bluuebunny/crossref_metadata_2025 huggingface dataset:
A stable transient boundary element method (BEM) for diffuser scattering
Authors: Hargreaves Jonathan A. , Cox Trevor J.
Published: October 2013

Boundary element methods (BEM) may be used to model scattering from hard rigid surfaces such as diffusers. They have the advantage over volumetric methods that only the surface need be meshed and the surface velocity potential found. Unlike the more widely used single frequency methodology, transient BEM discretizes integral equations to produce an iterative system that is marched on in time from known initial conditions to calculate how the velocity potential varies over time. This iterative process can be unstable, and this is one reason why transient BEM is not more widely used. Previous works on transient BEMs have focused on idealized surfaces, such as spheres and plates. However, little is published on the performance of these methods for more complex surfaces of interest, such as Schröder diffusers. Consequently, this paper presents an implicit scheme suitable for a surface comprising thin and solid sections. Such an implicit scheme has the benefits of not constraining time-step duration to the smallest surface detail, and brings stability benefits. Numerical integration is carried out efficiently and accurately by conversion to contour integrals. Accuracy and stability is investigated by comparison to a verified single frequency BEM.
A novel approach to achieving significant reverberation control in performance halls
Authors: Conant David A. , Chu William
Published: October 2013

Conventional methods for achieving broadband, variable sound absorption in large halls normally include heavy application of sound-absorptive drapery and/or thick fibrous panels, applied near available surfaces below, at, and in volumes above the catwalk plane. Occasionally, direct adjustments to room air volume are also provided to effect double-sloped decays. The novel method described here combines carefully located, broad scattering and absorption in singular architectural elements and was applied to a new, 1200-seat concert hall. A change of 0.70 s RT60 in midfrequency is achieved in a visually dramatic manner while neither materially changing room volume nor introducing often-maligned drapery. The aggregate of reverberation control methodologies employed reduces the unoccupied RT60 at midfrequencies from about 3.2 to 1.7 s in this space programed principally for music, including pipe organ. Results of MLS measurements including binaural measurements and binaural recordings of anechoic material and CATT-acoustic modeling and auralizations are discussed.
Sound-conducting mechanisms for echolocation hearing of a dolphin
Authors: Ryabov Vyacheslav A.
Published: October 2013

The morphological study of the lower jaw of a dolphin (Tursiops truncatus p.), and the modeling and calculation of its structures from the acoustic point of view have been conducted. It was determined that the cross-sectional area of the mandibular canal (MC) increases exponentially. The MC represents the acoustical horn. The mental foramens (MFs) is positioned in the horn throat, representing the nonequidistant array of waveguide delay lines (NAWDL). The acoustical horn ensures the traveling wave conditions inside the MC and intensifies sonar echoes up to 1514 times. This ‘‘ideal’’ traveling wave antenna is created by nature, representing the combination of the NAWDL and the acoustical horn. The dimensions and sequence of morphological structures of the lower jaw are optimal both for reception and forming the beam pattern, and for the amplification and transmission of sonar echoes up to the bulla tympani. Morphological structures of the lower jaw are considered as components of the peripheral section of the dolphin echolocation hearing.
An optimized toolchain for predicting directivity patterns from digital representations of biological shapes
Authors: Müller Rolf
Published: October 2013

Animals have evolved intricate shapes which diffract emitted or received sound and thereby generate a specific directivity pattern. Computer-tomographic methods can generate high-resolution digital representations of these morphological structures in the form of three-dimensional voxel arrays. However, predicting acoustic directivity patterns from these representations with numerical methods can incur high computational cost, e.g., for large structures with fine detail and/or high wave numbers (as in bats and dolphins). Here, the design of a toolchain is described which can handle all steps of deriving a directivity prediction from a voxel representation: generation of a finite-element mesh, assembly of the system matrix, computation of an approximate solution, forward projection into the far field. All individual operations are performed by self-contained tools, which communicate through files. This gives access to intermediate results and limits re-execution upon parameter changes to downstream steps. At each stage, optimizations can be made based on the specifics of the problem such as the regular structure of the voxel array and the distance independence of the directivity. Use of these optimizations has resulted in a highly efficient performance, which is documented by measures for execution speed, memory usage, and accuracy.
Equine acoustics: Anatomy of a whinny
Authors: Browning David G. , Scheifele Peter M.
Published: October 2013

Of the roughly nine different vocalizations of a horse, the whinny appears to be the most interesting. A whinny is a horse’s primary means of long range vocal communication; the bandwidth and variability offer the possibility of expression, at least at a primitive level. Acoustic analysis of a whinny shows three distinct domains: the initial frequency ramp-up running from 1 to 2 kilohertz in roughly 1 second, matched by a similar response in the second and third harmonics; secondly, this is followed by a nasal tremolo of a longer duration with generally a slight downslope in frequency (this is perhaps the stage most associated with the human perception of a whinny); and, lastly, a guttural tremolo, essentially the same sound as a nicker. In the samples analyzed, each domain seems to vary independently both in strength and duration. Attempts to link an aspect of a whinny with a particular behavior is still in a formative stage, complicated by the fact that a horse’s behavior is usually based primarily on visual rather than acoustic inputs.
Identifying individual sperm whales acoustically using self-organizing maps
Authors: Ioup Juliette W. , Ioup George E.
Published: October 2013

The Littoral Acoustic Demonstration Center (LADC) is a consortium at Stennis Space Center comprising the University of New Orleans, the University of Southern Mississippi, the Naval Research Laboratory, and the University of Louisiana at Lafayette. LADC deployed three Environmental Acoustic Recording System (EARS) buoys in the northern Gulf of Mexico during the summer of 2001 to study ambient noise and marine mammals. Each LADC EARS was an autonomous, self-recording buoy capable of 36 days of continuous recording of a single channel at an 11.7-kHz sampling rate (bandwidth to 5859 Hz). The hydrophone selected for this analysis was approximately 50 m from the bottom in a water depth of 800 m on the continental slope off the Mississippi River delta. This paper contains recent analysis results for sperm whale codas recorded during a 3-min period. Results are presented for the identification of individual sperm whales from their codas, using the acoustic properties of the clicks within each coda. The recorded time series, the Fourier transform magnitude, and the wavelet transform coefficients are each used separately with a self-organizing map procedure for 43 codas. All show the codas as coming from four or five individual whales. [Research supported by ONR.]
Directivity of singers
Authors: Jers Harald
Published: October 2013

Studies of acoustical balance between singers within a choir by means of room acoustical measurements have shown that the directional sound propagation of the source is important. For this reason the directivity of female and male singers for different vowels has been measured in this investigation. Measurements of a pilot study and some first measurements in 1998 have been supplemented with new measurements and an enhanced setup. A special measurement setup with reference and recording microphones was used to collect the directivity data. A resolution of 10 deg for azimuth and elevation angle was obtained. The results will be shown in 3D spherical plots with frequency adjustments in semitones from 80 to 8000 Hz. The measurements are compared to an artificial singer’s directivity, and the influence of a sheet music binder in front of a singer will be shown. The results give information on the directivity of singers and are relevant for the prediction of self-to-other-ratios that result from placement and formation aspects within a choir.
Sound transmission modeling of advanced multilayered composite structures using enhanced T-matrices for two-phase materials
Authors: Woodcock Roland L. , Bryant Rebecca S.
Published: October 2013

Advanced composite structures have been used for many years in the aerospace industry. When designing multilayered structures special attention must be paid to the bonding techniques since the interface conditions have a direct effect on the mechanical coupling between the individual layers. Previous studies have shown the overall acoustical performance such as transmission loss and surface absorption to be sensitive to this structural path mainly in the lower frequency range. The state of the art shows that a comprehensive model is still lacking in the framework of the transfer matrix Method. The present paper proposes a new analytical modeling approach to tackle systems with stiffeners in the low-frequency range. This technique is based on the so-called Series-Parallel network of the transmission line theory in the framework of the classical electro-acoustical analogies. The simulations show that in the typical case of a double plate with stiffeners, with regards to transmission loss the design change due to the mechanical path is captured and the increase of the overall stiffness of the system shifts the resonance to the higher frequencies. The other important acoustical properties of multilayered systems will be highlighted during the presentation with regards to optimizing the overall acoustical performance.
Minimization of resonance excitation of moving actuator and joint structures
Authors: Kovinskaya Svetlana , Khozikov Yuvenaly
Published: October 2013

Numerous devices have actuators moving from one immobile position to another under action of applied forces. Repositioning of actuators requires its acceleration and deceleration for faster moving. It is provided by subsequent application of constant forces of opposite directions. Duration of their action is much longer than the resonance periods of actuators or joint structures, and such constant forces excite no resonance. However, a sudden change of the force value results in the resonance excitation. Minimization of resonance excitation can be performed by control of the applied force. Considering the problem in the time domain, one must minimize energy at excited resonance by shaping the force profile while keeping the fast actuator reposition. An effective algorithm for shaping of initial profile based on an iterative procedure is suggested. At the first step of the iteration the profile is deformed (to minimize resonance excitation) by shaping functions which are equal unit outside a short instance. At the second step the deformed initial profile is shaped by the polynomial to meet basic requirements on moving (given distance and zero velocity by the end of reposition). Employment of the developed algorithm significantly reduces the residual vibration and noise radiated by a device.
Comparing the acoustics of voiced and voiceless fricatives in Deg Xinag
Authors: Wright Richard , Hargus Sharon , Miller Julia
Published: October 2013

Few studies have looked at the acoustic properties of fricative voicing and place in Native American languages despite their relatively rich fricative inventories of rarely studied fricative places. Deg Xinag, an endangered Athabaskan language spoken in Alaska, provides us with a rare opportunity to investigate fricative place and voicing within a single language: it has eight places of articulation for voiceless fricatives, six of which have voiced counterparts, including some rarely studied place contrasts (e.g., palato-alveolar versus retroflex, uvular versus glottal, lateral versus alveolar). In this study, pre- and post-vocalic fricatives were digitally recorded in the field from eight speakers (two males, six females) using a head-mounted mic to control for distance from the source. The segmental context was also controlled for, the neighboring vowel being [a] in all cases. Each speaker produced four repetitions of each word. Each fricative was analyzed qualitatively using impressionistic transcription and spectrographic investigation, and quantitatively using a set of widely employed measures: (a) widely employed spectral measures (center of gravity, skew, kurtosis, standard deviation, lowest spectral peak), peak and rms intensity of frication, overall duration and duration of voicing. [Work supported by NSF.]
Reflection of sound from finite-size plane and curved surfaces
Authors: Rindel Jens H.
Published: October 2013

The author’s research on reflectors over nearly 25 years is summarized. The influence of curvature was analyzed by a geometrical model in order to quantify the attenuation by a simple expression. Reflection from a finite-size plate was studied using the Kirchhoff–Fresnel approximation, and the design frequency for a single reflector was derived. Above the design frequency the attenuation due to the finite size can be neglected and the reflection is efficient in the specular direction. The method was extended to the case of a reflector array, and it was demonstrated that the performance of a reflector array can improve if the size of the panels is decreased. The same design frequency applies to a single reflector and a reflector array, but with different meaning; in the latter case the design frequency is the upper limit for useful reflections. This design rule was first used in the refurbishment of the concert hall of the Danish Radio in Copenhagen 1989, and later in many other halls. In order to describe the scattering due to edge diffraction, the directional characteristic of reflections from a finite-size plate has been studied and a simple approximation valid for octave bands has been derived.
The 60-dB rule for birds: An example of the application of a weighting function in environmental impact mitigation
Authors: Bowles Ann E. , Wisdom Sheyna
Published: October 2013

Over the last decade U.S. Fish and Wildlife Service managers in California have required millions of dollars in added expenditure for NEPA consultation, mitigation barriers, and project delays to reduce the effects of noise from construction activities on endangered passerine birds when the hourly A-weighted Leq is expected to exceed 60 dB. The rule was originally intended to prevent masking of species-typical songs of endangered birds such as the Coastal California Gnatcatcher. However, no research is available to demonstrate the effectiveness of the rule for any noise-related impact. Although A-weighting is probably a conservative estimator of bird exposure in the range from 125 Hz to 8 kHz, it may underestimate exposure at very low frequencies. Its utility as a weighting function has not been tested against other possible weighting procedures, such as use of the species-typical auditory threshold function. Additionally, where sources are intense but intermittent, Leq is unlikely to be a useful metric. These issues should receive more technical scrutiny before the 60-dB rule becomes entrenched in law. It is in widespread use for NEPA consultations, and is already being extended to other species, including large mammals.
Source levels of northern elephant seal vocalizations in-air
Authors: Insley Stephen J. , Southall Brandon L.
Published: October 2013

Accurate measurements of vocalization sound-pressure levels are necessary to determine the acoustical active space of animals in natural and human-altered ambient noise conditions. Despite this basic need, such data are limited or nonexistent for most species. Our study characterized aerial ambient noise and vocalization source levels for northern elephant seals during the breeding season. Subjects were adult males, lactating females, and dependent offspring (pups) at Año Nuevo State Reserve. Source level measurements were made using a Type 1 sound level meter and calibrated microphones on-axis: (1) at 1 m; (2) at several known distances (laser measured); and (3) simultaneously at 1 m and a second known distance. Concurrent ambient noise conditions were measured in situ (non-weighted 5 min Leq integrated averages) and recorded for later spectral analysis. Measurements were made at two sites, one relatively noisy and the other relatively quiet, to determine whether animals compensate for higher noise conditions by increasing source levels (Lombard effect). Results indicate a wide range in signal strength, particularly for adult males whose vocalization source levels appear to be correlated with dominance rank and related to ambient noise conditions. The Lombard effect was not observed for adult females or elephant seal pups.
Experimental validation of a species-specific behavioral impact metric for underwater noise
Authors: Nedwell Jeremy R. , Lovell Joe , Turnpenny Andrew W. H.
Published: October 2013

The regulation of noise from offshore activities in the UK requires a metric allowing the behavioral effects on underwater animals of man-made underwater noise on a wide range of species to be objectively assessed. The dBht(species) metric is a pan-specific metric incorporating the concept of ‘‘loudness’’ by using a frequency-weighted curve based on the species’ hearing threshold as the reference unit for a dB scale. A large number of controlled laboratory measurements have been made of the avoidance of a range of idealized noises, using fish with greatly different hearing as a model. Additional data, of many thousands of individuals, has been obtained by re-evaluation of fish avoidance of a large acoustic fish deflection system at an estuarine power station. All data, irrespective of source or species, indicate a dependence of avoidance reaction on the dBht(species) level. The data indicates three regions, ‘‘no reaction’’ below 0dBht (i.e., below the species’ threshold of hearing), a ‘‘cognitive avoidance’’ region where increasing numbers of individuals will avoid the noise from 0 to 90 dBht, and ‘‘instinctive reaction’’ at and above 90 dBht where all animals will avoid the noise. This probabilistic model allows the behavioral impact of any noise source to be estimated.
Choir singing in Subsaharan Africa: Acoustic factors of a regional style in southern Mozambique
Authors: Soeiro de Carvalho Joao
Published: October 2013

Choir singing is a most prominent form of expressive behavior in Subsaharan Africa. A vast majority of expressive modes involves multipart singing, both within the framework of European tonal system as well as other structured ways of combining vocal sounds of different frequencies. Vocal improvisation stands as an important process for the course of performance; individual voice ranges, as well as issues of social status and musical competence, determine the ways musicians participate in performance. Aesthetic validation is often expressed by the use of a nonverbal expressive mode, ‘‘kulungwani,’’ a vocal technique involving the action of the lower maxillae and tongue in order to produce a low-frequency interruption of sound emission. Choral singing intonation processes seem to rely on harmonic results, rather than melodic. A regional choral style in southern Africa seems to have developed, where a particular distribution of formant frequencies and an emphasis on low-frequency energy play a significant role.
An experimental investigation of velocity fields in divergent glottal models of the human vocal tract
Authors: Erath Byron D. , Plesniak Michael W.
Published: October 2013

In speech, sound production arises from fluid-structure interactions within the larynx as well as viscous flow phenomena that is most likely to occur during the divergent orientation of the vocal folds. Of particular interest are the flow mechanisms that influence the location of flow separation points on the vocal folds walls. Physiologically scaled pulsatile flow fields in 7.5 times real size static divergent glottal models were investigated. Three divergence angles were investigated using phase-averaged particle image velocimetry (PIV). The pulsatile glottal jet exhibited a bi-modal stability toward both glottal walls, although there was a significant amount of variance in the angle the jet deflected from the midline. The attachment of the Coanda effect to the glottal model walls occurred when the pulsatile velocity was a maximum, and the acceleration of the waveform was zero. The location of the separation and reattachment points of the flow from the glottal models was a function of the velocity waveform and divergence angle. Acoustic analogies show that a dipole sound source contribution arising from the fluid interaction (Coanda jet) with the vocal fold walls is expected. [Work funded by NIH Grant RO1 DC03577.]
Blind inversion and the perception/production link
Authors: Hogden John , Rubin Philip
Published: October 2013

Whether humans recover articulator positions from acoustics in the course of speech perception has been debated for years. Some of the arguments against recovering articulator positions are relevant for machine speech recognition as well. However, techniques for blind inversion, in which the mapping from acoustics to articulation is learned without known articulator trajectories, were not considered when some of these arguments were being developed. We discuss the impact of blind inversion on the debate, and conclude that there are pragmatic reasons to recover articulation from acoustics, particularly when blind inversion is used and the mapping from articulation to acoustics is many-to-one.
An experimental study of the aeroacoustic sound generated by vortex shedding in static and dynamic models of the glottis
Authors: Kucinschi Bogdan R. , DeWitt Kenneth J. , Scherer Ronald C. , Ng Terry T.
Published: October 2013

Flow-visualization with smoke particles illuminated by a laser sheet, performed with a high-speed camera, was used to obtain the flow patterns in two models of the human larynx, both scaled by a factor of 7.5. The first model was static, while the second was a driven dynamic mechanical model, which simulated the motion of the vocal folds during phonation. For the dynamic model, the glottal motion frequency was of the order of the average fundamental frequency of males. It was found that the vortical flow structures were shed at different locations within and downstream the glottis, depending on the transglottal pressure, geometrical configuration and glottal motion frequency. The vortex shedding frequency, which was much higher than the motion frequency of the vocal folds, was measured optically based on the high-speed visualization images, and compared to the frequency peaks in the sound spectra, determined by microphone measurements. Generally, it was observed that the vortex sheddeing frequency corresponds to the main peak in the sound spectrum. The intensity of noise, however, was found to be dependnet of the location of vortical structures relative to the glottal walls, indicating the presence of quadrupole- or dipole-type sound sources, due to ordered flow structures.
Vocal tract length development during the first two decades of life: A magnetic resonance imaging study
Authors: Vorperian Houri K. , Chung Moo K. , Gentry Lindell R. , Kent Ray D. , Choih Celia S. , Durtschi Reid B. , Ziegert Andrew J.
Published: October 2013

As the vocal tract length (VTL) increases more than twofold from infancy to adulthood, its geometric proportions change. This study assesses the developmental changes of the various hard and soft tissue structures in the vicinity of the vocal tract (VT), and evaluates the relational growth of the various structures with VTL. Magnetic resonance images from 327 cases, ages birth to age 20, were used to secure quantitative measurements of the various soft, cartilaginous and bony structures in the oral and pharyngeal regions using established procedures [Vorperian et al. (1999), (2005)]. Structures measured include: lip thickness, hard- and soft-palate length, tongue length, naso-oro-pharyngeal length, mandibular length and depth, and distance of the hyoid bone and larynx from the posterior nasal spine. Findings indicate: (a) ongoing growth of all oral and pharyngeal structures with changes in growth rate as a function of age; (b) a strong interdependency between structure orientation and its growth curve; and (c) developmental changes in the relational growth of the different VT structures with VTL. Findings provide normative data on the anatomic changes of the supra-laryngeal speech apparatus, and can be used to model the development of the VT. [Work supported by NIH-NIDCD Grants R03-DC4362 R01-DC006282, and NIH-NICHHD P30-HK03352.]
The effects of the glottal geometry on intraglottal pressure distributions
Authors: Sheng Li , Scherer C. Ronald , Wan MingXi , Wang SuPin
Published: October 2013

The purpose of this study is to explore the effects of the glottal geometry on intraglottal and transglottal pressures using a Plexiglas model and a commercially computational fluid dynamics code, fluent. Nine glottal angles (uniform, as well as convergent and divergent 5, 10, 20, and 40 deg), 18 inferior vocal-fold angles varied from 87.5 to −10 deg, and 19 superior vocal-fold surface angles varied from −85 to 45 deg for uniform, convergen 10- and divergent 10-deg glottal angle, and a wide range of entrance radii varied from 0.26 to 0.005 cm for different divergent glottis were selected separately to examine their pressure distribution effects. The empirical data were supported by computational results using fluent. The results suggest that the 10-deg divergence angle may correspond to least flow resistance, the vocal-fold surface pressures are essentially independent of the inferior and superior vocal-fold surface angles realistic for human phonation, and a small glottal entrance radius tends to lower the transglottal pressure, move the minimal pressure near the glottal entrance more upstream, and make the pressure dip more negative in value. These results suggest that the glottal geometry should be well specified when using physical, mathematical phonatory models.
Maximum-length-related sequences and a specialized deconvolution for multiple acoustic channel estimation
Authors: Xiang Ning , Daigle John N.
Published: October 2013

A wide variety of acoustic systems have multiple sources and receivers. This paper discusses a deconvolution technique for making acoustic measurements simultaneously with multiple sources. The deconvolution is based on a collection of known excitation signals of the maximum-length sequence (MLS) related classes, widely used in the spread spectrum communication, but less well known in acoustics applications. This technique is particularly valuable when characterization of multisource, multireceiver system must be accomplished in a limited time period. Since lengths of periodic MLS-related source signals are not suitable for FFT-based decovolutions, and the fast MLS transform based on fast Hadamard transform is not applicable to the MLS-derived combined signals, our effort has been given to an efficient deconvolution algorithm. The simulation and experimental results demonstrate the feasibility, fidelity, and potential applications of the deconvolution techniques in characterizing acoustic systems.
Alternative methods for assessing the omnidirectionality of sources for room acoustics measurements
Authors: Leishman Timothy
Published: October 2013

International standards provide guidelines for qualifying omnidirectional sources for use in room acoustics measurements. This paper presents additional methods that may be used for this purpose and explains their similarities and differences. In some cases the standard methods produce results that are at odds with the alternative methods. The paper explains the discrepancies and provides suggestions for their resolution.
Music to knowledge: A visual programming environment for the development and evaluation of music information retrieval techniques
Authors: Ehmann Andreas F. , Downie J. Stephen
Published: October 2013

The objective of the International Music Information Retrieval Systems Evaluation Laboratory (IMIRSEL) project is the creation of a large, secure corpus of audio and symbolic music data accessible to the music information retrieval (MIR) community for the testing and evaluation of various MIR techniques. As part of the IMIRSEL project, a cross-platform JAVA based visual programming environment called Music to Knowledge (M2K) is being developed for a variety of music information retrieval related tasks. The primary objective of M2K is to supply the MIR community with a toolset that provides the ability to rapidly prototype algorithms, as well as foster the sharing of techniques within the MIR community through the use of a standardized set of tools. Due to the relatively large size of audio data and the computational costs associated with some digital signal processing and machine learning techniques, M2K is also designed to support distributed computing across computing clusters. In addition, facilities to allow the integration of non-JAVA based (e.g., C/C++, MATLAB, etc.) algorithms and programs are provided within M2K. [Work supported by the Andrew W. Mellon Foundation and NSF Grants No. IIS-0340597 and No. IIS-0327371.]
Using instrument recognition for melody extraction from polyphonic audio
Authors: Eggink Jana , Brown Guy J.
Published: October 2013

A system is proposed that identifies the solo instrument in accompanied sonatas and concertos, and uses this knowledge to extract the melody line played by this instrument. The approach uses a feature representation based solely on the spectral peaks belonging to the harmonic series of a fundamental frequency (F0). Based on an initial approximate F0 estimation, this representation proved to be sufficient for instrument classification even in the presence of highly unpredictable background accompaniment. Once the solo instrument is known, a more accurate estimation of the melody line is carried out based on so-called melody models, which are trained on instrument-specific training material. In every time frame multiple F0 candidates are extracted and their likelihood is evaluated according to the chosen melody model. Additional temporal constraints take the form of frame-to-frame transition probabilities, and are obtained from the same training material. The two knowledge sources are combined in a statistical search for the overall most likely melody line. When evaluated on realistic recordings of classical sonatas and concertos, the system was able to find the correct F0 in 72% of frames, an improvement of over 20% compared to a simple salience based approach. a)Previously at University of Sheffield.
Lexical confusability and nasal coarticulation in French
Authors: Scarborough Rebecca
Published: October 2013

Previous research has revealed a relationship between lexical confusability and degree of coarticulation [Brown (2001); Scarborough (2004)]. In particular, English speakers produce confusable, or ‘‘hard’’ words with more nasal and vowel-to-vowel coarticulation than less confusable, ‘‘easy’’ ones. Thus, it has been suggested that speakers produce additional coarticulation in order to increase the intelligibility of ‘‘hard’’ words. Here, the relation between nasal coarticulation and lexical confusability is investigated for French, a language in which vowel nasality is phonemically contrastive (at least for a subset of vowels) and might constrain such a lexical effect. Acoustic measures of nasality show that ‘‘hard’’ words (those with low usage frequencies and many frequent, phonologically similar neighbors) exhibit more nasal coarticulation than ‘‘easy’’ ones (those with high frequencies and few, low-frequency neighbors) in French as well. Interestingly, however, the effect emerges only for words containing vowels that can exhibit phonemic oral-nasal contrasts (oral vowels with nasal counterparts). Thus, where the use of nasality in phonological contrast is constrained, coarticulatory nasality is constrained, too. But the existence of phonological contrast does not itself constrain the lexical confusability effect: increased coarticulatory nasality contributes to lexically motivated phonetic enhancement in French, while even more nasality provides the basis for phonemic contrast.
Syllabification effects on the acoustic structure of intervocalic /r/
Authors: Huffman Marie
Published: October 2013

Imaging and modeling studies suggest that American English /r/ has a complex articulatory profile. Gick [Phonology 16, 29–54(1999)] has proposed that dialectal differences in the presence of /r/ follow from the effects of syllable structure and prosody on component vocalic and consonantal gestures of /r/. This study presents acoustic data on word-medial, intervocalic /r/’s for speakers of two varieties of American English. Both varieties show an effect of /r/ on F3 and/or F4 of a preceding vowel. Where they differ is the acoustic properties of the constriction portion of intervocalic /r/. For one group, the intervocalic /r/ is very vocalic, with little difference in formant amplitude compared to the preceding vowel. For the other group, intervocalic /r/ is more consonantal, with clearly weaker formant structure than the preceding vowel. These differences in the acoustic profile of intervocalic /r/ co-vary with dialectal differences in production of final coda /r/. These results support a gestural account of /r/ variability, while also demonstrating the need for explicit principles of syllable organization which must be specified for each dialect. [Work supported by NSF Grant No. 0325188.]
Acoustic cues to vowel-schwa sequences for high front vowels
Authors: Slifka Janet
Published: October 2013

In a landmark-based model of lexical access [K. N. Stevens, J. Acoust. Soc. Am. 111, 1872–1891 (2002)], the presence of a vowel is marked by a peak in energy in the first formant region. However, when a vowel is followed by a schwa, the schwa frequently appears as a shoulder on the peak associated with the first vowel [W. Howitt, MIT (2000)]; two landmarks are not present. The purpose of this study is to examine duration and F2 movement as possible cues to the presence of a vowel-schwa sequence for [+high, +front] vowels. This subset of vowels presents at least two challenges to the detection of a vowel-schwa sequence: (1) duration is expected to contribute to the difference between /i/ and /I/, and (2) an F2 off-glide toward schwa is expected for /I/ in American English. For 613 tokens from the phonetically labeled TIMIT database, equally distributed between /i■/, /i/, and /I/, a measure of F2 curvature is a stronger cue than duration in classifying the tokens. Using F2 curvature, over 93% of the tokens are correctly classified. Using duration, 67% are correctly classified. F2 curvature may reflect a more extreme articulation for the /i/ prior to the schwa. [Work supported by NIH Grant DC02978.]
A novel procedure for examining pre-lexical phonetic-level analysis
Authors: Bashford James A. , Warren Richard M. , Lenz Peter W.
Published: October 2013

A recorded word repeated over and over is heard to undergo a series of illusory changes (verbal transformations) to other syllables and words in the listener’s lexicon. When a second image of the same repeating word is added through dichotic presentation (with an interaural delay preventing fusion), the two distinct lateralized images of the word undergo independent illusory transformations at the same rate observed for a single image [Lenz et al., J. Acoust. Soc. Am. 107, 2857 (2000)]. However, when the contralateral word differs by even one phoneme, transformation rate decreases dramatically [Bashford et al., J. Acoust. Soc. Am. 110, 2658 (2001)]. This suppression of transformations did not occur when a nonspeech competitor was employed. The present study found that dichotic suppression of transformation rate also is independent of the top-down influence of a verbal competitor’s word frequency, neighborhood density, and lexicality. However, suppression did increase with the extent of feature mismatch at a given phoneme position (e.g., transformations for ‘‘dark’’ were suppressed more by contralateral ‘‘hark’’ than by ‘‘bark’’). These and additional findings indicate that dichotic verbal transformations can provide experimental access to a pre-lexical phonetic analysis normally obscured by subsequent processing. [Work supported by NIH.]
Performance of a space-time trellis-coded multiple-input, multiple-output (MIMO) underwater acoustic communication system for the littoral
Authors: Ormondroyd Richard F. , Dhanoa Jasdeep S.
Published: October 2013

Conventional point-to-point communication systems generally use a single transmitter communicating to a single receiver. Recently, there has been considerable interest in exploiting the spatial diversity that exists in richly scattered communication channels using space-time methods that use multiple transmitters and receivers. These multiple-input, multiple-output (MIMO) systems differ from traditional spatial diversity systems because the data or coded symbols from each cochannel transmitter element are different, whereas for spatial diversity they are the same. MIMO systems can offer improved data rates and/or bit error performance, depending upon the system, when the multipath propagation is highly decorrelated. In this paper, a geometric ray model of a horizontal underwater acoustic channel in the littoral, which includes the effect of time-delay spread and Doppler spread, is used to obtain the time-varying, frequency-selective channel parameters that are applied to a discrete signal-processing model of a space-time trellis-coded MIMO system. Key parameters of this model are the separations of the multiple transducers at both the transmitting and receiving ends of the link, because these determine the degree of decorrelation in the multipath channel. The paper examines the performance trade-offs that are possible using this approach with realistic transducer separations at the transmitter and/or receiver.
Eigenvalues of the time-reversal operator for a small ellipsoid
Authors: Chambers David
Published: October 2013

Earlier analysis of the eigenvalues of the time-reversal operator for a small sphere showed there could be up to four eigenvalues for a planar array [Chambers and Gautesen, J. Acoust. Soc. Am. 109, 2616]. In this talk, we generalize this result to a small ellipsoid and show how the relative values of the eigenvalues depend on orientation, as well as distance and material parameters. We show specific calculations for short rods and small discs. [Work performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.]
An adaptive mutation breeder algorithm for determining equivalent circuit parameters of a liquid-filled piezoelectric cylinder
Authors: Chang Yao-Ting , Davies Jevon , Prenzlow Bjorn , Tapson Jonathan
Published: October 2013

Many acoustic systems require an equivalent electromechanical model to describe their behavior. As a result, a variety of models has been described in the literature including that of Mason, KLM, and Redwood. Although these models can describe complex acoustic systems, it is often difficult to extract circuit parameters for such systems using traditional theory. Aspects of mode superposition and frequency pulling between modes cause traditional theory to become increasingly complex in predicting equivalent circuit values. As a solution to this, an adaptive breeder algorithm is utilized as a means of predicting multiple resonance modes interacting with one another. A liquid-filled piezoelectric cylinder is used as an acoustic system to represent coupled piezoelectric and liquid vibrational modes. Using a variation of Mason’s transmission line model, an adaptive mutation breeder algorithm is used to predict the spectral response measured by an impedance analyzer. The acoustic model is shown to fit almost identically over the measured data for a variety of different-sized cylinders and liquids. It is further shown that the breeder algorithms may be used to predict the sound velocity and density of the liquid inside the cylinder.
Small-slope scattering strength for a rough stratified seafloor
Authors: Gragg Robert F.
Published: October 2013

A small-slope expression is developed for the bistatic scattering strength of a seafloor with random surface relief (characterized by a general power-law spatial spectrum) and arbitrary subsurface stratification. This is done by generalizing an existing formulation for homogeneous bottoms [Gragg et al., J. Acoust. Soc. Am. 110, 2878 (2001)]. The essential points are (i) that the earlier result can be rearranged so the geoacoustic parameters enter via R, the complex reflection coefficient for the same bottom without roughness; and (ii) that including stratification only requires introducing the appropriate layering into the form of R. These steps yield the scattering strength for a seafloor composed of a rough fluid sediment layer over an arbitrarily layered substrate, whose strata may involve elasticity and depth profiles. Implementation only requires an algorithm to generate R for such a layered bottom. Validation is done with Essen’s model environment {fluid sediment and elastic basement, both uniform [Essen, J. Acoust. Soc. Am. 95, 1299–1310 (1994)]} and the well-known analytic expression for R. Results are benchmarked against Essen’s first-order perturbation results. A BLUG substrate is then addressed, with R obtained from a subroutine borrowed from a standard propagation package. [Work supported by ONR.]
A preliminary sediment model for the Shallow-Water-2006 Experimental site on the New Jersey Coast
Authors: Potty Gopu , Miller James
Published: October 2013

A preliminary sediment model for the Shallow-Water-2006 Experiment site on the continental shelf off New Jersey is presented. This sediment model will describe the bottom as layers of sediments with different properties. The layering information will be based on geological, geophysical, and stratigraphy models. This layered approach to sediment modeling coupled with the Biot–Stoll (with reduced number of parameters) or Buckingham model (to define the sediment geoacoustic properties) has the potential for an efficient parametrization to set up a 3D sediment inversion scheme. The surface sediment description will be based on the ESME (effect of sound on marine environment) sediment models for the U.S. East Coast. This sediment model, developed as part of the ESME initiative, draws from a variety of data sources, including the sediment texture database maintained by the United States Geological Survey (USGS). Other sources of data which will be used to develop the preliminary sediment model include published sediment core data from the region and inversions results. This study will provide sediment data for the preliminary experimental design efforts prior to the experiment in 2006. [Work supported by ONR.]
Geoacoustic inversion of horizontal line array data from the Barents Sea
Authors: Tollefsen Dag , Wilmut Michael J.
Published: October 2013

Results from matched-field geoacoustic inversion of low-frequency acoustic field data recorded on a long horizontal array deployed at the seafloor are presented. Data are taken from a recent experiment conducted by FFI in the Barents Sea. Estimates of sediment parameters were obtained by inversions of multitone data from a towed source at source–array ranges of 1–6 km. The Fast Gibbs Sampler [S. E. Dosso, J. Acoust. Soc. Am. 111, 129–142 (2001)] was used to estimate posterior probability densities of model parameters. A number of different range-independent layered fluid seabed models were tested. Estimates of sound speed of Quaternary sediment were consistent with reference values from other geophysical data collected in the area. Details of the upper part of the sediment column that can be resolved from the short- and long-range data are presented. Sediment sound speed was better defined than density and attenuation.
Geoacoustic inversion by mode amplitude perturbation
Authors: Poole Travis L. , Lynch James F. , Pierce Allan D. , Frisk George V.
Published: October 2013

In a shallow-water waveguide the geoacoustic properties of the seafloor have a significant effect on the way sound propagates through the water. Because of this, measurements of the pressure field in the water can be used to estimate bottom properties. In this talk a perturbative method is presented which allows one to use measurements of the modal amplitudes to estimate a set of bottom parameters. A key component of the method is an expression for the derivative of the mode functions with respect to some bottom parameter. Following from the work of Thode and Kim [J. Acoust. Soc. Am. 116, 3370–2283 (2004)], the derivative is expressed as a weighted sum over all modes (both propagating and leaky). It is thought that this method can be used alongside eigenvalue perturbation [Rajan et al., J. Acoust. Soc. Am. 82, 998–1017 (1987)] to provide an inversion scheme more robust to measurement noise. To demonstrate its feasibility, the method is applied to synthetic and real data. [Work supported by the WHOI education office.]
Physics-based clutter via semi-deterministic simulation with bathymetric fractal realizations
Authors: Monjo Charles , Arvelo Juan
Published: October 2013

A semi-deterministic normal-mode reverberation model has been developed that accounts for bistatic bottom micro-slopes generated via bathymetric fractal realizations to simulate clutter scattering from seafloor interface features. This clutter simulator also accounts for uncertainties of the subbottom geoacoustics and on range-dependent interface scattering that varies with the seafloor sediment type. This physics-based approach is compared against measured clutter-rich bottom reverberation from the TMAST02 experiment. [This work is sponsored by ONR.]
Relating the distribution of bathymetry to clutter distributions
Authors: Newhall Bruce , Arvelo Juan
Published: October 2013

One source of clutter for active sonar in shallow water is backscatter from the rough ocean bottom. Backscatter may often be dominated by Bragg scale roughness. Bathymetry measurements are not generally made at sufficient resolution to determine the Bragg scale roughness distribution directly. We examine the distribution of ocean bottom slopes and determine power law relationships. These relationships can be used to define fractals which allow extrapolations of bathymetry to finer scale. The fine-scale bathymetry is then related to the distributions of sonar clutter. The generalized gamma distribution is particularly useful to describe clutter. The upper tail of this distribution approaches a power law related to the power laws in the bathymetry. [This work is sponsored by the Office of Naval Research (ONR).]