
Published: October 2013

Spherical windscreens are surprisingly effective at reducing wind noise at frequencies for which the turbulence scale is much larger than the windscreen. In the 1930s, Phelps postulated that the low-frequency reduction of windscreens could be explained by assuming that the dc flow pressure distribution around a sphere also applied to low-frequency fluctuations and wind noise. The area average of the dc pressure distribution was then calculated and shown to be smaller than the stagnation pressure. Morgan extended this idea by measuring the pressure distribution around a porous foam windscreen. Recent measurements [Webster et al., J. Acoust. Soc. Am. 118, 2009 (2005)] have shown that the pressure fluctuations at low frequency do not follow the dc distribution and that the velocity and pressure fluctuation correlations are drastically reduced by the presence of the windscreen. A simple calculation demonstrates that the decorrelation of the pressure fluctuations is sufficient to explain the observed low-frequency reduction afforded by the 9.0 cm diameter windscreen. [Research supported by the U.S. Army TACOM-ARDEC at Picatinny Arsenal, NJ.]
An investigation of reverberation in an urban environment
Authors: Libbey Brad , Perea James
Published: October 2013

Localization of an acoustic blast source in urban battle spaces is frequently complicated by multiple arrivals resulting from reflections within the acoustic environment. Temporal windowing can be used to isolate the direct arrival in situations where a direct path between source and receiver exists. However, if the source is located around a corner from a receiver, the first arrival would lead to an erroneous source location estimate. These complications have prompted the authors to perform initial measurements of reverberation in a semi-urban environment. These measurements will assess the salience of reverberation as a means for estimating range to a blast source.
Maximum likelihood estimation of the angle of arrival for waves propagating in atmospheric turbulence
Authors: Collier Sandra , Ostashev Vladimir , Wilson Keith
Published: October 2013

Physical effects such as refraction from temperature and wind gradients and scattering from atmospheric turbulence can have a significant impact on acoustic beamforming. Many current beamformers only account for the medium effects through use of an effective sound speed. Here we develop a maximum-likelihood estimator (MLE) for the angle of arrival of an acoustic signal that directly accounts for the effects of scattering from atmospheric turbulence. The MLE utilizes a statistical model for the received signal that is based on the theory of wave propagation in a random medium and realistic atmospheric turbulence models. The resulting MLE algorithm is tested using simulated data sets and is found to outperform an estimator that assumes a homogeneous medium.
Historical perspective on Robert T. Beyer: Connections and branches surrounding the Brown-Acoustics era
Authors: Korman Murray S. , Letcher Stephen V.
Published: October 2013

Starting from a timeline when R.T. Beyer graduated from Hofstra and went to Cornell in the fall of 1942 there are many branches which connect (back in time) to the so-called great-grandfather, grandfather and father advisors leading up to his own research advisor, Dr. Harry Sack, at Cornell. Dr. Sack had been a professor at the Free University of Belgium who worked for Dr. Peter Debye before the war and was a former student. The roots of Debye will be traced backward in time and then Beyer’s own family tree of graduate students will be developed. Bruce Lindsay (who worked with Niels Bohr in 1922 in Copenhagen, in his last year of graduate school at MIT) hired Beyer as an instructor starting in the summer of 1945. Professor Beyer’s first graduate student was Myron Smith, who used radiation pressure to measure the intensity of sound under his guidance. One of the authors (M.S.K.) was Beyer’s last graduate student (1981). The other author (S.V.L.) was a graduate student of Beyer’s in the 1960s and co-authored Physical Ultrasonics with his mentor. Some threads will be introduced with A.O. Williams and P.J. Westervelt—fellow nonlinear acousticians during Beyer’s career at Brown.
Artefact detection and sound source localization on ships and submarines
Authors: Seto Mae L.
Published: October 2013

DRDC’s Ship/Submarine Signature Management System (SSMS) detects acoustic artefacts based on arrays of sensors strategically mounted at the base of machinery and on the ship/submarine hull. Acoustic artefacts exceed some nominally acceptable level and could compromise a ship/submarine’s mission though its impact on the acoustic signature. After artefact detection the next tasks are localization and mitigation. Only localization is discussed. Localization challenges in the ship/submarine environment include machinery being on over very different time scales, multi-path, sound ducting, confusion over multiple sources in a small space, machinery changing speeds, fluctuating broad band levels. etc. SSMS source localization is achieved through judicious grouping of the detected machinery tonals both within and across multiple sensors and their time correlation against machinery activity, This is additionally coupled with knowledge of the machinery and ship layout. Sensors must be synchronously sampled, to within a small tolerance, over an environments that may distribute sensors over a 250 foot length. Such measures appear to increase the likelihood of a successful source localization to the machinery or structure that created the artefact. The SSMS and its localization algorithm and its validation are reported on.
Real time volumetric intensity visualization
Authors: Klos Jacob , Williams Earl G. , Tuss Joel , Sklanka Bernard J.
Published: October 2013

Near-field acoustical holography (NAH) microphone array measurement technologies are currently being investigated by NASA, the Naval Research Lab (NRL) and Boeing. One type of array geometry under investigation is a spherical arrangement of microphones that enables the computation of the intensity field surrounding the sphere using spherical NAH theory. Due to the simplicity of the required computation and the ability to pre-compute several of the required quantities, the intensity field in a volume surrounding the sphere can be reconstructed and rendered in real time as a measurement is being made. Thus, sound sources can be identified in real time by roving the spherical array around in a sound field near suspected sources and tracking the sound intensity back to the source. This presentation demonstrates the capabilities of a real time spherical NAH system that has been developed by NASA, the NRL and Boeing. The topology of the software will be discussed and the capabilities of such a system will be demonstrated.
The effect of phonetic similarity on L2 speakers in discerning L1 and L2 consonants
Authors: Chen Sally , Fon Janice
Published: October 2013

This study investigated how L1 and L2 sounds of different degrees of similarity are perceived by L2 speakers. Twenty-six participants were tested with six Mandarin-English C-/i/ syllable pairs varying in degrees of similarity in the initial consonant. Two competing models were examined, the speech learning model (Flege, 1995) and the perceptual assimilation model (Best, 1995). The former proposes that the greater the perceived dissimilarity between an L2 sound and its closest L1 counterpart, the easier it is for L2 speakers to discern the difference, while the latter proposes that L2-to-L1 assimilation corresponds to their articulatory distance. As for two L2 sounds corresponding to the same L1 target, perceptual performance may still differ depending on how similar the L2 sounds are to the target. Results showed that perceptual performance was independent of L2 proficiency. The SLM is supported in that the accuracy for discerning individual consonants of ‘‘dissimilar’’ pairs was higher than that for ‘‘similar’’ pairs, which in turn was higher than that for ‘‘identical’’ pairs. However, the accuracy for discerning ‘‘identical’’ pairs was still significantly higher than the chance level, indicating that L2 speakers are still able to tell the difference, which can be better explained by the PAM.
Benchmarking the variable rotated and mapping parabolic equation solutions
Authors: Collis Jon M. , Siegmann William L.
Published: October 2013

Improving the capability of handling variable sloping interfaces and boundaries with the parabolic equation method is an active area of research. The mapping solution [M. D. Collins, et al., JASA 107], and the variable rotated parabolic equation [D. A. Outing et al., JASA 115] are recent advances in this area. Both solutions handle variable bathymetry by approximating in terms of a series of regions of constant slope. The mapping solution transforms the bottom to a line, and the parabolic equation is solved in a coordinate system aligned with the interface. At junctions between regions, a phase correction is applied to the field. The variable rotated solution rotates the coordinate system in each region so that the parabolic equation is solved in a system that is aligned with the boundary. The junctions between regions are treated by overshooting the point where the slope changes and interpolating and extrapolating to obtain the field in the next region. Although both methods handle variable bathymetry, the variable rotated solution should provide greater accuracy, especially when there are relatively large slopes. The two solution methods are benchmarked against each other and an analytic solution. [Work supported by the Office of Naval Research.]
Acoustic propagation in uncertain waveguides with spatially varying wave speeds
Authors: Burkhardt John
Published: October 2013

Acoustic propagation in the littoral is a complex process involving acoustic interaction with the ocean surface, the ocean bottom, volume scattering as well as variable propagation characteristics throughout the volume. When modeled stochastically this problem has been approached using a variety techniques including the Monte Carlo method, Neumann expansions and the stochastic finite element method. The last of these has found considerable use because it offers computational efficiencies over the Monte Carlo method and fewer modeling restrictions than the Neumann expansions. This presentation will discuss the development of a one-dimensional stochastic finite element formulation that accounts for spatial variability in wave speed, an area of intense interest not currently addresses in the literature.
A snapshot of known animal communication via the vibration channel
Authors: Hill Peggy
Published: October 2013

When a new field, or sub-discipline, first emerges in the scientific arena, terminology is often borrowed from mostly compatible and closely related fields, or those fields from which the new one is emerging. Jargon is employed within the new field when the established vocabulary fails. A point is reached when the best interest of communication with those outside the new field requires development of a new vocabulary, or at least a specific redefinition of broadly used terms, so that the new field can continue to develop and fill its own niche. Animals from fiddler crabs to elephants communicate via the vibration channel. In fact, when researchers have suspected substrate borne signaling, it has almost always been confirmed. In this presentation, I will provide examples from the literature of animals across taxa that are known to communicate in this way, and the contexts within which signals are sent and received. Further, I will pose questions (with few answers) concerning selection for use of the channel, along with examples of instances where changes in the use of terminology over a couple of decades has restricted access to early work in this field.
The vibration sense in large mammals and its role in communication: Elephants as a case study
Authors: O’Connell-Rodwell Caitlin E.
Published: October 2013

All mammals have the ability to detect vibrations and there are some notable cases of small mammals dedicating much of their sensory world to vibration detection such as the star nosed mole, the golden mole, the blind mole rat. In large mammals, the concept of using vibrations as a form of prey detection, predator avoidance, or communication has not been explored to a great extent. A few cases of these three uses of vibrations will be reviewed as they pertain to and may benefit the lion, kangaroo, and elephant seal, respectively. Elephants are well suited to communicate seismically, given their high amplitude, low frequency vocalizations that couple with and propagate in the ground as seismic signals. A unique combination of anatomical structures found on the elephant would also facilitate seismic detection through either a bone conducted or somatosensory pathway, or both. A series of studies will be reviewed demonstrating the elephants ability to generate and propagate seismic energy from vocalizations and footfalls as well as their ability to detect and discriminate not only biologically meaningful seismic cues from noise, but also subtle differences between seismic vocalizations given in the same context.
Blood mimicking fluid for high-intensity focused ultrasound applications
Authors: Liu Yunbo , Maruvada Subha , Wear Keith A. , Herman Bruce A. , King Randy L.
Published: October 2013

A blood-mimicking fluid (BMF) having viscosity, attenuation, and backscatter similar to that of human blood has been developed for the acoustic and thermal characterization of HIFU ablation devices. The BMF consists of gellan gum, low density polyethelene particles, and nylon particles dispersed in water, glycerin, and alcohol. The BMF was characterized for attenuation coefficient, speed of sound, backscatter coefficient, viscosity, thermal diffusivity, and thermal conductivity. The low attenuation as well as the sound speed and the bloodlike backscatter indicate the usefulness of the BMF for ultrasound imaging and flow applications. These properties, along with thermal conductivity and diffusivity also within the range found in human tissue and the ability to withstand temperature increases above 70°C with no significant change in its properties, make this material appropriate for HIFU applications. This fluid also exhibits viscosity varying as a function of velocity (or shear rate). [This research was supported by the Defense Advanced Research Projects Agency (DARPA) through IAG No. 224-05-6016.]
Formation of shock waveforms and millisecond boiling in an attenuative tissue phantom due to high-intensity focused ultrasound
Authors: Canney Michael S. , Bailey Michael R. , Khokhlova Vera A. , Crum Lawrence A.
Published: October 2013

Nonlinear propagation effects during high-intensity focused ultrasound (HIFU) treatments can induce shocks in the acoustic waveform, dramatically accelerate heating rates, and result in rapid boiling of tissue at the focus. Localized boiling can be used for targeting and calibration of clinical HIFU treatments. In our previous work, millimeter size boiling bubbles were observed in several milliseconds in a weakly absorptive transparent tissue phantom, and temperature rise to 100°C was calculated using weak shock theory from experimentally measured and numerically simulated focal waveforms [Canney et al., J. Acoust. Soc. Am. 120, 3110 (2006)]. In this work, experiments are extended to an opaque phantom that has higher attenuation (0.5 dB/cm/MHz in the new phantom versus 0.15 dB/cm/MHz in the previous one) more similar to real tissue. Focal acoustic waveforms are measured using a fiber optic probe hydrophone and time to boil is monitored using a 20-MHz acoustic detector. Modeling of experimental conditions is performed with a KZK-type numerical model. Results demonstrate that although higher source amplitude is needed to attain the same focal amplitudes in the new, more attenuative phantom, similar amplitude shocks can be formed, resulting in equally fast heating rates. [Work supported by NIH DK43881 and NSBRI SMS00402.]
Lung hemorrhage at and near resonance: Pulse duration and pulse number
Authors: Dalecki Diane , Child Sally Z. , Raeman Carol H.
Published: October 2013

Research from our lab has shown that low-frequency (∼100–1000 Hz) underwater sound can produce mammalian lung hemorrhage. For adult mice, the pressure threshold for lung damage is ∼2 kPa for a 3-min continuous wave exposure at the lung resonance frequency (∼300 Hz). Sound-induced lung hemorrhage was studied for exposure below (200 Hz) and above (500 Hz) lung resonance. The threshold for lung damage is lowest for exposure at the lung resonance frequency. Furthermore, a series of experiments was performed to investigate effects of pulse duration and number of pulses on lung hemorrhage produced by exposure to underwater sound at lung resonance frequency. The resonance frequency of each mouse lung was determined using an acoustic scattering technique. In one set of experiments, the extent of lung hemorrhage was assessed for increasing pulse durations ranging from 1–180 s. In another set of experiments, extent of lung hemorrhage was assessed for increasing number of pulses. Extent of lung hemorrhage increased with increasing pulse duration and increasing number of pulses. The lung resonance frequency can shift higher or lower during sound exposure. The results of this work are relevant to establishing safety guidelines for swimmers and divers exposed to underwater sound fields.