bluuebunny/crossref_metadata_2025 huggingface dataset:
An image processing based neural network method of wave form classification.
Authors: Vipperman Jeffrey , Bucci Brian
Published: October 2013

In an effort to identify military impulse noise, as it relates to civilian damage and disturbance claims, several metric based approaches utilizing artificial neural networks and Bayesian classifiers have proven successful in addressing this issue. However, in the course of research, it became apparent that the noise sources to be classified, namely, various types of military impulse noise, wind noise, and aircraft noise, could be easily identified by a minimally trained observer by way of a simple visual inspection of the wave form. Additionally, since the noise classification algorithm is desired to be implemented on DSP boards with possibly limited computational resources, it may prove beneficial to avoid the computation of metrics which involve complex mathematical operations. Borrowing from proven artificial neural network techniques already proven in the field of optical character recognition, this proposed noise classifier views a captured wave form as a number of points located on a spatial grid. The density of points within each grid sector is then used as input to an artificial neural network. The resulting classifiers performed with accuracies up to 0.997 on testing data. [This research was supported by the U.S. Department of Defense, through the Strategic Environmental Research and Development Program (SERDP).]
Resonant forward scattering of sound in deep ocean environments.
Authors: Rypina Irina , Udovydchenkov Ilya , Brown Michael
Published: October 2013

Resonant forward scattering of sound in deep ocean environments occurs when a ray cycle (double loop) distance is equal to the wavelength of a spectral component of the sound speed perturbation field or, more generally, when these quantities are rationally related. In the presence of a sound speed perturbation field with a broad spectrum (e.g., an internal-wave-induced perturbation field), many resonances are excited and these can be expected to overlap everywhere. In spite of this complexity, there are theoretical reasons that lead to the expectation that forward scattering, in general, and mode coupling, in particular, are largely controlled by resonant scattering. Relevant theory will be briefly described and numerical simulations (ray, mode, and PE) will be presented to illustrate important concepts. [Work supported by ONR.]
Low mode-number scattering of transient signals in deep ocean.
Authors: Udovydchenkov Ilya , Brown Michael , Duda Timothy
Published: October 2013

A modal description of the propagation of transient signals in deep ocean environments is considered. The environment is assumed to consist of a range-independent background sound channel with a single sound speed minimum on which a structured range-dependent perturbation, due, for example, to internal waves, is superimposed. Mode coupling in such environments is predominantly local in mode number, leading, to an excellent approximation, to the diffusive spreading of energy in mode number with increasing range. Because mode number is non-negative, however, the simple diffusive spreading of energy in mode number requires modification for low mode numbers (corresponding to the near axial sound energy). Simulations of distributions of energy in (low) mode number and time are presented and compared to estimates based on the theoretical work of Virovlyansky et al. [J. Acoust. Soc. Am. 121, 2542–2552 (2007)]. The results presented are relevant to the analysis of measurements made during the recent long-range acoustic propagation experiment. [Work supported by ONR.]
Vertical profiling of ambient noise with Deep Sound.
Authors: Barclay David , Simonet Fernando , Buckingham Michael
Published: October 2013

Deep Sound is a free-falling high-bandwidth acoustic recording system designed to profile ambient noise from the surface to depths of 9 km. The recording platform is autonomous and descends under gravity to its preprogramed maximum depth, where a burn-wire releases weight, permitting the system to return to the surface under its own buoyancy. Two hydrophones are mounted at half meter vertical spacing allowing the noise spectrum and vertical coherence (directionality) to be obtained over four decades of frequency (10 Hz–100 kHz). The acoustic recordings are made continuously as the instrument descends and ascends along with measurements of sound speed and depth. The system's low power and large data storage capabilities allow round trips to the deepest trenches of the ocean. Alternative modes of operation include (1) synthetic aperture signal detection and (2) residence on the seabed with return to the surface at a later time. Deep Sound's design and acoustic characteristics will be described and data from initial shallow water deployments around San Diego will be reported. [Work supported by the Office of Naval Research.]
Deep shadow zone arrivals on the ocean bottom.
Authors: Stephen Ralph , Dzieciuch Matthew , Worcester Peter , Andrew Rex , Howe Bruce , Mercer James , Colosi John
Published: October 2013

To gain insight into the physical mechanisms responsible for deep shadow zone arrivals in long range ocean acoustic propagation we have characterized some key features of the replica correlated signals observed on an ocean bottom seismometer (OBS) deployed on the 2004 long-range ocean acoustic propagation experiment. We compare the vertical seismometer data from an OBS at 4973-m depth beneath the deep vertical line array (DVLA) with the deepest hydrophone on the DVLA at 4270 m depth. The results of the preliminary analysis show (1) that the vertical geophone channel has more arrivals than the deep DVLA hydrophone channels, (2) that the first arrivals on the OBS geophone and DVLA deep hydrophones correspond to energy in the first deep arriving path predicted by the parabolic equation solution, (3) that the later arrivals which are much larger in amplitude are not explained by the parabolic equation method, and (4) that it is the later arrivals that contribute to the long range (up to 3200 km) shadow zone “receptions.” Possible mechanisms for the later arrivals and some consequences of the observation are discussed. [This work was supported by the Office of Naval Research.]
Sound absorption in concert halls: Rectangular versus other shapes; Sabine versus Eyring equations
Authors: Beranek Leo L.
Published: October 2013

The accurate calculation of reverberation time in a concert hall in advance of construction is vital because it relates directly to the volume of the hall, a critical architectural parameter. The calculation can be by either the Sabine or Eyring equations which, broadly speaking, requires two quantities, the absorption coefficients of the seated audience plus orchestra and those of the nonaudience areas, i.e., side walls, ceiling, and the like. The two formulas require different sizes of absorption coefficients. The Sabine and Eyring equations are analyzed here, including their relative accuracies. A means for deriving the Eyring absorption coefficients when the Sabine coefficients are known is presented. Based on published acoustical and architectural data for 20 selected concert halls, which are of two shapes, the audience and chair absorption coefficients are calculated. It is concluded that for the same audience area and a given midfrequency reverberation time the volume of a hall is directly proportional to the midfrequency audience absorption coefficient, which, in turn depends on the type of chair and the shape of the hall. New audience absorption coefficients for medium and heavily upholstered chairs and for the two types of hall are presented.
An efficient algorithm for Bayesian energy-decay analysis in architectural acoustics
Authors: Xiang Ning , Calamia Paul
Published: October 2013

Sound energy-decay analysis, including experimental determination of reverberation times in single-space enclosures and decay-time estimation in acoustically coupled spaces, has relied primarily on Schroeder backward integration of room impulse responses. Recent work has demonstrated that model-based Bayesian approaches [Xiang et al., J. Acoust. Soc. Am. 110, 1415–1424 (2001); 113, 2685–2697 (2003); 117, 3705–3715 (2005)] can be very useful for such analysis in architectural acoustics. In order to remove any concern of a high computational load within the Bayesian framework, this paper describes a search algorithm for the model-based Bayesian approaches which leads to an efficient analysis method, not only for multiple decay rates in acoustically coupled spaces but also for classical reverberation time estimation. Implementation of the algorithm within the Bayesian framework is discussed, and its performance with respect to other existing algorithms is analyzed using experimentally measured room impulse responses.
Experimental investigations of acoustically coupled spaces
Authors: Su Zuhre , Xiang Ning , Summers Jason E.
Published: October 2013

Recently, architectural acousticians have been increasingly interested in halls that incorporate coupled-volume systems because of their potential for creating desirable effects in meeting conflicting requirements between clarity and reverberance. Previous works on coupled spaces include studies on theoretical formulation of energy exchange between coupled volumes and applications of Bayesian inference for estimating decay parameters in such spaces. Frequency dependence of sound-energy decay is one of the essential aspects of acoustically coupled spaces that has not yet been extensively investigated. In order to understand the behavior of sound-energy decay over different frequency ranges, experimental studies are carried out. Room impulse responses are collected through real-size and scale-model measurements. Schroeder integrations followed by Bayesian decay analysis reveal location sensitivities over different frequency bands in coupled spaces. This paper discusses extensive analysis results from Bayesian analysis of experimentally measured room impulse responses.
The causes and evolutionary consequences of a conflict between species and mate-quality recognition
Authors: Pfennig Karin S.
Published: October 2013

Mate choice typically involves the identification of conspecifics (species recognition) and the identification of mates that provide females with enhanced fitness (mate-quality recognition). When high-quality conspecifics possess advertisement signals that resemble those of heterospecifics, however, females may be unable to engage in both species and mate-quality recognition simultaneously. This conflict between species and mate-quality recognition may require that females trade off the benefits of mating with high-quality males with the risk of heterospecific matings. In spadefoot toads, females face a conflict between species and mate-quality recognition because the advertisement calls of high-quality conspecifics resemble those of heterospecifics. Because of this conflict, females compromise on male quality to ensure conspecific matings. Moreover, this trade-off has seemingly caused spadefoot toads to evolve smaller body size, reduced fecundity, and different patterns of sexual dimorphism in populations where heterospecifics are present (sympatry) versus populations where heterospecifics are absent (allopatry). Thus, a conflict between species and mate-quality recognition can have profound impacts on how females use male advertisement signals to choose mates, sexual selection, and morphological evolution in different populations, and even the fitness of individuals in sympatry relative to those in allopatry.
A chair’s introduction to brown tadpoles: What’s all the fuss about?
Authors: Holt R. Glynn
Published: October 2013

A brief background of the work in understanding irregular HIFU thermal lesion formation will be presented to motivate the current session. Several basic arguments for asymmetric lesion formation will be framed, highlighted by examples of in vivo occurrence. Several fundamental questions will be posed, with the hope that such questions will be addressed, clarified, and answered by the speakers and panel members (as well as the audience) by the end of the session. Along with conceptual discussions of relevant mechanisms, recommendations for usage of terms to describe and distinguish these mechanisms will be encouraged.
Interpreting passive cavitation detection signals during high-intensity focused ultrasound (HIFU)
Authors: Collin Jamie R. T. , Coussios Constantin C.
Published: October 2013

Inertial cavitation is known to be associated with significantly enhanced rates of heating during cancer treatment by high-intensity focused ultrasound (HIFU). However, during prolonged exposure, the cavitation region gradually shifts towards the HIFU transducer, causing shielding of the original focus. It is hoped that controlling the HIFU field to constrain cavitation to the focal region will lead to sustained enhanced focal heating, thus reducing treatment times and improving treatment resolution. Monitoring of cavitation can be achieved during insonation by using a focussed passive cavitation detector (PCD) to listen for broadband noise emissions resulting from microbubble collapse. The ability to effectively control the cavitation field relies on accurate interpretation of the PCD data. During HIFU exposure of a tissue-mimicking material, it was noted that the frequency content of the PCD signal shifted downwards with increasing phantom propagation path length to the PCD, as a result of depth-dependent attenuation. This has significant implications for the effective sensing volume of the PCD. In addition, it was noted that separate analysis of the peak and rms time-domain PCD values provides an incomplete description of inertial cavitation activity, but that combining these two parameters enables a better understanding of bubble cloud dynamics.
Effects of short-pulsed focused ultrasound: Histological study on the rabbit brain in vivo
Authors: Vykhodtseva Natalia , McDannold Nathan , Hynynen Kullervo
Published: October 2013

Histological effects of short-pulsed focused ultrasound at pressure amplitudes beyond the cavitation threshold were studied. One hundred thirty-one locations in the brains of 27 rabbits were sonicated using a 16-sector focused transducer (1.63 MHz; D/F=10/8 cm; burst lengths =1–100 ms; PRF =1–100 Hz, total exposure =10 s). A range of effects was observed: (1) Affected blood vessels without any damage to the brain parenchyma. (2) Local lesions with homogenized core, which consisted of a pudding-like mass arranged in a helically coiled, layered fashion in some lesions. In the large lesions, core was completely liquefied. (3) Hemorrhagic and torn regions with fragmented and liquefied tissues, characteristic of inertial cavitation effects. (4) Circular-shaped lesions with a concentric annular pattern: a small central core was surrounded by three or more morphologically different circular layers. (5) Thermal lesions, which had the features of thermal lesions produced by lower-power sonications. These findings appeared to be associated with the nonlinear ultrasound absorption and cavitation-related effects, which could be exploited for new therapies. [Work sponsored by: NIH Grant Nos. R01CA076550 and R25CA089017.]
Discrimination of noise-contaminated communication signals by grasshoppers
Authors: Ronacher Bernhard
Published: October 2013

When using acoustic signals in order to find—and possibly select between—mates, grasshoppers face two major problems: the arriving signals are usually degraded by various kinds of noise, while as much information as possible should be extracted quickly. Major cues for signal recognition are the temporal patterns of amplitude modulations of grasshopper songs. Within the nervous system, signal classification is rooted in the spike trains provided by the sensory neurons and will be constrained by the variability of spiking responses. Several intrinsic sources further contribute to spike-train variability, which can be considerable even in the case where undistorted acoustic signals arrive at the receiver. Using van Rossum’s [Van Rossum, M. Neural. Comp. 13, 751–763 (2001)] method to compute spike-train distances, we quantified the variability of neural responses and showed that the temporal information necessary to discriminate between songs of different conspecifics is preserved surprisingly well, even in the responses of single neurons. By comparing behavioral and neurophysiological data, we now aim at determining how well this information can be used by the animals, and how closely or remotely their nervous systems approach the performance of an ideal observer.
Mechanisms and evolution of chorusing interactions in acoustic insects and anurans
Authors: Greenfield Michael
Published: October 2013

Chorusing displays of acoustically signaling insects, and their counterparts among bioluminescent species, are acknowledged to include some of the great spectacles of the living world [Wilson, Sociobiology, Harvard University Press (1975)]. These communal displays are noteworthy for the sheer numbers of participating individuals, the volume of sound or brilliance of light produced, and a precise choreography in space and time, which often gives rise to striking alternation or synchrony between neighbors. Here, potential mechanisms that may generate such temporally structured choruses are reviewed and then the evolution of these communal displays is discussed. Under certain conditions alternation or synchrony may be adaptive per se, and the mechanisms that generate chorusing interactions are directly favored by selection. But, in other cases alternation and synchrony are merely epiphenomena, group effects that emerge as by-products of simple interactions between signaling neighbors; these interactions are, in effect, responses to psychoacoustic effects in perception. Simulation models inspired by various acoustic insects demonstrate how complex choruses may represent emergent properties of these simple responses. The models also show how feedback loops may arise by which these emergent properties can yet influence the simple interaction responses from which they originated.
Acoustic interactions in broods of begging nestling birds
Authors: Horn Andrew G. , Leonard Marty L.
Published: October 2013

Begging by nestling birds has become a model system in the study of the evolution of reliable signaling. The transmission and reception of begging signals, however, remain largely unexplored. Especially puzzling is how, or indeed whether, the calls that accompany most begging displays can convey information to parents, given that several nestlings may be calling at once within the cramped confines of the nest. Most previous work on groups of acoustic signalers has involved signalers that are much more widely spaced, such as chorusing insects and frogs. Here, we review our research on how the begging calls of tree swallows, Tachycineta bicolor, convey information to parents. Various call features correlate with nestling need, and playing back calls to parents affects both how often they deliver food to the nest and which nestling they feed once they arrive. Nestlings adjust their calls in response to signal interference, albeit crudely, by adjusting call rate and amplitude. Begging calls and the contexts in which they occur vary enormously across species, so that other species likely use different strategies to overcome acoustic interference. Indeed, begging displays offer promising and barely tapped opportunities for developmental and comparative studies of acoustic signaling in groups.
Bad vibrations: Mechanosensory risk assessment by red-eyed treefrog embryos
Authors: Warkentin Karen M. , Caldwell Michael S. , McDaniel J. Gregory
Published: October 2013

Red-eyed treefrogs, Agalychnis callidryas, lay gelatinous egg masses on vegetation overhanging ponds; tadpoles fall into the water upon hatching. Embryos hatch up to 30% prematurely in attacks by egg-eating snakes, but not in other intense but benign disturbances, such as storms. We used modal analysis and vibration recordings from clutches in natural disturbances to characterize the vibrational environment of embryos, and playbacks to assess if vibrations cue hatching, and how vibration characteristics affect hatching behavior. Escape hatching can be induced by snake vibrations, without actual snakes, and embryos distinguish between the vibrational patterns of snake attacks and rainstorms. Benign and dangerous disturbances overlap in individual temporal and frequency characteristics, but can be distinguished using combinations of features. Both frequency and temporal characteristics of vibrations affect the hatching response. Embryos use at least two temporal pattern elements—disturbance duration and interdisturbance interval—and respond to a limited range of low frequencies. These are all necessary elements of a composite cue. Moreover, higher frequencies, found in rainstorms but not attacks, reduce hatching. This is the most detailed examination of mechanisms underlying embryo decision making to date, and a demonstration of the importance of vibrational information in predator-prey interactions. [Work supported by NSF IBN-0234439.]
Bayesian layer-stripping inversion of seabed reflection data
Authors: Dettmer Jan , Dosso Stan E. , Holland Charles W.
Published: October 2013

This paper develops a Bayesian inversion technique for recovering multilayer geoacoustic profiles using seabed reflection data. The measured data originate from acoustic time series windowed for a single bottom interaction, which are processed to yield spherical reflection coefficients (i.e., a response function of frequency and angle analogous to plane-wave reflection coefficients). Replica data are computed using a wave number-integration model (OASES) to calculate the full complex acoustic pressure field, which is processed to produce a similar seabed response function. The inversion results are compared to those obtained using plane-wave reflection coefficients. To address the high computational modeling costs, the Bayesian algorithm is implemented for a massively parallel computer. Further, the data are time windowed and divided into several layer packets, wherein each packet contains the seabed response to a certain depth. This layer-stripping approach uses the results of the previous layer packet as prior information for subsequent packets. The resulting posterior probability density for the final packet is considered the full solution to the inverse problem, and is interpreted in terms of optimal parameter estimates, marginal distributions, credibility intervals, and parameter correlations.
Perturbation of arrival times in sound pulses propagating in shallow water through moving internal solitons
Authors: Badiey Mohsen , Grigorev Valery , Katsnelson Boris , Lynch James
Published: October 2013

Sound pulse propagation in shallow water is studied. We assume a geometry where an acoustic track crosses the wave-front of a moving internal soliton (IS) or train of solitons. During propagation, sound pulses undergo perturbation due to mode coupling. For each individual mode selected at the receiver, we observe a set of incoming pulses, each having different arrival times. Time-frequency analysis is carried out for the modal arrival times for different frequencies, emphasizing the dependence on position of the moving solitons. It is shown that the maximum amplitude of the incoming pulses created at the ISs due to mode coupling has approximately the same arrival time, independent of frequency. This invariant arrival time is determined by waveguide parameters and corresponds to maximal coupling of different pairs of modes. Analysis is carried out both for a model shallow water channel and for real experiment data (SWARM95, NRL acoustic track). Satisfactory agreement is demonstrated, and physical interpretation of observed effect is discussed. [Work is supported by ONR and RFBR.]
The Ionian Sea rainfall experiment
Authors: Nystuen Jeffrey , Amitai Eyal , Anagnostou Emmanouil , Anagnostou Marios
Published: October 2013

Rainfall on the sea surface generates a loud and distinctive sound underwater. This sound propagates downward and is attenuated, producing an effective listening area, or an equivalent ‘‘catchment basin’’ for a listening device that is a function of depth and frequency. Acoustical measurements of rainfall are reported from 60, 200, 1000, and 2000-m depths from a mooring in the Ionian Sea off the southwestern coast of Greece (37N, 21.5E) from January to April 2004. These measurements are compared to colocated high-resolution coastal X-band radar (XPOL) rainfall reflectivity measurements. The XPOL reports the spatial distribution of the rain over the listening areas of the acoustic rain gauges (ARGs). Roughly ten rainfall events, including drizzle, squall line, and heavy rainfall were recorded. The results demonstrate the inherent spatial averaging of the rainfall signal with depth. This spatial averaging is desirable when comparisons are made to satellite measurements of oceanic rainfall as such measurements also have inherent spatial averaging. The data also verify that a viable signal for acoustical rainfall measurement is present at 2000 m, allowing this technology to be transferred to deep-ocean instrumentation platforms such as ARGO floats and bottom-mounted cabled systems. [Work supported by NSF Oceanography.]
Results of flow-field quantities from computational fluid dynamics (CFD) analysis of a flow-excited Helmholtz resonator
Authors: Zoccola Paul , Slomski Joseph , Farabee Theodore
Published: October 2013

A flow-excited Helmholtz resonator was modeled using a hybrid RANS/LES CFD solver. Solutions were obtained for a speed where the excitation was fully coupled to the response of the cavity, and for a lower speed, where it was not. The cavity and speeds modeled were chosen to replicate a prior experiment by one of the authors. Flow-field quantities analyzed include the energy production term and the energy flow vector field. These were compared to experimental data where available. Results at resonant and nonresonant conditions were also compared.
Radiated noise signature of a ship in maneuvers
Authors: Vasiliev Boris
Published: October 2013

Underwater acoustic radiated noise of ships is usually measured for constant course and speed. The measurements are often averaged over the ship’s aspect to yield the radiated noise signature. Consequently, dependence of the radiated noise on the ship’s aspect or maneuvers is generally unknown. This talk will present measurements of the broadband and demodulated noise signatures of two research vessels. Variation of the signatures with ship aspect, acceleration, and turn rate will be discussed.
Reducing underwater radiated noise from gravel islands
Authors: Spence Jesse
Published: October 2013

Methods for reducing underwater noise radiated from gravel islands used for oil and natural gas production have been investigated. This study focused on operations for one gravel island, the Northstar, located in Prudhoe Bay, Alaska, during standard oil production activities in open water conditions. Various transmission paths have been examined, including direct airborne transmission, vibratory paths, and other secondary paths. Direct measurements of airborne noise, vibration, and underwater noise were used to determine the prominence of each noise path. General treatment options and details are given for those noise paths deemed to be significant. [The author would like to thank the U.S. Minerals Management Service for their funding and support, and BP Exploration (Alaska) Inc. and Greeneridge Sciences Inc. for their support and assistance.]
Acoustics at Brown during the late 1950s and early 1960s and its impact on two of its students
Authors: Butler John L. , Letcher Stephen V.
Published: October 2013

The Brown University Physics Department researched a wide range of acoustics covering the frequency band from infrasonic to ultrasonic and linear to nonlinear compression in gases and liquids. Although JLB’s research at Brown focused on the attenuation of sound in various liquids, he was mostly fascinated by the means for generating and receiving sound and still is today. SVL’s research also involved measuring sound absorption in various liquids. Except for one experiment we were two nonlinear holdouts in the heyday of the field. As a means for appreciating and understanding the activities in the acoustics lab at Wilson Hall, the paths of these two students will be traced. We start from their desire to go to Brown, through their experiences and research there, as well as their interaction with the other students and professors and on to their present positions and more recent research. Some of the research will be illustrated with photos, results, and FEA animation.
Ah well!—The unflappable A.O. Williams, Jr.
Authors: Rogers Peter H.
Published: October 2013

A student of Art Williams in the late sixties reflects on his experiences at Brown and on the career of his mentor.
Nonlinear interactions in the 1970s: Tribute to the work of Robert T. Beyer
Authors: Korman Murray S. , Stanton Timothy K.
Published: October 2013

Professor Beyer was our thesis advisor and supported, motivated, and directed both T.K.S’s and M.S.K’s Ph.D. research in the area of nonlinear underwater acoustics at Brown University. T.K.S performed experiments in an effort to measure the nonlinear interaction of sound with noise, while M.K.S did experiments involving the scattering of sound by sound in the presence of turbulence. Along the way T.K.S designed and built a complex intensity meter and measured the growth of the nonlinearly generated sidebands with propagation distance, while M.S.K designed and built a hot-film anemometer and measured the angular dependence of the spectral broadened sum frequency versus angle. We also learned ultrasonics and nonlinear acoustics from our mentor, who wove in the works of Rayleigh, Lighthill, and Westervelt along the way. Beyer also gave us a passion for the history that goes beyond the science. In the spirit of ‘‘once a graduate student, always a graduate student,’’ and ‘‘don’t just stand there go write a thesis,’’ in our tribute to Beyer we will try to tell the ‘‘vintage story’’ that is spun around Professor Beyer the scientist, author, and teacher who established B/A, and made the earliest measurements on the parametric array.
On the rate of decay of forward masking and its relation to cochlear compression
Authors: Lopez-Poveda Enrique A. , Alves-Pinto Ana
Published: October 2013

Recent psychoacoustic studies [e.g., Lopez-Poveda et al., J. Acoust. Soc. Am. 113, 951 (2003)] have suggested that cochlear compression extends to a wider range of frequencies in the apex than in the base of the cochlea. This conclusion was drawn from the analysis of the slopes of temporal masking curves (TMCs) on the assumption that forward masking decays at the same rate for all probe and masker frequencies. This study aims to verify the conclusion stated above using a different assumption. TMCs for normal hearing listeners were measured for probe frequencies (Fp) of 500 and 4000 Hz and for masker frequencies of 0.4, 0.55, and 1.0 times the probe frequency. Measurements were made for probes of 9- and 15-dB sensation level. The assumption was that given a 6-dB increase in probe level, linear cochlear responses to the maskers should lead to a 6-dB vertical shift of the corresponding TMCs, while compressive responses should lead to bigger shifts. Results are consistent with compressive cochlear responses to the 0.4Fp and 0.55Fp maskers at 500 Hz but linear responses at 4000 Hz, in line with the conclusions from earlier studies. [Work supported by the Spanish FIS (PI020343, G03/203), MEC (CIT-390000-2005-4), and FEDER.]
Processing of speech in complex listening environments by individuals with obscure auditory dysfunction
Authors: Block Kim , Gordon-Salant Sandra , Hawley Monica , Formby Craig
Published: October 2013

Obscure auditory dysfunction (OAD) is a disorder for which patients report excessive amounts of difficulty understanding speech in the presence of background noise, despite no obvious evidence of hearing loss. It has been hypothesized that OAD may be the result of mild cochlear dysfunction, central auditory processing deficits, and/or psychological disorders. We evaluated 10 persons with self-reported problems understanding speech in noisy environments and 10 controls. Both groups had normal-hearing sensitivity and excellent word recognition in quiet. The following tests were administered to each participant: DPOAE and ABR assessment, central auditory processing screening, personality inventory, and tests involving speech recognition in complex environments. The speech recognition measures were a subset of tests reported in Hawley et al. [J. Acoust. Soc. Am. 115, 833–843 (2004)] and were designed to probe binaural processing ability, as well as spectral and temporal processing of speech in complex environments. The OAD participants had poorer overall speech recognition ability than did the controls in both single- (1.5 dB, p=0.017) and two-competitor environments (0.9 dB, p>0.05). However, the reported problems in these OAD participants are not attributable to poor binaural processing. [Funding provided by NIDCD.]
Perception of roughness by people with normal hearing and sensorineural hearing loss
Authors: Tufts Jennifer B. , Molis Michelle R.
Published: October 2013

Anecdotal and laboratory evidence indicates that many people with sensorineural hearing loss have difficulty perceiving music clearly, even when the musical sounds are loud enough to be audible, or are amplified through hearing aids. A better understanding of the music perception difficulties faced by hearing-impaired people is required in order to improve assistive listening technology for music listening, performance, and appreciation. One important aspect of music appreciation is the perception of dissonance between combinations of tones (e.g., the tritone). A recent study [J. B. Tufts, M. R. Molis, and M. R. Leek, J. Acoust. Soc. Am. 118, 955–967 (2005)] showed that people with sensorineural hearing loss perceive differences in musical dissonance to be less salient than do normal-hearing people. Various acoustic and perceptual factors contribute to musical dissonance, but one of the most important is auditory roughness. In the present study, roughness regions for amplitude-modulated tones at several carrier frequencies, two different modulation depths, and several presentation levels were established using magnitude estimation techniques in normal-hearing and hearing-impaired listeners. Differences in the perception of roughness between the listener groups will be discussed with regard to implications for music perception in people with sensorineural hearing loss.
Perceptual absorption of listening context when perceiving musical instruments
Authors: Stilp Christian E. , Kluender Keith R.
Published: October 2013

Brief experience with reliable characteristics of listening context, such as a precursor sentence, alters perception of subsequent vowel sounds. In experiments focused on perception of vowels, effects of preceding context do not depend on sentences being intelligible speech [K.R. Kluender and M. Kiefte, J. Acoust. Soc. Am. 114, 2335 (2003)]. In the present studies, listeners identified musical instruments (tenor saxophone versus French horn) following a context of speech sentences that are modified by spectral envelope difference filters created to capture differences between saxophone and horn spectra. Precursor sentences were resynthesized renditions of a female talker saying ‘‘Please identify this instrument.’’ For a morphed series of sounds with 196 Hz fundamental frequency (G3) varying perceptually from saxophone to horn, listeners are more likely to report hearing a saxophone following a sentence filtered to emphasize spectral characteristics of the horn and vice versa. Consistent with previous studies, these effects are contrastive and indicative of the auditory system absorbing reliable (redundant) properties in the service of emphasizing change and maximizing transmitted information. Perceptual calibration to reliable spectral characteristics does not depend upon sounds being perceived as arising from the same source. [Work supported by NIDCD.]
Perceptual salience and acoustic distance: Evidence from Tagalog nasal-place contrasts
Authors: Narayan Chandan
Published: October 2013

The acoustics and perception of three Tagalog (Austronesian) nasal-onset places of articulation ([ma], [na], and [nga]) are investigated. In experiment 1, native speakers of Tagalog (n=13) were presented with the [ma]-[nga] and [na]-[nga] contrasts (as recorded by a native speaker of Tagalog) in an AX task. As expected, listeners performed according to Tagalog phonology, with successful discrimination of both contrasts (>90% correct). Listener performance on the [na]-[nga] contrast, however, was significantly lower than performance on [ma]-[na]. In a second experiment, designed to assess the perceptual salience of the [na]-[nga] contrast relative to the [ma]-[na] contrast, native-Tagalog listeners were tested (in an AX task) with the contrasts in signal-dependent (though uncorrelated) noise. Findings are discussed in light of acoustic measurements of multiple repetitions of [ma], [na] and [nga] as produced by three speakers of Tagalog. These acoustic results show that, in F2×F3 space (measured at the NV juncture), [na] is more similar to [nga] than it is to [ma]. In addition, the acoustic and perceptual findings will be interpreted relative to recent findings in the development of nasal-place perception in infancy. [ng=velar nasal.]
An acoustic and perceptual investigation of the geminate and singleton stop contrast in Japanese
Authors: Idemaru Kaori , Guion Susan
Published: October 2013

Segmental durations are known to be heavily influenced by changes in speech rate such that the durations of members of two contrasting length categories may overlap [Pickett et al. ‘‘Effects of speaking rate on singleton/geminate contrast in Italian,’’ Phonetica 56, 135–157 (1999); Hirata & Whiton, ‘‘Relational acoustic invariance in the single/geminate stop distinction in Japanese,’’ J. Acoust. Soc. Am. 117, 2569 (2005)]. Given this, questions arise as to how category distinction is achieved for contrasts signaled by differences in segmental duration. This study investigates the question by examining the production and perception of the Japanese singleton versus geminate stop contrast by adult native speakers. Six native Japanese speakers produced disyllabic words with medial singleton and geminate stops at three speaking rates. Duration of stop closure and a number of relational timings between the closure duration and other segments were examined as potential rate-independent measures distinguishing the two categories. The ratios of stop closure to the preceding mora as well as stop closure to the following vowel remained stable across speaking rate and accurately classified naturally produced tokens. Ten native Japanese listeners participated in an identification task to examine the perceptual relevance of these relational timings. The results indicated an influential role of preceding mora duration and a small role of following vowel duration. The results also suggested that nondurational factor(s) influence perception of the stop length contrast.
Acoustic and phonetic discrimination in speech using event-related potentials: A mismatch negativity paradigm
Authors: Robertson Erin K. , Newman Randy Lynn , Joanisse Marc F.
Published: October 2013

The interaction of acoustic and phonetic discrimination in speech was studied using event-related potentials (ERPs). Participants consisted of 14 neurologically normal right-handed adults. Data were recorded in response to strong and weak acoustic changes signaling consonant distinctions, using a 64-channel encephalogram and a mismatch negativity (MMN) paradigm. The MMN is an automatic response evoked by stimulus change and is elicited when a train of repeated stimuli (standard) is interrupted by an oddball (deviant) stimulus. Stimuli consisted of one standard and two deviants that differed in their acoustic difference from the standard. All three stimuli were synthetic speech syllables in which F2 was manipulated to create a continuum between the syllables ‘‘ba’’ and ‘‘da.’’ The standard was the endpoint item ‘‘da.’’ The ‘‘strong deviant’’ was the ‘‘ba’’ endpoint item; the ‘‘weak deviant’’ was a more intermediate ‘‘ba’’ item, and therefore acoustically closer to the standard. MMNs were identified for both deviants, but the amplitude was smaller for the weak deviant condition. The data suggest that MMNs are sensitive to both phonetic change and also the magnitude of the acoustic difference within this change. The results are discussed with respect to theories of phonetic and acoustic discrimination in speech perception.
Gradient effects of continuous acoustic detail revealed by event-related potentials
Authors: Dennhardt Joel , McMurray Bob , Luck Steven , Toscano Joseph
Published: October 2013

A growing body of research has demonstrated that lexical activation during online word recognition is systematically sensitive to continuous detail in the speech signal (Andruski et al., ‘‘The effect of subphonetic differences on lexical access,’’ Cognition 52, 163–187 1994; McMurray et al., ‘‘Gradient effects of within-catagory phonetic variation on lexical access,’’ Cognition 26, B33–B42 2002). However, investigations of within-category sensitivity to continuous phonetic cues using electrophysiological measures have typically been consistent with categorical perception (Sharma et al., ‘‘Acoustic versus phonetic representation of speech as reflected by the mismatch negatively event-related potential,’’ Electroencephalography & Clinical Neurophys.: Evoked Potentials, 88, 67–71 1993; Phillips et al., ‘‘Auditory cortex accesses: Phonological categories: An MEG mismatch study,’’ J. Cogn. Neurosci. 12, 1038–1055 2000). This raises the possibility that these findings of gradiency are artifacts of the small number of comparisons made in priming experiments or the eye-movement tasks themselves. This issue was addressed with event-related potentials in a P3 categorization paradigm. Subjects heard tokens from beach/peach or dart/tart continua (9 steps, 0–40 ms of VOT). In each block of trials, one of the four words was the target; one button was pressed for the target word and a different button for any of the nontarget words. The amplitudes of the P2 and P3 components decreased continuously as VOT departed from the target. This was the case even when trials in which subjects identified the token as nontarget were excluded. These results favor a gradient view of lexical activation: lexical processing is gradiently sensitive to continuous speech cues and such cues may facilitate word recognition.
Time reversal and the adjoint imaging method with an application in underwater communication
Authors: Dorn Oliver
Published: October 2013

A direct link is established between the time-reversal technique and the so-called adjoint method for imaging. The latter one has been used successfully in medical imaging applications, for example for the early detection of breast cancer in ultrasound tomography. In this application, ultrasound waves are sent through the unknown medium of investigation, and the differences between detected and predicted measurements are computationally back-propagated into the estimated medium in order to determine the correct acoustical parameters. In the application of underwater acoustic communication, the goal is to optimize a given signal, emitted by a base station, such that it focuses on the target user in the desired fashion without interfering with other users who might share the same environment. It turns out that efficient optimization schemes can be derived for achieving this goal, which are very similar to those applied in the above-mentioned medical imaging application, but which can be realized physically in the true (unknown) ocean by iterated physical time-reversal experiments. The close relationship, as well as some differences, between these two applications will be highlighted in this talk. [Financial support for this work from the U.S. Office of Naval Research under Grant N00014-02-1-0090 is gratefully acknowledged.]
Applications of adjoint models in underwater acoustics
Authors: Hursky Paul , Porter Michael B. , Cornuelle Bruce D. , Hodgkiss W. S. , Kuperman W. A.
Published: October 2013

Complementing a forward model with its adjoint has some nice features that can be helpful in inverse problems. We will review our previous work on constructing an adjoint for forward propagaton using an implicit finite-differences parabolic equation model and some simulated results in inverting for the sound speed in the water column. We will also review how an adjoint can aid in model identification, or the question of how the inverse problem should be modeled (e.g., in inverting for the properties of the bottom, how many layers should be used to parametrize the bottom). We will demonstrate this for a range-dependent inversion, in which in one case there is a bottom inclusion (bottom properties are abruptly different over some range interval between the source and receiver), and another case where there is an internal wave. After reviewing these examples, we will discuss some practical issues in applying adjoint models to real data.
The 2004 Sumatra earthquake and tsunami: Multidisciplinary lessons from an oceanic monster
Authors: Okal Emile
Published: October 2013

The 2004 Sumatra earthquake was the largest seismic event recorded in 40, perhaps 44, years. The death toll from its tsunami was unprecedented in documented history. Remarkably, the earthquake and tsunami were recorded by many technologies designed for strikingly different purposes, including hydroacoustic sensors of the International Monitoring System of the CTBT, which captured standard (Rayleigh) waves, acoustic (T) phases, as well as the pressure component of the tsunami wave itself. I will discuss the contributions of such records, and other systems, to the investigation of the earthquake’s source and to the nature of the ‘‘high’’-frequency (10–20 MHz) components of the tsunami wave in the far field.
Effect of honeycomb structure in the back cavity on the absorption characteristics of microperforated panel absorbers
Authors: Yairi Motoki , Minemura Atsuo , Sakagami Kimihiro , Morimoto Masayuki
Published: October 2013

Since the principle of microperforated panel absorbers (MPPs) was established, many studies have been made on their practical applications. MPPs are typically made of very thin metal or plastic panels to obtain high absorption. However, such a thin, limp panel is in many cases not suitable for an interior finish of room walls because of its insufficient strength. The authors have proposed to use a honeycomb structure attached behind an MPP to stiffen it without deteriorating its acoustical performance. The honeycomb behind an MPP can also be expected to enhance its absorption performance, considering previous studies on porous sound-absorbing layers with the back cavity completely partitioned by a honeycomb structure. In this paper, the effect of honeycomb structure in the back cavity on the absorption coefficient of MPP was experimentally studied. The results suggest that the reverberation sound absorption characteristics become close to those of an MPP without a honeycomb structure for normal incidence. This means that the characteristics are improved with the honeycomb structure to show a higher and broader absorption peak. MPPs can be used more efficiently in more various situations with applying elaborated configurations of backing structures. [Work supported by the Kajima Foundationfs Research Grant.]