bluuebunny/crossref_metadata_2025 huggingface dataset:
Marine mammal auditory evoked potential measurements using swept amplitude stimuli.
Authors: Finneran James J.
Published: March 2010

Auditory evoked potentials are routinely used to characterize hearing in marine mammals for whom behavioral testing is not practical. For frequency-specific audiometry, the most popular evoked potential method has been the measurement of the auditory steady state response (ASSR). These tests normally entail measuring the ASSR to a sequence of sinusoidally amplitude modulated tones so that the ASSR input-output function can be defined and the auditory threshold estimated. In this study, an alternative method was employed, where thresholds were estimated in response to a single amplitude modulated stimulus whose sound pressure level varied linearly with time. The tone sound pressure was therefore swept over a range of levels believed to bracket the threshold. The input-output function was obtained by analyzing the resulting grand average evoked potential using a short-time Fourier transform. The swept amplitude technique was performed with bottlenose dolphins and California sea lions, with the resulting thresholds similar to those obtained with constant amplitude tones. The tradeoffs between the swept amplitude technique and the traditional, constant amplitude approach will be discussed. [Work supported by ONR.]
Vocalization in a neonatal Amur tiger cub.
Authors: Walsh Edward J. , Smith Adam B. , Armstrong Douglas L. , McGee JoAnn
Published: March 2010

Although the acoustical features of a small number of calls representing the vocal repertoire of adult tigers have been studied and reported, calls produced by developing tigers representing any subspecies have not been described. In that light, the acoustical features of calls produced by an Amur cub during the first two postnatal weeks of life will be considered. The vocal repertoire of the cub observed during recording sessions was limited, consisting primarily of neonatal cries composed of three distinct types: an intense, harmonically rich phonation, an aperiodic cry (dysphonation), and a compound cry exhibiting both dysphonation and harmonically rich phonation segments. Overall acoustic power of the harmonically rich phonation was uniformly distributed across a frequency band ranging from approximately 0.6–2.0 kHz and that was centered on roughly 1.2 kHz on the second postnatal day. While the same basic pattern was observed on postnatal day 13, inter-harmonic differences were smaller, and between days 2 and 13 the mean fundamental frequency dropped from ∼260 to ∼200 Hz; typically, f0 varied during each utterance at each age studied. These findings will be considered in relation to the spectrographic character of calls produced by adult Amur tigers. [Funding was provided by NSF Grant 0823417.]
Diffraction pattern recognition method for drastically improving image resolution and diagnostic sensitivity.
Authors: Wen J.J.
Published: March 2010

Compared with the two other mainstream medical imaging methods, CT and MRI, the worst weakness of ultrasound imaging is poor resolution—the ability to resolve tiny variations in tissue structure or texture. Due to sound wave diffraction and the way imaging ultrasound signal is retrieved, a point target in object domain does not generate point image in image domain, but an image spot with sophisticate spot pattern and considerable spot size as functions of point target location relative to the transducer—the most direct cause of poor resolution. The mainstream techniques aimed at reducing the image spot, either by shortening the impulse signal or by sharpening the beam focusing, are unavoidably accompanied by the deteriorated sensitivity and depth of penetration. It is a common consent in medical ultrasound community that ultrasound imaging is very close to its theoretical resolution limit. This article presents a different approach we named E-mode imaging that uses a diffraction-theory-based spot pattern recognition technique to account for the effects of image spot pattern in image processing. With the same set of ultrasound data that B imaging is based on, E-mode imaging achieved five to ten times better resolution and diagnostic power in computer simulations.
Middle-ear input impedance and middle-ear sound transfer.
Authors: Rosowski John J. , Nakajima Hideko H. , Cheng Jeffrey T. , Hamadeh Mohamad A. , Ravicz Michael E.
Published: March 2010

Measurements of the acoustic input impedance of the human eardrum, or tympanic membrane (TM), have been used as indicators of middle-ear sound transfer for over 70 years. Modern measurements include (i) middle-ear input impedance in single- and multi-frequency tympanometry, (ii) impedance-based estimates of ear-canal reflectance, a description of sound power absorption at the TM, and (iii) laser-Doppler measurements of the sound-induced velocity of specific points on the TM surface. The advantages and disadvantages of these techniques are discussed, and their use in identifying and estimating the effects of different middle-ear pathologies is illustrated. A new technique, opto-electronic holography, which allows measurements of the volume displacement of the visible surface of the TM, is also discussed. Common themes are (i) the impedance of the middle ear varies widely within populations of normal hearing subjects and (ii) input-impedance based estimates of sound transfer through the middle ear are hindered by the presence of flexibility within the ossicular chain. It is concluded that while middle-ear input impedance may adequately describe the acoustic load on hearing-aid receivers, this impedance, by itself, is not always an accurate indicator of pathological alterations in sound transfer through the human middle ear.
A world beyond the banjo.
Authors: Wheeler Paul A.
Published: March 2010

The American banjo, a long-necked plucked lute developed by slaves from Africa and an important instrument in Bluegrass music, derives its characteristic timbre from the membrane belly of the instrument. Even though the banjo is the best known membrane-style lute in music of the western hemisphere, there are many musical traditions across the eastern hemisphere which have used their own version of the banjo long before the development of the American banjo. This paper will introduce some of these instruments and the musical cultures using them. These include the ngoni of western Africa (possibly the source of the American banjo), the cumbus and tar from the Middle East, the rawap of central Asia, the sarod of India, and the shamisen and sanxian of Japan and China. As diverse as these cultures may be, the characteristic timbre of the banjo is an important element in their music.
Validation of a polyimide foam model for use in transmission loss applications.
Authors: Bolton J. Stuart , Hong Kwanwoo , Wang Tongan , Maxon John , Howerton Brian , Cano Roberto J. , Weiser Erik S. , Lorenzi Tyler , Jensen Brian J. , Silcox Richard J.
Published: March 2010

In this paper, the use of polyimide foam as a lining in double panel applications is considered. Polyimide foam has a number of attractive functional attributes, not the least of which is its high fire resistance, thus making its use desirable in some sound transmission applications. The configuration studied here consisted of two 0.04×94 thick, flat aluminum panels separated by 5 in., with a 3 in. thick layer of foam centered in that space. Random incidence transmission loss measurements were conducted on this buildup, and conventional poro-elastic models were used to predict the performance of the lining material. The Biot parameters of the foam were determined by a combination of direct measurement (for density, flow resistivity and Young’s modulus) and inverse characterization procedures (for porosity, tortuosity, viscous and thermal characteristic length, Poisson’s ratio, and loss factor). The inverse characterization procedure involved matching normal incidence standing wave tube measurements of absorption coefficient and transmission loss of the isolated foam with finite element predictions. When the foam parameters determined in this way were used to predict the performance of the complete double panel system, reasonable agreement between the measured transmission loss and predictions made using commercial statistical energy analysis codes was obtained.
Quiet honeycomb panel.
Authors: Palumbo Dan , Klos Jake
Published: March 2010

Sandwich honeycomb composite panels are lightweight and strong and, therefore, provide a reasonable alternative to the aluminum ring frame/stringer architecture currently used for most aircraft airframes. The drawback to honeycomb panels is that they radiate noise into the aircraft cabin very efficiently provoking the need for additional sound treatment which adds weight and reduces the material’s cost advantage. A series of honeycomb panels incorporating different strategies aimed at reducing the honeycomb panels’ radiation efficiency while at the same time maintaining its strength. The majority of the designs were centered around the concept of creating areas of reduced stiffness in the panel by adding voids and recesses to the core. The effort culminated with a reinforced/recessed panel which had 6 dB higher transmission loss than the baseline solid core panel while maintaining comparable strength. Attempts were made to damp the panels’ vibration energy by the addition of lightweight particles to the honeycomb cells. These designs were very difficult to build given the particles’ tendency to pollute the bond interface between the honeycomb and the face sheet. Well constructed panels exhibited very little benefit from the treatment that could not be attributed to the added mass alone.
Observed frequency and depth effects on attenuation of ambient ground vibration.
Authors: Amick Hal , Gendreau Michael
Published: March 2010

This article presents observed relationships between depth and frequency with regard to ambient ground vibration. Typically, site vibration studies are conducted on undeveloped locations (grass fields, parking lots, etc.) to assess the ambient vibration conditions for a potential building site. However, the vibration-sensitive equipment of concern is frequently placed below grade, such that the final ambient vibration conditions it experiences might be quite different from that shown in the field survey. An earlier study [NoiseCon (2007)] presented data illustrating how several factors—including building foundation stiffness, ground stiffness, and building geometry—all have an effect on the propagation from “ambient” vibration sources. This presentation extends that work, specifically examining the relationship between depth, frequency, and extent of attenuation associated with below-grade spaces.
Analysis and design of new floating slab track for special trackwork using finite element analysis.
Authors: Phillips James
Published: March 2010

This paper discusses the development of a new vibration isolation system for tunnel crossovers in a future rail line extension. The previous design included ballasted track on top of continuous concrete slabs on rubber vibration isolators. The goal of the new design was to replace the ballast and tie track with rails fastened directly to discrete slabs similar to the vibration isolation system utilized on running portions of track within existing tunnels. Finite element analysis (FEA) was used to evaluate the dynamic interaction between the vehicle, rails, resilient rail fasteners and the vibration isolation system. The results of the analyses guided the design in determining the size and thickness of the inertia slabs, the stiffness and design of the rubber vibration isolation pads, and the rail fastener selection.
Three-dimensional finite-difference time-domain simulation of low-amplitude sonic boom diffraction around a rectangular test structure and building spiking effect.
Authors: Cho Sang I. , Sparrow Victor W.
Published: March 2010

A finite-difference time-domain (FDTD) approach is used for a three-dimensional numerical modeling of pressure loading on the exterior surface of a building due to an incident low-amplitude sonic boom. For these “low-booms,” the linearized Euler equations suffice to describe the boom-structure interaction. A second-order centered-difference scheme and fourth-order Runge–Kutta time integration scheme are applied. The FDTD simulation models a field test performed by Virginia Tech in 2008, where a rectangular test structure representing a residential building was instrumented to measure its vibroacoustic response to a boom generated by detonation cord. By matching the geometries of the simulated structure to the actual test structure and using the waveform of a measured boom as the input to the simulation, a direct comparison of numerical and experimental data is made possible. The simulation result agrees well with the experiment and also shows expected pressure doubling and diffraction effects. An interesting observation is made in both numerical and experimental data and is called the “building spiking” effect, which can be attributed to frequency-selective diffraction by the building. [Work supported by NASA. The authors appreciate Virginia Tech and NASA making the 2008 detonation cord test data available for this work.]
Detailed finite element analysis of sonic boom transmission into residential building structures.
Authors: Kim Beom Soo , Sparrow W. Victor , Sizov V. Natalia , Manning T. Ben
Published: March 2010

Finite element modeling is a powerful and cost-effective tool for solving problems in structural dynamics and acoustics, particularly at low frequencies. In the present work the transient responses of the sonic boom transmission from outdoors to indoors were studied. Detailed finite element models of individual rooms from two residential structures were built. The simulated geometries were matched to the physical geometries of two houses exposed to sonic booms that were heavily instrumented by NASA in the summers of 2006 and 2007. The residential building walls were composed of studs and sheathing, and these were modeled using MSC NASTRAN/PATRAN software. To match the normal mode frequencies of the walls, it was necessary to not only match material coefficients but also the actual connections between the studs and the sheathing. The fluid structure coupling between the walls and the air was utilized to analyze the acoustic response of the sonic boom in the room interior. In order to verify the correctness of the model, the vibration responses of the structure and the acoustic cavity were compared with measured data. [Work supported by NASA.]
Sound source localization of a dipole by the plainfin midshipman fish (Porichthys notatus).
Authors: Zeddies David G. , Fay Richard R. , Alderks Peter W. , Acob Andrew , Sisneros Joseph A.
Published: March 2010

Localization of a dipole sound source was studied in female plainfin midshipman fish (Porichthys notatus). Experiments were conducted and videotaped in a 3.65-m-diameter tank using a dipole underwater speaker system placed near the center of the tank. The sound was a 90-Hz tone, approximately the fundamental frequency of the male’s advertisement call. Pressure and particle motion components of the sound field were mapped with 9-cm resolution. Pressure was measured using an eight-hydrophone array, and particle motion vectors calculated from the pressure gradients. Mapping confirmed that the projector was operating as a dipole. Gravid fish were released 70 cm from the sound source at two different positions relative to the dipole axis: one near the dipole axis and one near the pressure null axis. Twenty-five positive responses were recorded from each release site. The phonotactic response pathways along the dipole axis consisted of slightly curved tracks to the sound source, whereas pathways from the null axis consisted of greatly curved tracks to the source that followed the particle motion vectors. Results confirm that fish can locate a dipole sound source and are sensitive to the direction of acoustic particle motion. [Work supported by NSF.]
Effects of individualized headphone equalization on front/back discrimination of virtual sound sources.
Authors: Guru Abhishek , Martens William L. , Lee Doheon
Published: March 2010

Individualized head related transfer functions (HRTFs) were used to process brief noise bursts for a two-interval forced choice front/back shift between virtual sound source locations presented via two models of headphones, the frequency responses of which could be made nearly flat for each of 21 listeners using their own individualized headphone equalization filters. In order to remove tone coloration differences between virtual sources processed using individualized HRTFs measured in front or in back of each listener, the spectral centroid of the “back” source was adjusted to more nearly match that of the source processed using the “front” HRTF. This manipulation resulted in chance levels of discrimination performance for 12 out of 21 listeners. For the remaining nine listeners showing good discrimination, the virtual sources presented using individualized headphone equalization supported significantly better front/back discrimination rates than did virtual sources presented without correction to headphone responses.
The talker-specific nature of spoken language processing.
Authors: Nygaard Lynne C.
Published: March 2010

During spoken communication, listeners must contend with a physical speech signal that carries information not only about the linguistic content of a talker’s utterance but also about a host of talker-specific attributes such as talker identity and emotion. Traditionally, the recovery of linguistic structure has been thought to be independent of the recovery of these indexical or surface characteristics of speech. Recent research, however, suggests that listeners remember the perceptual quality of spoken words, flexibly adapt to informative indexical variation in speech, and use this variation to guide their understanding of spoken words. This talk will review evidence for indexical specificity effects across a range of perceptual and memory tasks and will examine the linguistic, attentional, and cognitive constraints that may mediate the role of surface form in spoken language processing. Implications of these effects for accounts of linguistic representation and processing will be discussed. [Work supported by NIDCD.]
Investigating whether ease of lexical processing affects listeners’ ratings of the strength of talkers’ foreign accent.
Authors: Shah Amee , McLennan Conor
Published: March 2010

Many research studies in spoken word recognition have examined the role that different types of surface variability have on listeners’ perception of spoken words (e.g., influence of same versus different talker manipulations). In our ongoing research program, we are investigating the other direction of this relationship. Our initial two experiments investigated whether linguistic complexity affects listeners’ overt subjective impressions of the strength of talkers’ foreign accents. Ease of lexical processing was manipulated in two ways, namely, sentence context and long-term repetition priming. In the sentence context experiment, participants made accent ratings on the last word of each sentence presented to them; this word was either related or unrelated to the sentence context. In the long-term repetition priming experiment, participants made their accent ratings to isolated spoken words, which they either had (primed) or had not (unprimed) heard earlier in the experiment. Stronger accent ratings in the unrelated sentence context and unprimed conditions were predicted. Response time to provide their accent rating responses to sentence context and priming manipulations was also studied. Our results should lead to a greater understanding of the role that lexical processing plays in listeners’ perception of foreign accents and perhaps other types of surface variability.
Interactive processing in speech perception: The facts of feedback.
Authors: Mirman Daniel
Published: March 2010

Context plays a critical role in human speech processing. Rapid, efficient integration of context and input is accomplished by interactive processing: bottom-up input information and top-down context information work together to constrain the percept. One domain where this is most clear is the effects of word context on perception of speech sounds. Behavioral experiments and computational model simulations show that interactive processing confers both benefits (robust perception in noisy environments and tuning in response to changes in input patterns) and costs (errors and delays in perception when the input is inconsistent with the context). Context effects are also prevalent is the constraining effect of global communication context on activation of different meanings of ambiguous words (i.e., homophones): when only highly imageable meanings are consistent with the context (a word-to-picture matching task), concrete noun meanings (e.g., the tree-related meaning of bark) become more activate than less imageable meanings (e.g., the dog-related meaning of bark). These findings are consistent with an interactive graded constraint satisfaction view of speech perception in which bottom-up input and top-down context simultaneously constrain the final percept.
Analyzing acoustic scenes in reverberant environments: A bird study.
Authors: Blumenrath Sandra H. , Dooling Robert J.
Published: March 2010

In reverberant environments, the auditory system processes complex signals that are distorted and overlapped by tails of echoes of preceding sounds. These reverberation effects can be used to discriminate between different types of acoustic environments and to locate a sound source, but it also limits the transfer of biologically important information. To examine the positive impact of reverberation on acoustic scene analysis, we used psychophysical methods to test the ability of canaries, zebra finches, and budgerigars to discriminate between reverberation differences. Negative effects were investigated by asking whether birds can segregate reverberated songs from multiple individuals despite degraded auditory grouping cues. Birds were able to hear small changes in reverberation, although this ability was somewhat dependent on both the species and, in particular, the type of signal. Species-specific vocalizations as well as broadband signals posed the smallest difficulty. Interestingly, the non-oscine, flock-living budgerigar out-performed the other two oscine species. Moreover, birds were less able to “hear out” a target song among a cacophony of other songs when all vocalizations were reverberated. The results suggest both positive and negative impact of reverberant environments on the perception of vocal signals and the analysis of complex acoustic scenes in the tested species.
Analysis of animal blast overpressure study data to compare current impulse noise criteria and propose some new criteria.
Authors: Goley Steve , Song Wonjoon , Kim Jay , Murphy William J.
Published: March 2010

The effects of high-intensity impulsive noise on the auditory system are complex and difficult to quantify in a simple criterion. Several impulse noise criteria (e.g., MIL-STD 1474D, Pfander, Smoorenburg, LAeq8hr, and a model-based method called AHAAH) are studied for their analytic structure to understand their underlying basic assumptions. Then, these criteria are compared for their performances based on animal blast overpressure data obtained from 905 chinchillas exposed to 137 exposure conditions. The noise exposures consisted of different impulse sources, peak levels, number of impulses with various temporal spacing, and presentations in reverberant and non-reverberant conditions. The noise data are analyzed using the analytic wavelet transform to study their time-frequency structures in relation to patterns of measured auditory damage of chinchillas. Based on these studies, a few new metrics are proposed by taking advantage of capabilities of the advanced signal analysis tool. The statistical correlations of the new metrics with the chinchillas’ observed auditory damage are compared with the MIL-STD 1474D, Pfander, Smoorenburg, LAeq8hr, and the AHAAH model damage risk criteria. Possibility of developing a new impulse noise standard according to the approach adopted in this study as well as remaining challenges are discussed.
Output-only modal testing of simple residential structures and acoustic cavities using the response to simulated sonic booms and ambient excitation.
Authors: Corcoran Joseph , Haac Ryan , Remillieux Marcel , Burdisso Ricardo , Reichard Georg
Published: March 2010

Structural modal properties of single-room and two-room rectangular structures built with typical residential construction are extracted using only the vibration responses to (1) a sonic boom simulated with a linear distribution of detonating cord and (2) ambient excitation. Then, the acoustic modal properties of the cavities enclosed by the residential structures are extracted using the pressure responses to the same two types of excitation. The technique involves cross-correlating the responses measured at many points to the responses at a few different reference points on the structure or in the cavity. This allows for the calculation of impulse responses at many points around the structure or cavity due to excitation at the reference points. Structural natural frequencies, modal damping ratios, and mode shapes obtained from the output-only analyses are presented and compared to the results from conventional impact hammer modal testing and from a finite element model, demonstrating good agreement. Acoustic natural frequencies and modal damping ratios extracted in the output-only analyses are presented and compared with room pressure spectra measurements made with speaker noise excitation and analytically calculated results for the single room and the two room configurations, also showing good agreement between analyses. [Work supported by NASA Langley.]
Synthesis of sonic boom noise inside structures: An innovative experimental approach.
Authors: Ravetta Patricio , Burdisso Ricardo , Macko Nikolas
Published: March 2010

Current approaches to evaluate the impact of sonic booms on structures are rather few and limited. In this work, an innovative approach was developed and experimentally validated. It consists in simulating the distributed boom load on the structure using an array of discrete forces. Each discrete point force is the integrated sonic boom pressure loading (from experimental data or a diffraction code) over an area associated with that force. Under the assumption that the structure behaves linearly, each discrete force is applied sequentially and the desired vibro-acoustic responses recorded simultaneously with the applied force. The vibro-acoustic responses due to all forces applied simultaneously (and simulating the sonic boom load) can then be obtained simply as a linear superposition of the individual responses. Since the actual force time history due to the sonic boom does not need to be generated, the approach can be implemented using a shaker or modal hammer. Thus, it is sufficient to measure the transfer function between the input force and the vibro-acoustic response of interest. The vibro-acoustic data are then synthesized using the measured transfer functions and the loading on the structure to estimate the time histories of the forces due to the booms.
Modification of the nonlinear wave progressive equation model for sonic booms in a stratified atmosphere.
Authors: McDonald B. Edward , Piacsek Andrew A.
Published: March 2010

The nonlinear progressive wave equation (NPE) model [McDonald and Kuperman, J. Acoust. Soc. Am. 81, 1406 (1987)] is modified to simulate sonic boom physics in a stratified atmosphere using a wave—following window whose dimensions are much less than atmospheric scale heights. (The NPE was originally formulated for time domain weak shock propagation in the ocean, where the ambient density is nearly constant.) This allows simulation of sonic boom propagation in a refracted ray tube in which the ambient density may vary considerably as the simulation window moves along. Energy conservation places a strong constraint on the form of the resulting nonlinear wave equation. Properties of the modified NPE and some illustrative solutions are presented. [Work supported by the Office of Naval Research.]
Locating a small change in a multiple scattering environment (LOCADIF): Application to monitoring concrete.
Authors: Planes Thomas , Larose Eric , Rossetto Vincent , Margerin Ludovic
Published: March 2010

Most conventional imaging techniques are operated in single scattering media where the Born approximation is found relevant. In the multiple scattering regime where this approximation does not hold, the wave forgets its initial direction after a few scattering events and we cannot have access to the precise trajectory of the wave. All waves are mixed together in phase, amplitude, and wavevector, which defines the diffuse regime. This paper presents an imaging technique to locate a weak perturbation in a multiple scattering environment. We derive a formula to predict the spatio-temporal decorrelation of diffuse coda waves induced by an extra-scatterer. Locating this new defect is then formulated as an inverse problem which is solved by a maximum likelihood approach. Using elastic waves in the 100–350-kHz frequency band, we show that the position of a millimetric hole drilled in a heterogeneous concrete sample can be retrieved with a precision of a few cm. We illustrate the robustness of the method and define an optimal time of propagation that depends on the geometry of the acquisition and the diffusion constant of the medium. Applications to monitoring civil engineering structure are discussed.
Semi-analytical study of wave propagation in wire waveguides.
Authors: Guers Manton J. , Tittmann Bernhard R.
Published: March 2010

Guided ultrasonic waves in wire waveguides are useful for various applications including position monitoring and in-situ measurements of specimens in harsh environments. In corrosive environments, it has been observed that the velocity of the guided waves changes due to the growth of an oxide layer on the waveguide. Previous work by Grossman [IEEE Trans. Sonics Ultrason. 31, 25–31 (1984)] analyzed this phenomenon by calculating the change in rod velocity due to oxide thickness. In this paper, the semi-analytical finite element (SAFE) method was used to determine how the velocity changes with respect to oxide thickness and frequency. In addition, the effects of protective coatings on the waveguide have been considered. Results demonstrate that the SAFE method is effective for determining the dispersion characteristics of a waveguide comprised of two distinct materials.
Effects of semantic and syntactic cues in (non) native speech perception in noise.
Authors: Li Bin , Wayland Ratree
Published: March 2010

Non-native listeners (NNLs) are reported to be less tolerant with the degradation of speech (e.g., speech in noise) than native speakers (NSs). In addition, benefits from clear speech in such conditions have been shown to be greater for NSs than for NNLs in speech perception. This study aimed to examine whether poor perception by NNLs is due to their limited usage of the contextual information or their abilities in processing acoustic-phonetic signals, by investigating Chinese listeners’ ability in perceiving English sentences in varying linguistic contexts, such as semantic and syntactic cues, under different listening conditions. Sentences differing in degrees of semantic or syntactic acceptability produced by NSs of English were judged a different group of naive NSs of English on degrees of acceptability. All sentences were digitized and masked with white and babble noises with different signal-to-noise ratios (−4 and −8 dB). Listeners from three language backgrounds were recruited. Results showed that semantic and syntactic cues, as well as listening conditions, exhibited different degrees of facilitation in rewriting of keywords. Chinese speakers benefited more from marked syntactic structures, whereas English speakers found marked semantic contexts more facilitating.
Application of the chaotic cavity transducer concept for imaging in non-reverberant media.
Authors: Van Den Abeele Koen , Van Damme Bart , Delrue Steven , Bou Matar Olivier
Published: March 2010

The concept of chaotic cavity transducer utilizes a combination of a piezoelectric ceramic disk glued on a cavity of chaotic shape on the hardware side, with the time reversal (or inverse filter) technique on the software side. Using a two step procedure of direct excitation-reception and time reversed excitation-reception, it is possible to focus energy anywhere inside a non-reverberating sample, thanks to the ergodicity of the chaotic cavity. Moreover, the same basic concept can be used to create a virtual phased array using a single channel device. Both experimental data and simulations will be provided to illustrate the concepts. The goal is to use the chaotic cavity transducer concept to enhance the localization of micro-damage coupled to nonlinear elastic wave spectroscopy methods.
Critical listening research on reproduced sound in diffuse environments.
Authors: Martens William L. , D’Antonio Peter
Published: March 2010

In critical listening rooms designed to monitor precisely small signal processing changes, what can be heard is influenced by the room’s modal response and the degree to which reflections are controlled by absorptive, reflective, and diffusive boundary surfaces. In exploring the problem of room acoustics affecting the results of such important listening activities, it is informative to explore the boundary conditions. For example, the acoustics industry utilizes absorption and reverberation chambers to explore related auditory phenomena. Recently, a diffusion chamber was created with broadband diffusion on walls and ceiling. Modal frequencies were also controlled with dedicated plate resonators effective down to 50 Hz. Impulse response measurements in this diffuse chamber revealed a dense reflection pattern 30 dB or more below the direct sound. The initial perception in this room was precise sonic images, a comfortable sense of ambiance and an apparent transparency to the subtleties of reproduced imagery that support decisions of sound engineers. Related experiments being carried out in other controlled listening rooms will be reviewed to place the current work in context.
Acoustic calibration of the exterior effects room at the NASA Langley Research Center.
Authors: Faller Kenneth J. , Rizzi Stephen A. , Klos Jacob , Chapin William L. , Surucu Fahri , Aumann Aric R.
Published: March 2010

The exterior effects room (EER) at the NASA Langley Research Center is a 39-seat auditorium built for psychoacoustic studies of aircraft community noise. The original reproduction system employed monaural playback and hence lacked sound localization capability. In an effort to more closely recreate field test conditions, a significant upgrade was undertaken to allow simulation of a three-dimensional (3-D) audio and visual environment. The 3-D audio system consists of 27 full-range satellite speakers and four subwoofers, driven by a real-time audio server running a derivation of vector base amplitude panning. The audio server is part of a larger simulation system, which controls the audio and visual presentation of recorded and synthesized aircraft flyovers. The focus of this work is on the calibration of the 3-D audio system, including gains used in the amplitude panning algorithm, speaker equalization, and absolute gain control. Because the speakers are installed in an irregularly shaped room, the speaker equalization includes time delay and gain compensation due to different mounting distances from the focal point, filtering for color compensation due to different installations (half space, corner, and baffled/unbaffled), and crossover filtering.
Processing burst pulse waveforms from odontocetes.
Authors: Hursky Paul , Porter Michael B. , Olmstead Tyler , Roch Marie , Wiggins Sean , Hildebrand John
Published: March 2010

A number of marine mammals produce an interesting vocalization called a burst pulse, which consists of a series of clicks whose repetition rate increases to the point that the entire waveform sounds more like a continuous buzz. These animals also produce individual clicks at a much less frequent rate, sometimes with a consistent inter-click interval, sometimes without. However, because these animals are often observed in groups that number in the hundreds at low rates, it is difficult to associate individual clicks with individual animals or to group multipath arrivals. A burst pulse waveform avoids these association ambiguities—the clicks making up a burst pulse are so frequent, and so consistent in amplitude and inter-click interval that they are easily associated with a single animal, and any multipath structure is consistently revealed. We will present results of processing a variety of burst pulses observed on array sensors from a series of experiments off the coast of California and discuss algorithms for detecting burst pulse waveforms and for extracting classification features from these waveforms.
Probabilistic bioacoustic signal extraction within spectrograms.
Authors: Brandes T. Scott
Published: March 2010

A methodology for probabilistic bioacoustic signal extraction within spectrograms of natural sound recordings is proposed. Probabilistic models of signal attributes are described for generating a host of likelihoods used to estimate the probability that individual pixels within a spectrogram represent part of a bioacoustic signal. The pixel probabilities result in a transformation of the spectrogram into a probability map of bioacoustic signal presence. It is shown that these probability maps create a dramatic increase in the bioacoustic signal-to-noise ratio within the spectrogram. These probability maps along with threshold filtering provide a means for image segmentation of the spectrogram, creating blocks of pixels that represent bioacoustic signals, facilitating feature and signal extraction. This methodology is applied to natural sound recordings of three quality types in a wide range of signal-to-noise ratios. In each instance, the probability mapping greatly increases the signal-to-noise ratio and, when applied as a threshold filter, is far more selective with pixel inclusion than threshold filtering applied based on sound level. Suggested applications include automated call recognition of birds, frogs, and insects from field recordings within a wide range of ambient noise.
Observed space-time scales of internal waves and finescale intrusions on the New Jersey Shelf and their likely acoustic implications.
Authors: Colosi John , Duda Tim , Lin Ying-Tsong , Lynch Jim , Newhall Arthur
Published: March 2010

It has been known for some time that ocean density surfaces possess multi-scale variations in temperature (T) and salinity (S), termed spice (hot and salty, cold and fresh) by Munk in 1981. Compensating T and S variations along a surface of constant density have reinforcing sound speed anomalies and thus have important acoustic implications. With the advent of new technologies to observe small scale, rapidly changing ocean thermohaline structure, spice variations, and their acoustic effects are just starting to be understood. Better known are the impacts of internal waves which vertically advect ocean sound speed structure. This talk will present analysis of moored T and S observations on the New Jersey Shelf region during the SW06 experiment in which the sound speed effects of internal waves and spice can be approximately separated. These results will be contrasted with similar measurements made in the deep waters of the Philippine Sea. Using recent results from coupled mode theory, some discussion of the acoustic implications of the internal wave and spice structure will be presented. In particular, the phase randomizing effects of linear internal waves and spice will diminish the mean acoustical influence of intense but localized nonlinear internal waves.
Using ocean ambient noise cross-correlations for noise-based acoustic tomography.
Authors: Leroy Charlotte , Sabra Karim G. , Roux Philippe , Kuperman William , Hodgkiss William , Walker Shane
Published: March 2010

Recent theoretical and experimental studies have demonstrated that an estimate of the Green’s function between two hydrophones can be extracted passively from the cross-correlation of ambient noise recorded at these two points. Hence monitoring the temporal evolution of these estimated Green’s functions can provide a means for noise-based acoustic tomography using a distributed sensor network. However, obtaining unbiased Green’s function estimates requires a sufficiently spatially and temporally diffuse ambient noise field. Broadband ambient noise ([200 Hz–20 kHz]) was recorded continuously for 3 days during the SWAMSI09 experiment (next to Panama City, FL) using two moored vertical line arrays (VLAs) spanning the 13-m water column and separated by 150 m. The feasibility of noise-based acoustic tomography was assessed in this dynamic coastal environment over the whole recording period. Furthermore, coherent array processing of the computed ocean noise cross-correlations between all pairwise combinations of hydrophones was used to separate acoustic variations between the VLAs caused by genuine environmental fluctuations–such as internal waves–from the apparent variations in the same coherent arrivals caused when the ambient noise field becomes strongly directional, e.g., due to an isolated ship passing in the vicinity of the VLAs.
Cavitation and vaporization threshold of perfluorocarbon droplets.
Authors: Schad Kelly , Hynynen Kullervo
Published: March 2010

Focused ultrasound therapy can be enhanced with microbubbles by thermal and cavitation effects. However, localization of treatment becomes difficult as bioeffects can occur outside of the target region. Spatial control of gas bubbles can be achieved with acoustic vaporization of perfluorocarbon droplets. This study was undertaken to determine the acoustic parameters for bubble production by droplet vaporization and how it depends on the acoustic conditions and droplet physical parameters. Droplets of varying sizes were sonicated in vitro with a focused transducer and varying frequencies and exposures. Simultaneous measurements of the vaporization and inertial cavitation thresholds were performed. The results show that droplets cannot be vaporized at low frequency without inertial cavitation occurring. However, the vaporization threshold decreased with increasing frequency, exposure, and droplet size. In summary, we have demonstrated that droplet vaporization is feasible for clinically relevant sized droplets and acoustic exposures.
Observations of microbubble translation near vessel walls.
Authors: Chen Hong , Kreider Wayne , Brayman Andrew A. , Bailey Michael R. , Matula Thomas J.
Published: March 2010

To exploit the potential clinical applications of ultrasound contrast agents, it is important to understand the basic physics of bubble-vessel interactions. In this work, high-speed micrography was used to investigate the dynamics of microbubbles inside vessels from ex vivo rat mesentery under the exposure of a single ultrasound pulse. The study included arterioles and venules. The ultrasound pulses were about 2 μs long with a center frequency of 1 MHz and peak negative pressures between 1 and 7 MPa. High-speed photographs reveal that interactions between microbubbles and vessels caused bubbles to move away from nearby vessel walls. The motion depended upon the standoff distance between the bubble and the nearest vessel wall, where a normalized standoff γ can be defined as the ratio of the standoff distance to the maximum bubble radius. For γ <1, obvious bubble movement away from the nearby vessel wall was observed during collapse. At γ=0.3, a bubble inside a venule was observed to translate over 16 μm during 1.5 μs, achieving velocities over 10 m/s. Bubble translation away from the vessel wall may be caused by the rebound of the vessel wall that was distended during bubble expansion. [Work supported by NIH Grants EB00350, AR053652, DK43881, and DK070618.]
PiggyBac transposon-based gene delivery with cationic ultrasound contrast agents into SCID and CD-1 mice.
Authors: Anastasiadis Pavlos , Matsunaga Terry O. , Moisyadi Stefan , Allen John S.
Published: March 2010

Efficient integration of a functional gene, along with suitable transcriptional regulatory elements, poses a fundamental difficulty for the application of successful gene therapy. Though inducible gene expression after somatic cell gene transfer has been achieved by employing viral vectors, issues associated with cargo capacity, host immune response, the risk of insertional mutagenesis, and the requirement for separate viruses are limiting factors. Several researchers have used transposon-based approaches for gene delivery, and the piggyBac transposon system has recently been shown to be effective in human cell lines and for the transgenesis in mice. The use of engineering helper-independent plasmids with the mouse codon-biased piggyBac transposon (mPB) gene in combination with cationic ultrasound contrast agents (UCAs) is investigated for a range of insonification parameters. The plasmid pmGENIE-3 deactivates the mPB gene after insertion of the transposon, eliminating potentially negative effects which may occur from the persistence of an active piggyBac gene post-transposition.
A comparison of sound localization methods in a room environment using a spherical microphone array.
Authors: Barnhill Colin , West James E.
Published: March 2010

Enclosures are one of the most challenging environments for source localization, especially for teleconferencing where the main goal is to enhance desired speech signals while suppressing noise. This can be accomplished using beamforming but the speech source locations must be known. Three passive methods will be compared for room environment localization: generalized cross-correlation (GCC), spherical harmonic-based multiple signal classification (MUSIC), and spatial power signal characteristics and gradients (SPSGs). SPSG is a new localization algorithm designed for room environments based on wideband third order beamforming and power signal characteristics, differences, and gradients. MUSIC is a subspace method that relies on an eigen-decomposition of the beam correlation matrix and GCC is a time delay estimation algorithm based on microphone signal correlation. MUSIC and GCC are methods that perform well in their optimal environments but suffer in noisy and reverberant conditions. Results will be shown for multiple source situations with reverberation and noisy interferers.
Microphone array sensor node for distributed wireless acoustic beamforming.
Authors: Abdeen Alaa A. , Ray Laura E.
Published: March 2010

The presentation will illustrate the use of field programmable gate arrays (FPGAs) in microphone array digital signal processing for wireless acoustic beamforming in source localization. We have developed a prototype of a node composed of ten microphone channels interfaced with a Xilinx-based FPGA board. The methodology involves basic signal conditioning and delay-and-sum beamforming programmed by VHDL. The prototype results illustrate significant increase in the sensitivity to acoustic sources in the direction of a signal, while rejecting noise from other directions. The sensitivity is also enhanced in relationship to the number of channels. This node prototype is a building block for a wireless sensor network, capable of distributed beamforming at about 10-kHz sample frequencies. Each node is designed to maximize throughput so that broadband acoustic sources are accommodated. We are now performing parametric studies to optimize the node design and microphone array geometry to provide maximum bandwidth, dynamic range, and adequate special resolution, while preserving the ability to resolve time delays between the microphones.