bluuebunny/crossref_metadata_2025 huggingface dataset:
Adapting to Jozef Zwislocki
Authors: Smith Robert L.
Published: October 2013

Dr. Joe Zwislocki has been a source of excellent advice throughout my career. However, two very important things he told me were wrong as will be disclosed in the presentation. Nevertheless, among the many fundamental things I learned from him was how one must attempt to take the data, and turn it over and over again until the hidden patterns and quantitative inter-relationships emerge. It was because of Joe that I first began to study auditory-nerve adaptation. His challenge to me was to find a model of adaptation that was not only functionally useful but also physiologically realizable, and that quest is still continuing, on my part and that of many others in our field. When Joe suggested auditory-nerve adaptation as a possible source of psychophysical overshoot, our analysis showed that could be true, but only for an on-frequency overshoot of several dB. Consequently the sources of the large off-frequency overshoot remain enigmatic. New results showing overshoot in cochlear implant listeners will be presented and some implications for acoustic overshoot discussed. However, my overall conclusion is that I still have not adapted to Joe Zwislocki, and he continues to be a significant ongoing source of new insights and analysis.
Limits on the performance of Distributed Vibration Absorbers for the control of broadband disturbances
Authors: Johnson Marty , Harris Tony , Fuller Chris
Published: October 2013

Distributed Vibration Absorbers (DVAs) have been shown to be useful passive control devices for reducing the vibration levels on lightly damped aerospace structures subjected to broadband excitation. These devices work by coupling to the modes of the structure and efficiently adding damping. One advantage of the DVA over the classic vibration absorber (VA) is that it acts over a large area instead of at a single attachment point. This paper investigates how this spatial distribution allows the absorber mass to be re-used multiple times in order to control multiple modes. In order to quantify the benefit of using a DVA this paper compares the mass of the DVA under investigation to the mass of a set of VAs that produce the same vibration reduction. This mass ratio (R) is therefore a measure of the effectiveness of the DVA. The effect of the complexity of the DVA design and the spatial extent of the DVA on R, are both investigated and results are presented. Using a computational model of a cylinder it will be shown that large mass reductions can be achieved using DVAs but that they must act over a large area and are susceptible to variations in structural properties. [Work supported by Boeing.]
Adaptive time-discontinuous Galerkin finite element methods for acoustic scattering
Authors: He Dantong , Thompson Lonny L.
Published: October 2013

Comprehensive self-adaptive procedures with efficient sparse multi-level iterative solution algorithms for the time-discontinuous Galerkin space–time finite element method (DGFEM) including high-order accurate nonreflecting boundary conditions (NRBC) are developed for acoustic scattering problems. An h-adaptive space–time strategy is employed based on a superconvergent patch recovery (SPR) technique, together with a temporal error estimate. The use of sub-time steps with pre-integrated local space–time elements to efficiently track waves in space–time are also demonstrated. For accurate data transfer (projection) between meshes, new superconvergent interpolation (SI) procedures are developed. Numerical studies of transient acoustic scattering demonstrate the accuracy, reliability and efficiency gained from the adaptive strategy. [Work supported by NSF.]
Acoustical wave propagator technique for time-domain analysis of dynamic stress in a step plate
Authors: Peng Shuzhi , Pan Jie
Published: October 2013

In this paper, we introduce an explicit acoustical wave propagator technique to describe the time-domain evolution of acoustical waves in two-dimensional plates. This technique uses a combined scheme with Chebyshev polynomial expansion and fast Fourier transformation for implementation of the operation of the acoustical wave propagator. We also apply the acoustical wave propagator for studying dynamic stress in a step plate in time-domain.
A test of the orthographic recoding hypothesis
Authors: Gaygen Daniel E.
Published: October 2013

The Orthographic Recoding Hypothesis [D. E. Gaygen and P. A. Luce, Percept. Psychophys. 60, 465–483 (1998)] was tested. According to this hypothesis, listeners recognize spoken words heard for the first time by mapping them onto stored representations of the orthographic forms of the words. Listeners have a stable orthographic representation of words, but no phonological representation, when those words have been read frequently but never heard or spoken. Such may be the case for low frequency words such as jargon. Three experiments using visually and auditorily presented nonword stimuli tested this hypothesis. The first two experiments were explicit tests of memory (old–new tests) for words presented visually. In the first experiment, the recognition of auditorily presented nonwords was facilitated when they previously appeared on a visually presented list. The second experiment was similar, but included a concurrent articulation task during a visual word list presentation, thus preventing covert rehearsal of the nonwords. The results were similar to the first experiment. The third experiment was an indirect test of memory (auditory lexical decision task) for visually presented nonwords. Auditorily presented nonwords were identified as nonwords significantly more slowly if they had previously appeared on the visually presented list accompanied by a concurrent articulation task.
Perception of coda voicing from properties of the onset and nucleus of led and let
Authors: Hawkins Sarah , Nguyen Noël
Published: October 2013

Syllable-onset [l] is longer and often has different (usually lower) F2 frequency before a voiced coda. Five experiments (E1–E5) explore the perceptual power of these properties and f0. Listeners identified as led or let synthetic syllables whose latter part was replaced by noise 80 ms after vowel onset. The duration and F2 frequency of [l] steady-state were varied in E1–E5, f0 of [l] in E1, vowel formant frequencies in E2–E5, and stimulus randomization principles in E3–E5. In E1, [l] had one of six durations, two F2 frequencies, and two f0 starting frequencies. E2 continued F2 differences into the vowel, as in natural speech. E3–E5 varied F2 independently in [l] and vowel rather than together; stimuli were presented in one session, or blocked by vowel F2. Shorter [l]s, higher f0, and higher F2 in [l]+vowel produced more let responses. F2 in [l] (alone) mainly affected responses when vowel quality was constant. However, listeners learned which cues were systematic, and some who initially used F2 frequency switched to duration of [l] relatively late in a session. The results suggest coda voicing is a property of the whole syllable, and support word recognition models that are sensitive to systematic variation in subtle phonetic detail.
The effect of syllabification and gemination on F2 onsets in Swedish
Authors: Agwuele Augustine
Published: October 2013

The quest to explain the continuousness of speech on the physical level has been dominated by the co-production theory [Hman, J. Acoust. Soc. Am. 41 (1966)]. According to this view, the production of a VCV sequence involves a diphthongal movement from V1-to-V2, with a superimposed consonantal gesture. However, data from recent studies are at variance with this position—Modaressi [Ph.D. dissertation, UT Austin, 2002], Perkell [Coarticulation Strategies Speech Commun. 5, 47–68 (1986)]. These studies document a trough-phenomena, which suggests a discontinuity in muscular activity during the production of the consonant. This paper provides additional acoustic evidence in support of sequential programming of consonant-vowel events as advocated by Joos [Acoustic Phonetics Lang. 24 (1948)]. It examines symmetrical VCV sequences in Swedish natural speech with syllable boundaries and duration of consonant gemination altered to produce different types of temporal interval between V1 and V2; i.e., V♯CV, VCC♯V, VC♯CV, VCC♯CV. F2 of V1mid, V1offset, V2onset, and V2mid were measured. Locus equations were plotted for all VC contacts. Statistical analysis of these data show: (1) de-activation of tongue movement at the CV boundary, (2) a reduction of the influence of V1 on V2 as a function of increasing consonant duration, and (3) a weak degree of CV coarticulation.
The recognition of accented and unaccented English words by native speakers of Spanish and English
Authors: Imai Satomi , Flege James , Walley Amanda
Published: October 2013

This study examined effects of foreign accent and lexical factors (word frequency and neighborhood density) on the recognition of English words in noise. Two groups of native Spanish (NS) adults differing in overall degree of foreign accent (FA) in English (weaker versus stronger FAs) participated as well as a native English (NE) group. Participants identified words that had been spoken by a NE and a NS speaker. It was hypothesized that: (1) the stronger FA group would have less nativelike phonological representations than the weaker FA group, and so would benefit more from hearing Spanish-accented English words; (2) words in dense lexical neighbors would require finer discrimination of English sounds, necessitating more nativelike phonological representations. The results showed that the weaker FA group recognized as many low-neighborhood-density English words as the NE group. For high-neighborhood-density words, the weaker FA group recognized fewer unaccented English words than the NE group, but more accented English words. The stronger FA group recognized as many accented words as the other groups, but fewer unaccented words. The differences between the weaker and stronger FA groups were interpreted as reflecting a change in their phonological representations for English words. [Work supported by NIH.]
Perception of place-of-articulation information by monkeys versus humans
Authors: Sinnott Joan M. , Gilmore Casey S.
Published: October 2013

Four monkeys and six humans representing five different native languages were compared in the ability to categorize natural CV tokens of /b/ vs /d/ produced by four talkers of American-English (two male; two female) in four vowel contexts /i,e,a,u/. A two-choice left/right procedure was used in which percent correct and response time data were compared between species. Both measures indicated striking vowel context effects for monkeys, but none for humans. Specifically, monkeys performed better for back vowels /a,u/ than front vowels /i,e/. Since back vowels have more distinctive F2 onset transitions differentiating /b/ vs /d/, these results imply that monkey perception is more dependent than human perception on the actual acoustic structure of the syllables. We conclude that humans do not use general mechanisms in place perception, rather they use some sort of special mechanism to eliminate vowel context effects. While monkeys do not provide accurate models of adult humans, they may be able to provide a model of the preverbal human infant before it learns a more speech-specific adult strategy of place information extraction. [Work supported by NIH.]
The role of air pressure and contact force in shaping obstruent consonant onset
Authors: Chen Lan
Published: October 2013

Soft tissues (the tongue or lips) are used to form the narrow oral constriction for turbulence noise generation during the production of obstruent consonants. The displacement of the soft tissue subject to oral pressure buildup is comparable to the vertical dimension of the constriction. The contact force during the closure of stop consonants and affricates provides a pressure load over 5 times larger than the air pressure at the surface in contact. It can influence the time variation of the constriction size at onset in the form of elastic energy stored in the compliant structure forming the constriction. A finite element fluid–structure interaction program has been used to simulate the effect of these external forces during the onset of obstruent consonants. Preliminary results from a 2-D tongue tip constriction/closure model show that air pressure and contact force can introduce movement on the order of 0.1–0.2 mm during the first tens of milliseconds after release, which is enough to affect the size of the constriction at onset and the nature of release burst. The results of this kind can be used for speech synthesis, guiding the modification of the trajectories of articulators at the consonant onset. [Work supported by NIH.]
Language-specific vocal tract configurations during nonspeech
Authors: Gick Bryan , Cook Clare
Published: October 2013

Previous work has been found to be surprisingly low within-speaker variability in baseline articulator positions during inter-utterance nonspeech [Gick, Phonetica (2002)], raising the question of whether these baseline positions may in fact be active in speech production. If so, then they should be specified and should vary systematically across languages. A study was conducted to test for cross-language differences in inter-utterance articulator positions. Individual video frames were extracted at the midpoint of interutterance pauses in x-ray films of 5 French and 5 English speakers. Measures were made of articulator positions relative to fixed bone points, and values normalized to jaw size. Frames with potentially confounding surrounding phonetic contexts were omitted. Results for lip measures indicate that French speakers have significantly greater protrusion of the lower lip, but significantly less upper lip protrusion, than English speakers. Additional results will be presented for lingual articulators. Thus these baseline vocal tract configurations do appear to be specified differently for different languages. Additional implications will be discussed, such as possible roles these configurations may play in phonology, potential influence on vowel systems (especially schwa), and cross-language vowel normalization. [Research supported by NSERC and NIH.]
An articulatory examination of variable word-final flapping at phrase edges and interiors
Authors: Fukaya Teruhiko , Byrd Dani
Published: October 2013

Formulations of flapping as a symbolic phonological rule suggest clear articulatory differences between flaps and stops and offer no overt explanation for why phrase boundaries should block the alternation. A current articulatory phonetic study of word-final coronals by de Jong (1998) explored the possibility that gradient changes in articulatory dimensions might give rise to quantal difference in the percept of these coronal stops. In particular, increased overlap between the coronal and the following vowel may result in spatial reduction of the coronal gesture via blending. We present results from an experiment with three speakers examining tongue tip movement and acoustic data for word-final [t], phrase internally and at phrase boundaries, with falling and level stress contours. The results confirm that flaps did not occur at phrase boundaries. Phrase-internally, flaps occurred for one subject invariantly and for another subject variably. While the acoustic durations of flaps were expectedly shorter, this did not correspond directly to their closing movement durations. There was also some tendency for flaps to have a shorter acceleration phase and no change in deceleration duration, arguing against an overlap account. Finally, the phrase boundary was associated with articulatory and acoustic lengthening, both incompatible with patterns seen for flapped tokens. [Work supported by USC Zumburge Grant and by NIH.]
Speech task and timing considerations in MRI research
Authors: Epstein Melissa A. , Stone Maureen
Published: October 2013

In order to create dynamic magnetic resonance images, subjects must repeat tokens as much as 30 times in a row, therefore, their precision is critical for image quality. Word repetition rate can be 1 or 1.5 s, and is matched to the rate of image recording. Unlike reciting tokens to the beat of a metronome, subjects must say each token during an extended period of noise that lasts about 75% of the repetition period. Furthermore, some tokens may be more difficult to say repetitively in these conditions. Therefore, this study simulated the acoustics of a MRI recording session to examine the effects of subject, token, and repetition rate on temporal precision. Subjects repeat up to ten mono- to trisyllabic words 30 times each at two repetition rates. Measurements are made of onsets and offsets of one or more phonemes within each word. Preliminary results (five subjects) indicate that there is an effect of subject and word. Further subjects are being measured to corroborate these results and to determine if one repetition rate is better than another and to test subject reliability.
The effect of spectrally and temporally altered auditory feedback on speech intonation by hard of hearing listeners
Authors: Barac-Cikoja Dragana , Tamaki Chizuko , Thomas Lannie
Published: October 2013

Eight listeners with severe to profound hearing loss read a six-sentence passage under spectrally altered and/or delayed auditory feedback. Spectral manipulation was implemented by filtering the speech signal into either one or four frequency bands, extracting respective amplitude envelope(s), and amplitude-modulating the corresponding noise band(s). Thus, the resulting auditory feedback did not preserve intonation information, although the four-band noise signal remained intelligible. The two noise conditions and the unaltered speech were each tested under the simultaneous and three delayed (50 ms, 100 ms, 200 ms) feedback conditions. Auditory feedback was presented via insert earphones at the listener’s most comfortable level. Recorded speech was analyzed for the form and domain of the fundamental frequency (f0) declination, the magnitude of the sentence initial f0 peak (P1), and the fall–rise pattern of f0 at the phrasal boundaries. A significant interaction between the two feedback manipulations was found. Intonation characteristics were affected by speech delay only under the spectrally unaltered feedback: The magnitude of P1 and the slope of the f0 topline both increased with the delay. The spectral smearing diminished the fall–rise pattern within a sentence. Individual differences in the magnitude of these effects were significant.
The impact of rate reduction and increased vocal intensity on coarticulation in dysarthria
Authors: Tjaden Kris
Published: October 2013

The dysarthrias are a group of speech disorders resulting from impairment to nervous system structures important for the motor execution of speech. Although numerous studies have examined how dysarthria impacts articulatory movements or changes in vocal tract shape, few studies of dysarthria consider that articulatory events and their acoustic consequences overlap or are coarticulated in connected speech. The impact of rate, loudness, and clarity on coarticulatory patterns in dysarthria also are poorly understood, although these prosodic manipulations frequently are employed as therapy strategies to improve intelligibility in dysarthria and also are known to affect coarticulatory patterns for at least some neurologically healthy speakers. The current study examined the effects of slowed rate and increased vocal intensity on anticipatory coarticulation for speakers with dysarthria secondary to Multiple Sclerosis (MS), as inferred from the acoustic signal. Healthy speakers were studied for comparison purposes. Three repetitions of twelve target words embedded in the carrier phrase ‘‘It’s a —– again’’ were produced in habitual, loud, and slow speaking conditions. F2 frequencies and first moment coefficients were used to infer coarticulation. Both group and individual speaker trends will be examined in the data analyses.
Motion compensation for adaptive horizontal line array processing: A beam domain approach
Authors: Yang T. C.
Published: October 2013

Large aperture horizontal line arrays have small resolution cells and can be used to separate a target signal from an interference signal by array beamforming. High-resolution adaptive array processing can be used to place a null at the interference signal. But these features are significantly degraded by the source motion, which reduces the time period under which the environment can be considered stationary. For adaptive array processing, a large number of data samples are generally required to minimize the variance of the cross-spectral density between the array elements. The penalty of integrating over a large number of samples, when the source and/or interference moves, is the spread of signal and interference energy to many eigenvalues and consequently, the ability to suppress the interference suffers. We adapt a beam domain approach to compensate for the source motion allowing the beam covariance matrix of the signal to be integrated over a large number of data samples without signal energy loss. We employ an equivalent of a rotating coordinate frame to track the signal bearing-change and use the waveguide invariant theory to compensate the signal range-change by frequency shifting. [Work supported by ONR.]
Reduced beamset adaptive matched field processing
Authors: Tracey Brian , Turaga Srinivas , Lee Nigel
Published: October 2013

Matched field processing (MFP) offers the possibility of improved towed array performance at endfire through range/depth discrimination of contacts. One challenge is that arrays with limited vertical aperture can often resolve only a small number of multipath arrivals. This paper explores ways to capture the array resolution by re-parametrizing the set of MFP replicas. A reduced beamset can be created by performing a singular value decomposition on the MFP replica set. Alternatively, clustering techniques can be used to generate MFP cell families, or regions of similar response. These parametrizations are applied to adaptive MFP algorithms to show speed and performance gains. The use of cell families/regions instead of individual MFP cells also provides a framework for increasing the robustness of MFP by defocusing the MFP beamforming operation. The techniques are demonstrated for shallow-water towed array scenarios. [Work sponsored by DARPA-ATO under Air Force Contract No. F19628-00-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the Department of Defense. Approved for Public Release, Distribution Unlimited.]
ASA education outreach
Authors: Hansen Uwe J. , Everbach E. Carr
Published: October 2013

A number of very successful Hands-on demo sessions for high school students have been a part of regular ASA meetings for some time. In addition, the Education Committee has organized a series of teacher workshops. These workshops are designed to give high school teachers relatively sophisticated tools to enhance their laboratory content. Workshops for teachers in the elementary grades prepare teachers to use music as a vehicle to introduce additional science concepts. Content and methods associated with both workshops will be discussed. Cyberspace outreach by the ASA was accelerated by the establishment of a Home Page Committee, and more recently by the On-Line Education committee, which is creating an educational website. The website provides a fun way for users to access information including acoustics information, history, demos, and links to the Technical Committee’s webpages. The ASA has joined other AIP member societies in developing additional mechanisms, including road shows and nightly news spots.
Practical considerations for the design of bellows seals in thermoacoustic refrigerators
Authors: Smith Robert W. M.
Published: October 2013

In many acoustic sources designed for thermoacoustic refrigerators, the means to provide coupling from a reciprocating electrodynamic machine to the thermoacoustic load has been a flexible metallic seal (bellows). Employing bellows provides for improved efficiency and less stringent assembly tolerances in comparison with clearance seal designs, at the cost of a part that must endure high cycle fatigue. Often the dominant contribution to the stresses in the bellows is associated with deflection. Because the compressional wave speed in the bellows can be small (15 m/s) one must consider the effect of dynamic stress enhancement. For a given bellows geometry and desired end deflection, an optimum bellows length exists which minimizes the deflection stress. Interestingly, the selection of this optimum length also provides some intrinsic reduction in sensitivity of the computed stresses associated with commercial fabrication tolerances in the bellows. It will be shown that with a given bellows geometry, material design stress limit, and a design using the optimum length, results effectively in an end velocity limit on the bellows. In this way, design with conventional bellows can constrain the power available from some commercially available machines. [Work sponsored by ONR.]
Localizing a large-dimensional field of sonobuoys
Authors: Collison Nicole E. , Dosso Stan E.
Published: October 2013

For target localization, multistatic sonar systems require an adequate knowledge of both the source and receiver positions. In this paper, we use a regularized acoustic inversion method on measured direct-arrival times from several impulsive sources to track a freely drifting sonobuoy field. The shallow-water experiment involved 11 sonobuoys within a 6×8 km field, with 6 sources over approximately 70 min. Regularization allows prior information to be built into the inversion, which in this case consists of estimates (with associated uncertainties) of the source and initial sonobuoy drop positions determined from the GPS position of the aircraft at the instant of drop, as well as a model for smooth sonobuoy tracks. Closely spaced sonobuoys move along similar tracks, although there is considerable movement in different directions over the entire field (260–700 m). Positioning uncertainties are estimated using a Monte Carlo appraisal procedure to be approximately 100 m (absolute) and 65 m (relative). Submitted for the Signal Processing Young Presenter Award.
If you can’t take the room out of your mix, you can’t take your mix out of the room!
Authors: D’Antonio Peter
Published: October 2013

The key issue in any recording studio is transferability—the ability of a mix to transfer to other listening environments outside the studio. For a mix to faithfully transfer to a wide range of acoustical environments, it must be created in a room with minimal acoustic distortion. The music industry is very aware of electronic distortion; however, the audible effects of acoustic distortion are only now being fully appreciated. The four forms of acoustic distortion are modal coupling, speaker boundary interference response, comb filtering and poor diffusion or a sparse spatial and temporal reflection density. These phenomena will be explained and methods to minimize them will be suggested.
Studio with a view
Authors: Hoover Anthony K.
Published: October 2013

Berklee College of Music (in Boston) needed a new studio in which to teach stereo mixing and critical listening. A small synthesis lab (adjacent to the main lobby, directly over the cafeteria kitchen, penetrated by exhaust ducts, and next to a bathroom) was chosen for renovation. The primary requirements were for maximum visibility to assure hopeful future engineers a full view of all the cool gear, and comfortable seating for fifteen students. The challenges, to be discussed, included isolation with a view, quiet HVAC, and great sound, in a space that was acoustically too small and in the wrong place. The best verification of success is its popularity, which has prevented the author from booking time for listening or testing.
Signals and speciation in plant-feeding insects
Authors: Cocroft Reginald , Rodriguez Rafael , Hunt Randy
Published: October 2013

Communication can play a role in speciation when differences in signaling systems reduce gene flow between diverging lineages. However, the observation that closely related species have different signals leaves open the question of cause and effect, because divergence in signals can also occur after speciation is completed. The relationship of signals and divergence is being investigated in the Enchenopa binotata species complex of treehoppers, a group of plant-feeding insects that communicate using substrate-borne vibrational signals. Speciation in the E. binotata complex is hypothesized to have resulted from repeated shifts to novel host plants. Sources of selection on the signals of these treehoppers can be studied not only in fully differentiated species, but also in experimental populations in the early stages of divergence. Some unique features of vibrational communication through plant stems will be discussed, as well as how shifts to novel host plants may influence signaling systems, and what role(s) communication may have played in the process of evolutionary divergence in this group.
Comparison of St. Lawrence blue whale vocalizations with field observations
Authors: Berchok Catherine , Bradley David , Gabrielson Thomas , Sears Richard
Published: October 2013

During four field seasons from 1998–2001, vocalizations were recorded in the presence of St. Lawrence blue whales using a single omni-directional hydrophone. Both long duration infrasonic calls (∼18 Hz, 5–20 s) as well as short duration higher frequency calls (85–25 Hz, ∼2 s) were detected and compared with field observations. Two trends were noted. First, the long infrasonic call series were concentrated primarily in the deep (300 m) channel. These call series appear to compare well with blue whale vocalizations recorded by others in the deep open ocean. Second, the shorter audible calls were more evenly distributed over bathymetry and seem to be a form of short distance communication with at least one case occurring during an agonistic interaction. A comparison of these calls with biological parameters such as density of whales in the area, percentages of paired versus single whales, and numbers of males versus females will also be discussed. [Project supported by ARL/PSU, NSF, and the American Museum of Natural History.]
Bifurcations of diffusive soliton solutions to Kuznetsov’s equation
Authors: Jordan Pedro M.
Published: October 2013

Exact traveling wave solutions are determined for Kuznetsov’s equation, a nonlinear PDE of 3rd order which describes finite amplitude acoustic disturbances in thermoviscous Newtonian fluids. Specifically, it is shown that traveling wave solutions exist, and assume the form of diffusive solitons, if and only if the Mach number is less than or equal to a bifurcation value. It is also shown that the wave speed v is always supersonic, that Max[v] occurs at the bifurcation value of the Mach number, and that a shock develops as the Reynolds number tends to infinity. Finally, special cases and asymptotic results are listed, a relationship to Burgers’ equation is noted, and 3-D bifurcation diagrams are given.
On the ability of bounded inhomogeneous waves to experimentally verify the behavior of infinite inhomogeneous plane waves
Authors: Declercq Nico F. , Degrieck Joris , Leroy Oswald
Published: October 2013

Infinite inhomogeneous plane waves have been controversial because of the appearance of a reflection coefficient exceeding unity in some cases. Even though it had already been shown that this is consistent with the principle of energy conservation, and results in a shift in position, full acceptance of the notion of infinite inhomogeneous plane waves appeared only after some experiments have been performed that produce results that are in agreement with theory. However, experiments can only be performed by means of bounded inhomogeneous waves. The current paper answers the ultimate question why bounded inhomogeneous waves are able to behave as if they were infinite inhomogeneous waves and what exactly is the physical and mathematical connection between bounded inhomogeneous waves and infinite inhomogeneous waves. [Work supported by The Flemish Institute for the Encouragement of the Scientific and Technological Research in Industry (I.W.T.).]
Modified Born approximation for solving scattering problems
Authors: Oboznenko Igor L. , Genis Vladimir , Tran Dat H.
Published: October 2013

Scattering of ultrasonic waves in inhomogeneous media is described by the inhomogeneous differential equations. Such equations could be solved using a method of consecutive approximations, such as the Born approximation. The Born approximation is applicable when (n−1)<1 and 2ka(n−1)<1, where n is the refraction index and ka is the wave dimension of the scatterer. For the Born approximation, it is assumed that the acoustic field inside of a scatterer is substituted by the acoustic field of the incident wave, along with the wave number of the surrounding media. In this work, the modified Born approximation is used, where the acoustic field inside of a scatterer is substituted by the acoustic field of the incident wave, along with the wave number of the scatterer. A similar approach is used for solving the scattering problems of multilayered scatterers, which have weak scattering properties. The computed and experimental scattering characteristics for the elastic scatterers with various acoustical impedance are presented. It is demonstrated that the modified Born approximation more accurately describes the scattering problems for the scatterers with ka>1.
Cocktails for Franssen: Asynchronous transient bias and other attentional factors in auditory localization
Authors: Whitmer William M. , Brown Christopher A. , Dye Raymond H. , Jurcin Noah F.
Published: October 2013

The cocktail-party paradigm was applied to nonspeech signals. Pure-tone stimuli were used in an extension of the Franssen effect, an auditory illusion wherein the location of a slow-onset signal is perceived to be the same as a simultaneous, contralateral sudden-onset signal. Listeners heard simultaneous sudden-onset (transient) and contralateral slow-onset (steady-state) tones in a reverberant environment with a second delayed transient from a third azimuthal location. Results showed that the Franssen effect was either maintained or ‘‘reset,’’ but not reduced. The ongoing steady-state tone was perceived either at the initial-transient and then delayed-transient location, or at the initial transient location only. None of the listeners showed a location bias to the delayed transient tone when its frequency differed from the initial signal frequency or was replaced with noise. In additional conditions based on the ‘‘false Haas effect,’’ consonant–vowel pairs representing transient and steady-state signals were segregated contralaterally in a reverberant space. Results showed no resemblance to the Franssen effect. In general, results indicated that the role of attention is fundamental to the localization of an ongoing stimulus. [Work supported by NIH.]
Effects of reverberation and experience on distance perception in simulated environments
Authors: Schoolmaster Matthew , Kopco Norbert , Shinn-Cunningham Barbara G.
Published: October 2013

Individually measured head-related-transfer functions were used to simulate different acoustic environments in order to see how listener experience influences auditory distance perception. Three environments were simulated: an anechoic space, a classroom with the listener in the room center, and the same classroom with the listener in the room corner. Each subject completed two series of trials consisting of 360 trials in each environment. Each series consisted of six experimental sessions, with only one session performed per day. In the fixed-room series, one environment was tested in each session (ordered randomly). In the mixed-room series, trials from the three environments were intermingled within each session. Listeners were divided into two groups: Group A performed the fixed-room series followed by the mixed-room series, while Group B did the reverse. Sources were simulated from ahead and to the right of the listener at distances ranging from 0.15 to 1.7 m. Preliminary analysis indicates that performance improves with experience in the fixed-room but not the mixed-room trials. These results suggest that listeners learn to calibrate auditory distance percepts based on recent experience with the reverberation and echoes in a particular environment. [Work supported by AFOSR and the Sloan Foundation.]
Cues for ‘‘front-back confusion.’’
Authors: Matsumoto Mitsuo , Terada Kiyoaki , Tohyama Mikio , Nakajima Hirofumi
Published: October 2013

Front-back confusion in the median plane disturbs sound image localization, especially for a sound image simulated using a transaural system and a dummy head. In the median plane, the spectral cue is a major cue for front-back discrimination. The front-back difference in HRTF characteristics between real heads and a dummy head was measured. For real heads, the frequency amplitude at 1.5 kHz with a front-source HRTF was significantly smaller than with a rear-source HRTF. In contrast, for the dummy head, no significant difference was found. Two signals band-limited up to 8 kHz in a subjective test were used: one had a dip amplitude frequency of −15 dB at 1.5 kHz on the frequency axis (characteristic of gfronth) and the other had a peak of 15 dB (characteristic of grearh) at the same frequency. A sound image reproduced by an actual frontal sound source and the signal with the peak was perceived ambiguously. A sound image reproduced by an actual rear sound source and the signal with the dip was perceived to be ambiguous.
Relationship between acceptance of background noise and hearing aid use
Authors: Nabelek Anna K. , Burchfield Samuel B. , Webster Joanna D.
Published: October 2013

Background noise produces complaints among hearing-aid users, however speech-perception-in-noise does not predict hearing-aid use. It is possible that hearing-aid users are complaining about the presence of background noise and not about speech perception. To test this possibility, acceptance of background noise is being investigated as a predictor of hearing-aid use. Acceptance of background noise is determined by having subjects select their most comfortable listening level (MCL) for a story. Next, speech-babble is added and the subjects select the maximum background noise level (BNL) which is acceptable while listening to and following the story. The difference between the MCL and the BNL is the acceptable noise level (ANL), all in dB. ANLs are being compared with hearing-aid use, subjective impressions of benefit (APHAB), speech perception in background noise (SPIN) scores, and audiometric data. Individuals who accept higher levels of background noise are more successful users than individuals who accept less background noise. Mean ANLs are 7.3 dB for full-time users (N=21), 12.6 dB for part-time users (N=44), and 13.8 dB for rejecters (N=17). ANLs are not related to APHAB, SPIN, or audiometric data. Results for about 120 subjects will be reported. [Work supported by NIDCD (NIH) RO1 DC 05018.]
Effects of multiple background talkers on word recognition and response awareness
Authors: Goshorn Edward L. , Robertson Elizabeth K.
Published: October 2013

Effects of background talkers (0, 1, 2, 3, 4, 5, 7, 10, and 14) on word recognition and awareness of errant/accurate responses were examined. Diagnostic Rhyme Test (DRT) words and background talkers were presented at 70 dB SPL (sound field) to ten normal-hearing subjects. DRT words and background talkers were digitally processed to produce equal VU meter levels. Three replicates were obtained for each condition. Performance measures were: (1) percent correct, corrected for guessing, transformed to rational arcsine units (PCGRAU); (2) subject’s awareness of accurate responses (AA); (3) subject’s awareness of errant responses (AE); and (4) a geometric-based symmetric awareness (SA). Awareness measures were derived from subject’s confidence ratings to DRT stimuli. Both informational and direct masking effects were present. PCGRAU varied nonlinearly as number of talkers increased. One talker provided significantly more masking than two talkers and was equally effective as three, four, five, seven, and ten talkers as well as speech-spectrum noise. Fourteen talkers provided the most masking and was equally effective as white noise. In general, AA tended to diminish while AE tended to improve as additional background talkers were added. SA was best for 14-talker background noise but poorest for one-talker and speech-spectrum noise.
Evidence for distinct types of ‘‘perfect pitch.’’
Authors: Ross David A. , Gore John C. , Marks Lawrence E.
Published: October 2013

The ability to identify and reproduce sounds of specific frequencies, typically called ‘‘perfect pitch,’’ is remarkable and uncommon. Whether this skill is learned early in life or inherited has been a matter of great controversy. Further, a substantial literature suggests that ‘‘perfect pitch’’ may be heterogeneous. Previously, we proposed a model to account for heterogeneity. The model subdivides individuals capable of naming notes accurately into two groups: possessors of true absolute pitch (AP), who automatically encode the frequency of all tonal stimuli, precategorically and independent of their source; and possessors of heightened tonal memory (HTM), who identify tones by comparing them to a memorized tonal template. The ability of individuals with HTM to identify tonal stimuli should depend strongly on the tones’ acoustical properties, such as timbre or chroma. Three experiments sought to test this hypothesis directly. Individuals claiming ‘‘perfect pitch’’ were recruited and initially classified as having AP or HTM. Consistent with the model, the two groups differed significantly in their sensitivity to the targets’ timbre, chroma, and tonal context, suggesting that they may use different mechanisms to identify tonal stimuli. The model may help reconcile the long-standing controversy between early learning and genetic theories of ‘‘perfect pitch.’’
Effects of pitch, level, and tactile cues on speech segregation
Authors: Drullman Rob , Bronkhorst Adelbert W.
Published: October 2013

Sentence intelligibility for interfering speech was investigated as a function of level difference, pitch difference, and presence of tactile support. A previous study by the present authors [J. Acoust. Soc. Am. 111, 2432–2433 (2002)] had shown a small benefit of tactile support in the speech-reception threshold measured against a background of one to eight competing talkers. The present experiment focused on the effects of informational and energetic masking for one competing talker. Competing speech was obtained by manipulating the speech of the male target talker (different sentences). The PSOLA technique was used to increase the average pitch of competing speech by 2, 4, 8, or 12 semitones. Level differences between target and competing speech ranged from −16 to +4 dB. Tactile support (B&K 4810 shaker) was given to the index finger by presenting the temporal envelope of the low-pass-filtered speech (0–200 Hz). Sentences were presented diotically and the percentage of correctly perceived words was measured. Results show a significant overall increase in intelligibility score from 71% to 77% due to tactile support. Performance improves monotonically with increasing pitch difference. Louder target speech generally helps perception, but results for level differences are considerably dependent on pitch differences.
Objective limits for four varieties of putative loudness adaptation
Authors: Weiler Ernest M. , Dou Hongwei , Warm Joel S. , Sandman David E.
Published: October 2013

The four varieties included three monaural techniques: (1) tone decay (TD); (2) simple adaptation (SA); (3) ipsilateral comparison paradigm (ICP); and the binaural (4) simultaneous dichotic loudness balances (SDLB). ‘‘Loudness adaptation’’ indicates that over time, under some conditions, there is a perceived decrease in loudness, when the initial baseline stimulus is progressively assessed. The authors have found the following limits: (1) the classic TD occurred within about 30 dB of threshold for all values tested (250 to 8000 Hz). (2) Except near threshold, SA for the loudness of a continuous unmodulated tone was observed at or above 40 dB when the stimulus reached 6000 Hz, or more. (3) ICP adaptation, which depends on at least 5-s intensity modulation, was found at all values tested from 40 to 80 dB, and from 250 to 8000 Hz. It correlates significantly with TD, with suppression of transient evoked otoacoustic emissions, and at 8000 Hz with SA adaptation. (4) Binaural SDLB adaptation has been repeatedly found at 20 to 100 dB, at all frequencies tested. Factor analysis indicated that binaural SDLB has at least four component factors, including binaural interaction. Unless factors are separated, SDLB adaptation does not correlate with monaural adaptation.
Radiation efficiency of a fluid-loaded rib-stiffened finite cylindrical shell
Authors: Hwang Y. F. , Bonness W. K.
Published: October 2013

Due to the difficulty of computing the free modes of heavily fluid-loaded structures, radiation efficiency of such structures has been frequently calculated from the forced vibratory responses, which are usually contaminated with the direct radiation of the force field. This paper discusses two methods of calculating the radiation efficiency of a fluid-loaded rib-stiffened finite cylindrical shell. Solutions in both methods are obtained from Fourier series expansion of fluid loading and rib dynamic stiffness in terms of the shell in vacuo modes. In the first method, the forced radiated power and the spatial mean-square vibratory velocity are calculated excluding the supersonic elements of the forcing function. In the second method, free modes of the fluid-loaded and rib-stiffened shell are calculated from the coupled equations of motion in terms of in vacuo modes as generalized coordinates. From this, the modal radiated power and the modal spatial mean-square velocity are calculated. Radiation efficiency is determined from the ratio between the radiated power and the product of rc, surface area, and the spatial mean-square vibratory velocity. Calculated results from the two methods are discussed. Membrane waves’ contributions to the radiation efficiency are also discussed. [Work supported by ONR, Code 333.]
Development of a new spectral energy formulation based on structural driving point mobilities or impedances
Authors: Kim Seungbo , Singh Raj
Published: October 2013

A new approximate method is proposed here that characterizes harmonic kinetic and potential energies of a system based on the driving point impedance or mobility. The proposed complex-valued formulation is compared with an existing, real-valued dynamic energy approximation method [J. Sound Vib. 217, 351–386; 247, 683–702]. The scope of this study is limited to the frequency domain analysis and harmonic excitation is applied to a linear time-invariant (LTI) system. Longitudinal and flexural motions of a finite beam along with some discrete system examples are employed to illustrate the proposed scheme. Our method is based on an alternate interpretation of the associated driving point transfer functions and it approximates total time-averaged harmonic kinetic and potential energies. Numerical results show that our method yields a more accurate estimate than the existing method. Further, the proposed scheme is found to be insensitive to the driving point measures as consistent results using either impedance or mobility formulations, unlike the existing method, are predicted. Our characterization method is suitable for a moderately damped system at low and mid-frequencies, like the existing method.