bluuebunny/crossref_metadata_2025 huggingface dataset:
Articulation of fricatives: Evidence from X-ray microbeam data
Authors: Shadle Christine H. , Iskarous Khalil , Proctor Michael I.
Published: October 2013

Articulatory changes in /s/ over time give rise to the onset and offset of turbulence noise, but the small tolerances involved make it difficult to separately consider the effects of movement, phonetic context, and subject variation. Aerodynamic estimates of the constriction area have been shown to demonstrate a marked asymmetry, with the /s/ onset more rapid than offset [C. Scully, Speech Commun. 11, 1992]. Previous articulatory studies led us to expect an invariant tongue tip position, with jaw raising dependent somewhat on the following vowel. In order to investigate the timing of the constriction formation in fricatives, X-ray microbeam data [Westbury et al., 1994] for citation forms of /sVd/ for 15 vowels were studied. In fact, the tongue marker patterns during [s] vary both by following vowel and subject; subjects seem to have different apical-laminal strategies. The jaw reaches maximum height during [s] for each subject studied; that height does not appreciably vary with vowel. This indicates that jaw height is important specifically for /s/ production. One possibility is that the constriction is formed by the tongue, and turbulence noise is then maximized by the lower teeth being brought into position. [Work supported by NIH NIDCD R01 DC 006705.]
A range of intonation patterns produced in an elicitation task
Authors: Brugos Alejna , Barnes Jonathan , Shattuck-Hufnagel Stefanie , Veilleux Nanette
Published: October 2013

A production task was designed to elicit a specific intonation contour, characterized by an exaggerated rise-fall-rise in f0 (L+H*L−H% in ToBI terms), conveying an attitude of ‘‘dismayed surprise.’’ Speakers were given models, a short practice period, and a preceding context for each utterance. A targetlike rise-fall-rise contour (including H*L−H% variants) was successfully elicited for each of the contexts, but in less than half the utterances: Of 1134 utterances, 631 (56%) were judged by a panel of 3 experienced ToBI labelers as different from the intended contour, e.g., L*H−H%. Of these, 261 were produced with contours perceptually similar to the target, with a sustained flat or minimally rising f0 after the fall from the pitch accent, or with the rise occurring early in the next phrase. Alignment characteristics and individual speaker data may determine whether these are one contour with a continuum of realizations, or separate contours. These results (a) suggest that speakers have more than one way of signaling a given attitude and resist being limited to using only one, and (b) support the need for careful postexperiment transcription to characterize which contours subjects have actually produced. [Work supported by NSF 0345627 and NIH DC00075.]
Errors and strategy shifts in speech production indicate multiple levels of representation
Authors: Gick Bryan
Published: October 2013

An earlier pilot study [Gick, J. Acoust. Soc. Am. 112, 2416 (2002)] observed that speakers producing challenging sequences of articulatory movements exhibit categorical shifts in production strategies. For example, a speaker may initiate all two-flap sequences with an upward tongue movement, then shift to a downward movement, then shift again. The present study attempts to determine how these strategy shifts can inform phonologists as to levels of representation. Ten subjects produced sequences of flap allophones of English /t/ and /d/ in an experimental paradigm similar to the pilot study. Results show strategy shifts in the speech of 7/10 subjects, such that: (1) shifts are more likely to occur following speech errors; (2) errors are more likely to occur in sequences with more flaps and more conflicts; (3) errors in response to articulatory conflicts occur at multiple levels of representation (segmental, lexical, etc.); (4) strategy shifts occur at multiple levels of representation (subsegmental, segmental, whole word); (5) word frequency does not affect strategy shifts. These results suggest that speech processing is active in parallel at multiple levels associated with phonological representation. [Work supported by NSERC.]
Production of American English word-initial stops in the vicinity of a voiceless stop
Authors: Eydlin Elina , Abdelli-Beruh Nassima
Published: October 2013

This study examined how native-American English speakers produced the stop voicing distinction when word-initial stops were positioned before a voiceless stop (/t/) in the sentence repeat CVC ten times. Sentence durations, durations of vowel (/i/) before word-initial stops, number of produced stop closures (/t/, /c/), durations of voicing in closures and VOT were measured. Preliminary analyses on three speakers show that they produced only one closure in most cases. Speakers occasionally produced two closures when slowing down their speaking rate. Vowels preceding /b, d, g/ were barely longer than vowels before /p, t, k/. When speakers produced one closure, closures were occupied by voicing for both /b, d, g/ and /p, t, k/. However, the average durations of voicing in closure were consistently longer for /b, d, g/ than for /p, t, k/. In addition, /b, d, g/ were produced in most cases with short-lag VOT, except when there were two closures, in which case, /b, d, g/ were produced with lead VOT. All /p, t, k/ were produced with VOT greater than 30 ms. Articulatory studies are needed to assess how the sequence of stops is produced and whether the gestures for /t/ are completely or partially eliminated.
Modeling the effects of the lower airway on vowel spectra
Authors: Lulich Steven M.
Published: October 2013

Computational models of the acoustics of the lower airway (below the glottis) have been implemented by researchers in the speech and respiratory sciences. In general, these models are symmetrical and are studied independent of acoustic coupling to the vocal tract. We have constructed a new model that is asymmetrical and based on human morphometric data. The acoustic properties of the model are explored and compared with symmetrical models, and the effects of the model on vowel spectra are studied for varying amounts of lower airway and vocal-tract coupling via the glottis. Cochlear excitation patterns are also computed for the vowel spectra, and the effects of the lower airway acoustics on these excitation patterns are discussed.
Intrinsic vowel pitch in tracheo-esophageal speech
Authors: Kiefte Michael , Didrachnik Natalie , Roswell Jillian
Published: October 2013

The tendency for high vowels to have higher fundamental frequency (f0) than low vowels, or intrinsic vowel pitch (IF0), has been found in both laryngeal and esophageal speech [e.g., Gandour and Weinberg, Phonetica 25, 140–164 (1980)]. In the present study, eight tracheo-esophageal speakers were asked to produce five repetitions of each of the four point vowels and f0 was measured. Results showed significantly higher f0 for high vowels than for low vowels, consistent with previous findings for laryngeal and esophageal speakers. In addition, f0 was measured from two laryngectomees over a period of 4 months immediately following surgery to determine whether IF0 is produced automatically or whether it develops over time. Neither of these subjects produced differences in IF0 at any time within the 4-month period. These preliminary data appear to indicate that IF0 is not an automatic consequence of either speech physiology or acoustics. More data from additional subjects will be presented. [Work supported by SSHRC.]
Modal analysis of a time-varying vocal tract with losses: A comparison of left and right eigenfunctions
Authors: Ramsay Gordon J.
Published: October 2013

Sound propagation during speech can be modeled by a linear wave operator describing the spatiotemporal evolution of acoustic pressure and velocity distributions on a bounded domain representing the interior of the vocal tract. The eigenvalues of the wave operator determine the formant frequencies and bandwidths. The right eigenfunctions describe the standing wave patterns associated with each formant, whereas the left eigenfunctions describe how an arbitrary source distribution projects onto each formant. In speech research, it has always been implicitly assumed that left and right eigenfunctions are identical. This only holds if the wave operator is self-adjoint, which cannot be true when losses due to viscous damping, radiation effects, and wall vibration are taken into account. To examine this issue, a time-domain finite-volume simulation of acoustic wave propagation in the vocal tract was developed, including the above loss mechanisms. Eigenvalues and eigenfunctions were calculated from the resulting state-space recursion, for time-varying geometries representing VCV sequences containing fricatives and stops. Left and right eigenfunctions are similar in shape, but there are differences in the zero-crossing points and the amplitudes of the different lobes. Predictions based on right eigenfunctions alone will be incorrect. [Work supported by NIH.]
The interaction of linguistic and affective prosody in a tone language
Authors: Dara Chinar , Pell Marc D.
Published: October 2013

To address how a common set of acoustic properties of speech prosody modulate to convey linguistic and affective meanings concurrently, this study investigated the influence of phonemic tones on the expression of emotion (happy, sad, angry) and linguistic modality (declarative, interrogative) in a tone language, Punjabi. Base stimuli consisted of neutral sentences with either of the three contrastive tones in Punjabi (falling, level, high-rising) varying at the object position of the sentence only. Each of these sentences was elicited as a statement or a question for each of the three emotions by 6 native Punjabi speakers. Utterances were validated for adequate representation of the target emotion, and reliable exemplars for each of the emotions and linguistic modality were subjected to detailed acoustic analysis. Fundamental frequency and duration measures were analyzed for the stressed vowel of the keywords (subject, object, verb) and the whole utterance for each of the tokens. Results demonstrated ways that the acoustic correlates of tone at the word level interact with that of the intonation and emotion at the sentence level, which were further compared with previous results on the effect of focus on intonation and emotional prosody [M. D. Pell, J. Acoust. Soc. Am. 109, 1668–1680 (2001)].
The scope of effect of prosodic boundaries in articulation
Authors: Krivokapic Jelena
Published: October 2013

An articulatory study of the scope of prosodic boundary effects across boundaries of varying strengths is presented. Sentences in each of three prosodic conditions contain the following string: C1VC2VC3♯VC4VC5VC6, where C is an alveolar consonant, V is a vowel, and ♯ is a prosodic boundary. The boundaries are of three degrees of strength. Using articulator movement-tracking data (EMA) for the tongue tip articulator, consonant constriction formation and release duration, acceleration duration, and spatial magnitude are measured. Leftward and rightward temporal effects of the boundary on the consonants are investigated. Based on earlier studies (e.g. Cambier-Langeveld, Linguistics in the Netherlands, 13–24, 1997; Shattuck-Hufnagel and Turk, Proceedings 16th International congress on Acoustics and 135th Meeting Acoustical Society of America, 1235–1236, 1998; Berkovits, J. of Phonetics 21, 479–489, 1993) and predictions of the prosodic gestural model (Byrd and Saltzman, J. of Phonetics, 31, 149–180, 2003), it is expected that (1) the amount of articulatory lengthening will increase with boundary strength and (2) the degree of lengthening will decrease with distance from the boundary. Three subjects participated. The results show that at the boundary, gestures have longer constriction and acceleration durations, and the effect of the boundary increases with boundary strength, distinguishing up to three levels of boundary strength. The effect is local and diminishes with distance from the boundary. These results support the initial hypotheses. [Work supported by NIH.]
Realizing question intonation in Mandarin with neutral tone
Authors: Liu Fang , Xu Yi
Published: October 2013

Previous research has found that postfocus pitch range is lowered in Mandarin even in questions, although the amount of lowering is smaller than in statements. This study investigates whether postfocus pitch range is raised in questions where the postfocus words carry the neutral tone, which, being conventionally considered targetless, may be better suited for manifesting intonation. Eight native speakers of Mandarin each produced 80 statements and 80 questions. The sentences ended either with a sequence of 5 neutral tones or with 3 neutral tones followed by 2 high tones. The sentences had two alternative focus locations, one on the full tone (high, rising, low, or falling) immediately preceding the neutral tone sequence, and the other on the low tone before the full tone. Results show that (1) postfocus lowering occurred in the neutral-tone-final sentences in both statements and questions, just as in the full-tone-final sentences, and (2) sentence-final neutral tone had falling F0 even in questions, thus contrasting with sentence-final high tone, which had rising F0 in questions. The findings are interpreted as indication that the neutral tone, being associated with weak articulatory effort, is not as effective as full tones in realizing the statement/question contrast.
Rhythm in English clear speech
Authors: Smiljanic Rajka , Viau Josh , Bradlow Ann
Published: October 2013

This study investigates the effect of hyperarticulated, intelligibility-enhancing clear speech on English speech rhythm. Ramus et al. [Ramus et al., ‘‘Correlates of linguistic rhythm in the speech signal,’’ Cognition 72, 265–292 (1999)] showed that temporal properties of a speech signal such as the percentage of vocalic intervals (%V) and variability of consonantal and vocalic intervals (C, V) can be related to phonological properties such as presence/absence of unstressed vowel reduction and syllable structure complexity, and are consequently quite successful at grouping languages into the traditional rhythmic classes (stress-, syllable-, and mora-timed). Here, we explore whether/how clear speech affects stress-timed characteristics of English sentences in terms of these measures. Results revealed that the proportion of vocalic intervals (%V) within sentences remained stable across speaking styles, i.e., consonants and vowels were lengthened equally in clear speech. However, variability of both vocalic and consonantal intervals (V, C) was higher in clear than in conversational speech. The increase in V and C was achieved primarily through insertion/strengthening of short vocalic and consonantal segments that were dropped or coarticulated with surrounding sounds in conversational speech, making word and syllable boundaries more salient. These results suggest that increased intelligibility of clear speech can in part be attributed to prosodic structure enhancement by means of enhanced syllable and word boundaries demarcation.
Sensitivity of Mandarin speech to loudness-shifted voice feedback perturbation
Authors: Liu Hanjun , Zhang Qianru , Larson Charles R. , Xu Yi
Published: October 2013

Recent studies have demonstrated that loudness-shifted voice auditory feedback leads to compensatory adjustments in voice amplitude during production of vowels. In this study we asked the question of whether Mandarin-speaking subjects would respond to loudness-shifted voice feedback during speech. Twenty-two native-speaking subjects with normal hearing and neurological background served as subjects. They said the Mandarin phrase ba ma, with the high tone on both syllables, as answers to three randomized prerecorded questions. The questions induced focus on the first or the second syllable, or on both syllables. During each production a ±3 dB, 200- or 400-ms perturbation in voice feedback was presented 250 ms following voice onset. Randomized control trials were intermixed with test trials. Digitized voice records were converted to an rms trace representing voice amplitude. Traces were aligned with stimulus onset for event-related averaging. Results demonstrated that subjects responded to the loudness perturbation with compensatory adjustments in voice amplitude. The data extend recent findings indicating that voice feedback is used to help control amplitude during speech. [This work was supported by NIH Grant No. DC006243-01A1.]
Waveform design for electroseismic exploration
Authors: Hornbostel Scott C. , Thompson Arthur H. , Ross Warren S.
Published: October 2013

Electroseismic (ES) exploration remotely identifies the presence of hydrocarbons using the conversion of electromagnetic energy to seismic energy. These conversions are relatively larger in a porous, permeable resistive body (such as an oil or gas reservoir) when compared with background conversions. Typical ES signals, however, may be several orders of magnitude below the expected ambient noise levels, thus requiring repetitions of long source sequences. In addition, the ES signals may vary linearly or nonlinearly with the input current. Two classes of coded waveforms are presented for the detection of these linear and nonlinear conversions. The linear conversions are detected using a Golay sequence pair with side lobes that cancel when the correlated pair is summed. A set of pseudo-random binary sequences (PRBSs) can be modified to detect a nonlinear squared response with minimal side lobes while removing undesired linear conversions. These source waveforms are implemented in the power waveform synthesizer (PWS) that is capable of switching three-phase power to create the specified waveforms. The PWS is an important part of the overall electroseismic exploration system that includes source electrodes, pickup-free receivers, and acquisition and processing features aimed at effective detection of small ES signals.
Small-scale geophysics inversion using surface wave extracted from noise cross correlation
Authors: Gouedard Pierre , Roux Philippe , Campillo Michel
Published: October 2013

Green’s functions between receivers can be retrieved from the correlation of ambient noise or with an appropriate distribution of sources. We demonstrate this principle in geophysics at small scales. We used a 22.5-m-long line of 16 geophones and recorded noise signals in the bandwidth of 5 to 150 Hz. Noise was generated by human steps for a 10-min walk in the alignment of the geophones line (5 min on each side). The correlations of the records gave us the Green’s functions associated with each pair of geophones, which exhibit two Rayleigh modes. We applied a frequency wave number transformation to separate those two modes and we measured the dispersion curve of each mode. We used these dispersion curves to perform an inversion and obtain the 1D velocity profile of the near surface (about 10 m deep).
Passive correlation imaging of a buried scatterer
Authors: Lobkis Oleg I. , Larose Eric , Weaver Richard L.
Published: October 2013

Waveforms obtained by correlation of diffuse fields are now widely used to estimate times of flight and ballistic Green’s functions. Theory, however, predicts that such passively obtained waveforms should equal the full Green’s function of a medium, and thereby convey information on the details of a structure and the presence of isolated scatterers. Here, we investigate diffuse field correlations in a reverberant elastic body and demonstrate that their shear and Rayleigh waves allow to image internal and surface features. Resolution in the resulting images is comparable to standard echographic and seismic images. The experimental setup is analogous to a real seismic experiment.
Finite-frequency seismic tomography
Authors: Shen Yang
Published: October 2013

The use of 3-D sensitivity kernels in tomographic inversions has received much attention in the seismological community. Conventional tomographic studies are based on ray theory, which assumes that the arrival time of a body wave depends only on the velocity along the ray path between the source and receiver. Observed seismic waves are finite frequency signals, and their travel times are sensitive to a 3-D volume around the geometrical ray and subjected to wavefront healing, scattering, and other diffractive effects. As a result, seismic waves passing through velocity heterogeneities with dimensions smaller than the width of the Fresnel zone undergo significant wave-front healing, which results in reduced travel-time shifts compared to the values predicted by ray theory. 3-D sensitivity kernels take into account the effects of wave diffraction and scattering. This presentation will provide a brief review of finite-frequency tomography, which is in a stage of rapid development. With the advancement of computer technology, it has become increasingly practical to construct 3D sensitivity kernels based on 3D reference models using full waveform simulations. This holds the promise of a new level of the integration and joint interpretation of finite-frequency waves propagating in complex media.
Multichannel inversion of scattered teleseismic waves for migration imaging and separation of noise
Authors: Rondenay Stephane , Campman Xander
Published: October 2013

In recent years, a substantial increase in the availability and fidelity of broadband seismographs has led to new opportunities for multichannel processing of scattered teleseismic body waves, allowing for high-resolution imaging of subsurface structure. Here, we discuss the theoretical foundation and the implementation of such a technique. The problem is posed for forward- and back-scattered wave fields generated at discontinuities in a 2-D isotropic medium, with the backprojection operator cast as a generalized radon transform (GRT). The approach allows for the treatment of incident plane waves from arbitrary backazimuths, and recovers estimates of perturbations in material property (P and S wave velocities) about a smoothly varying reference model. In its current implementation, the method can be applied to low-pass filtered data (0.3-Hz cutoff) for imaging structure in the lower crust and lithospheric mantle. Examples from the Cascadia and Alaska subduction zones are shown. Ongoing work is being conducted to render the method applicable to higher frequency data by identifying and canceling noise generated by near-surface scatterers (e.g., mountains, sedimentary basins).
An earthquake detection, identification, and location system for the northeastern U.S. Based on the wavelet transform
Authors: Ebel John E.
Published: October 2013

In order to optimize the ability of the New England Seismic Network (NESN) to detect all local earthquakes to the smallest possible magnitude, Weston Observatory of Boston College has developed an automated event detection and identification system based on the wavelet transform. This software system performs a wavelet transform on the data from each station being received and uses the time, frequency content, and energy of the first arrival, the highest energy arrival, and the end of the detection to compute the Bayesian probability that the detection was a distant earthquake (teleseism), regional earthquake, local earthquake, quarry blast, Rg wave from a quarry blast, or transient noise. At each station, these measured parameters are used to estimate the origin time, epicentral distance, and magnitude for each detection. The systems attempts to associate the detections from different stations that have a common event identification as a teleseism, regional/local earthquake, or quarry blast. If three or more stations associate, an automatic event location and magnitude (if a regional or local earthquake) are computed. This wavelet-transform detector and identifier has greatly increased the sensitivity of detecting and locating small earthquakes and quarry blasts in the New England region.
Measurements and modeling of low-frequency air-sea-interface scattering
Authors: Gauss Roger C. , Fialkowski Joseph M. , Wurmser Daniel
Published: October 2013

The acoustic scattering response of the undersea air-sea interface can be quite sensitive to ocean surface conditions, scattering geometry, and acoustic frequency. This paper presents both measurements and modeling of low-frequency (<1500 Hz) scattering strength. The modeling is based on a small slope approximation (SSA) that accounts for directional surface-wave roughness spectra with low-wave-number cutoffs. To provide an operationally useful predictive tool, a set of surface-wave spectral parameters (strength, exponent, and peak) are determined by nonlinear, multi-parameter fits to broadband, vertically bistatic surface backscattering strength data, leading to a semi-empirical bistatic model environmentally parameterized solely by the wind speed. The same SSA theory is also used to estimate the coherent-reflection loss given the frequency, angle, and wind speed. These broadband models are then used to explore the dependence of both incoherent and coherent sea-surface scattering on frequency, angle, and wind speed. [Work supported by ONR and PEO C4I & Space (PMW-180).]
How significant is the wave height of a moving surface on low-frequency propagation?
Authors: Williams Duncan P.
Published: October 2013

The ocean can carry low-frequency acoustic waves to surprisingly long range, but the ocean is ever changing and acoustic propagation is rarely unaffected by its interaction with the moving sea surface. The clarity of low-frequency acoustic communications at long range can be corrupted by this interaction. This is unsatisfactory for reliable communication and it is necessary to explain the effects introduced by the nature of the sea-surface scattering. This paper looks at the relationship between the power spectra of the received surface scattered signal and the sea surface. The surface can be conveniently characterized by its swell and wind-sea parts that can, in turn, be expressed as a function of their significant wave height and peak frequency. Basic properties of a surface spectral model are reviewed. A new model-based approach to computing the scattering from a moving sea surface is introduced. This approach is based on ray theory and a simple physical model for the response function of the surface. The model is compared with long-range experimental data and then results are shown to illustrate the effects of wave height and peak frequency on simple broadband waveforms.
Gravity wave focusing in the littoral zone
Authors: Deane Grant
Published: October 2013

One of the unique environmental factors impacting acoustic propagation in the littoral zone is the presence of shoaling surf. Surface gravity waves act as acoustic mirrors, creating high-intensity cusps and caustics in the reflected sound field. The focal points of sound move through the water column as the gravity waves shoal, and can disrupt the performance of underwater communications systems and impact sonar performance. Analytical and numerical calculations of the focusing properties of shoaling gravity waves are described and used to predict the motion of the focal regions through time. [Work supported by ONR.]
A brief review of modeling in support of bubble-enhanced scattering from the air/sea interface
Authors: Keiffer Richard
Published: October 2013

By 1995 or so, the long-standing disparity (at low to moderate frequencies) between sea surface (backscatter) reverberation data and interface scattering models was solved by the incorporating a bubble cloud scattering mechanism into reverberation models. At that time (and still today), a comprehensive description of the spatially and temporally varying bubble population was lacking, so critical environmental parameters needed for the bubble cloud scattering models were inferred from the differences in the scattering levels predicted by interface scattering models and measured scattering strengths. This modeling development generally ignored another mechanism through which the bubbles may influence the reverberation: the bubbles will also cause upward refraction near the air/sea interface and this upward refraction may significantly increase the scattering from the air/sea boundary. In this presentation, a brief review of the published modeling supporting the bubble-enhanced interface scattering phenomenon will be presented. [Work supported by ONR/NRL.]
Wavefront modeling of scattering from surface waves
Authors: Tindle Chris
Published: October 2013

The scattering of sound from any particular smooth realization of ocean surface waves can be calculated using wavefront modeling. The method uses ray tracing to locate the wavefronts and stationary phase analysis to determine the phase and amplitude of the sound field. Waveforms due to reflection of short pulses can be found directly and compare well with experimental results. Reflection at a curved surface leads to foci and caustics and the field is determined numerically from Pearcey and Airy functions, respectively. The method uses the time domain and is fast and accurate. [Work supported by ONR.]
A time domain approach to sea-surface scattering
Authors: Siderius Martin , Porter Michael B. , Abawi Ahmad T.
Published: October 2013

Solutions to scattering problems are often formulated in the frequency domain which, for ocean acoustics, implies the surface is frozen in time. This may be reasonable for short-duration signals but breaks down if the surface changes appreciably over the time of the transmission. Additionally, frequency-do-main solutions are impractical for source-receiver ranges and frequency bands typical for applications such as acoustic communications (e.g., several kilometers, 3–50-kHz band). The time-varying nature of the sea surface adds to the complexity, often leading to a statistical description for the variations in received signals. A purely statistical description likely limits the insight that modeling generally provides. In this presentation we describe a time-domain modeling approach to the sea-surface scattering problem. The Helmholtz integral equation is used with the Kirchhoff approximation. The Green’s functions representing the impulse response from all scattering points on the surface to the receivers are computed in terms of arrival amplitudes and time delays. This time-domain framework allows for including both broadband signals and the time-varying sea surface. The method will be compared with exact solutions for a subset of problems (frozen, rough surfaces) to determine limitations. Further, scattering results will be compared with those using Gaussian beam tracing.
Further work on the relationship between the coherent-to-incoherent ratio (CTIR) and the sea surface wave height for one-way propagation in a shallow ocean channel
Authors: Culver R. Lee , Bradley David L. , Roux Philippe , Kuperman William A. , Mark Stevenson
Published: October 2013

A 29-element source array and 32-element receiver array have been deployed 8.6 km apart in a 120-m-deep ocean channel. Both arrays spanned most of the water column. Linear frequency-modulated (LFM) pulses 150 ms long and 4 kHz wide centered at 3.5 kHz were transmitted from one source at a time and recorded at all receivers during a several day period. During the recordings, the sound speed profile was approximately iso-velocity and the significant wave height varied from 0.3 to 1.1 m. We average the received signal coherently and incoherently for each source-receiver pair, average over all pairs, and take the coherent-to-incoherent ratio (CTIR). Log(CTIR) is found to depend linearly on time after the initial arrival, with slope proportional to the significant wave height. An earlier talk showed that the average reflection coefficient times the number of surface bounces N was a good predictor of the slope, but subsequently we find that it alone is not sufficient. Here we report a more complete theory that combines N, the average reflection coefficient, and the density of the arrivals. A predictive model for slope versus surface wave height is presented and compared with the measurements. The method can incorporate ray tracing and be extended to non-iso-velocity environments.
Detection in a nonstationary waveguide using orthogonal codes to measure the invariants of the time reversal operator
Authors: Philippe Franck , Prada Claire , Clorennec Dominique , De Rosny Julien , Fink Mathias
Published: October 2013

In underwater acoustics, time reversal (TR) techniques using an array of acoustic sources are commonly known for their efficiency in applications such as communication and detection. However, as TR methods assume stationary conditions, they are clearly affected by fluctuations of the medium. Among them, the decomposition of the time reversal operator (DORT method), although highly efficient for separating the echo from two close targets through a complex medium, suffers from the long acquisition time required. Indeed the whole interelement responses are needed meaning that N signals are acquired for an N-transducer array. The measurement is then at least N times longer than travel time. To reduce the acquisition time, orthogonal codes can be used [Folgot et al., J. Acoust. Soc. Am. 117, 3757–3765 (2005)]. These codes are tested in a laboratory detection experiment: a small-scale model of a shallow-water wave guide in which we add artificial surface waves of different frequencies and different amplitudes. The perturbations induced by the surface waves on the invariant of the time reversal operator are analyzed. Different methods which greatly reduce the acquisition time like Kasami and AIRS codes are compared.
``Flowers and Wreaths'': Radio theater and surround
Authors: White Ean
Published: October 2013

Originally produced in late 1992, ``Flowers and Wreaths'' is a setting for poems by Jacques Prvert (paroles Prvert) in French and in English translations by Lawrence Ferlinghetti and me. Prvert's success in France after World War II was largely due to his unabashed use of street language and his staunch antiwar, antirational political stance. The performance featured much original instrumentation: an amplified skull-resonator dental floss violone, a 35-ft.-long infrasonic electric monochord, a naval signal lamp, mechanized moving audience seating, the amplified electrocution of vegetables, unconventional speaker placement, etc. Mari Novotny-Jones and I continued to perform the piece through 1993. ``Flowers and Wreaths'' was decidedly a kind of live radio theater, but far too contingent, too phenomenological to expect that it could actually be recorded and distributed in any satisfactory way. Nevertheless, this work continued to be pursued through the mid-nineties, finally producing Radio Etudes (with Sarah Hickler and technical help from the late Robert Moog), which addressed directly the issues of reproduction before being given up entirely. Now, on the brink of a new era in broadcast technology, imagine a radio theater renaissance.
Convergence
Authors: Carballeira Andrew
Published: October 2013

convergence seeks to show the potential beauty of a world at peace through the manipulation of dissonance/consonance and spatial information. As a noncomposed experimental piece, the principal task is sifting through a wealth of improvised free music to gleam the sections most pertinent to the aims of the work. Thereby, convergence is, in many ways, a continuation of the concept adopted by Columbia editors on Miles Davis later works (‘‘Bitches Brew’’ and ‘‘Live/Evil’’ among them) which places the engineer/editor at the forefront of the creative process. In the spatial domain, this work draws heavily on the multi-channel spatialization techniques developed by IRCAM ( et al.) and convolution with impulse responses, sampled and synthesized, to create the environment in which sound sources interact and ultimately join together with one voice.
The creation of a surreal five-channel sound environment using human mobile microphone stands
Authors: Plsek Thomas
Published: October 2013

The notion of creating a piece for a discrete five-channel audio environment calls for one to consider ways in which a piece could be created that could only exist in this environment, i.e., it would not be a documentation of a performance, nor could it even exist in the real acoustic world. Considering low-tech solutions to these problems led to the idea of doing a recording of solo trombone using human mobile microphone stands (or HMMS). This allows for real-time movement of both the source and the receivers during the recording process. This gives the possibility of creating a surreal audio environment that could only be created with extreme difficulty (if at all) any other way. As source material for composition, the poem, ‘‘Rather the flight of the bird passing and leaving no trace,’’ by Alberto Caeiro, who was one of many heteronyms of the Portuguese poet Fernando Pessoa, was chosen. Espcially notable is the line, ‘‘What’s past is nothing and remembering is not seeing.’’
Temporal/spatial convergence in surround sound
Authors: Moore Stephan
Published: October 2013

A discussion of the musical composition ‘‘Thaw/Twist at Bailey’s,’’ in which a field recording of the 2004 spring thaw at Thomas Bailey’s farmhouse in Richland, MI is used to explore the phenomena of temporal/spatial convergence and dispersal. This presentation will cover the creation of the piece, its initial installation for a site-specific 16-channel array of custom-built speakers, and the challenges and merits of adapting it for 5.1 surround sound.
The evolution of new counterpoint through electro-acoustic music
Authors: Chasalow Eric
Published: October 2013

It is widely believed that the advent of electronic music during the mid-20th century redefined music fundamentally. It may be shown, however, that a number of composers found rather more evolutionary ways of elevating basic acoustical elements to enrich the long tradition of music making. Examples from Davidovsky and the author demonstrate this history. Additional examples demonstrate the continuing evolution enabled by historical artifacts and surround technology.
Detection and discrimination of fish prey by echolocating odontocetes
Authors: Au Whitlow W. L. , Benoit-Bird Kelly J. , Kastelein Ronald
Published: October 2013

The echolocation detection range of the Atlantic bottlenose dolphin Tursiops truncates and the harbor porpoise Phocoena phocoena have been either measured or estimated in nonmasking and noise-masking environments using human-made targets. These experiments provide little information on the detection range for fish prey in a natural environment. Backscatter and corresponding target strength measurements were performed on four species of fish, Atlantic cod, gray mullet, pollock, and sea bass, using simulated dolphin and harbor porpoise echolocation signals. Backscatter measurements were also performed on several species of snappers using simulated bottlenose dolphin echolocation signals. The fish subject was anesthetized and placed in a monofilament net bag which was attached to a monofilament curtain attached to a rotor. The target strength and backscatter characteristics were determined as a function of angle in the lateral plane. The results of detection experiments using real targets were used to estimate echolocation detection range for the different fish species. In a nonmasking environment, a bottlenose dolphin should be able to detect a cod between 84 and 135 m and a porpoise detection range should be between 12 and 23 m. We also examined the cues echolocating animals could use to discriminate fish species.
Numerical insights into the mechanisms of biosonar beamforming
Authors: Müller Rolf
Published: October 2013

The pronounced interspecific variability in the outer ear and nose shapes of bats suggests that the beamforming action of these structures is functionally important to the animals’ biosonar systems. Numerical methods bring three major advantages to the study of the underlying mechanisms: efficiency in producing high-resolution directivity estimates, exploration of wave properties in the near field, and integration with digital shape manipulations. High-resolution directivity estimates reveal the shape of main- and sidelobes as well as their interplay over frequency. In two case studies, sidelobes were found to be prominent directivity features with significant sensitivity. In one case, they were even part of a dynamic pattern in which the maximum sensitivity alternates between mainlobe and sidelobes over frequency. Shape manipulations can be applied to the study of such features as the tragus or antitragus and prominent ledges around the pinna rim. These features can either be digitally removed or continuously transformed (e.g., rotated or scaled). The effects of multiple features can be studied by generating all combinations of presence or absence of the individual features. All prominent morphological features studied so far were found to have an effect mainly on sidelobes.
Simulating neural responses to biosonar signals
Authors: Mountain David C.
Published: October 2013

The mammalian auditory system is a highly evolved acoustic signal-processing system that performs well even in highly reverberant and cluttered acoustic environments. In echolocating species, the auditory system is even more highly evolved and is generally more important than vision for navigation and foraging. Since invasive physiological experiments using echolocating species is challenging at best and is illegal for protected species, other methods must be sought if we are to understand how biosonar systems function. Biophysically based computer models provide a method by which we can extrapolate from physiological experiments performed on species that can be used for invasive experiments to those species that cannot be used. Results will be presented for simulations of physiological responses in the auditory nerve and brainstem to biosonar signals for several species. The simulations were done using the EARLAB (http://earlab.bu.edu) desktop simulation environment. Model parameters for species of interest were estimated from behavioral audiograms and from other available data. The models can be used to predict how different types of biosonar signals are represented in neural firing patterns and how the neural representation degrades in the presence of anthropogenic noise. [Work supported by ONR and NSF through the NOPP program.]
Echolocating big brown bats shorten interpulse intervals when flying in high-clutter environments
Authors: Petrites Anthony E. , Mowlds Donald S. , Eng Oliver S. , Simmons James A. , DeLong Caroline M.
Published: October 2013

Insectivorous big brown bats (Eptesicus fuscus) use frequency-modulated ultrasonic echolocation calls to locate and capture prey, often while navigating through highly cluttered areas of vegetation. To test how their calls change while flying through different clutter densities, a matrix of vertically hanging chain links was constructed in a 4.5-m-wide, 10.5-m-long, and 2.6-m-high flight room. Three different clutter densities (low, medium, and high) were created by varying the number of chains in the matrix (9, 114, and 150, respectively). Four wild-born bats were trained to fly through curved gaps in the chain network. These flights were recorded in the dark with a stereoscopic pair of thermal imaging cameras and a heterodyne bat detector. The bats were flown first through the high-, then the low-, and finally the medium-density configuration over a period of 40 days. Preliminary analysis of the pulse intervals of the bats sounds during flight reveals that the interpulse intervals shorten considerably under high-clutter conditions as compared to medium or low clutter. The data suggest that bats flying through high clutter become limited to shorter interpulse intervals in order to ensonify their immediate environment at the expense of larger-scale navigation. [Work supported by NIH.]
Nonlinear Rayleigh waves in soft tissue
Authors: Zabolotskaya Evgenia A. , Ilinskii Yurii A. , Hamilton Mark F.
Published: October 2013

Linear and nonlinear Rayleigh waves in soft elastic, tissuelike media are investigated theoretically. When the shear modulus is much smaller than the bulk modulus, as it is for soft tissue, the medium can be modeled as being incompressible provided shear stress alone is sufficient to support a particular mode of propagation. Such is the case for Rayleigh waves. Propagation speeds and penetration depths of the transverse and longitudinal components of Rayleigh waves are evaluated under these conditions. Differences between Rayleigh waves in ordinary solids and in soft elastic media are discussed. In tissuelike media, the transverse component obeys a wave equation, and the longitudinal counterpart obeys the Laplace equation. It is also shown that Rayleigh waves in soft elastic media are degenerate in the sense that the potential and solenoidal components cannot be separated. The analysis is based on Hamiltonian mechanics, following an approach developed by the authors for modeling nonlinear surface acoustic waves in both isotropic and anisotropic solids. Nonlinearity coefficients are estimated that characterize the rate of waveform distortion and harmonic generation. Numerical simulations of nonlinear propagation effects in soft elastic incompressible media are simulated in the quadratic approximation. [Work supported by NIH Grant EB004336.]
Transcranial longitudinal and shear sound speeds in animal models
Authors: White P. J. , Clement G. T. , Hynynen K.
Published: October 2013

For nearly every experimental procedure or device developed for clinical application, animal models are vigorously pursued to not only ensure efficacy and safety of the tool, but as research models for the sequential observation of phenomena arising from simple systems to the complex. When novel procedures are introduced or proposed for study, it is imperative to ensure that effects observed in animal models are congruous to the expected effects in humans. In the case of transcranial ultrasound, the recently proposed application of ultrasound through the skull bone at incident angles to induce shear mode transmission required the quantitative assessment of shear sound speeds in human and animal skull bone. Using time-of-flight measurement methods with fresh and formalin-fixed skulls, measurements of longitudinal and shear sound speed were performed on pig, sheep, rabbit, and rat skull bone specimens. Discrepancies were observed in some cases between sound speeds in animal skull bone and those obtained from earlier studies of human skull bone. Results from these measurements will give indication as to whether certain animal models are sufficiently suited for transcranial longitudinal and shear mode ultrasound studies. [Work supported by NIH: R01EB003268 and R21EB004353.]
Ultrasonically determined thickness of long cortical bones
Authors: Moilanen Petro , Talmant Maryline , Laugier Pascal
Published: October 2013

Recent experimental studies have shown that an ultrasonically determined thickness (U-Th), based on a fit between measured and theoretical velocity of a fundamental flexural guided wave, correlated significantly with the cortical thickness (C-Th) of human radius bones. In this study, suitability of the theoretical model for fitting with experimental results for bones was evaluated. Numerical model, based on 3-D x-ray reconstructions of human radii (n=29), was developed, and wave propagation was simulated using the finite-difference method. In spite of variations in cortical thickness along the propagation path, a wave mode consistent with A0 Lamb mode was identified, and U-Th (2.7±0.6 mm) was indeed strongly correlated (r2=0.90, p<0.001) with C-Th (3.0±0.6 mm) (2D results). Three-dimensional simulations were then performed yielding similar results. These results were in good accordance with the previous in vitro experiments. Particularly, slight variation in geometry of bone did not affect too strongly the dispersion of fundamental guided waves, and simple analytical theory can be used as a satisfactory model for the average geometrical properties of cortical bone.