bluuebunny/crossref_metadata_2025 huggingface dataset:
Angular Doppler effect in the scattering of a helicoidal wave by a rotating target
Authors: Marston Philip L.
Published: October 2013

The phase of an acoustic helicoidal wave advances linearly with angle around a propagation axis at a rate characterized by an angular index m. For m=1 and 2, the phase advances are 360 deg and 720 deg, respectively, for an angular advance of 360 deg. There is null in the amplitude along the beam axis. A transducer for approximating such a helicoidal beam near the axis has been demonstrated [B. T. Hefner and P. L. Marston, J. Acoust. Soc. Am. 106, 3313–3316 (1999)]. In the new work, the scattering by small objects that rotate around the helicoidal beam axis is considered. The wave scattered to a receiver on the axis will be shifted in frequency. The shift is constant and is given in magnitude by the product of the target’s rotation rate and the helicoidal wave’s angular index m. The shift is a consequence of the angular dependence of the phase of the helicoidal wave and the sign of the shift depends on the sign of m and the direction of the rotation of the target. A similar angular Doppler effect should also be present in the scattering of electromagnetic helicoidal waves. [Work supported by ONR.]
A higher-order on-surface radiation condition derived from an analytic representation of a Dirichlet-to-Neumann map
Authors: Calvo David C. , Collins Michael D. , Dacol Dalcio K.
Published: October 2013

An approximate solution to a scattering problem can be obtained efficiently using an on-surface radiation condition (OSRC) [G. A. Kriegsmann et al., IEEE Trans. Antennas. Propag. 35, 153–161 (1987)], which is an approximation of the Dirichlet-to-Neumann map. A higher-order OSRC is derived using an analytic representation of the Dirichlet-to-Neumann map for a circle, which involves a Hankel function with a tangential operator appearing in the index. This operator formalism is related to the well-known square root of an operator that arises in the parabolic equation method and is asymptotic to the square root in the high-frequency limit. The Hankel function is approximated with a rational function to obtain an OSRC for the circle. An OSRC for a more general convex object is obtained by fitting osculating circles to the surface and allowing the coefficients of the rational approximation to depend on curvature. Since the computation time increases only linearly with frequency, accurate solutions are obtained with substantial computational savings in comparison with other approaches. The OSRC can be constructed to any desired accuracy in scattering angle and surface curvature. [Work supported by ONR.]
Infant-directed vowels are easier to learn for a computer model
Authors: de Boer Bart , Kuhl Patricia K.
Published: October 2013

When addressing infants, caretakers use a special register, called ‘‘motherese’’ or ‘‘parentese.’’ Kuhl et al. (Science, 1997) demonstrated that the formant patterns of the centers of vowels in this register are farther apart than those in adult-directed speech, and postulated that this helps children learn the categories of speech in their language. In this study, this hypothesis was tested with a computer model. Three words were used: sock, shoe, and sheep. Recordings of these words were available from ten mothers in both infant-directed and adult-directed registers. The first two formants were automatically extracted from the voiced parts of each word. Automatic formant extraction often results in formant patterns with errors, but no corrections were made. After formant extraction, their distributions were compared and a mixture of three Gaussians was fitted to the data points. The results demonstrated that infant-directed tokens not only used a larger part of the acoustic space, but also resulted in a better distribution of the centers of the Gaussians, indicating better patterning of the input. Better patterning of the input makes it easier to learn the categories of speech sounds. [Research supported by the NIH and the Talaris Research Institute.]
Age-related changes in the acoustic characteristics of voiceless English fricatives
Authors: Fox Robert Allen , Nissen Shawn , McGory Julie , Rosenbauer Kimberly
Published: October 2013

This study examines the acoustic characteristics of voiceless fricatives in American English ([f, θ, s, ∫]) in children and adults (ranging in age from 3 to 70 years). Twenty speakers from seven different age groups produced four different examples of each fricative in word-initial position (in 20 different monosyllabic words varying in terms of medial vowel). Each speaker also produced these fricatives intervocalically (in the context [ɑ Cɑ]). These data are drawn, in part, from a large-scale acoustic database developed in collaboration with ATR. All tokens were recorded using high-quality microphones and direct analog-to-digital conversion to disk at a sampling rate of 22.05 kHz. Acoustic measurements include fricative duration, vowel duration, spectral moments, spectral peak locations, absolute and relative noise amplitude, spectral tilt, and F2 onset frequency. Of primary interest is to determine whether these four fricatives can be distinguished using the same subset of acoustic properties as reported in Jongman and colleagues [Jongman et al., J. Acoust. Soc. Am. 108, 1252–1263] across variations in the age and gender of the speaker. [Work supported, in part, by an INRS Award from NIH and research funding from ATR, Fox, P.I.]
The relation between first graders’ reading level and vowel-production variability and presentation format
Authors: Baker Kandice , Fowler Anne , Bell-Berti Fredericka
Published: October 2013

The purpose of this research is to determine if children with reading difficulties produce vowels with greater variability than children with normal reading ability. This study examines variability in vowels produced by first grade students as a function of whether they were reading words presented individually in random or blocked format or were naming pictures representing words within a story context. The vowels chosen for this study are /I/, ε, and æ, occurring in real monosyllabic words. The specific focus of this research is variability of temporal and spectral aspects of vowel production: vowel duration and F1 and F2 frequency at vowel onset and at 50 ms intervals through the vowel. The results will be compared with spelling ability (a good measure of reading ability for first graders), to determine if good and poor readers differ in vowel production variability. The results will also be examined to determine if mode of presentation (picture or read word) influences production variability. [Work supported by the U.S. Department of Education, McNair Scholars Program.]
Binaural dichotic presentation to reduce the effect of increased temporal and spectral masking in sensorineural hearing impairment
Authors: Pandey Prem C. , Jangamashetti Dakshayani S. , Cheeran Alice N.
Published: October 2013

Sensorineural hearing loss is characterized by increased temporal and spectral masking, resulting in degraded speech perception. Earlier investigations have shown that binaural dichotic presentation using comb filters with complementary magnitude responses improved speech perception, particularly the place feature. Further, inter-aural switching with periodic trapezoidal fading functions improved the perception of duration feature. For simultaneously reducing the effect of the two types of masking, a scheme has been devised with a pair of time-varying comb filters, with bands corresponding to auditory critical bands. Thus the spectral components in neighboring critical bands do not mask each other, and the sensory cells on the basilar membrane get a relaxation time due to sweeping of the filter passbands. The scheme was implemented using linear phase 256-coefficient FIR filters. Magnitude responses were cyclically swept with 20-ms period, in steps by selecting the filter coefficients for each step from a pre-calculated set. Listening tests involved closed set identification of 12 vowel–consonant–vowel syllables. The processing scheme resulted in the improvement of recognition scores, response time, and transmission of features, particularly place and duration, indicating reduction in the effect of spectral and temporal masking.
Comb filters for binaural dichotic presentation to improve speech perception by persons with bilateral sensorineural hearing impairment
Authors: Cheeran Alice N. , Pandey Prem C. , Jangamashetti Dakshayani S.
Published: October 2013

Intelligibility of speech for persons with sensorineural hearing impairment gets reduced due to increased spectral masking. For persons with bilateral loss, improved speech perception has been reported with binaural dichotic presentation using comb filters having complementary magnitude responses, based on auditory critical bands. In this scheme, spectral components in adjacent critical bands do not mask each other as they get presented to different ears. The objective here was to design a set of comb filters with transition crossovers adjusted for a low perceived spectral distortion. For this, a slowly swept tone presented through the two comb filters should not have a change in its perceived loudness at crossover frequencies. Experiments showed that the change in loudness was negligible with crossover response lying between −4 dB and −6 dB with respect to passband response. With this constraint for response at the crossover frequencies, comb filters with responses corresponding to 18 critical bands were designed as 256-coefficient linear phase FIR filters, using frequency sampling technique. The filters have pass band ripple of 1 dB and stop band attenuation of 30 dB. These filters have resulted in improvement in speech quality and speech perception.
Gesture-speech interaction in the SmartKom project
Authors: Schweitzer Antje
Published: October 2013

The goal of the SmartKom project is to create an intuitive multi-modal dialog system. Information is presented on the display by an artificial lifelike character, combining the output modalities speech, mimics, and gesture. Multi-modality poses new requirements for speech synthesis. Speech may be accompanied by gestures, adding three new aspects: First, synchronization of lip movements; second, temporal alignment of speech and gesture; and third, effects of gestures on prosody. This paper focuses on the last two points. Building on de Ruiter’s (2000) Sketch Model, speech is synthesized independently from the temporal structure of the accompanying gesture. Preparation phase and retraction phase of gestures can be adjusted to align the relevant speech material with the stroke phase. Concerning prosody, results of a pilot study on intonation of deictic elements show that speech material accompanied by gestures is more likely to be prosodically prominent. Gestures in the SmartKom system are always triggered by linguistic properties of the accompanying speech. Most of the gestures are pointing gestures, which are triggered by deictic elements. Such linguistic information is integrated into the concept input to the synthesis module and is taken into account during prosody generation.
Preliminary results of water tunnel acoustic measurements using a time reversal mirror
Authors: Barber Christopher , Lauchle Gerald C. , Kottke Nelson J.
Published: October 2013

A concept demonstration test was recently conducted at the Garfield Thomas Water Tunnel at the Penn State University Applied Research Laboratory using a time reversal mirror to acquire acoustic measurements of a cavitation noise source. The objective of the test was to demonstrate improved acoustic measurement capabilities compared to conventional underwater acoustic measurement techniques. A preliminary analysis of the data indicates an increased signal-to-noise ratio resulting from the time-reverse playback of recorded data compared to real-time measurements made using either omnidirectional or sum-beam sensors. Experimental results are presented, including a novel method for source localization based on the difference between the time-forward and time-reverse playback of recorded data. [Work supported by ONR Code 334, Naval Surface Warfare Center Carderock Division, and the Applied Research Laboratory.]
Robust time-reversal focusing in a random ocean channel
Authors: Kim Seongil , Kuperman W. A. , Hodgkiss W. S. , Song H. C. , Edelmann G. F. , Akal Tuncay , Millane Rick P. , DiIorio Daniela
Published: October 2013

Since time reversal focusing utilizes the reciprocity of a static medium, its performance can be degraded in a nonstatic medium, where the propagation conditions change during the time of forward and backward propagations. In this study, a method for robust time-reversal focusing is investigated based on a method developed for matched-field processing [Krolik, J. Acoust. Soc. Am. 92, 1408–1419 (1992)]. Instead of using a single probe source pulse, the robust method employs multiple probe source signals obtained over a period of time where each ping represents a different propagation condition. A singular value decomposition of the signal matrix of the received probe source pulses shows that over 90% of the acoustic energy is represented by the first few singular values, suggesting that the effective dimension of the pressure field resulting from the sound speed fluctuations is small. The back-propagated field weighted by the linear combination of the dominant singular vectors produces stable focusing for longer time than that with a single probe pulse. The method is useful in nonstatic propagation conditions and in a situation where frequent probe signals are not available. [Work supported by ONR.]
Detection based on multiple time-reversal guide-sources
Authors: Gaumond Charles F.
Published: October 2013

The problem of inclusion of multiple guide-sources in a time-reversal detection system is discussed. The objective of the detector is the coverage of a given volume over range and depth in a known environment. This detector should rely on as few guide-sources as possible. This detection problem is analyzed in terms of a separable kernel receiver (SKR). The performance of the SKR in terms of the number and placement of guide-sources is shown to depend on the 2-D inner-product of the guide-source covariance with the expected signal covariance. This single number can be used as an overall measure of system quality. Numerical examples are shown for several shallow water environments with various numbers and placements of guide-sources. The use of extended reflectors for use in an active system is also considered. [Work supported by ONR.]
The regulatory agency’s perspective on noise and marine mammals
Authors: Gentry Roger L.
Published: October 2013

The community is a little closer to resolving this issue now than it was at the 1999 Columbus symposium. The same laws, guidelines, agencies, researchers, and sources of money apply now as before, only now results are limited more by a shortage of researchers than of money. A few important advances have been made in research. The use of these results by regulators to make decisions is being opposed by a new mistrust of all science conducted by the government. Several interwoven factors, new since March 2000, are affecting the way the marine mammal/noise issue is being managed. These include the Bahamian beaked whale stranding, use of the general public as a weapon to force decisions on complex acoustic issues, and increasing interest in acoustics by federal legislators. This paper will discuss these new factors, and will guess at changes that may occur in the near future.
Hot topics in animal bioacoustics
Authors: Hastings Mardi C.
Published: October 2013

Recent discoveries in the field of animal bioacoustics include everything from active auditory mechanics in insects to the behavior of large marine mammals in response to manmade sounds. Using laser Doppler vibrometry, Göpfert and Robert found that active auditory mechanics in male mosquitoes provides tuning that allows them to detect flying females. Their exciting discovery revealed new similarities between insect and vertebrate hearing. Many researchers have reported the behavior of fishes and marine mammals in response to underwater manmade sounds that is most likely controlled by other factors than the sound itself. Wardle and his colleagues found that repeated firing of seismic air guns had little effect on the day-to-day behavior of reef fishes off the coast of Scotland unless the explosions were visible. Madsen and Mo/hl also reported no change in behavior or click rate of sperm whales when detonators were discharged off the coast of Norway. Thus marine animals may not swim away from anthropogenic sounds even though they could be harmful. Gerstein determined masked thresholds and critical ratios for manatees that may prevent them from detecting boat noise in their natural habitat. His findings will lead to new solutions enabling manatees to detect boats and avoid collisions.
Source motion compensation using waveguide invariant theory
Authors: Zurk Lisa M.
Published: October 2013

Passive detection and localization of quiet, submerged sources moving in shallow water in the presence of shipping noise is a critical problem for the ASW community. Past work has demonstrated that adaptive processing can be applied to detect and localize stationary sources while mitigating loud interferers. However, source motion can cause significant signal gain degradation, loss of localization accuracy, and incomplete interference rejection. The severity of the motion loss is channel dependent, and a function of the amount of motion during the observation interval. Motion compensation techniques have been demonstrated in past work with data from the Santa Barbara Channel Experiment. These algorithms utilized a normal mode propagation model and a velocity hypothesis to successfully compensate for source motion. However, the technique requires good environmental knowledge and can be computationally expensive if a large hypothesis space must be searched. In this paper, the waveguide invariance principle is used to combine the time-frequency snapshots acquired from a broadband source to compensate for motion. The technique does not require knowledge of the underwater environment for the compensation and the search across the velocity space can be structured so it is computationally efficient. Results from this technique will be presented and discussed.
The mudslide effect
Authors: Tappert Frederick D. , Spiesberger John L. , Wolfson Michael A.
Published: October 2013

A novel range-dependent propagation effect occurs when a source is placed on the seafloor in shallow water with a downward refracting sound speed profile, and sound waves propagate down a slope into deep water. Small grazing-angle sound waves slide along the bottom downward and outward from the source until they reach the depth of the sound channel axis in deep water. They then detach from the sloping bottom and continue to propagate outward near the sound channel axis. This ‘‘mudslide’’ effect is one of a few robust and predictable acoustic propagation effects that occurs in range-dependent ocean environments. Consequently, a bottom mounted source in shallow water can inject a significant amount of energy into the axis of the deep ocean sound channel that propagates to very long ranges. Numerical simulations with a full-wave range-dependent acoustic model show that the Kaneohe experiment had the appropriate source, bathymetry, and sound speed profiles that allowed this effect to operate efficiently. This supports the interpretation that some of the near-axial acoustic signals, received near the coast of California from the Kaneohe source on Oahu, Hawaii, were injected into the sound channel of the deep Pacific Ocean by this mechanism. [Work supported by ONR.]
Computer model studies of RASTI values in classrooms
Authors: Siebein Gary W. , Kim Bumjun , Paek Hyun , LoRang Mark
Published: October 2013

Computer models of classrooms were used to study the effects of room shape, furniture arrangement and interior finish materials at various background noise levels. The background noise levels used in the computer models were obtained in field measurements of actual classrooms and varied from approximately Noise Criterion (NC) 25 to NC 65. A sound source was configured to approximate the level, frequency and directionality of the normal speaking voice of a teacher in the room. RASTI, reverberation time, loudness, and early energy ratios were estimated for multiple seating locations in each room for each background noise level. RASTI was related to background noise level (NC rating), distance and room finish materials with a second order equation with a model r2 of 0.96. The background noise level had the primary effect on RASTI values in the rooms. Once a background noise level of NC 35 or less was achieved, the amount and distribution of absorbent materials in the room became important factors. Reflective materials in parts of the ceiling of the rooms contributed to increased loudness and higher RASTI values at most seating locations.
Review of marine mammal temporary threshold shift (TTS) measurements and their application to damage-risk criteria
Authors: Finneran James J. , Carder Donald A. , Ridgway Sam H.
Published: October 2013

Intense anthropogenic underwater sound may adversely effect the hearing and behavior of many marine mammals. Exposure to intense sound may produce an elevated hearing threshold, also known as a threshold shift (TS). If the threshold returns to the pre-exposure level after a period of time, the TS is known as a temporary threshold shift (TTS); if the threshold does not return to the pre-exposure level, the TS is called a permanent threshold shift (PTS). PTS and TTS data were used to establish noise exposure limits in humans and TTS data are often used to help predict the effects of anthropogenic noise on marine mammals in the wild. Previous studies of TTS in marine mammals conducted at SSC San Diego have examined the effects of exposure to single 1 s pure tones and underwater impulsive waveforms. This paper reviews the TTS studies conducted at SSC San Diego over the last 5 years and summarizes the resulting data. The application of these data to the development of damage-risk criteria for marine mammals will also be discussed.
Sediment tomography in the East China Sea: Preliminary results
Authors: Potty Gopu R. , Miller James H. , Chen Chuen-Song , Lazauski Colin J. , Dahl Peter H.
Published: October 2013

This paper discusses the early results from the acoustic bottom interaction experiment conducted in May–June 2001 in the East China Sea as part of the ASIAEX-2001. Explosive sources (38 g and 1000 g) were deployed in the experimental area from a Chinese Research vessel (Shi Yan 2) during the experiment. These shots are deployed in circular pattern of radius 30 km and on radial tracks. The acoustic signals from these explosive sources were received at the vertical line array hung from R/V Melville near the center of the circular pattern. The sediment properties show a sharp contrast on either side of a sediment front. The presence of high-speed sand and low speed mud–sand on either side of the front has been confirmed by core data from ASIAEX-2000. Extensive coring to determine the sediment information in more detail is planned in August 2001. The time-frequency scalograms of the received explosive signals have been constructed using wavelet analysis. This analysis yields the dispersion characteristics of the acoustic signals and clearly shows the modal arrivals. The dispersion behavior of the acoustic modes from either side of this sediment front is presented. These modal dispersion diagrams form the basis for our sediment inversion technique. [Work supported by ONR.]
Acoustic wave reflection from the transition layer of surficial marine sediment
Authors: Kimura Masao
Published: October 2013

It has been recently reported that the porosity and the density, etc. in the surficial marine sediment vary largely with the depth. The characterisitics of acoustic wave reflection from such transition layers of the surficial marine sediment seem to be very different from that of uniform sediments. In this study, the incident angle dependence of the reflection coefficient for the transition layer of the surficial marine sediment model is calculated using OASES (Biot–Stoll model). The effects of the transition layer and the frequency dependence of the reflection coefficient characteristics are investigated. Next, the characteristics of the incident angle for the reflection coefficient are measured in water tank and in situ. Beach sand (fine sand) is used for water tank measurements, and in situ measurements are done in a very fine sand bottom. The operating frequency is 150 kHz. The incident angle are 0, 20, 50, and 60 deg. The measured results are compared with the calculated results using OASES (Biot–Stoll model), and the effects of the transition layer on the characteristics of the reflection coefficient are investigated.
Observations of sediment shear velocity in the San Diego Trough
Authors: Dorman LeRoy M. , Sauter Allan W.
Published: October 2013

We report observations of shallow seafloor shear velocity structure in the San Diego Trough, whose depth is about 1100 m. Dispersed Scholte waves were generated using a new implosive source, described elsewhere in this meeting, and observed using ocean-bottom seismographs. Preliminary estimates of the surficial shear velocities are in the 16–25 m/s range, which is very low. The Scholte waves are observed in the 1–8 Hz frequency range and dispersion is well-developed after 100 m of propagation. Higher modes appear in addition to the fundamental mode, which exhibits a smooth increase in frequency from 2 to an Airy phase at about 3 Hz. The group velocity of the Airy phase approximates the surficial shear velocity. In the work area, the topographic relief is only a few meters. Geologically, the sediments are turbidites distributed by a channel and levee system. High-resolution multibeam bathymetry is available from NOAA and is being used to aid geological interpretation.
Application of single crystal relaxor ferroelectric materials to medical imaging arrays
Authors: Zipparo M. , Oakley C.
Published: October 2013

Single crystal relaxor ferroelectrics have been shown to possess extremely high electromechanical coupling coefficients, in some materials approaching 95% in length extensional mode. This high coupling allows the design of electroacoustic transducers with better sensitivity or bandwidth than can be achieved with conventional piezoceramic materials. These improved properties come at the expense of lower depoling temperatures, increased material fragility, poorer property uniformity, and increased cost. These issues preclude the adoption of single crystals as a direct drop-in replacement for conventional piezoceramics. Most issues can be addressed through refined crystal growth and transducer design or processing methods. This paper reviews the application of single crystals to transducers for medical imaging, including: characterization of material properties including the complete matrix of elastic, dielectric, and piezoelectric coefficients; design of high bandwidth transducers; modeling of transducer operation, including 1-D and finite element approaches; development of alternate fabrication processes; and measurement of the transducer performance improvement which has been obtained to date. Progress toward the goal of fabricating a single transducer which can operate effectively over the range of multiple conventional probes will be described.
Musical acoustics in teaching engineering to first-year undergraduates
Authors: Everbach E. Carr
Published: October 2013

Since most high school programs lack any introduction to the fields of engineering, first-year undergraduates often take an ‘‘inspirational overview’’ course to see if they wish to pursue the field. Musical acoustics provides accessible examples of phenomena and concepts that can draw such students into further engineering applications. Furthermore, the programming environment Matlab, a long time staple of engineering analysis, has evolved such sophisticated capabilities that nearly real-time analysis and synthesis of musical acoustics demonstrations is possible in the lecture hall. Examples of linear and nonlinear systems in musical acoustics will be demonstrated and the Matlab source code (m-files) freely available via anonymous ftp at ftp://fubini.swarthmore.edu
Comparison of measured versus modeled aircraft noise levels
Authors: Eagan Mary Ellen
Published: October 2013

The Integrated Noise Model (INM) is the primary tool used for predicting aircraft noise in the vicinity of civil airports in the U.S. and throughout the world. The INM contains a substantial database of more than 200 aircraft types for use in preparing noise contours. Validation of aircraft noise data in the database under field conditions has shown consistent underprediction for modeled versus measured data. Case studies of such observations will be presented.
Giant acoustic stop bands for cubic arrays of air bubbles in water
Authors: Kushwaha M. S. , Djafari-Rouhani B. , Dobrzynski L.
Published: October 2013

A systematic and extensive evidence is presented for the existence of complete, multiple, huge stop bands in the band structure for cubic arrays of air bubbles in water. This has been demonstrated by investigating face-centered cubic (fcc), body-centered cubic (bcc), and simple-cubic (sc) arrangements using the Fourier series expansion methodology, which does not require matching of the messy boundary conditions usually needed for the inhomogeneous composite systems. The lowest stop bands are largest for a volume fraction f≤10%, with a gap/midgap ratio of ≊1.8 for all the three geometries. Surprisingly interesting but rigorously justifiable is the fact that the low-frequency flat passbands for the perfectly periodic systems correspond to the discrete modes of a single bubble. This is an artifact of the low filling fraction and huge density contrast in air and water. It is stressed that such a simple inhomogeneous system as made up of air bubbles in water exhibits the widest stop bands ever reported for phononic as well as photonic crystals. Some conclusive remarks will also be made on the reverse situation, where one can investigate the periodic system of water balloons in air.
Fluid coupling analyses using in vacuo modes as basis functions
Authors: Fahnline John B.
Published: October 2013

Similar to some of the earliest papers on fluid coupling analyses, the present formulation uses in vacuo modes as basis functions, and thus the basic solution technique is well known. However, the inherent difficulties in generating the frequency dependent acoustic impedance and modal coupling matrices have prevented this type of analysis from being applied to practical engineering problems. In the numerical implementation, the matrices are computed using a boundary element analysis and many of the typical limitations are avoided by using a number of recently-developed techniques. First, different structural and acoustic meshes are employed to properly represent the variations in the physical quantities. This is especially important at low frequencies for in-water analyses where the structural wavelength is much smaller than the acoustic. Second, because the acoustic matrices are slowly varying functions of frequency, their individual terms can be interpolated from values calculated at sparse intervals. A preliminary analysis is required to map out the matrices as a function of frequency, but the subsequent frequency response calculations are orders of magnitude faster than if they were performed directly. Several examples are given to demonstrate the validity of the computations, including a cantilever plate, a circular cylinder, and a bass-reflex loudspeaker.
Structural constraints in the perception of English stop-sonorant clusters
Authors: Moreton Elliott
Published: October 2013

Native-language phonemes combined in a non-native way can be misperceived so as to conform to native phonotactics; e.g., English listeners are biased to hear syllable-initial [tr] rather than the illegal [tl] (Massaro and Cohen, 1983; Pitt, 1998). What sort of linguistic knowledge causes phonotactic perceptual bias? Two classes of models were compared: unit models, which attribute bias to the listeners differing experience of each cluster (such as their different frequencies); and structure models, which use abstract phonological generalizations (such as a ban on [coronal][coronal] sequences). Listeners (N=16 in each experiment) judged synthetic 6×6 arrays of stop-sonorant clusters in which both consonants were ambiguous. The effect of the stop judgment on the log odds ratio of the sonorant judgment was assessed separately for each stimulus token to provide a stimulus-independent measure of bias. Experiment 1 compared perceptual bias against the onsets [bw] and [dl], which violate different structural constraints but are both of zero frequency. Experiment 2 compared bias against [dl] in CCV and VCCV contexts, to investigate the interaction of syllabification with segmentism and to rule out a compensation-for-coarticulation account of Experiment 1. Results of both experiments favor the structure models. [Work supported by NSF IGERT.]
Frequency and predictability effects on the duration of content words in conversation
Authors: Gregory Michelle , Bell Alan , Jurafsky Daniel , Raymond William
Published: October 2013

This study carefully examines the proposal that word forms in conversation are shorter when they have higher probability, where this includes all factors of their context (Jurafsky et al., Frequency and the Emergence of Linguistic Structure, edited by Bybee and Hopper, 2001, pp. 229–254). Higher word frequencies have long been known to be linked to shorter durations. But it has been hard to confirm a direct relationship between the two. One confound is with predictability or conditional probability, which also affects surface form and is closely related to frequency. Another difficulty is controlling factors related both to duration and contextual probability. Linear regression (and sampling to avoid violating independence assumptions) was used to control for phonological form, speech rate, prosodic prominence, previous uses, and neighboring disfluencies. Both greater word frequencies and greater conditional probabilities given the following word have a strong shortening effect on durations of content words. The effect of other probability measures considered did not reach significance. The study is based on a sample of about 1000 content words from a portion of the Switchboard corpus, phonetically transcribed at ICSI, Berkeley, and coded for intonation by P. Taylor, M. Ostendorf, and S. Shattuck-Hufnagel. [Work supported by NSF.]
Representational specificity of lexical form in the perception of spoken words
Authors: McLennan Conor T. , Luce Paul A. , Charles-Luce Jan
Published: October 2013

The specificity of form-based lexical representations of spoken words was examined. Using a repetition-priming paradigm, we attempted to determine (1) if flapped intervocalic alveolar stops in American English are mapped onto underlying representations of /t/, /d/, or both or (2) if flaps have an independent representational status. Participants shadowed or made lexical decisions to spoken words in two blocks of trials. Stimuli in the first block served as primes and those in the second block as targets. Primes and targets consisted of flapped and carefully articulated bisyllabic words. We measured reaction times to target words in the second block as a function of prime type. The results provide evidence for both underlying and surface perceptual representations.
Measured performance of an endfire superdirective line array in littoral water
Authors: Hines Paul C. , Hutt Daniel L. , Young Victor
Published: October 2013

Superdirective line arrays can provide high gains whenever the interelement spacing is much less than half a wavelength. In practice these arrays have fallen short for two reasons: First, performance degrades appreciably in the presence of uncorrelated system noise. Second, the optimum array weights are specific to the form of the noise field and the choice of these weights is often sensitive to deviations from that noise field. Furthermore, since the process involves computing signal differences between hydrophones, the signal to noise ratio (SNR) degrades as the steering angle approaches broadside. In spite of these drawbacks, a superdirective array can provide substantial improvement over a conventional array in specific instances. For example, the present application requires an endfire array of limited extent (1 m in length) and wide bandwidth (1–5 kHz) making a conventional array impractical. Moreover, improvements in array hardware have substantially reduced uncorrelated system noise, and increased computer speed makes it reasonable to process data using several weighting schemes. In this paper, the superdirective array will be described and its measured performance will be compared to theoretical predictions.
Measurement of underwater sound intensity and determination of source bearing angle
Authors: Hutt Daniel , Hines Paul , Young Victor
Published: October 2013

Measurements of the underwater acoustic pressure and pressure gradient can be used to calculate the components of the acoustic intensity vector. The intensity vector points in the direction of net power flow and can therefore be used to find the direction or bearing angle to an acoustic source. Use of intensity measurements for determination of bearing is of interest because high-angular resolution can be achieved using a relatively small array with physical dimensions less than 1/4 of the wavelength. The usefulness of this technique was investigated in a series of experiments on the Scotian Shelf in 70 m of water. The intensity sensor is an array of six hydrophones arranged as three orthogonal dipoles. The hydrophone spacing is 11.4 cm with a frequency range of 500–4000 Hz. For signal-to-noise ratios greater than 10 dB, bearing angles to a source were determined with a standard deviation of less than 0.1 deg. However, offsets of several degrees from the correct bearing angle were often present. The offset error is believed to be due to acoustical scatter from supporting structures. The effect of noise, gain error, and phase error on intensity measurements is discussed.
Automatic identification of sound source direction based on neural networks
Authors: Czyzewski Andrzej , Krolikowski Rafal
Published: October 2013

Automatic identification of sound sources direction is still an unsolved problem in contemporary teleconferencing systems. Speech signals coming from various directions not only interfere with the target signal but also can obscure it. People have difficulty in understanding speech with background noise, high reverberation, and/or with many concurrent speakers. Source identification system should allow tracking a target speaker automatically without much delay in order to avoid picking up concurrent speakers by the same microphone channel. In literature one can find two approaches to this problem. One of them is a classical approach to this problem based on delay-summation algorithms, superdirective arrays and adaptive algorithms, and nonlinear frequency domain microphone array beamformers, etc. The second solution to this problem was proposed among others by the authors in their previous studies, namely, they applied Artificial Neural Networks (ANNs) for the purpose of the automatic sound source localization. In this paper a method for automatic detection of sound source was studied. Both standard feed-forward ANNs and Recurrent Neural Networks were employed for that purpose. Comparison of the results obtained is given. Conclusions are also derived. [Research sponsored by the Committee for Scientific Research, Warsaw, Poland, Grant No. 8 T11D 00218.]
Reverberation and diffusion in layers with rough boundaries
Authors: Berman David H.
Published: October 2013

A pulse of sound is emitted from a point source located between two surfaces, one of which is rough. After a long time, sound that is returned to the source is governed by a diffusing remnant of the scattered sound. The diffusing remnant leads to algebraic, as opposed to exponential, decay of the reverberation when there is no absorption. An admittance formalism is used to describe this diffusive mode. Particular attention is given to the case in which the sound speed profile confines sound to the neigborhood of the scattering surface. As in the case of light scattering by discrete particles, the frequency dependence of the scattering operator leads to a correction to the diffusion constant that is simply described in terms of the sound speed contrast between the region near the surface and far from the scattering surface. This result builds on a two-frequency generalization of the Ward identity for energy-conserving scattering.
Multistatic active system performance modeling in shallow waters
Authors: Fromm David M.
Published: October 2013

The Bistatic KRAKEN Reverberation (BiKR) model is an active system performance prediction model for bistatic source/receiver geometries based on adiabatic normal mode propagation [W. A. Kuperman, M. B. Porter, J. S. Perkins, and R. B. Evans, J. Acoust. Soc. Am. 89, 125–133 (1991)]. By exploiting ray-mode analogies, it can provide detailed predictions of reverberation, target echo, and signal excess for low-frequency (<1 kHz) multistatic systems in range-dependent environments. This paper presents an overview of the models underlying principles and analysis capabilities such as the estimation of signal spreading loss. Data/model comparisons that required the inclusion of losses due to shear will be presented for a recent sea test on the Heceta Bank off the Oregon coast. [Research sponsored by ONR.]
General considerations regarding the acoustic comfort conditions in architectural spaces
Authors: Rodriguez-Manzo Fausto
Published: October 2013

Recently the matter of acoustic conditions of various types of architectural spaces has been taking great importance. Such is the case of classrooms, open plan, and private offices. These types of rooms can be considered as noncritical acoustic rooms in opposition to theaters and concert halls that are traditionally considered as acoustic spaces. However, all kinds of architectural spaces can be considered as acoustic spaces. There are acoustically critical spaces and acoustically natural spaces. Acoustically critical spaces need specialized acoustic consulting. Acoustically natural spaces need criteria for acoustic comfort. Acoustic comfort is not a matter of precision, but a matter of criteria. This paper establishes the relation between architecture and the science of sound through the concept of acoustic comfort, enhancing the importance of the acoustic conditions of all types of architectural spaces. Acoustic comfort levels are theoretically examined according to several author conceptions, and finally an acoustic comfort criterion including speech intelligibility conditions for specific types of architectural spaces is presented.
Merging EASE for sound reinforcement systems and CAESAR for room acoustics
Authors: Ahnert Wolfgang , Feistel Stefan , Olson Bruce C. , Schmitz Oliver , Vorländer Michael
Published: October 2013

The combination of EASE with a state-of-the-art room acoustical simulation engine CAESAR, merging the advantages of both to form a multipurpose simulation tool, is introduced. The new tool is useful for consultants in room acoustics (ISO3382) and for the first time for electroacoustics as well. Advantages of combining a high quality speaker database and a powerful 3D-CAD interface including mapping presentations with a hybrid image source/ray tracing algorithm including diffuse scattering will be discussed. Details about the new EASE module CAESAR and its limitations as well as the extended possibilities of the system are the main topics of this presentation.
A new technique of measurement of airborne sound insulation by means of adaptive processing
Authors: Minguez Antonio , Grundman Jorge , Sancho Juan , Ulin Vladimir
Published: October 2013

In situ measurement of the airborne sound insulation, according to the ISO 140 Part IV specifications, needs the sound level pressures taken in the source room and in the receiving room, and the background noise level in this last room. Whenever the receiving room presents a great sound insulation, a high sound pressure level excitation is required in the source room in order to guarantee the appropriated margin over the background noise level. This higher sound pressure level is not ever attainable due to the limitations of the conventional sound sources. This procedure describes a new technique of measurement of the airborne sound insulation using a classical adaptive filter configuration that separates the background noise from the excitation sound in the receiving room so that a lower power excitation level can be used. Also, due to the possibility to obtain simultaneously and during a single measurement process the receiving sound pressure level and the background noise level, this technique allows to measure the actual background noise instead of a prior or post estimation of this magnitude once the receiving room level is measured.
The impacts of anthropogenic sounds on fishes
Authors: Popper Arthur N.
Published: October 2013

There is considerable concern that increases in marine sounds may be negatively impacting marine organisms. While most of the concern in the literature and in the press revolves around marine mammals, it is important to recall that the bulk of the marine vertebrate biota is made up of numerous fish species, and that many fishes are important in the food chains of marine mammals and humans. Moreover, since fishes use sound to learn about their environment and for communication, changes in ambient noise may have a significant impact on behavior and physiology of fishes, and thus on organisms higher in the food chain. Though there is a call to increase our knowledge of the impact of anthropogenic sounds on marine mammals, there have been few parallel studies looking at fishes (or on invertebrates and marine reptiles). This paper will review the little that is known about the impact of sound on fish behavior and physiology, and discuss the usefulness of these data in evaluating the impact of anthropogenic sounds on marine fishes. In addition, the paper will suggest a number of studies that are needed in order to have a better understanding of the impacts of anthropogenic sounds on fishes.
Parameters affecting seismic survey sound levels versus distance and marine mammal safety
Authors: Greene Charles R. , Burgess William C. , Richardson W. John
Published: October 2013

Measurements of airgun sounds were made from 1996 through 1999 in the coastal waters north of Alaska (the Beaufort Sea). Sound levels versus distance (typically 100 m to ca. 6 km) from the source were measured for two single airguns and nine airgun arrays. Parameters of the measurements were number and size of airguns, array geometry and depth, receiver and water depths, and aspect. The total volume ranged from 10 to 120 in.3 for the single airguns and from 56 to 1500 in.3 for airgun arrays. The number of airguns ranged from 4 to 16. The U.S. National Marine Fisheries Service (NMFS) presently states that pinnipeds and cetaceans should not be exposed to received levels of pulsed sounds above 190 and 180 dB re: 1 μPa (rms over duration of pulse), respectively. NMFS often expresses concern that the disturbance may occur above 160 dB re: 1 μPa (rms). For each airgun source, distances within which animals might receive these three levels were determined. An effort is being made to relate the physical parameters of airgun operation to azimuthally radiated sound levels. [Work supported by BP Exploration (Alaska), Inc. and WesternGeco.]