bluuebunny/crossref_metadata_2025 huggingface dataset:
Small room production before large room performance.
Authors: Case Alex U.
Published: October 2009

Large scale works almost always begin their acoustic life in a small room. Sound designers and composers need studio spaces that enable creativity while keeping technical matters in check. The stereo recording studio requires a paradigm shift when scaling up to four, eight, or more channels. While fundamental issues of isolation, noise control, user comfort, and ergonomics remain ever-important, new challenges arise. Despite the growth in electroacoustic complexity that accompanies multichannel systems, the sound/music creator needs core issues of level, timbre, localization, distance, envelopment, space, and so on to be presented as faithfully as possible, predictive of the future large space performance, without corruption by the small room.
I did not see that one coming.
Authors: Talaske Richard , Miller Gregory , Harrison Byron , Way Evelyn
Published: October 2009

Occasionally we encounter something we have not before, to our detriment. Only by looking back do we gain the proper perspective to know how to avoid similar concerns in the future. We will share several examples from the Talaske body of work where things turned out differently that we had anticipated. Examples will include a theatre wall system which provided more diffusion and absorption than laboratory tests had indicated, a contractor construction error that had negative acoustic implications which were not caught until it was too late to correct, and an acoustic isolation concern between a dance studio and a theatre that passed the boundaries of our analytical assumptions. In each case, the analytical, practical, and political hurdles required to resolve each issue will be presented.
Flatte fluctuation theory and its use by the US Navy.
Authors: Baggeroer Arthur B.
Published: October 2009

Fluctuations of narrowband signals and spreading of broadband ones are important concepts in the design of the sonar receiver. The first determines how long one can integrate or equivalently how narrow a bandwidth can be used to increase the gain and the second leads to the convolution of the ambiguity function and the scattering function to determine where energy from the transmission will appear in the range-Doppler plane, hence the region over which one wants to collect energy for a detection. The seminal book “Sound Transmission through a Fluctuating Ocean” by Flatte et al. essentially defined the concepts of saturated, partially saturated, and unsaturation transmissions which parsed the problem in the “lambda-phi” for designing sonar transmitters and receiver appropriate for the dynamics of an oceanographic region.
Comparison of three coordinate mapping methods for sound propagation over irregular terrain.
Authors: Parakkal Santosh , Gilbert Kenneth E. , Di Xiao
Published: October 2009

In propagation calculations, a coordinate mapping to “flatten” irregular terrain is an attractive approach. However, coordinate mapping methods can be as computationally intensive as the propagation calculation itself. Hence a judicious choice of the mapping method is critical for practical calculations. We compare three coordinate mapping methods: (1) conformal mapping; (2) transformation to polar coordinates; and (3) a simple mapping introduced 30 years ago by Beilis and Tappert . The first two methods are essentially exact, while the third is, in principle, applicable only to small slopes and low propagation angles. The three approaches are outlined and a comparison is made of the accuracy and computational demands of the methods. Also, the theoretical predictions from the three methods are compared to field measurements of sound propagation over a hill. [Research supported by the U.S. Army TACOM-ARDEC at Picatinny Arsenal, NJ.]
Molecular simulation of sound propagation in a gas.
Authors: Yano Takeru
Published: October 2009

Molecular dynamics simulation is carried out to clarify the propagation process of high frequency and large amplitude sound in a gas. Numerically, the inter-molecular potential is assumed to be the Lennard-Jones 12-6 potential and the motions of molecules are determined by solving Newton’S equation of motion for each molecule with the leap-frog method. The gas, where the sound propagates, is sufficiently rarefied or low density so that its behavior may be governed by the Boltzmann equation. Comparison of the numerical results based on the molecular dynamics, the Boltzmann equation, and the Navier–Stokes equations, the nonequilibrium effects due to the high frequency and nonlinearity are demonstrated.
Sound propagation classes for long-range assessment algorithms.
Authors: Swearingen Michelle E. , White Michael J.
Published: October 2009

Preparing noise assessments for military training activities is a significant challenge due to the short duration of the individual signals and the lack of highly detailed atmospheric conditions, due to either an absence of necessary meteorological sensors or a need to perform the assessment without prior atmospheric knowledge. To overcome these difficulties, a set of sound propagation classes has been developed. These classes narrowly define the atmospheric and ground properties and have associated mean and variance as a function of distance. This talk will provide a description of these classes and examples of how they are used.
Exact image solution approach for multiple reflections.
Authors: Bhatta Ambika , Raspopvic Miroslava , Denis Max , Thompson Charles
Published: October 2009

In this paper a modified method using the solution of the Laplace transform based formulation for the Sommerfeld integral to determine the strength of image sources and boundary reflections is presented. It is shown that multiple reflections can be expressed in terms of elemental branch integrals. This formulation allows for a rigorous derivation of the pressure field using numerical methods.
Turbulence-shear interaction pressure contributions to wind noise.
Authors: Raspet Richard , Yu Jiao , Webster Jeremy
Published: October 2009

In an earlier paper [Raspet et al., J. Acoust. Soc. Am. 123, 1260–1269 (2008)], the mean shear-turbulence interaction pressure predicted by George et al. [J. Fluid Mech. 148, 155–191 (1984)] was calculated for outdoor wind noise measurements. It was found that the mean shear-turbulence interaction pressure predictions overestimated the spectral levels at low wave numbers and were not consistent with measurements. A new calculation based on Kraichnan’s method [J. Acoust. Soc. Am. 28, 378–390 (1956)] includes two significant improvements: It uses a logarithmic wind velocity profile instead of a linear wind velocity profile, and it models the reduction in the vertical turbulence spectrum as the ground surface is approached. The effects of the change in vertical spectrum with height and the curvature of the wind profile are analyzed by comparing the two calculations. The height dependence of the predicted turbulence-shear interaction pressure spectrum is also calculated. The predictions with the improved method agree with measurements made within large (1.0 m) wind-screens. [Research supported by the U.S. Army TACOM-ARDEC at Picatinny Arsenal, NJ.]
Computational thermoacoustics in fibrous media.
Authors: Jensen Carl , Raspet Richard
Published: October 2009

A computational method for investigating the thermoacoustic properties of fibrous media has been developed that simulates the time-varying acoustic flow through the micro-geometry of fibrous material samples. The fibrous sample is represented in the simulation as an array of straight, cylindrical fibers, and a lattice Boltzmann based thermal fluid solver is used to calculate the response from an acoustic signal passing through the modeled geometry. It was found in development that the boundary conditions at solid surfaces must be represented to high accuracy as well as providing sufficient resolution to capture boundary layer effects near the walls and throughout the domain. These issues place limits on memory capacity that restricts the use of the method on samples of higher porosity. These issues will be discussed, and some results of the simulations will be presented.
Talker recognition using envelope modulation spectra.
Authors: LeGendre Susan J. , Liss Julie M. , Lotto Andrew J. , Utianski Rene
Published: October 2009

The envelope modulation spectrum (EMS) is a spectral analysis of the low-rate (0–10 Hz) amplitude modulations of the envelope for the entire speech signal and within specific frequency bands. Using a set of predictor variables computed from these spectra, LeGendre et al. [J. Acoust. Soc. Am. 125, 2530–2531 (2009)] were able to classify sentences by dysarthric subtypes with a remarkable degree of accuracy, presumably because the EMS encodes rhythmic perturbations characteristic of each subtype. In the current study, we tested whether the EMS encodes perturbation differences within a subtype by attempting to classify sentences according to individual talkers. Stepwise discriminant analyses were performed on five sentences produced by 12 speakers with ataxic dysarthria. The 60 sentences were accurately assigned to talker 93% of the time. Thus, individual patterns of motor disruption are readily observed in the speech amplitude envelope. A similar analysis was performed with a set of normal control speakers and, again, classification of sentence by talker was remarkably high. These results suggest that talkers have idiosyncratic rhythmic patterns in their speech production that are independent of linguistic content (which was controlled in this study). The EMS may be a useful measure for talker recognition. [Work supported by NIH/NIDCD].
A time-frequency approach for studying propagation effects on underwater sound.
Authors: Loughlin Patrick J.
Published: October 2009

Sound is perhaps the primary means for communication, navigation, and exploration in the ocean, for both man (e.g., sonar) and marine animals (e.g., whale and dolphin vocalizations). The propagation of underwater sound can undergo frequency-dependent effects, especially in shallow water, which can cause the sound to change from location to location. Spectrograms, or more generally time-frequency analysis, of underwater sounds shows in a natural and dramatic way the changes that can occur as the sound propagates. In this talk, we review and illustrate time-frequency analysis of sounds, with a focus on characterizing propagation effects such as dispersion and damping. A simple but accurate time-frequency approximation method is also discussed, which suggests a feature extraction approach to obtain metrics of the sound that are invariant to particular propagation effects. These features may be useful for automatic classification of different animal vocalizations. We also show how modern time-frequency methods, such as the Choi–Williams and Zhao–Atlas–Marks distributions, can reveal detail in vocalizations that is obscured in spectrograms. [Work supported by ONR 321US.]
Identifying individual clicking whales acoustically II: From click rhythms.
Authors: Sidorovskaia Natalia , Schexnayder Philip , Ioup George E. , Ioup Juliette W. , Tiemann Christopher O. , Bernstein Alan , Ekimov Alexander , Sabatier James
Published: October 2009

Many species of marine mammals live in socially organized groups and exhibit cohesive behavior. Since acoustics is their primary communication tool, it has been suggested that acoustic signal characteristics and emission patterns carry attributes of individuals among the group. A dynamic approach for rhythmic analysis of echolocation and communication signals is presented. The algorithm provides detection of a particular species in a continuous stream of broadband acoustic data and a robust (to low signal-to-noise ratio) method for association of rhythmic frequencies with individuals. The method is applied to passive acoustic recordings collected by the Littoral Acoustic Demonstration Center (LADC). The efficacy of the method for sperm whale echolocation clicks and codas, and beaked whale clicks is addressed. The algorithm is a part of an integrated tool proposed by LADC for identification of individual animals in a group. In parallel, multi-attribute similarity analysis and source localization are applied to the same volume of data. The results are integrated and compared to provide reliable identification. The proposed approach is beneficial for passive acoustic studies of marine species population and social behavior and may contribute to understanding acoustic communication among marine mammals. [Research supported by the Louisiana Optical Network Initiative, ONR, and SPAWAR.]
What has been learned by tracking flying bats from their sonar broadcasts.
Authors: Simmons James A.
Published: October 2009

Echolocating bats are active at night, often in total darkness. Although thermal-imaging infrared video is effective for documenting the unexpected diversity of bat activity, the cost and availability of cameras is a big limitation. Infrared strobe-flash photography or night-vision video both require illumination of the scene, which means the site of bat activity has to be known in advance. By far, most observations of bat behavior have been conducted acoustically, using bat detectors for listening to biosonar broadcasts or for plotting the time-frequency structure of the sounds to identify species. In the past decade, ultrasonic microphone arrays have come into use for tracking the flight of bats. Some methods involve widely spaced microphones for three-dimensional reconstruction of flight-paths in large spaces enclosed by the array. Other methods are more focused, using arrays to pinpoint the location of the sounds from off to the side, sometimes using two arrays and triangulation of the sounds sources. Important findings have emerged about the bat’s sense of surrounding space and orientation of the sonar beam during flight. Acoustic-array methods coordinated with video recordings reveal new details about how bats look at scenes or interact when flying in groups. (Work supported by ONR and NIMH)
Low-frequency seismo-acoustic propagation near thin and low-shear speed ocean sediment layers.
Authors: Collis Jon M.
Published: October 2009

Accurate and efficient prediction of propagation over realistic models of elastic ocean sediments has been achieved recently using parabolic equations. A concern has been low-shear wave speed sediments that can become singular as the wave speed tends toward zero. A historic approach for treating a sediment of this type has been to assume that it is a fluid and that effects due to elasticity are negligible. This approach does not account for second order effects such as energy loss due to frequency-dependent attenuation. In addition, thin sediment layers typical of that found at the ocean bottom interface have been difficult to treat numerically. At low frequencies, layers of this type can be treated as a massive interface between the water and higher-shear speed sediment basement layers. To satisfy interface conditions across the layer, Rayleigh jump conditions are imposed [F. Gilbert, Ann. Geophys. 40, 1211 (1997)]. A consequence of this approximation is that interface and other wave types become dispersive where they were not previously. In this presentation, the massive elastic interface is benchmarked with an elastic parabolic equation and the effects of resultant errors are quantified. In addition, the energy partition between compressional and shear energies is determined.
Qualification of anechoic chambers: 70 years on and we are still trying to get it right.
Authors: Cunefare Kenneth A.
Published: October 2009

There are now three equally “acceptable” techniques in common use for qualification of anechoic and hemi-anechoic chambers. The historical approach for modeling the inverse square law decay uses the measured sound pressure level at a given reference position from the source and applies the inverse square law therefrom to compute “theoretical” levels at other distances. A second approach, explicitly embodied in ISO 3745:2003 Annex A, seeks to estimate a source strength and source center offset location that yields a theoretical decay that matches the observed decay in a least-squares sense. This method is motivated by the concern that the true acoustic center of a sound source may not coincide with a visually identifiable point on or near the source. More recently, a third method has come into use which determines an apparent source strength that maximizes the qualified span of a traverse. Nonetheless, the 3745 standard does not constrain the analysis routine, such that one can fully conform to the standard through use of any of these three methods (or other!) and yet obtain different results from the same data. The challenges of qualification are all the more confounded by issues related to sound sources, signal type, and spatial resolution.
Effect of placement of test hardware on measured sound pressures in a hemi-anechoic chamber.
Authors: Ristroph Einar G. , Black Michael C. , Phillips John A.
Published: October 2009

Anechoic chamber design includes a focus on minimizing interior exposed reflective hardware such as doors, integrated test fixtures, fire suppression and safety systems, etc. Albeit, a limited amount of exposed reflective hardware is unavoidable. Oftentimes additional specimen and microphone positioning equipment is put into the chamber for actual testing after the acoustic field has been qualified by experts. The effects of reflective objects typical of specimen or microphone positioning systems on measured steady-state sound pressure levels was evaluated experimentally using collinear measurements at successive distances away from a sound source, both with and without reflective objects of specific geometries and positions relative to source and receiver placed in the acoustic field. The size and position of the reflecting objects were varied. Results are presented, and from these data, acoustic experimental design guidelines are derived.
Inter-laboratory variation in sound power levels in qualified reverberant rooms.
Authors: Stabley Robert
Published: October 2009

Reverberant acoustic test facilities can be qualified to determine the sound power levels of broadband and tonal noise sources using the procedures defined in Air-Conditioning, Heating and Refrigeration Institute (AHRI) Std. 220, “Sound Power Testing Using Reverberant Rooms for HVAC Equipment.” Member companies from AHRI’s Technical Committee on Sound participated in a round robin test program in which tonal noise sources were shipped to, and tested in, a number of qualified reverberant rooms. This report summarizes the results of this effort. The mean and standard deviations of the sound power levels for multiple locations/orientations of the noise sources in each facility and for all facilities are presented. The standard deviations as a function of frequency for these sources were found to be generally less than the values established for broadband sources and therefore less than those allowed for tonal sources. Based on the comparisons of round robin test results, accurate determinations of sound power levels can be made using the substitution method in rooms qualified in accordance with AHRI Std. 220, Technical Committee on Sound, Air-Conditioning, Heating, and Refrigeration Institute
Statistics of the forward field propagated through three-dimensional random internal waves in an ocean waveguide.
Authors: Ratilal Purnima , Chen Tianrun , Makris Nicholas
Published: October 2009

Internal waves randomize the forward propagated acoustic field in both continental shelf and deep water environments. This has implications in underwater communications and remote sensing using wide area sonar systems. Here, we derive compact analytic expressions for the mean, variance, mutual intensity, spatial covariance, and temporal coherence of the acoustic field propagated through three-dimensional (3-D) random internal waves. These take into account multiple forward scattering effects and are derived in terms of the statistics of the internal waves. For typical continental shelf environments, we show that when internal wave height exceeds the acoustic wavelength, the acoustic field becomes so randomized that the expected total intensity is dominated by the field variance beyond moderate ranges. This leads to an effectively saturated field that decays monotonically and no longer exhibits the periodic range-dependent modal interference structure present in nonrandom waveguides. 3-D scattering effects become important when the Fresnel width exceeds the cross-range coherence length of the internal wave field. Our derivation makes it possible to predict the coherence time scale of field fluctuations in ocean-acoustic measurements from knowledge of the oceanography. It is used to explain the time scale of acoustic field fluctuations observed at megameter ranges in various deep ocean-acoustic transmission experiments.
Robust observables for mode tomography.
Authors: Chandrayadula Tarun K. , Wage Kathleen E. , Mercer James A. , Howe Bruce M. , Andrew Rex K. , Worcester Peter F. , Dzieciuch Matthew A.
Published: October 2009

Deep water tomographic inversions should include the low modes to improve estimates of the axial sound speed. Unfortunately, the low-mode signals are strongly affected by internal wave fluctuations, making it very challenging to estimate their arrival times. This talk describes the use of matched subspace detectors (MSDs) to measure mode travel times for ranges up to 400 km. The MSD approach was first proposed by Scharf and Friedlander [IEEE Trans. Signal Process. 42, 2146–2157 (1994)] as a way to detect signals that lie within a particular subspace. In this work the subspace for each mode is defined by analyzing simulations of mode propagation through independent realizations of the internal wave field. Simulations show that the MSD-based travel time estimation approach yields higher accuracy and less variance than other methods such as peak-picking. The end result is improved inversions for sound speed near the sound channel axis. In addition to the simulation study, mode signals from the 2004 Long Range Ocean Acoustic Propagation EXperiment (LOAPEX) are used to invert for the sound speed profile (SSP) across the LOAPEX path. The inverted SSP is compared with environmental measurements made during LOAPEX. [Work sponsored by ONR.]
Arrival time variations of pulses in shallow water and low-frequency acoustical underwater positioning.
Authors: Katsnelson Boris , Badiey Mohsen
Published: October 2009

Variations in acoustic arrival time in shallow water are presented to establish a method for long range underwater acoustical positioning systems (UWPSs) with possible applications for underwater vehicles. At the present time, there are different methods used for UWPS for only short distances (about a few hundred meters), relating the sound signals to distance based on ocean physical properties. It is possible to use arrival times of high-frequency signals (up to 100 kHz) radiated by a set of reference sound sources (such as 3–4), placed at different points in an area to determine the position. However, the main problem for long range positioning (i.e., operation area of several hundred to thousand kilometers) is significant spatial and temporal variabilities of waveguide environmental properties affecting the signal travel time. To establish limits for low-frequency acoustical UWPS, here we use recent field observations in the SW06 experiment to estimate signal arrival time variations caused by different hydrodynamic conditions observed simultaneously during acoustic transmissions. Based on preliminary mapping of the operation area, and the subsequent optimization, the accuracy related to the waveguide dynamics is presented. [Work supported by ONR321OA and CRDF.
Response of ultrasound contrast agents to static overpressure.
Authors: Chitnis Parag V. , Lee Paul , Mamou Jonathan , Ketterling Jeffrey A.
Published: October 2009

This study investigated the static pressure threshold for contrast agent (CA) rupture. Polymer-shelled CAs (mean diameter of 3 μm) with a constant shell-thickness-to-radius ratio (STRR) were subjected to overpressure in a cylindrical test chamber containing an optical window on its top and bottom faces. A video-microscope (50× magnification, 128 μm FOV, 1 Mpixel CCD) was used to image the CAs while static pressure was increased from 0.5-22 psi by pumping water into the chamber at a constant flow rate. An image processing algorithm was used to determine the change in diameter as a function of static pressure for each CA (total of 130). The majority of CAs did not respond to static overpressure until the threshold for shell rupture was exceeded, resulting in abrupt destruction. The probability density function of rupture pressures exhibited four lobes and four subsets that were obtained by a k-means algorithm. Measurements indicated that mean rupture pressures in each group were independent of CA diameter. This observation is in agreement with the classical theory for a perfectly spherical shell, which predicts that the critical compression load is a function of STRR and not of the diameter alone. [Work supported by NIH EB006372.]
The relationship between acoustic backscattering and heating during bubble mediated high intensity focused ultrasound.
Authors: Zhang Peng , Porter Tyrone
Published: October 2009

It has been demonstrated that cavitating bubbles can increase the heating rate during HIFU thermal ablation. We are developing a pressure-sensitive phase-shift nanoemulsion (PSNE) to nucleate acoustic cavitation in a controlled manner. In this study, we demonstrate the ability to nucleate cavitation with PSNE dispersed throughout acrylamide gels. This allowed us to investigate the acoustic power scattered and radiated by cavitating bubbles in a controlled manner. PSNE was vaporized with short pulses from a 1.133–MHz-HIFU transducer. An spherically focused broadband transducer (10 kHz–20 MHz) positioned coaxially with the HIFU transducer was used to receive emissions from bubbles located at the overlapping foci. The rf signal from broadband transducer was split into two channels. One was filtered with a 10-MHz high-pass filter while the other was not, to record emissions from inertial cavitation (IC) and total backscattered signal, respectively. The temperature change was measured with a thermocouple embedded in gels. A strong correlation was found between temperature change, IC emission, and total backscattered acoustic energy. The relationship between temperature change and bubble density was studied by changing the amount of PSNE suspension added to the gel. Finally, the roles of scattering and IC in the heating effect were discussed.
Acoustic droplet vaporization for enhancement of thermal therapies.
Authors: Carson Paul L. , Zhang Man , Fabiilli Mario L. , Kripfgans Oliver D. , Haworth Kevin J. , Roberts William W. , Fowlkes J. Brian
Published: October 2009

Vaporization of superheated microdroplets of perfluorocarbon can be triggered by transcutaneous ultrasound for the local production of gas bubbles. Acoustic droplet vaporization (ADV) was performed in the canine renal artery or segmental artery for blood flow control by capillary occlusion to accelerate rf ablation exclusively in the target vascular bed and for future trapping of released drugs. Occlusions of 82% were obtained for >20 min in the two best exteriorized canine kidneys with intracardiac droplet injections. Intravenous injection studies avoided induced cardiac arrhythmias. In four of the six IV studies, mean achieved renal artery flow reduction was 75% for 3 min. Perfusion by colored microspheres showed larger regional reductions in some cases. Droplets that administered IV or intra-arterially were vaporized by transcutaneous ultrasound in five studies with 3.5–5.5-cm tissue paths to produce increased kidney cortex echogenicity, but not substantial occlusion. Improved occlusion is expected by enhanced bubble coalescence and creation of a narrower droplet size distribution at diameters close to the transpulmonary limit. Achieved ADV bubble concentrations also appear adequate for enhancement of HIFU therapy by reflection of acoustic energy exiting the focus, increasing absorption exclusively therein, and revealing targeted tissues. [Work supported in part by NIH Grants R01-EB000281 and S10-RR022425.]
Bending waves and pressure waves in solid rods.
Authors: Hansen Uwe J.
Published: October 2009

Dimensionally identical aluminum rods are excited by a hammer impulse. One rod is suspended by rubber bands at a distance of nearly 1/4 of the length of the rod near the rod’s ends. The rod is excited near the end in a direction perpendicular to the rod axis. The other rod is supported by a clamp at the middle of the rod. This rod is excited by an impulse on the rod’s end face in the direction along the rod’s axis. In the first case the standing bending wave has a wavelength of nearly the length of the rod. In the second case the length of the standing wave is nearly twice the length of the rod. The resulting pitches observed clearly indicate that the propagation speed of the longitudinal wave by far exceeds the propagation speed of the transverse wave.
A demonstration of acoustic damping using bubbly liquid for Project Listen Up.
Authors: Wilson Preston S. , Argo Theodore F. , Greene Chad A.
Published: October 2009

Acoustic resonances are exploited in many natural and human-made systems, and demonstrations of the phenomena have been presented previously [Greene et al., J. Acoust. Soc. Am. 124, 2568 (2008); Argo IV et al., J. Acoust. Soc. Am. 125, 2625 (2009)]. In practice, resonance is always accompanied by energy loss, which limits the maximum excursion of a system. When sufficiently large, this loss can alter the resonance frequency of the system. An air bubble in water is an example of a lossy acoustic resonator and is well-suited for demonstrating acoustic damping in the Listen Up paradigm. For the proposed demonstration, students will observe the resonance of a water-filled drinking glass by striking it with a metal spoon to produce a strong ringing sound. They will then introduce damping into the system by using a stream of water to entrain bubbles which will deaden the ringing response of the system. The primary mechanism for the acoustic energy dissipation is conversion into heat during bubble oscillation. An explanation of this process is presented with a detailed description of the proposed experiment.
Effect of phonological neighborhood density on word duration in spontaneous speech.
Authors: Yao Yao
Published: October 2009

It has been widely shown that words with many phonological neighbors are harder to recognize than words with few neighbors (L. & Pisoni 1998, among others). However, the effect of phonological neighborhood density on word production is less clear. On one hand, high-density words are easier to produce (Vitevitch 1997, 2002), which suggests that they should be reduced in speech. Meanwhile, these words are often hyperarticulated, probably to make it easier for the listener (Wright 1997, Munson & Solomon 2004, Scarborough 2002). The present work aims to distinguish the two accounts by examining the effect of neighborhood density on word duration. We use data from the Buckeye corpus, which has 40 American English speakers, each recorded for about an hour. A mixed-effect model is built to predict the durations of all CVC monomorphemic content words in the corpus, with speaker and word as random effects. The results show that, after controlling for other factors, neighborhood density has a small but robust negative effect on word duration, i.e., the more neighbors a word has, the shorter it becomes. The effect of average neighbor frequency is in the same direction. Present results provide unambiguous evidence for the talker-oriented account concerning word duration.
Fine-grained control of voice-onset time production, lexical usage-frequency, and phrasal context.
Authors: VanDam Mark , Silbert Noah H. , Port Robert F.
Published: October 2009

Voice-onset time (VOT) in English maps onto the phonological categories voiced or voiceless, but fine-grained control of VOT production may vary as a function of additional linguistic features (e.g., lexical frequency, phrasal context, indexical features). This study investigated the patterns of VOT production in words that varied (a) by lexical usage-frequency (high versus low) and (b) in selected linguistic contexts (isolation, carrier phrase, unfamiliar phrase, familiar phrase). Results show that talkers produced longer VOT for voiceless stops in low-frequency words in unfamiliar and familiar phrases but not in isolation or carrier sentences. Neither lexical frequency nor phrasal context seemed to induce changes in VOT in voiced stops. Thus, it appears that talkers make use of fine temporal distinctions within the voiceless category but not the voiced. This suggests a complex asymmetry in how continuously varying VOT maps onto more discretely varying phonological categories.
Gestural drift in Serbian-English speakers.
Authors: Tobin Stephen
Published: October 2009

Following Tobin [J. Acoust. Soc. Am. 125, 2757 (2009)], perceptually guided changes in speech production were examined in a group of Serbian-English speakers. Participants were recorded producing Serbian and English sentences after periods of time in the US and in Serbia. Voice onset times (VOTs) and vowel formants were examined with the aim of determining whether gestural targets as well as patterns of gestural timing are affected by exposure to a language. It is predicted that in both Serbian and English, VOTs will be longer after time in the US and shorter after time in Serbia. Based on comparisons of available American English and Serbian vowel formant data, it is expected that F1’s will increase and F2’s will decrease after time in Serbia while F1’s will decrease and F2’s will increase after time in the US. The results will be compared with those of Tobin’s Spanish-English speakers and discussed with relation to recent research on phonetic convergence, attunement, and articulatory setting.
Preliminary report of devoiced vowels in Chinese.
Authors: Shirai Setsuko , Yang Li-Chin , Lai Yuda
Published: October 2009

This is the preliminary report of the devoiced vowels in Chinese spoken in Taiwan. We are currently investigating the environments of devoiced vowels. We recorded the sentences read by ten Taiwanese who were born and grew up in the center of Taiwan. The sentences ended with high vowels ([i] or [u]) following aspirated consonants. The tones of these final vowels varied. We observed no voice marks after the final consonants in some sentences. In addition, some vowels consist of a couple of waves. The observed devoiced vowels are as follows: [i] in [xuechi] “wiping out of disgrace,” [cuopi] “turf,” [dajuchi] “big molar tooth,” and [ruci] “in this way,” and [u] in [dongdoufu] “dried tofu.” Although these devoiced vowels were observed, not all speakers produced these devoiced vowels. The highly devoiced vowel was [i] in [xuechi] “wiping out of disgrace,” whose final vowel [i] four out of ten speakers devoiced. In addition, the vowels produced by other two speakers consist of only two waves. Furthermore, we observed a very short vowel in the middle of the sentence (the first [u] in [tuputaopi] “spit out the skins of grapes”).
Acoustic and ultrasound investigation of English vowel-to-vowel coarticulation.
Authors: Yip Jonathan C. , Beddor Patrice S.
Published: October 2009

This study examined the hypothesis of whether vowel-to-vowel coarticulation effects are stronger when a particular vowel segment is under focus in clarified speech than when it is not under a condition of focus. In one condition, native speakers of American English produced disyllabic word pairs that varied in the quality of their first vowel (stressed V1), while in the second condition, the same group of speakers produced the word pairs that varied in the quality of their second vowel (V2). The degree of coarticulation was determined by the amount of spectral and/or articulatory displacement that occurred during the production of V2-position [schwa] due to the influence of V1. Due to the need to increase the likelihood of coarticulatory effects during speakers’ productions, recording trials were sped up to a conversational speaking rate. Spectral measurements (first and second formants) of ə in both conditions were taken, as well as tongue-surface position measurements pertaining to the position of tongue body during the production of ə under the two conditions. Preliminary acoustic analysis indicates that speakers produced V2-position ə with greater coarticulatory effects in the V1-clarifying condition than in the V2-clarifying condition.
Physically constrained maximum-likelihood mode filtering and its application as a pre-processing method for underwater acoustic communication.
Authors: Papp Joseph C. , Preisig James C. , Morozov Andrey K.
Published: October 2009

Mode filtering is most commonly implemented using the sampled mode shapes or pseudo-inverse algorithms. [Buck et al. (1998)] placed these techniques in the context of a broader maximum a posteriori (MAP) framework. However, the MAP algorithm requires that the signal and noise statistics be known a priori. Adaptive array processing algorithms are candidates for improving performance without the need for a priori signal and noise statistics. A variant of the physically constrained, maximum-likelihood (PCML) algorithm [Kraay and Baggeroer (2007)] is developed for mode filtering that achieves the same performance as the MAP mode filter yet does not need a priori knowledge of the signal and noise statistics. The central innovation of this adaptive mode filter is that the received signal’s sample covariance matrix, as estimated by the algorithm, is constrained to be that which can be physically realized given a modal propagation model and an appropriate noise model. Simulation and data processing results from the Shallow Water 2006 experiment are presented along with the application of the mode filter as a broadband pre-processor for multichannel underwater acoustic communication systems. [This work was supported by ONR through ONR Grant Nos. N00014-05-10085 and N00014-06-10788.]
Minimum Hellinger distance classification of passive underwater acoustic signals.
Authors: Bissinger Brett E. , Culver R. Lee , Bose N.K.
Published: October 2009

Passive source classification in the underwater environment is a challenging problem in part because propagation through the space- and time-varying media introduces variability and uncertainty in the signal. Acoustic propagation codes can predict received fields accurately but they are sensitive to input environmental parameters which cannot be known exactly. This uncertainty in environmental knowledge used in signal predictions results in imperfect statistical class models. Classifiers that rely on simulations of the environment must therefore be robust to imperfect statistical models. Maximum likelihood methods provide ideal performance when the class models are correct but their performance quickly deteriorates when class models are imperfect. Minimum distance methods generally offer robustness to mismatches at the expense of performance, with that trade-off governed by the distance metric used. Several well-studied distance metrics are discussed and it is explained how the Hellinger distance offers robustness to outliers while retaining the performance of a maximum likelihood method, properties that make it well-suited for classification of passive underwater acoustic signals. Examples are provided to quantify the robustness properties of the Hellinger distance when applied to classification of passive underwater acoustic signals and compare its performance to the maximum likelihood method. [Work supported by ONR Undersea Signal Processing.]
Underwater channel estimation and tracking using mixed norm optimization techniques.
Authors: Sen Gupta Ananya , Preisig James
Published: October 2009

A mixed norm optimization technique to track the impulse response of the underwater acoustic channel is presented. The channel is assumed to follow a delay-Doppler spread function model, which is known to be sparsely distributed over the complex channel coefficients. The ill-conditioned nature of this estimation problem, along with the need to optimize over a complex field, poses challenges to employing popular sparse estimation techniques that currently exist in the literature. The time-varying nature of the underwater channel also makes efficient tracking difficult. The motivation behind our proposed algorithm is to robustly estimate and efficiently track the sparse delay-Doppler coefficients directly over the complex field. We have formulated the channel estimation problem as that of minimizing over a convex combination of the L1 norm of the sparse coefficients to be estimated and the L2 norm of the estimation error. We analyze the difference between our proposed algorithm to existing L2-constrained L1 optimization techniques and present results showing performance on simulation generated and field data. [Work supported in part by ONR Grant Nos. N00014-05-10085 and N00014-07-10184 and in part by Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution, with funding provided by the Doherty Foundation.]
Underwater speed of sound and ranging measurements using the sliding discrete Fourier transform.
Authors: Assous Said , Hopper Clare , Lovell Mike , Linnett Laurie , Gunn David , Jackson Peter , Rees John
Published: October 2009

It is often desirable to extract parametric information from a signal in order to determine its properties with high accuracy. Such parameters might be the time delay, the amplitude, the frequency, and/or the phase. These parameters are usually highly correlated with the material through which the signal has passed or from which it has been reflected. Time delay estimation is a fundamental step in source localization or beamforming applications, and has attracted considerable research attention over the past few decades in many fields. In this paper, we propose a novel time delay estimation approach based on the sliding discrete Fourier transform (DFT). The analysis window is slid sample by sample over the received single frequency tone burst signal with the DFT evaluated successively. The optimal peak spectrum and its corresponding phase are used to estimate the time delay of the signal. We use the corresponding time as the first estimate, which is improved based on the related phase. Simulated examples are given with synthetic signals. An underwater application for speed of sound measurements using this approach compared to those obtained by a commercial device is then demonstrated. Finally, the proposed method is shown to outperform standard correlator-based approaches.
Noise performance of a novel total least squares approach to source location estimation.
Authors: Frazier Wm. Garth , Gilbert Kenneth E. , Di Xiao
Published: October 2009

One of the advantages of the time-of-arrival (TOA) representation for the source location problem is that it can be formulated such that the unknown variables appear linearly in the describing equations. It is known that to obtain a unique three-dimensional solution four measurements are required in the TOA case. Typically, more measurements than the minimum are available and this naturally leads to an over-determined problem for which an optimal estimate is sought. One method of solution is weighted least-squares (LS). The noisy measurements include the TOAs of the impulse at each acoustic receiver as well as the locations of the receivers. In the linear formulation these measurement values appear on both sides of the equation Ax=b, and not just on the right side. Application of a linear total least-squared (TLS) error method permits representation of the uncertainty on both sides of the equation. Moreover, the additional computations required in the TLS approach are not significantly greater than the LS approach. In this paper, we examine the noise performance of TLS solutions and demonstrate the significant reduction in bias obtained over the LS approach at the expensive increased sensitivity. Results from simulation and field experiments are provided.
Statistical characterization of bistatic acoustic clutter from a shipwreck in the 0.8–3.5-kHz region.
Authors: Preston John, R.
Published: October 2009

Sonar clutter is defined as target like echoes that are detected and tracked by automated signal processors. Sonar clutter is one of the primary limitations to active ASW. Some statistical analysis of clutter from bistatic measurements will be presented. The received data are taken from the Five Octave Research Array that has been used to collect extensive monostatic and bistatic data in two recent sea trials on the Malta Plateau off Sicily called Clutter 07 and BASE 07. Statistical characterizations of bistatic clutter from and near a shipwreck are presented. Related work by D. Abraham focused on monostatic characterizations of clutter. This work uses data from the above mentioned sea trials to characterize non-Rayleigh behavior of bistatic clutter from pulsed sources and to compare bistatic clutter with monostatic clutter. K-distributions with their shape and scale parameters are used to describe non-Rayleigh behavior together with the models of Abraham and Lyons to infer scatterer densities. The ability to geo-reference key statistical measures of clutter near the shipwreck that can allow CFAR processors to properly set thresholds and reduce false alarms is demonstrated. Also included are presentations of the shape parameter versus bistatic aspect angle. [Work supported by ONR code 321US.]
Cost efficient sensor placement and configuration to fulfill spatially inhomogeneous coverage preferences.
Authors: Vecherin Sergey N. , Wilson D. Keith , Pettit Chris L.
Published: October 2009

Finding a most cost efficient sensor network to fulfill specified coverage requirements is an important practical problem. Current research presents a strict formulation of this problem as the binary linear programming problem. The solution addresses the questions of how many, what type, and where to place sensors to fulfill arbitrarily complicated coverage preferences with minimal cost. Cost can reflect different sensor attributes, e.g., actual sensor values, their number, or accessibility of the terrain in which they are placed. Sensor performance is evaluated in terms of a detection probability and is applicable to any type of sensor, including acoustic. Geometrical spreading and attenuation of a signal from its source to a sensor are taken into account when calculating detection probability. For large spatial grids of candidate sensor locations, it is infeasible to determine the strict, optimal solution. To overcome this problem, a fast algorithm is presented for finding a suboptimal, but highly satisfactory, solution. The algorithm accommodates many practical needs, such as sensor availability, relocation of existing sensors to improve their coverage, and sensor-to-sensor communication. The efficiency of the algorithm is demonstrated through a comparison with another heuristic sensor placement strategy that places sensor one-by-one in the previously worst covered spots.
Using wireless networks for real-world acoustic measurement applications.
Authors: Veggeberg Kurt
Published: October 2009

Wireless technology extends the concept of personal computer based data acquisition beyond the limits of cables and wired infrastructure for new remote or distributed measurement applications. This is an overview of wireless networking basics and how to deploy reliable wireless measurement in a variety of outdoor or harsh environments for reliable and secure data acquisition systems. Examples of distributed outdoor noise monitoring systems will illustrate networking layers and topologies for specific applications using IEEE 802.11 networks for reliable and secure wireless data acquisition systems. These include a distributed, synchronized data acquisition system for the extended measurement of sonic booms and a portable noise and vibration management system with multiple front ends connected wirelessly throughout a construction site to be compliant with local regulations and contractual obligations for noise and vibration levels.