bluuebunny/crossref_metadata_2025 huggingface dataset:
Using ultrasound articulatory signals to investigate the phonetic motivations of English /æ/ tensing
Authors: Mielke Jeff , Thomas Erik R. , Carignan Christopher
Published: October 2015

A common simplifying technique in ultrasound studies of variation is to select a single representative frame for each token, sacrificing dynamic information that is often critical for understanding the phonetic motivations of phonological phenomena. We examine the phonetic motivations for tongue body raising in English /æ/ tensing (e.g., Labov et al. 2005) in 23 North American English speakers using phonetically meaningful time-varying articulatory signals extracted directly from ultrasound video. An articulatory measure of /æ/ tenseness is generated using regression to find the linear combination of articulatory principal components (found using EigenTongue Feature Extraction; Hueber et al. 2007) that best accounts for the F2-F1 difference in front vowels. We have previously shown (Carignan et al. 2015) that tensing before /m n/ involves tongue body raising that is timed to the vowel nucleus, whereas tensing before /ɡ ŋ/ involves anticipating the velar closure to different degrees in different dialects. Here, we examine the phonetic motivations for this /æ/ tensing. An articulatory measure of velar fronting shows increased /ɡ/ fronting in speakers who tense /æ/ before /ɡ/, and a purely lingual analog of F1 shows that the effect of nasalization on F1 is much smaller than the phonological effect of pre-nasal /æ/ tensing.
Using automatic alignment on child speech: Directions for improvement
Authors: Knowles Thea , Clayards Meghan , Sonderegger Morgan , Wagner Michael , Onishi Kris , Nadig Aparna
Published: October 2015

Phonetic analysis is labor intensive, limiting the amount of data that can be considered. Automated techniques (e.g., forced alignment based on Automatic Speech Recognition, ASR) have recently emerged allowing for larger-scale analysis. While forced alignment can be accurate for adult speech (e.g., Yuan & Liberman, 2009), ASR techniques remain a challenge for child speech (Benzeghiba et al., 2007). We used a trainable forced aligner (Gorman et al., 2011) to examine the effect of four factors on alignment accuracy with child speech: (1) Datasets CHILDES (McWhinney, 2000):—Spontaneous speech (single child)—Picture naming (multiple children, Paidologos data); (2) Phonetic Transcription—Manual—Automatic—CMU dictionary (Weide, 1998); (3) Training data—Adult lab data—one dataset of child data—All child data—Child & adult lab data; (4) Segment—voiceless stops—voiceless sibilants—vowels Automatically generated alignments were compared to hand segmentations. While there were limits on accuracy, in general, better results were obtained with (1) picture naming, (2) manual phonetic transcription, (3) training data including child speech, and (4) voiceless stops. These four factors increase the utility of analyzing children’s speech production using forced alignment, potentially allowing researchers to conduct larger-scale studies that would not otherwise be feasible.
Time varying broadband acoustic response compensation at very low signal to noise ratio
Authors: Maharjan Praswish , Gendron Paul J.
Published: October 2015

Shallow water ocean acoustic environments are challenging due to their multi-path arrival structure and the various Doppler processes that are associated with platform motion and surface interactions. For moving platforms, each acoustic arrival exhibits a Doppler offset that can be quite significant, which results in an overall response that is doubly spread, one which disperses signals in both time and frequency. A virtual ocean acoustic laboratory based on the Bellhop ray tracing model is used to study the distortion of broadband waveforms through dynamic shallow water ocean acoustic environments. Acoustic response functions are presented in order to illuminate the challenges posed by shallow water environments and mobile platforms. The shared Doppler process of the arrivals is illustrated in order to illuminate the value of bulk Doppler compensation schemes. This virtual acoustic laboratory is used to test spread spectrum communication performance at very low SNR. Bulk Doppler compensation schemes derived from joint estimation of symbols and the acoustic response are compared to the actual path dilation processes. Simulation results are presented for fixed source with moving receiver shallow water environments at diverse center frequencies and bandwidths.
Remote sensing for bottom inversion
Authors: Jesus Sergio M.
Published: October 2015

The scenarios of interest for estimating bottom and sub-bottom physical properties now encompass both deep and shallow, or very shallow, coastal waters, for the deployment of renewable energy platforms (e.g., wind farms and wave/tidal energy plants). This new paradigm, together with the continuous requirement for reducing survey time (and cost), spinned out the concept of a distributed and reconfigurable seismic survey system composed of a fleet of autonomous underwater vehicles (AUV) carrying acoustic sensing arrays. Such system poses a number of technical as well as scientific challenges, among which that of sensor positioning for optimal bottom inversion performance in a given scenario. The present work addresses this issue through the eye of the sensor configuration that maximizes diversity and proposes sampling incoherence bounds for 1, 2, and 3D array systems. Random sampling is a concept that favors diversity and allows for the usage of low-complexity inversion schemes such as those based on compressed sensing. Simulations on realistic environments illustrate the proposed concept. [This work is part of project WiMUST—Widely Scalable Mobile Underwater Sonar Technology funded under program H2020 of the European Union.]
Source depth discrimination: An evaluation and comparison of several classifiers
Authors: Conan Ewen , Bonnel Julien , Chonavel Thierry , Nicolas Barbara
Published: October 2015

Source depth estimation with a vertical linear array generally involves mode filtering, followed by matched-mode processing. However, this method has two main limitations: the problem of mode filtering is ill-posed in the case of partially spanning arrays; matched-mode processing is sensitive to environmental mismatch. Therefore, concerns for robustness motivate a simpler approach. The problem of depth estimation is reduced to a binary classification problem: source depth discrimination. Its aim is to evaluate whether the source is near the surface or submerged. These two hypotheses are formulated in terms of normal modes, using the concept of trapped and free modes. Several classification rules, based on modal filtering or on subspace projections, are studied. Monte-Carlo methods are used to evaluate their performance and compute receiver operating characteristics. This allows the choice of a discrimination threshold according to some expected performance. The benefits of considering a source depth discrimination problem rather than a source localization one are highlighted. The influence of noise and environmental mismatch are investigated, as well as the choice of the discrimination depth and the choice of the limit between trapped and free modes.
The relation between the waveguide invariant and array invariant
Authors: Song Hee-Chun , Cho Chomgun
Published: October 2015

The waveguide invariant β is based on the dependence of group speed on phase speed and summarizes the robust interference phenomenon in the range-frequency plane. Over the last decade the elegant approach has been utilized for various applications including passive source ranging. Separately, the array invariant approach [Lee and Makris, J. Acoust. Soc. Am., vol. 119, pp. 336–351 (2006)] has been proposed for a robust source-range estimator from beam-time intensity data using either a horizontal or vertical array. In this letter, it is shown that the array invariant can be derived from the waveguide invariant theory assuming β = 1.
Single and multiple snapshot compressive matched field processing
Authors: Gemba Kay L. , Hodgkiss William S. , Gerstoft Peter
Published: October 2015

Matched field processing is a generalized beamforming method which matches received array data to a dictionary of replicas to locate and track a source. The solution set generally is sparse since there are considerably fewer sources than replicas. This underdetermined problem can be solved with sparse processing (SP) which potentially is attractive for several reasons. The traditional spatial matched-filter problem is reformulated as a convex optimization problem subject to a sparsity constraint. For example, an elastic net seems to be an appropriate penalty in order to find the best match among a correlated group of replicas. Another advantage is that SP does not require inversion of the sample covariance matrix and therefore can outperform conventional high-resolution processors in snapshot deficient scenarios (i.e., fast moving sources). A third potential advantage is that SP can achieve super-resolution at high SNR and discriminate between closely spaced sources. Here, we demonstrate the performance of single and multi-snapshot SP to track a towed source using the SWellEx-96 data set. Results are benchmarked using the Bartlett and the white noise constraint processors. We further discuss the processing of multiple frequencies in order to improve the source tracking.
Three-dimensional iterative parabolic approximations
Authors: Petrov Pavel S.
Published: October 2015

A hierarchy of the 3D coupled parabolic equations is derived by the method of multiple scales. The solutions of the derived equations represent the successive terms in an asymptotic expansion of the solution of the 3D Helmholtz equation. The equations are complemented with the consistent interface and boundary conditions. The Cauchy initial conditions for the parabolic equations are set up in such a way that the solution in the far field approximates the solution of the Helmholtz equation in the unbounded 3D space. The derived parabolic equations are used to solve a problem of the propagation in a perfect 3D wedge. The comparison to the image source solutions is used for the validation of the proposed parabolic approximation.
Stochastic-basis matched-field processing
Authors: Finette Steven I. , Mignerey Peter C. , Oba Roger M.
Published: October 2015

Matched-field processing (MFP) suffers serious degradation due to environmental mismatch between received acoustic-field vectors and modeled replica vectors. Physical reasons for degradation include uncertainty caused by incomplete descriptions of the parameters and fields necessary for correct specification of the acoustic waveguide (i.e., environmental uncertainty), and system uncertainty associated with incomplete knowledge of the array configuration, source depth, etc. Recent research in the theory of stochastic-basis expansions (polynomial chaos) provides a mathematically consistent way of incorporating both types of uncertainty into MFP. Such expansions are used efficiently to construct replica matrices that steer high-rank subspaces capable of capturing signals with uncertain wavefronts. When combined with cross-spectral density matrices, stochastic-basis steering matrices enable the design of new processors with properties not previously evaluated in a MFP context. A maximum likelihood processor is developed which incorporates environmental uncertainty through polynomial chaos expansions. The processor can be written as a Frobenius product between an estimated cross-spectral density matrix and the inverse of a stochastic-basis replica matrix. This talk will outline the theoretical foundation of stochastic-basis MFP, and illustrate the method with some simulations. [Work supported by the Office of Naval Research.]
Hydroacoustic survey of geotechnical activities for the Virginia offshore wind technical advancement program
Authors: Kalapinski Erik J. , Varnik Kristjan A.
Published: October 2015

As offshore wind energy development increases across the eastern seaboard, there is a growing need to determine the short and long-term effects of activities associated with this development on marine ecosystems. One area of particular importance is the potential effects of underwater noise on marine life. To better characterize underwater sound levels associated with geotechnical activities, a hydroacoustic measurement program of geotechnical survey activities was completed in support of Dominion’s Virginia Offshore Wind Technical Advancement Program. An important component of this project was the advancement of new technologies and the use of best available science to collect data for more accurate impact determinations. The overall goal of the hydroacoustic measurement program was to field-verify the projected acoustic impacts during geotechnical activities. This new insight will support both decision making in the execution of offshore wind site characterization surveys, and reduce the potential for future impacts. Measurements were made using a combination of equipment including a cabled real-time hydroacoustic analysis systems and fixed autonomous static recorders. Upon conclusion of the hydroacoustic survey, data were downloaded and directly correlated with daily activity logs from the vessels used in performing the offshore geotechnical work thereby providing the means to coordinate acoustic events.
Ultrasonic and superfast: Design constraints on echolocation in bats
Authors: Ratcliffe John
Published: October 2015

Recent work from our group demonstrates that two exceptional characteristics of bat biosonar—bats’ extremely high call emission rates and these calls’ ultrasonic frequencies—reflect biomechanical constraints of the vocal apparatus. We hypothesized that smaller bats, with their smaller mouths, emit higher frequencies to achieve sufficiently directional sonar beams, and that variable directionality is critical for bats. We found that six aerial hawking, vespertilionid bat species produced sonar beams of similar shape and volume, and we predict that many bats adjust their acoustic field of view to suit habitat and task. We speculate that sonar beam shape has been an evolutionary constraint on echolocation and explains the bat size-call frequency correlation. During the terminal phase of an aerial hawking attack on an insect, bats produce a “buzz,” increasing information update rates by producing >160 calls/second. We discovered that bats use specialized superfast muscles to power these rapid call rates. We also show that laryngeal motor performance, not call-echo overlap, limits maximum call rate. We suggest that the advantages of rapid auditory updates on prey movement have selected for superfast laryngeal muscle. Taken together, our results provide further evidence that bat biosonar is a dynamic sensory system, a sensory system that allows bats to adjust and optimize their acoustic fields of view and to update their auditory scene at rates >160 times/second to optimize airborne prey detection and tracking.
Geographic variation in contact calls emitted by a leaf-roosting bat suggest distinct modes of vocal transmission
Authors: Montero Karina , Gillam Erin H.
Published: October 2015

Group behaviors, such as coordination and information exchange, are typically mediated by acoustic signals known as contact calls. Although these vocalizations are widespread, the mechanisms driving variation in acoustic features within and between populations remain poorly understood. Our study examines whether patterns of variation in two contact calls emitted by Spix’s disk winged bats, Thyoptera tricolor, are congruent with patterns of genetic distance among populations isolated by a geographic barrier. T. tricolor is a leaf roosting bat that forms stable social groups and exhibits all-offspring philopatry. To evaluate if vocal variation between groups is influenced by genetic distance, we studied the variation in microsatellite allele frequencies at multiple sites on the Caribbean and Pacific mountain slopes. We found that the geographic variation patterns differed between the two types of calls studied, and we argue that this indicates distinct modes of vocal transmission. Our results suggest that one contact call is likely socially transmitted via vocal learning, while the congruence between patterns of genetic differentiation and acoustic variation for the second call type suggest this is an inherited trait. Further research is needed to better understand the role of vocal learning and genetic transmission of contact calls emitted by T. tricolor.
Territorial calls analysis in the broad tailed bat (Nyctinomops laticaudatus)
Authors: Montiel Reyes Fernando J. , Bohn Kirsten , Ortega Jorge
Published: October 2015

Some bat families perform vocalizations called “songs” to mate, conformed by three element types: chirps, trills, and buzzes. Also, those might be territorial warning calls; but its syntax remains to be understood. Our goal is to get information about mating calls’ patterns and its clarified function for a molossid bat species. We used ultrasound microphones to record vocalizations from a colony of Nyctinomops laticaudatus, during three periods through 2013–2014. We performed spectrogram analysis to characterize vocalizations with chirp number, duration, and acoustic frequency measurements. Results show males perform structured and complex songs. Vocal repertoire features two chirp types, trills, and buzzes as in other species. Chirp A is a short descendant frequency modulated pulse of 8.05 ms (SD = 3.53 ms); chirp B is a downward FM larger than A with an upward final segment of 43.93 ms total length (SD = 14.85 ms). Distinctively Nyctinomops laticaudatus performs songs of a series of three to nine compound chirps, starting with B element of high plasticity. Additionally structure is modified by the syntax, with shorter phrases when the first element is a trill or a buzz.
Experimental design for sediment characterization in the New England Mud Patch
Authors: Potty Gopu R. , Miller James H. , Lynch James F.
Published: October 2015

This study focuses on the design of an experiment to estimate the shear wave properties of ocean bottom sediments at a location in the southern New England Continental Shelf called the “New England Mud Patch.” The mud patch is a 13,000 square kilometer area covered by fine-grained sediment. The inversion technique is based on collecting interface wave (Scholte wave) data using geophones on the sea bottom. The data for the inversion consist of Scholte wave phase velocity dispersion calculated from the geophone array data. The present study aims at applying this Scholte wave based shear wave inversion technique to the “mud patch” area. Two different interface wave measurement systems will be presented. Appropriate source to receiver ranges will be explored based on simulations. The engineering challenges associated with deploying the system in a soft seabed will be investigated and design modifications will be investigated. Acoustic and sediment data from the 1996 Shelf Break Primer experiment, which was conducted in the western side of the mud patch, will be reviewed. The simulations will be based on historic sediment and acoustic data. [Work sponsored by Office of Naval Research, code 322 OA.]
Comparisons between a spherical aggregation of scatterers, and hard and soft spheres using single-frequency and pulsed signals
Authors: Mookerjee Adaleena , Dowling David R.
Published: October 2015

When sound is projected into the ocean, the backscattered signal may provide information about the object(s) from which the sound has scattered. When the backscattered sound comes from an aggregation of strong scatterers, such as a school of fish at their swim-bladder resonance frequency, a phenomenon called Coherent Backscatter Enhancement (CBE) may occur, and this phenomenon could aid in discriminating fish schools from other similar-strength scatterers in the ocean water column. When CBE occurs, the addition of in-phase scattered waves from propagation path pairs produces a scattered field intensity enhancement of as much as two in the direction opposite to that of the incident wave. This presentation describes the results of CBE simulations of spherical aggregations of scatterers based on the Foldy (1945) equations, and provides comparisons to backscattering from single perfectly reflecting spheres. Interestingly, a spherical aggregation of 4200 strong scatterers with wave number scaled radius ka = 32 may provide backscattering equivalent to that from a single larger perfectly-reflecting sphere with ka = 53. Additional simulation comparisons involving the statistics and time histories of harmonic and frequency sweep incident waves are shown. [Work supported by the Office of Naval Research and by Advanced Research Computing at the University of Michigan.]
Compressive ocean acoustic sound speed profile estimation in shallow water
Authors: Bianco Michael , Gerstoft Peter
Published: October 2015

The estimation of ocean acoustic sound speed profiles (SSPs) requires the inversion of an acoustic transmission model using limited observations. Provided the parameters of the inverse model are sparse, Compressive Sensing (CS) can help solve such underdetermined problems accurately, efficiently, and with enhanced resolution. Here, CS is used to estimate range-independent acoustic SSPs in shallow water ocean environments using a normal-mode representation of the acoustic field. Two sparse parameterizations of the SSPs are considered. The first parameterization assumes that change in the sound speed with depth is sparse and that the SSP can be constructed from a limited number of dominant changes in sound speed. The second case assumes a priori information about the ocean SSP variability in terms of Empirical Orthogonal Functions (EOFs), estimating the dominant EOFs describing the current SSP. For both cases, both real and synthetic acoustic data are processed. It is shown that in the CS framework, both of the optimizations can be solved with increased resolution and robustness over traditional methods.
Using broadband acoustic signals and modal behavior to assess scales of ocean variability in shallow water waveguides
Authors: Badiey Mohsen , Orr Marshall H.
Published: October 2015

The sound speed fields of the continental shelf water column are anisotropic and have “fronts” related to propagating internal wave packets. The angle between a broadband acoustic signal’s source–receiver propagation track and the propagating “fronts” affects its modal composition. If the temporal variability of the modal behavior of the acoustic signals are monitored in time and space, one might identify the fluid process that causes the changes to the sound speed field. In this paper, we first present a heuristic view of how the modal properties of broadband signals can be affected by the sound speed field variability caused by propagating internal wave packets. We then present three days of acoustic field data acquired on vertical and horizontal arrays placed in ~100 m of water about 20 km from the location of acoustic signal sources. Temporal changes in the received acoustic signal's modal composition will be compared to numerical simulations. The changes in modal composition will be correlated to internal wave induced variability in the horizontal refraction of the signals.
Input impedance of sheng pipes augmented with resonators
Authors: LeDuc Matthew F. , Haerr Nathan K. , Boomershine Chevelle N. , Cottingham James P.
Published: October 2015

The sheng is a free reed mouth organ constructed of bamboo pipes with a free reed in each pipe near one end. A version commonly available today has 17 pipes in a circular arrangement with the reeds enclosed in a wind chamber. The pipes are nearly cylindrical over a significant portion of their length, but the bore near the reed end becomes approximately conical. A traditional instrument of China, the sheng, has a long recorded history, but a number of enlarged and modernized versions were created in the twentieth century, some featuring keys and additional pipes. The sheng in the current study is a standard 17-pipe configuration, with cylindrical metal pipe resonators attached to most of the pipes. These resonators amplify the radiated sound and also alter the tone quality. Calculations of input impedance have been made for the pipes, with and without the resonators attached, taking into account the position of the reed along the pipe, tuning slots, finger holes, and non-circular pipe cross sections. These calculations are compared with the measured pipe impedances as well as the measured sounding frequencies and sound spectra. [Research supported by NSF REU grant PHY-1004860.]
Empirical study of violin acoustics and its perception under various mutes
Authors: Mousavion Sina , Sarkar Suchetana
Published: October 2015

Violinists often practice with mutes, the purpose of which is to reduce the volume so the sound does not disturb other people. There is however a great disadvantage; practice mutes not only lower the volume but change the timbre dramatically, making it unpleasant to the ear. Previous researches mostly focus on how to find the elusive “Stradivarius Sound.” On the other hand, via sound analysis, we empirically study different mutes, in order to identify the markers that allow the violin to retain its “Signature Sound.” The general problem lies in the complexity of violin sound propagation and its perception. Here, we show that all types of mutes necessarily diminish the frequency band of 1.5–2.5 kHz, which tips the balance of the sound toward a darker color. The results demonstrate that unless a proportional balance between the amplitude of the harmonics of each tone is maintained, the sound loses its Brilliance character. In addition, some mutes tend to add spurious resonance peaks at lower frequencies, which further emphasizes the imbalance of tones in the lower regions. These factors can aid in the development of a mute that does not inhibit the intrinsic characteristic of the violin.
Acoustic and structural resonance characteristics of the cajon
Authors: Pehmoeller John , Ludwigsen Daniel
Published: October 2015

The cajon is a percussion instrument with origins in 16th century Peru. Literally translated “crate,” the cajon was originally a crate that players sat upon and struck to make rhythmic patterns. The modern version is a wooden box, closed except for a hole in the back panel. The front panel is struck with the hands or one of several types of beaters. The front panel is thinner than the others and is often attached with a slightly loose top edge for a snare-like effect. Alternatively, the snare sound is obtained with wires or guitar strings placed against the inside surface of the front panel, and these rattle when the panel is struck. Measurements of acoustic transfer functions with impulse excitation and roving hammer structural measurements explore the acoustic and structural resonances of the cajon with rattling strings removed. Spectra from recordings establish timbral features of the instrument, both with and without the rattling strings. By comparing results from measurements and recordings, the important features of the particular instrument tested in this study are identified, and possible directions for improved the designs are suggested.
Improving reliability of measurement algorithms in differentiated electroglottograph and audio signals
Authors: Bernadin Shonda , Morris Richard
Published: October 2015

The purpose of this work was to develop an optimized algorithm for determining the closed quotient (CQ) measurements of the vocal folds of female singers. This study extends previous results which showed that the measurement algorithm for differentiated electroglottograph (dEGG) signals and differentiated audio (dAUDIO) signals gave moderately reliable results with a correlation coefficient of r = 0.79. Additional performance studies indicate that the reliability may be improved by combining the differential signals and modifying the measurement algorithm to reduce the amount of signal overlap. Preliminary results using the modified measurement algorithm yield a significant increase in the correlation coefficient (r = 0.83). This works contributes to the development of a computational framework for determining accurate and reliable measurements for characterizing register shifts through an octave in female singers using electroglottography.
Complex point source model to calculate the sound field radiated from musical instruments
Authors: Ziemer Tim , Bader Rolf
Published: October 2015

A simple method is described to record the radiated sound of musical instruments and to extrapolate the sound field to distances further away from the source. This is achieved by considering instruments as complex point sources. It is demonstrated that this simplification method yields plausible results not only for small instruments like the shakuhachi but also for larger instruments such as the double bass: The amplitude decays in a given manner and calculated interaural signal differences reaching the listener decrease with increasing distance to the source. The method is applied to analyze the sound radiation characteristics as well as the radiated sound field in a listening region regardless of room acoustical influences. Furthermore, it has been implemented in a psychoacoustic wave field synthesis system to generate the impression of a certain source width. Implementations in terms of room acoustical simulations, spatial additive synthesis and sound field synthesis are discussed.
Stroboscopic illumination for electronic speckle pattern interferometry
Authors: Gavin Colin , Tufte Steve
Published: October 2015

A common realization of holographic interferometry is called Electronic Speckle Pattern Interferometry (or ESPI)—a technique capable of measuring harmonic modes of vibrating objects. We present a method of improving the contrast and quality of fringe patterns recorded with a simple, table-top ESPI system. In particular, by using stroboscopic illumination generated by an optical chopper, we are able to produce fringes that follow a cosine pattern, rather than the Bessel pattern fringes that result from time averaging. Since Bessel function amplitudes rapidly decrease for subsequent maxima, the stroboscopic cosine fringes show much better contrast. Also, because the zeros of cosine fringes are evenly spaced, it is much simpler to interpret the images to extract quantitative deformation amplitudes. We show that our results agree well with the theoretical predictions. This system was developed for use in musical acoustics research as a Senior Thesis project by an undergraduate student (Gavin). This low-cost, simple modification of the commonly used ESPI system could benefit other colleges and universities using holographic interferometry for acoustics research.
Construction of a Finite Element Model of the Japanese koto and its comparison with the reference instrument
Authors: Coaldrake A. Kimi
Published: October 2015

As a first step toward developing a generic model of the Japanese koto(13 string plucked zither) and related Asian zithers to understand the physical characteristics of the instruments and how they contribute to the overall sound quality, a finite element model of the koto was constructed. Samples of paulownia wood from a reference instrument were examined by SEM to establish the physical properties of this less well-characterized wood. The model was validated against the chladni patterns of Ando’s 1986 experiments. Eigenfrequencies and mode shapes were calculated before coupling the instrument to a sphere of air. Frequencies corresponding to the standard tuning of the 13 strings were applied at the same point where plucking normally occurs. A steady state response of the instrument was recorded that showed standing waves within the cavity of the instrument. Frequency scans were also undertaken. Finally, the transient response of the model to the string frequencies were measured and compared with the playing of the reference instrument. Overall, the model predicts the main features and some subsidiary ones of the reference instrument and point to directions for future work for characterizing the sound quality of the koto.
Timbre maps to characterize the sound quality of the Japanese koto
Authors: Coaldrake A. Kimi
Published: October 2015

The Japanese koto and related zithers in East Asia are known for their distinctive sound quality (timbre), but the precise origins of the characteristics remain elusive. In an attempt to extend the knowledge of these characteristics, a finite element model of the Japanese koto(13 string plucked zither) was constructed using Comsol Multiphysics 5.1 based on a koto of known provenance and parameters. A series of experiments to identify the acoustical properties of the instrument were compared against results of the model. The results were then collated into a series of timbre maps to establish patterns of responses. This included overlaying eigenfrequencies, individual peaks from the spectra of the thirteen strings for the standard (hirajōshi) tuning, hidden peaks identified by the fourth derivative frequency scans and spectra from mechanical tapping of the reference instrument. The study shows that the anisotropy of the paulownia wood of the koto plays an important role in the vibration modes and frequency response spectrum. The timbre maps then identifies characteristics of the non harmonic responses that contribute to the koto’s distinctive sound and provide a template for the study of sound quality associated with culturally specific timbral preferences for East Asian zithers.
Studying of the noise sources in a pneumatic nail-gun process
Authors: Nili Ahmadabadi Zahra , Laville Frédéric , Guilbault Raynald
Published: October 2015

Despite generating high noise levels responsible for hearing loss among workers, nail-guns have been used to connect wood pieces since the 50s. The present study belongs to a broader investigation aiming to reduce noise emissions in nail-guns. This noise reduction objective may be achieved by a nail-gun concept design improvement. This requires a study of the noise sources in time domain. The study uses an advanced measurement setup to identify the existing noise sources and their causes in each time interval. The setup includes nine microphones, two accelerometers, two pressure transducers, and a high-speed camera. Three major noise sources were identified during the nailgun process: the air exhaust, the body of the machine, and the workpiece. The air exhaust noise is radiated from the air exhaust holes mostly before the nail driving operation and during the air exhaust process. The noise radiated from the body of the machine is caused by vibrations of different internal/external parts of the machine and air movements. It persists almost throughout the whole duration of the nailgun process. Finally, the workpiece noise is radiated from the vibrating workpiece starting simultaneously with the nail driving operation and ending before the start of the air exhaust process.
Scattering by a thin and flat elliptic object: How the conformal mapping approach allows addressing numerical issues
Authors: Cassereau Didier , Mézière Fabien , Muller Marie , Bossy Emmanuel , Derode Arnaud
Published: October 2015

In this work, we are interested in modeling the propagation of an ultrasonic field in the complex trabecular bone structure. For this purpose, we use a simplified formulation, based on a representation of the bone tissue as thin and flat elliptic scatterers. With an ultrasonic inspection frequency of 1 MHz, the largest dimension of the ellipse is about half a wavelength, while the smallest dimension is 7–10 times smaller. The computation of the scattered field is based on a modal decomposition, generalized to the case of scatterers of arbitrary geometry (Chati et al., “Modal theory applied to the acoustic scattering by elastic cylinders of arbitrary cross section,” J. Acoust. Soc. Am. 116, 2004). Due to the very thin and flat geometry, this approach suffers huge numerical difficulties that require the use of enhanced precision and very long computation times. In this paper, we illustrate these issues. An alternative has been proposed (Liu et al., “Conformal mapping for the Helmholtz equation: Acoustic wave scattering by a two dimensional inclusion with irregular shape in an ideal fluid,” J. Acoust. Soc. Am. 131, 2012), based on a conformal mapping of the ellipse. We compare the two formulations and show how the conformal mapping allows reducing drastically the numerical issues resulting from the standard approach.
Stress and energy transmission by inhomogeneous plane waves into dissipative media
Authors: Woods Daniel C. , Bolton J. Stuart , Rhoads Jeffrey F.
Published: October 2015

The characteristics of sound transmission into real, or dissipative, media differ from those of transmission into lossless media. In particular, when a plane wave in a fluid is incident upon a real, dissipative elastic material, the transmitted waves are in general inhomogeneous, even when the incident wave is itself homogeneous and incident at a sub-critical angle; and more significantly, energy transmission occurs even above the critical angle. In addition, for any real incidence angle, the parameters of an incident inhomogeneous wave may be tuned so that there is no reflection from the surface of a viscoelastic solid. That phenomenon may be exploited in applications requiring energy transmission into solids. In this work, the transmission of incident inhomogeneous, as well as homogeneous, acoustic waves into solid materials is characterized; a hysteretic damping model is assumed. Numerical results are presented for the transmitted stress and energy distributions for typical solid materials, including polymer-based solids. The conditions for total transmission, i.e., no reflection at the interface, are explored, where the propagation angle, degree of inhomogeneity, and frequency of the incident wave are varied for a given material. These investigations show substantial transmission gains in the vicinity of the zero of the reflection coefficient, compared to homogeneous incident waves.
Cost-effective potential application of acousto-optic Bragg imaging of biological tissue
Authors: Teklu Alem , Declercq Nico , McPherson Michael
Published: October 2015

Acousto-Optic Bragg Imaging is a technique that uses the interaction of light with ultrasound to optically image obstructions in acoustical fields. Existing reports of Acousto-Optic Bragg Imaging based on transmission of acoustic fields through obstructions exhibit strong acoustic impedance mismatches manifested by poor image quality and missing details of physical structures of obstructions. In this work, the image quality was improved to exhibit detailed physical structures of an object by using an improved Bragg imaging system. This project investigates the possibility of extending an acoustic Bragg imaging technique in transmission mode to image animal or plant tissues; a small Azalea leaf is used as an illustration in this case. The Bragg image produced clearly shows the veins of the vascular azalea leaf serving as a proof of concept for cost-effective potential application of acoustic Bragg imaging of biological objects in the medical field. Moreover, acousto-optic Bragg imaging is potentially harmless to biological cells and is sensitive to density and elastic variations in the tissue.
Acoustical activity of lithium niobate crystals
Authors: Akhmedzhanov Farkhad R.
Published: October 2015

Acoustical activity in Lithium Niobate crystals was investigated by method of Bragg light diffraction. Transverse acoustic waves were excited in the range of 0.4–1.6 GHz using quartz piezoelectric plates. LiNbO3 samples were oriented at small angles to the axis Z in the crystallographic plane (010). Specific rotation of the polarization plane of transverse waves was determined from the dependence of the intensity of the diffracted light of the distance from the piezoelectric transducer along the acoustic wave propagation. The observed large specific rotation of the polarization plane of the acoustic waves can be used in devices controlling the intensity of light by the phenomenon of acoustical activity. Components of the imaginary part of the generalized Christoffel tensor taking into account the spatial dispersion have been determined also. It is shown that in crystals of class 3m the imaginary components of the Christoffel tensor for all the directions in the symmetry plane (100) are zero.
Numerical hybrid TMM-modal finite element method prediction of the vibroacoustic of sandwich panels with add-on damping
Authors: Rzig Imen , Atalla Noureddine , Razhi Dilal
Published: October 2015

This paper discusses the numerical modeling of the vibroacoustic response of sandwich-composite panels with add-on damping, under a diffuse acoustic field (DAF) excitation. A modal synthesis approach is used for the calculation of the structural response and the Rayleigh’s integral is used for the acoustic response. Since the panel has a viscoelastic core, a methodology is presented to handle efficiently the modeling of the frequency depended properties of the viscoelastic layer. A hybrid TMM-modal FEM method is used to predict the acoustic response at high frequency, using the equivalent damping of panel which are calculated from strain energies. Next, a parameters study on the effect of the viscoelastic layer location is presented. In particular, three locations are compared: within the Honeycomb core, within the skins and added to the skin with a constraining layer. The effects of the excitation type on the vibration and acoustic response are also discussed. Key words: Sandwich NIDA, Modal FEM method, TMM method, viscoelastic damping, acoustic response, equivalent properties.
A modal solution for finite length rods with non-uniform area
Authors: Hull Andrew J.
Published: October 2015

This talk derives a modal solution to the displacement field of a finite length rod whose area is varying with respect to its length. This method facilitates a solution to any problem where the area and derivative of the area can be represented as analytical functions. The problem begins by writing the longitudinal displacement of the non-uniform area rod as a series of indexed coefficients multiplied by the eigenfunctions of the uniform area rod. This series solution is inserted into the non-uniform area rod equation, multiplied by a single p-indexed eigenfunction and integrated over the interval of the rod. The resultant expressions can be written as a set of linear algebraic equations and this yields a solution to the displacement of the system. Five example problems are included: the first one has a non-uniform area that corresponds with a known analytical solution, the second has an area that can be represented by a Fourier series, and the third and fourth have areas that do not have a known analytical solution and the fifth is a generic second order non-constant coefficient differential equation. Four of these problems are verified with other methods. Convergence of the series solution is discussed.
The effect of elastic point contact: theory and experiment
Authors: Photiadis Douglas , Goldstein David
Published: October 2015

It has recently been pointed out that nearfield deformation in the neighborhood of an elastic point contact can have significant phenomenological effects, producing shifts of resonance frequencies and serving as a source of loss. In order to take these effects into account, it is necessary to employ three dimensional elasticity theory, precluding the use of lower dimensional dynamic models, for example, plate elements in a finite element analysis (FEA) computation. This is a very significant limitation because the frequency response of many large complex structures can only be predicted using such models. We propose here a theoretical modeling approach that resolves this problem and enables the use of lower dimensional models in the analysis of such systems. We have found the predictions of the model to be in good agreement with experimental measurements in the cases we have examined so far, translational and cantilever resonators. Research funded by the Office of Naval Research.
Determining optimal equivalent source positions in wave superposition method by self-adaptive searching algorithm
Authors: Wu Shaowei , Xiang Yang
Published: October 2015

The calculation accuracy of wave superposition method is influenced greatly by equivalent sources, their positions, and the frequency. What’s more, nonuniqueness occurs at eigenfrequencies when monopole or dipole is used as the equivalent source. Although tripole can overcome the nonuniqueness, the computational overhead is very large due to its complex expression and the accuracy is still affected greatly by the positions. A method is proposed to reduce the calculation errors. In this method, monopole, which is the simplest source, is used as the equivalent source. The upper limit frequency for a radiator under a certain meshing pattern is predicted by using the fictitious pressure generated via a reference source. Then, the optimal equivalent source positions for each frequency corresponding to the actual vibration velocity boundary condition, in which the average rate of pressure change is minimal, are determined within the upper limit frequency by a searching algorithm. Numerical simulation results of a complex structure show that the calculation errors are significantly reduced. At last, the method is verified by an experiment for a cuboid radiator. Experimental results show that the proposed method is practicable and good at accuracy.
Production of emotional intonation among Mandarin and English speakers
Authors: Wayland Ratree , Zhu Yiqing , Perdomo Michelle
Published: October 2015

Some researchers claim that intonation can be used to express specific emotion while others argue against the existence of emotion specific intonation patterns. In addition, languages differ in their use of intonation pattern to deliver similar emotion, and that L2 learners have the tendency to use L1 knowledge to produce intonation. Previous research shows that a falling successive addition boundary tone was used to express “disgust” or “anger” while a rising successive addition tone was used to convey “surprise” and “happy” emotions in Mandarin. In this study, we compare intonation patterns used to express five emotions: anger, disgust, surprise, joy, and neutral by 10 Mandarin and 10 English speakers in 1, 2, or 5-word utterances in English. Mandarin speakers were also asked to produce all 5 emotions in 1, 2 and 5-word utterances in Mandarin. Preliminary analyses from one Mandarin speaker showed that mean F0 of utterances produced with different emotions are significantly different in all three utterance lengths in both Mandarin and English. Inconsistent with previous research, a “falling” successive addition tone is used in all five emotions in Mandarin and in four emotions, except disgust, in English.
L + H* and H* pitch accents in Mandarin Chinese
Authors: Zhu Yiqing , Wayland Ratree
Published: October 2015

In this study, we examine acoustic correlates of L + H* and H* pitch accents in Mandarin Chinese. In English, L + H* denotes “exclusiveness” and H* conveys “new” information. For example, L + H* A. Katie did not pet the cat, (Kellie did). H* B. Katie did not pet the cat (she pet the dog). Ten Mandarin speakers were asked to produce the English equivalent L + H* and H* pitch accents in Mandarin as in C and D: L + H* C. 咪妮 没有 摸 猫， 妞蒙 摸 了 猫 MiNi meiyou mo mao, NiuMeng mo le mao. MiNi did not pet the cat, it is NiuMeng who petted the cat. H* D. 咪妮 没有 摸 猫，咪妮也 没有 摸 狗 MiNi meiyou mo mao, MiNi ye meiyou mo gou. MiNi did not pet the cat, and she did not pet the dog either. MiNi and NiuMeng were produced with all combinations of four Mandarin tones. Preliminary findings from one speaker suggest an interaction between tones and pitch accents such that pitch contour and pitch height of both types of pitch accents vary as a function of tones.