bluuebunny/crossref_metadata_2025 huggingface dataset:
Rain noise level measurements in a performing arts center
Authors: Coffeen Robert C.
Published: September 2008

Noise level measurements made in a performance hall and in related spaces with subjectively described light, moderate, and heavy rainfall on the facility roof are presented in octave frequency bands, and as described by associated A weighted sound pressure levels and noise criteria (NC) ratings. Rain noise levels are also compared with HVAC noise and ambient noise without the HVAC system operating.
Comparison of interior noise levels produced by rain impinging on several commercial roof constructions
Authors: Coffeen Robert C.
Published: September 2008

Noise produced within architectural spaces by rain on roofs is difficult to quantify, due to varying rain intensity, water drop size and velocity, roof construction, and interior acoustical characteristics. However, it is possible to compare interior rain noise levels when rain conditions and the interior space conditions are constant. This paper compares rain noise levels for several commercial roof constructions with noise level measurements and rain generation in general conformance with ISO 140-18 ‘‘laboratory measurement of sound generated by rainfall on building elements.’’ [This research was conducted through the School of Architecture and Urban Planning at the University of Kansas.]
Optical spectroscopy of transient cavitation at high pressure
Authors: Hiller Robert , Gaitan Felipe , Tessien Ross , Alstadter Jeff
Published: September 2008

The UV-VIS spectrum of light emitted from transient cavitation events in a high-pressure acoustic resonator is measured to determine the contents and state of matter in the plasma hot spot at the collapse. Spectra are measured for spontaneous cavitation events in water and other liquids at static pressure up to 300 bar, both degassed and with various gases dissolved in the liquid. Spectra are captured with a grating monochromator using a gated detector, or multiple detectors with bandpass filters, to partially resolve the temporal structure of the emission event. These data are used to estimate the temperature and duration of the implosion. [Work supported by SMDC Contract No. W9113M-07-C-0178.]
Measurement of shock velocity from cavitation collapse in high static pressure liquids using Schlieren and shadowgraphy
Authors: Schaefer James , Tessien Ross A. , Gaitan D. Felipe
Published: September 2008

High amplitude shock waves due to collapse of a cavitation bubble were photographed using a high power pulsed laser diode driven with an avalanche transistor pulser. The strong implosions of high pressure bubble cavitation travel initially at several times the local speed of sound. This method was used to measure shock wave velocity in water at static pressures up to 300 bars. The photographs were taken between 30 and 60 ns of the bubble implosion. Schlieren and shadowgraphy techniques were used and compared. The purpose is to characterize the pressure conditions that exist shortly after the implosion of a high pressure sonoluminescence bubble. [Work supported by SMDC Contract No. W9113M-07-C-0178.]
A model for the interaction of clustered bubbles and particles under acoustic excitation
Authors: Hay Todd A. , Hamilton Mark F.
Published: September 2008

An analytical model has been presented previously for the interaction between a spherical bubble and a spherical particle [e.g., Hay and Hamilton, J. Acoust. Soc. Am. 120, (2006)]. The present work extends this model to the case of a cluster of spherical bubbles and particles that are free to pulsate and translate. The bubbles and particles may be of arbitrary size, the particles may be elastic or rigid, and the external acoustic source excitation is included to an order consistent with the accuracy of the model. Effects of liquid compressibility are included in the equations of radial motion, and bubble coalescence is taken into account according to a set of conservation relations. Numerical simulation results will be presented for a number of cluster configurations and source excitations relevant to practical applications, such as shock wave lithotripsy. [Work supported by the NSF Graduate Research Fellowship.]
A methodological note on signal-to-noise ratios in speech research
Authors: Van Engen Kristin J.
Published: September 2008

In speech-in-noise tests that utilize a range of signal-to-noise ratios (SNRs), SNR is usually manipulated either by changing the noise level relative to a constant signal level or by changing the signal level relative to a constant noise level. In the HINT, for example, noise level is held constant while target sentence level changes. Such manipulations entail differences in overall energy delivered to the ear across SNR conditions. It is possible, then, that overall energy changes are partially responsible for behavioral differences observed across SNRs. For example, [Van Engen and Bradlow (2007)] showed that English 2-talker babble was more detrimental than Mandarin 2-talker babble for English sentence recognition by native English listeners at difficult SNRs, where SNR was varied by raising the noise level with respect to the target sentence level. In the present study, it is shown that releveling the mixed signal and noise files to a single output level across SNRs yields similar results. Thus, the interaction of the noise language effect with SNR observed in the previous study and the general difference across easy (0 dB) and hard (−5 dB) SNRs cannot be attributed to overall energy changes across SNRs, but rather reveal speech-in-noise processing effects.
Articulatory coordination and real-time spoken word recognition
Authors: Choi Susie , Byrd Dani
Published: September 2008

This study investigates how listeners use information regarding articulatory timing in consonant sequences during lexical access. Research in spoken word recognition of assimilated consonant sequences has shown that listeners make use of detailed variation in the acoustic signal and knowledge of systematic phonological variability [e.g., Gaskell and Marslen-Wilson (1996), Gow and McMurray (to appear)]. However, no earlier work has reported on real-time processing of consonant sequences for which articulatory data is available. This study combines articulator movement-tracking with real-time eye-movement monitoring to relate the articulatory timing properties associated with assimilation with use of the resulting acoustic signal in word recognition. Using magnetometry, words to be used as stimuli in an eye-tracking task are recorded. These contain consonant sequences with a continuum of intergestural overlap obtained by varying prosody and speech rate. In the eye-tracking experiment, listeners hear two-word stimuli such as ‘‘bad ban,’’ some of which are perceived with an assimilated final consonant in the first word, and select a picture that matches the stimulus. The recorded eye movements provide a window into real-time processing [see Altmann and Kamide (2004)], allowing us to investigate listener behavior in using articulatory timing cues for lexical access. [Supported by NIH.]
The interaction of respiratory drive and linguistic structure
Authors: McGuire Grant , Tilsen Sam
Published: September 2008

During high respiratory drive competition between the need for oxygen and the needs of speech breathing are in conflict. This conflict provides a way of exploring linguistic structure in two domains. Syntactically, talkers must breath more frequently such that inhalations occur within sentences, a rarity in Collins 1979, Doust & Patrick 1981, Bailey & Hoit 2002). Phonetically, high respiratory drive provides competition between between the high expiratory airflow rates needed to purge carbon dioxide and the high subglottal pressure necessary for phonation. This paper presents acoustic and physiological data from a study where American English talkers are exercised until in high respiratory drive and asked to read a syntactically-controlled passage. Preliminary results suggest that even in high respiratory drive, subjects respect constituency structure such that higher level phrase boundaries are correlated with more frequent inhalations. Further, subjects show less control over vocal fold control and must periodically exhale excess carbon dioxide, resulting in acoustic effects on the preceding word.
Accuracy and response times in identifying foreign accents: Are listeners all over the map?
Authors: Shah Amee
Published: September 2008

The present study aims to increase the understanding of how listeners process different foreign accents. Specifically, listeners were presented with 50 varieties of foreign accented speech samples and asked to point to the general area on a world map where they thought the accent was from, and also provide a label/name for the accent. Accuracy and response times were obtained for both methods of accent-identification, and a correlation between these two methods was performed. Errors in identification were further analyzed to investigate the consistent patterns of confusion across listeners’ scores. Prosodic similarities across certain types of accents, or geographical proximities across these confusable accents were further studied as potential sources of the consistent patterns of confusion across some accents. Furthermore, listener-related variables, including age, education level, travel experience, linguistic and phonetic experience, and musicality were analyzed further to determine each of their roles in influencing the accuracy in identification of foreign accents. Results help to understand the variables involved in processing foreign accented speech, and crucially, to determine the kinds of segmental, prosodic, and/or extralinguistic information listeners use to represent and store the different varieties of foreign accents in their memory.
Enhancing learning on foreign-accent adaptation with a combination of active training and passive stimulus exposure
Authors: Baese Melissa , Bradlow Ann , Wright Beverly A.
Published: September 2008

Improvement on most perceptual tasks requires active performance of the target task during training. However, there has been little consideration of whether that active performance is necessary throughout the entire practice period. Suggesting that it is not, there is recent evidence that active performance on a simple frequency-discrimination task, interleaved with passive stimulus exposures, can yield more learning than the active performance alone. The current study examines whether these findings extend to a speech-learning task, specifically foreign-accent adaptation. Native-English speakers transcribed sentences spoken in English by non-native speakers. Participants who performed the target task for half the training period and received passive stimulus exposures while performing a distracter task for the other half out-performed participants who received the same amount of active training, but no passive exposures during the distracter task, suggesting that passive exposures enhanced learning. The active-passive group also out-performed participants who received only passive exposures—and performed as well as a group who performed only the target task—for the entire training period. Taken together, these results suggest that the combination of active training and passive stimulus exposure may play a key role in real-world perceptual learning for speech. [Work supported by NIH/NIDCD.]
Augmented visual feedback in second language learning: Training Japanese post-alveolar flaps to American English speakers
Authors: Levitt June S. , Katz William F.
Published: September 2008

Recent studies suggest beneficial effects of kinematic feedback in the articulatory training of individuals with speech disorders [Katz et al. (2002)]. To better understand the nature of speech motor learning in healthy individuals, the present study examines how adult monolingual speakers of American English learn to produce a non-native consonant: The Japanese post-alveolar flap. Eight participants were randomly assigned to one of two training groups: (1) Conventional L2 training, and (2) conventional L2 training with electromagnetic articulography (EMA)-based kinematic feedback on tongue tip position. Participants completed three baseline recording sessions, eight training sessions, and two post-training sessions (four weeks after training). During training, participants practiced a total of 16 disyllabic non-words containing the post-alveolar flap in word-initial or word-medial position. Participants practiced trained words 20× in blocked fashion, with summarized oral feedback given after every five repetitions. The data were analyzed in terms of flap consonant duration. Preliminary results indicate: (1) Before training, participants produced longer flap durations than native Japanese speakers; (2) with training, flap durations approximated native norms; and (3) kinematic feedback with EMA appears to facilitate the acquisition of novel speech sound production.
The effect of language experience on the perception of coronal stop bursts
Authors: Khan Sameer ud Dowla , Shilman Molly
Published: September 2008

The difficulty of perceiving a phonetic contrast not present in one’s native language is well known. However, there is also research showing that discrimination of non-native sounds that are sufficiently far from a listener’s language is possible even in adulthood, as in the case of English speakers discriminating Zulu clicks [Best et al. (1988)]. This raises the question of whether listeners’ ability to discriminate contrasts can hinge on whether listeners are perceiving sounds as speech or non-speech. To test whether language experience affects all auditory perception or only linguistic perception, the current study investigates the ability of Bengali and English speakers to identify isolated Bengali dental and post-alveolar stop bursts in an ABX task, where the bursts are first described as sounds in nature (i.e., non-linguistic context) and later as sounds in language (i.e., linguistic context). It is predicted that, due to the phonemic contrast of dental and post-alveolar stops in their language, Bengali speakers will perform better than English speakers in the linguistic context, and that English speakers will perform better in the non-linguistic context than in the linguistic context.
Nested autonomy—A paradigm for distributed, undersea acoustic sensing and surveillance
Authors: Benjamin Michael R. , Balasuriya Arjuna , Schmidt Henrik
Published: September 2008

Undersea surveillance networks using acoustic communication between nodes are severely bandwidth-limited. Equally critical, operational constraints often require a gateway vehicle to surface and quickly relay messages to and from the operator, with typical latencies of 10–30 min. Therefore, in contrast to above-sea systems, the data processing and control of the underwater assets cannot be performed centrally but must be distributed, and the individual and clusters of assets must be capable of autonomously exploiting the environmental acoustics and completing the mission objectives, such as detecting, classifying, localizing, and tracking (DCLT) of a target. The resulting target solution must be assembled in a track report, which must be transmitted back to the operators within the constraint of the communication system. Constrained by small individual acoustic apertures, the net-centric systems may exploit adaptive and collaborative sensing and control for enhancing system performance. Under the ONR PLUSNet program, a nested, autonomous command and control architecture is being developed, with fully integrated sensing, modeling, and control within each autonomous node and clusters of nodes. It enables autonomous adaptation to the environmental and tactical situation, and collaborative target tracking by multiple platforms. The operator controls the autonomous mission behaviors by very simple commands tailored to the limited communication bandwidth. The performance of the nested autonomy paradigm will be demonstrated by examples using a high-fidelity simulation environment, and by results from the PN07 field experiment. [Work supported by ONR.]
National Defense Industrial Association distributed netted anti-submarine warfare systems study
Authors: Casey Thomas A.
Published: September 2008

The NDIA Undersea Warfare Division was tasked by the US Navy, Director Sea Shield, OPNAV, N87 to formulate new DNS concepts to hold enemy forces at risk, to secure a friendly maneuver area, and to assure access world-wide. The new DNS concepts are focused on the Port Egress and Sea Base scenarios, end-points in the spectrum of ASW operations. The threat comprises a large number of widely dispersed, quiet, diesel-electric, AIP, and nuclear submarines in the year 2015. The study team established that new DNS concepts derive advanced capability from expansion of four critical DNS functions: Deployment, sensing, communications, and C2. Seven Port Egress and five Sea Base concepts are each described including: An operating concept, identification of critical components, description of capabilities that each concept offers, and a functional binning diagram. The new DNS concepts were ranked and scored on a set of ASW utility attributes specific to either the port egress or sea base scenario. Concepts were evaluated for potential reductions in the detect to engage sequence and enabling technologies were identified. The study summary, conclusions, and recommendations were presented to the Chairman, ASW Cross-Functional Board, RADM C. Van Mauney on 5 June 2007.
Design criteria for in-buoy geoacoustic inversion using ship noise
Authors: Turgut Altan
Published: September 2008

Recent analysis of the ship noise data from R/V Oceanus, collected during the RAGS03 winter and base 2007 summer experiments, showed that robust geoacoustic inversions are possible under both winter and summer conditions. In littoral waters, fast-traveling surface ships provide an excellent (broadband) source of opportunity to characterize the sea floor with a lightly populated vertical array. A well-mixed and stable water-column during the winter provides robust geoacoustic inversions up to 20 km in range. Under summer conditions, robust inversions are only possible up to 5 km in range, due to the near-surface mixed-layer and highly-dynamic water-column effects of internal waves. Matched-field inversion results from both RAGS03 and Base07 experiments are presented using noise data from different ships at different ranges. Design criteria of a distributed system using single-element receiver nodes for geoacoustic inversion and oceanographic monitoring are also discussed. [Work supported by ONR.]
Acoustical observation of randomly fluctuating interior of shallow oceans
Authors: Yamamoto Tokuo , Yamaoka Haruhiko
Published: September 2008

Acoustic reciprocal transmission experiments are conducted at two locations (90 m and 120 m in depth) on the outer continental shelf near New York Byte. The transmission ranges between three transceivers are 3, 4, and 5 km. The moderate-frequency acoustic sources (5.5 kHz) are used with the source level of 192 dB re 1 mcPa at 1 m. Environmental data of fine scale currents and temperature are measured by CTD and inverted ADCP. Characteristics of hydrodynamic fluctuations are determined by transmission data and simulation by a PE code. The sound transmission data and inversion results are severely randomized by the spatial and temporal fluctuations due to fluid dynamic processes, such as turbulent flows, internal waves, and internal solitons. The vertical and temporal coherence analyses are conducted as the techniques for the waveform analyses. These techniques separate the received signals into the coherent component corresponding to the mean state of current velocity and sound speed, and the incoherent component due to fluid dynamic fluctuations. [Work supported by ONR.]
A simple ocean noise exposure metric based on naturally occurring noise levels and biological thresholds
Authors: Stocker Michael , Reuterdahl Tom , Horn Libbie , Hurley Gail
Published: September 2008

Anthropogenic noise is compromising the habitat for marine mammals, fish, and, potentially, other marine organisms. Determining acceptable thresholds is confounded by the fact that marine animals have adapted to some exceedingly loud naturally occurring sounds, whereas exposure to certain anthropogenic noises at equivalent or lower amplitudes causes harm. It is clear that mitigation levels cannot be established by signal amplitude alone. This proposed metric helps establish exposure levels based on broadband and temporal representation of a subject noise compared to a set of spectral curves based on ambient noise levels and biological thresholds.
Preliminary acoustic data analysis from Littoral Acoustic Demonstration Center 2007 (LADC07) passive acoustic experiment
Authors: Sidorovskaia Natalia A. , Ioup George E. , Ioup Juliette W. , Tashmukhambetov Arslan M. , Rayborn Grayson H. , Newcomb Joal J. , Field Robert , Norton Guy
Published: September 2008

The Littoral Acoustic Demonstration Center conducted a passive acoustic experiment in the Northern Gulf of Mexico, about 120 nmi south of the Mississippi delta between July 5 and July 17, 2007. The primary objective of the experiment was to make probably the first passive acoustic recordings of beaked whales in the Gulf of Mexico. Six environmental acoustic recording system (EARS) buoys were deployed in two triangular configurations in about 1,500 m water with the hydrophones located at a 1,000 m depth. The distance between the two triangles was about 20 nmi. Each EARS buoy recorded in the frequency band of 100 Hz–96 kHz for ten consecutive days, with a total data amount collected of about 3 Tbytes. More than ten different marine mammal species were identified in the vicinity of the buoys during visual observations, which supported the experiment including three different types of beaked whales. Preliminary environmental and acoustic data analysis, including average noise curves and different species identification by using newly developed frequency-domain detectors, is presented. Assessment of the density of recorded acoustic phonations of different species is discussed. [Research supported through SPAWAR PMW-180 PE63207N.]
Multibeam and single-beam sonar observations of Atlantic herring in the Gulf of Maine
Authors: Weber Thomas C. , Pena Hector , Jech J. Michael
Published: September 2008

In September 2006, several schools of Atlantic herring were simultaneously imaged with a Reson 7125 SeaBat multibeam sonar (400 kHz) and a Simrad EK60 Scientific echo sounder (38 kHz, 120 kHz, and 200 kHz) on Georges Bank in the Gulf of Maine. One school was imaged five separate times over the span of one hour. These two sonar systems, along with pelagic trawl catch data collected on a separate ship, provided a synoptic view of the fish school as it changed depth and size, fragmented, and eventually dispersed. Of particular interest is the combination of data from the two sonars. The multifrequency, split-beam EK60 provided estimates of the fish school density directly under the ship, but was not capable of accurately extrapolating these measurements to the entire fish school, which was largely out of the EK60 field of view. The multibeam sonar was generally able to image the entire fish school and provided useful information on school volume, fragmentation, and general school morphology, but was more difficult to use for quantifiable measurements, due to the unknown angle of ensonfication of the fish in the outer beams.
Effects of otolith geometry on steady streaming flows in the fish ear
Authors: Kotas Charlotte W. , Rogers Peter H. , Yoda Minami
Published: September 2008

The dense, bony otolith contained in the fish ear oscillates relative to its fluidic surroundings in the presence of a sound wave. How the otolith actually transduces this acoustically induced fluid motion into the hair cell displacements that the fish hears is not fully understood, however. Nevertheless, it is likely that the complicated geometry of the otolith, including the groove (sulcus) where most of the hair cells are found, contributes in some fashion to shaping the flow patterns that excite the hair cells. The effect of these grooves on the induced steady streaming flows was studied experimentally using both oscillating grooved spheroids and scaled models of actual otolith sulci to simulate acoustically induced motions of the otolith for oscillation orientation angles ranging from 0 deg to 90 deg. Particle-image velocimetry and flow visualization results obtained from images phase-locked to the oscillations are presented for normalized oscillation amplitudes, ε≡s/L=0.05–0.2 and Reynolds number, Re≡ωL2/ν≊1–102, where s is the oscillation amplitude, ω is the oscillation frequency, L is a typical otolith length scale, and ν is the fluid kinematic viscosity. The effect of phase on these data was also studied. [Work supported by ONR.]
Tidal time-scale variations of sound propagation in the Hudson River Estuary
Authors: Radhakrishnan Sreeram , Sutin Alexander , Blumberg Alan
Published: September 2008

The nowcast and forecast of sound propagation in an urban estuary is important for the development of acoustic surveillance systems. Sound propagation in an estuary is highly affected by the temporal and spatial variability of salinity and temperature due to tides, freshwater inflows, winds, etc. Estuarine processes are analyzed here focusing on the formation and breakdown of the salinity and temperature stratification and their influence on sound attenuation. Transmission loss (TL) variability was determined first using real-time data collected in the Hudson River near Hoboken, New Jersey. For TL forecasting, 24-h forecasts of salinity and temperature distributions from a high-resolution New York harbor observing and prediction system (NYHOPS) developed at Stevens were used (www.stevens.edu/maritimeforecast/). These forecasts provided the basis for calculating sound speed profiles. A parabolic equation based acoustic model was implemented to simulate the acoustic field structure. Real-time TL measurements were made by transmitting sweep frequency signals (1–100 kHz) to a distance of 175 m. The observed tidal time-scale TL variation of 10 dB was in good agreement with the model calculations. The results indicate that TL can be predicted within the context of the NYHOPS system. [Work supported by ONR Project No. N00014-05-1-0632: Navy Force Protection Technology Assessment Project.]
Applying data nullspace projection method on matched-field source localization in a random internal wave field
Authors: Lin Ying-Tsong , Lynch James F. , Newhall Arthur E.
Published: September 2008

In a random internal wave field where temporal varying water-column soundspeed profiles are very difficult to measure, matched-field source localization methods can be greatly degraded due to water-column model mismatch. In this paper, the data nullspace projection is applied to this source localization technique to reduce the effect of unknown water-column soundspeed variations. The basis of this method is to project the acoustic signal onto a data nullspace that is insensitive to water-column soundspeed fluctuations. This method only requires the mean and the second-order statistics of temporal varying water-column soundspeed profiles to calculate soundspeed empirical-orthogonal-functions. It does not require measurements of the exact soundspeed field, i.e., each snapshot, for the matched-field processing. In a simulation test case, a linear wave model is used to generate a random internal wave field, an acoustic source continuously transmits a single frequency tone, and the matched-field processing is implemented with the signal received on both a VLA and a HLA, respectively, for localizing the source position. The simulation results show that applying the data nullspace projection method can dramatically improve the robustness and accuracy of the matched-field source localization, resulting in a random internal wave field.
Coherence function of a sound field in an oceanic waveguide with horizontally isotropic random inhomogeneities
Authors: Voronovich Alexander G. , Ostashev Vladimir E.
Published: September 2008

Closed equations for the coherence function of a monochromatic sound field propagating in a 3-D oceanic waveguide with random inhomogeneities were derived in many works, e.g., see [A. Voronovich and V. Ostashev, J. Acoust. Soc. Am. 119, 1406–1419 (2006)] and references therein. However, due to high dimensions of matrices appearing in these equations, their numerical solution still remains problematic. In this paper, a closed equation for the coherence function due to a point omnidirectional source in an oceanic waveguide is derived for the case of random inhomogeneities, which are statically isotropic in a horizontal plane. Due to cylindrical symmetry of the problem, dimensions of the matrices appearing in the derived equation are significantly reduced, as compared to a general case. This makes the equation for the coherence function readily amenable for numerical calculations. Using this equation, the effects of internal waves with the Garret-Munk spectrum on the coherence function of a sound field propagating in an oceanic waveguide are studied numerically.
Effect of ocean internal waves on the interference component of the acoustic field in the Long-range Ocean Acoustic Propagation Experiment
Authors: Grigorieva Natalie S. , Fridman Gregory M. , Mercer James , Andrew Rex , Howe Bruce , Wolfson Michael , Colosi John
Published: September 2008

The propagation of energy along the sound-channel axis cannot be described in terms of geometrical acoustics because of the presence of cusped caustics repeatedly along the axis. In neighborhoods of these cusped caustics a very complicated interference pattern is observed. Neighborhoods of interference grow with range and at long ranges they overlap. This results in the formation of a complex interference wave-the axial wave-that propagates along the sound-channel axis like a wave belonging to a crescendo of near-axial arrivals. In this paper, the axial wave is simulated for the LOAPEX CTD data measured at seven different ranges from the vertical line array. A signal with the center frequency of 75 Hz and 37.5-Hz bandwidth is used for computations. This signal well approximates one transmitted m-sequence in the LOAPEX experiment. The effect of environmental variability, induced by internal waves, on the axial wave is studied. The sound-speed fluctuations caused by ocean internal waves are obtained with the use of the buoyancy frequency profile measured in the LOAPEX. Calculations are based on the integral representation of the axial wave in a local coordinate system introduced in the vicinity of the range-variable sound-channel axis. [Work supported by ONR.]
Horizontal coherence of low-frequency shallow water signals
Authors: Collis Jon M. , Duda Timothy F. , Lynch James F. , Newhall Arthur E. , von der Heydt Keith , DeFerrari Harry , Nguyen Hien Ba
Published: September 2008

Signals from moored sources at a range of approximately 20 km distant from a fixed L-shaped receiver array (joint horizontal and vertical line array) on the New Jersey area shelf have been analyzed to determine horizontal coherence properties of the signals. The signals, from 100 Hz to 800 Hz, do not arrive broadside to the horizontal array. Subsequently they show phase and amplitude fluctuations attributable to interference within a field having an azimuthally uniform normal mode structure, and azimuthal variations of the modal structure. Synthesis of an interference pattern using the acoustic field measured with the vertical array is used to distinguish between the two effects. High temporal variability of the inferred azimuthal variation of modal content correlates with internal wave activity observed along the path. Horizontal coherence lengths are often of the order of ten acoustic wavelengths. [Work supported by ONR.]
Observations of temporal coherence for broad band acoustic transmission in shallow water
Authors: Deferrari Harry
Published: September 2008

The temporal coherencies of broadband signals are computed with data from fixed system measurements at two experimental sites. The acoustic source for both measurements was the Miami Sound Machine (MSM) which transmits continuous signals at 6 carrier frequencies from 100 to 3200 Hz in octave steps. Each signal has a bandwidth of 25% of carrier. The bandwidth of the acoustic signal allows the identification of paths by arrival time, so that coherence can be estimated for individual paths and for multipath groupings. The relation between internal wave energy and acoustic signal coherence times is explored. Internal wave energy is estimated with moored T-D instruments along the path of propagation. The sound speed variability resulting from internal waves at the two sites is markedly different: one is driven by locally generated nonlinear solitary waves and, the other, by offshore internal waves that propagation into the shallow water. The low frequency signals are directly modulated in amplitude and phase at the period of the wave passing the site, whereas, the higher frequencies have saturated statistics without evidence of direct modulation. A puzzling observation is that coherence times do not change much while the IW energy increases by 2 orders of magnitude.
Optimized translation of microbubbles driven by acoustic fields
Authors: Toilliez Jean O. , Szeri Andrew J.
Published: September 2008

The problem of a single acoustically driven bubble translating unsteadily in a fluid is considered. The investigation of the translation equation allows for identifying the inverse Reynolds number as small perturbation parameter. The objective is to obtain a closed-form, leading order solution for the translation of the bubble, assuming nonlinear radial oscillations and a pressure field as the forcing term. The result is the ability to predict and explicitly understand the rapid and slow transients of bubble displacement, which is proportional to the average acoustic radiation force. The periodic attractor of the Raleigh-Plesset equation serves as basis for an optimal acoustic forcing designed to achieve maximized bubble translation over one dimensionless period. At moderate acoustic intensity, maximizing the radial variance, thereby enhancing bubble collapse, leads to displacement many times larger than the case of purely sinusoidal forcing. The survey covers a wide spectrum of driving ratios and bubble diameters physically relevant to biomedical applications. Shape stability issues are considered. Together, these results suggest new ways to predict some of the direct and indirect effects of the acoustic radiation force in biomedical applications: e.g., targeted drug delivery, selective bubble driving and accumulation. [Work supported by NASA Microgravity Fluid Physics Program.]
Ultrasound-mediated release of calcein from echogenic liposomes
Authors: Kopechek Jonathan A. , Chrzanowski Stephen M. , Smith Denise A. B. , Gaskins Whitney B. , Abruzzo Todd A. , Huang Shaoling L. , McPherson David D. , Holland Christy K.
Published: September 2008

Echogenic liposomes (ELIP) have been developed for drug encapsulation. The gas contents in ELIP present a potential mechanism for ultrasound-triggered release of drug contents. Calcein, a fluorescent dye, was loaded in ELIP as a drug substitute (C-ELIP) and ultrasound-induced release was quantified with fluorescence spectrophotometry. Pulsed 6.0-MHz color Doppler from a clinical diagnostic ultrasound scanner (CL15-7 transducer, Philips HDI 5000, MI of 1.3, 150 Hz pulse repetition frequency) was applied to samples of C-ELIP in an in vitro flow phantom (2.2 ml/min). For comparison, Triton X-100 was added to C-ELIP to release calcein. Control samples of C-ELIP were not treated with ultrasound or Triton X-100. The echogenicity of C-ELIP (expressed as mean digital intensity in a 0.5 cm2 region of interest) decreased by 9.6±2.1 dB after exposure to ultrasound. The observed calcein concentration (μg/ml) was 3.1±0.1 for the untreated sample, 4.5±0.1 after Triton X-100 treatment, and 4.2±0.2 after ultrasound exposure. 65.6% of encapsulated calcein was released with ultrasound. These results demonstrate that ultrasound-mediated release of drugs from ELIP using a clinical diagnostic ultrasound scanner is feasible. [Work supported by an AIUM Education and Research Grant and NIH 1R01 HL074002, and NIH 1RO1 NS047603-01S1.]
Characterization of low-profile fresnel lenses for annular high-intensity focused ultrasound radiators
Authors: Woolworth David , Raymond Jason , Mobley Joel
Published: September 2008

As part of an effort to develop high intensity focused ultrasound (HIFU) applicators for remote hemostasis, we are investigating the use of low-profile stepwise Fresnel lenses for varying the focal depths of single-element annular HIFU transducers. The Fresnel lenses are interchangeable and represent a cost-effective approach to variable HIFU focusing in comparison to multi-element phased array systems. In this work, we report on the characterization of a Fresnel lens coupled with a 1.2 MHz annular transducer as the inner radius of the annulus is varied. We present data derived from hydrophone-based measurements of the pressure field of the transducer/lens system. In addition, we compare our findings with simulations derived using the angular spectrum technique.
Flexible tools for time reversal acoustics focusing applications
Authors: Fillinger Laurent , Kurtenoks Viktors , Rosenblum Sam , Sutin Alexander , Sarvazyan Armen
Published: September 2008

Time reversal focusing of acoustic waves has numerous biomedical applications including medical imaging, HIFU treatment, and targeted drug delivery. These various applications pose different requirements. Imaging requires a small spatial focused spot, which can be scanned in 2-D or 3-D; therapy requires high deposited energy and controlled-shape extended focus. Artann Laboratories is developing flexible tools including hardware, algorithms, and software with user-friendly interface as a universal platform for wide-range applications, based on the use of the time reversal focusing of acoustic waves. We have built a ten-channel electronic system with sampling frequency up to 33.3 MHz. It enables simultaneous broadcasting of independent arbitrary signals and recording of the response by a scanning receiver/beacon. A set of functions were developed to enable the control of this setup within Matlab, which offers a high level computing language for numerical computation. With a developed system, a diverse variety of experiments and data analysis can be conveniently conducted within the same platform. Illustrative results on numerous biomedical applications of the time reversal focusing obtained within this framework will be presented.
Coverage metric for track planning and location of stationary bottom targets
Authors: Dennis Steven M.
Published: September 2008

With the increasing dependence on optimization algorithms in track generation in the presence of variable or uncertain environments, the desire for a more environmentally-sensitive metric of sensor performance has arisen. A measure of performance based upon acoustic coverage area has shown promise as a basis for sensor utilization and optimized track generation applications, and is presented here for the case of a bi-static, active sensor used in the search for stationary bottom targets (e.g., wrecks). Coverage can be defined as the areas throughout which a sensor has a sufficiently high signal-to-noise ratio or alternatively, probability, of making positive observations of objects on the seafloor. For the purposes of determining optimal sensor placement and track generation, the area of interest is divided into a sufficiently sampled grid of calculation points. Computing and compiling acoustic sensor coverage area information for grid points throughout the area of interest into an acoustic coverage map gives immediate visual feedback on locations of optimal performance for a specific sensor in the current ocean environment. [The authors appreciate and acknowledge the funding support from the Naval Research Laboratory Base Program.]
Acrylic plate acoustic transmission experiment and theory
Authors: Dowling David R. , Chang Natasha A.
Published: September 2008

An approximate model of the transmission of sound waves in water through a plate of PMMA was developed for a point source. The model is based on spherical wave propagation and plane-wave transmission through a solid layer, and it is calibrated by identifying the properties of the plastic. By minimizing the error between the modeled and the experimentally measured acoustic wave, the mechanical properties of PMMA can be estimated for PMMA plates of varying thickness d for the d/fluid range of 0.04 to 2.5, and sound-incident angles of 0 deg to 35 deg. This calibration requires only the compression wave ray-path information and was shown to achieve 90% correlation between experimental and predicted waveforms for synthetic cavitation pulses with a nominal bandwidth from 40 kHz to 200 kHz. At larger angles of incidence as measured based on the compression wave, it was necessary to track the various waves that occur in the solid, i.e., compression, shear, and evanescent. The acoustic pressure waves that they generate have to be appropriately added at the receiver location to then recreate the experimentally-measured acoustic signal. The achieved model-experiment correlation at these greater angles of incidence was 80%. [Work supported by ONR.]
Better soundscapes for all—Report on the Workshop in Standardization for Soundscape Techniques held in Salt Lake City, 5 June 2007
Authors: Schulte-Fortkamp Brigitte , Brooks Bennett M.
Published: September 2008

The goal of the Soundscape Workshop in Salt Lake City (153rd ASA meeting) was to explore standardization as a possible future advancement in the evolving field of Soundscape measurement, analysis, and design. The perception of the soundscape can provide comfort, tranquility, and needed information to the person concerned, or may be a source of annoyance. The combination of physical acoustical measurements with scientific evaluation of perceptual responses to environmental sound, known as soundscaping, is an essential method for the assessment and actualization of positive outdoor environments. Engineering and aesthetic soundscape design may only proceed based on a complete characterization of the acoustical environment, including the nature of the sound sources and the reactions of the perceivers. Soundscaping provides for the measurement, analysis, and design of environmental sound by applying the knowledge of both science and community experts. Much fundamental and practical research has been conducted to establish the bases for the soundscape field. The next step is for researchers and practitioners to standardize the available soundscape techniques to allow for more comparison of test and survey results and wider application in design. This presentation outlines the proposed methods and means developed at the workshop for follow-up and further action.
From global and semantic evaluations to physical measurements and modeling
Authors: Dubois Daniele S.
Published: September 2008

Soundscape research has now largely pointed out the limits of indicators solely (directly) grounded in pressure level measurements and other simple static acoustic parameters to account for nuisance as well as sound quality, as perceived by human listeners. Advances in cognitive research has allowed to identify semantic categories of soundscapes contrasting pleasant areas versus annoying ones with source identification and evaluation as one major criterion of categorization. The present challenge, both theoretical and pragmatic, is therefore to connect such global semantic (psychological) evaluations to analytical (physical) instrumental measurements. We suggest that physical modeling of source signatures and artificial intelligence models of source identification processes could now provide formal representations of typical environmental categories, that could be the missing link to fill the gap between these two types of sound descriptions and interpretations. We will present a state of art concerning our present day knowledge of the structural properties of categorical structures we identified in psychological and semantic investigations, to specify the conditions under which cognitive modeling could account for the structural complexity of source contribution to soundscapes evaluation.
‘‘The Grand Canyon’’ vs. ‘‘Soundscape of Nowhere.’’
Authors: Hingson Dickson J
Published: September 2008

Twenty years have elapsed since the National Parks Overflights Act of 1987 targeted the once quiet but aviation-imperiled Grand Canyon National Park soundscape as worthy of an expeditious, potentially difficult ‘‘substantial restoration.’’ Within several more months, this protracted acoustic effort reaches its long-standing presidential deadline (April, 2008) for completion, as according to specifications/standards set by the National Park Service. A preliminary assessment (first presented by this author at ASA’s June biennial meeting) will be refined/updated in view of subsequent developments. Primary and emerging supplemental noise indicators and long-established (or possibly revised) Park Service restoration standards-based mainly on audibility and ‘‘restored’’ acreage—will be reviewed. Pertinent words and dimensions of soundscape assessment from this and other soundscape studies will be reviewed and compared, particularly re concepts of ‘‘wilderness character’’ and ‘‘beauty.’’ Effectiveness of anticipated management actions in the face of ongoing political/legal controversy will be examined, pitting restoration of the authentic Grand Canyon wilderness soundscape against a relatively unsavory option, ‘‘The Soundscape of Nowhere.’’ The Grand Canyon soundscape situation situation will be compared with preservation/restoration needs facing other similarly imperiled, iconic national parks in the West, which are at continuing risk for long-term aviation noise impairment.
Development of soundscape assessment and design methods for large institutional projects
Authors: Siebein Gary W. , Lilkendey Robert M. , Paek Hyun
Published: September 2008

Soundscape assessment and design processes were used to develop design criteria for noise mitigation strategies for the expansion of an institutional complex in a medium-sized city. A series of long-term acoustical measurements of average A-weighted sound levels in the community as well as more detailed octave band measurements and calibrated aural recordings of specific acoustic events that comprised the ambient sounds were mapped for the neighborhood. Sound walks were conducted at various times of day to understand the dynamics of the acoustical environment and to identify issues. Focus group discussions among stakeholders and team members developed the long-term plans for the community and appropriate architectural and acoustical design criteria for the project. Analysis of auralizations of various design options by stakeholders and team members using sophisticated multi-channel playback systems and full-scale aural demonstrations on site were used as part of the evaluation process.
Toward a less chaotic sound environment for nurses: A study investigating the relationship between layout design, aural connectivity, and user activities
Authors: Okcu Sele , Zimring Craig
Published: September 2008

An intensive care unit has a particularly demanding aural environment, where nurses must be able to hear and respond to numerous alarms, hear critical orders, and respond to patients and family members. This study explores a network measure called aural connectivity that reflects the overall pattern of where users can hear and respond to all key sounds. Aural connectivity is explored in a 20-bed neuro-ICU in a major teaching hospital by mapping locations where each alarm and key sound from the patient rooms can be heard, using both self-report and objective measures of sound. This study explores how aural connectivity relates to tasks, unit layout and design, and the nature of noise sources. Aural connectivity has the promise of being a useful overall design and evaluation tool because it allows movement and tasks to be mapped onto a network of where effective auditory monitoring can occur.