bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling dialect-related variability in American English plosives
Authors: Purnell Thomas
Published: May 2008

Socially motivated variation in speech often lies in the differential use of phenomena described in identical or near-identical terms. This paper investigates the hypothesis that dialect differences may result from the relative distribution of an acoustic characteristic with respect to trading relations with other co-varying characteristics, or by variations in the characteristic within regions of linguistic stability. Plosive variation among European American and African American English speakers in the upper Midwest is examined. Speakers from both dialect groups may produce plosives instead of interdental fricatives in syllable initial position, and devoice or glottalize apical plosives in syllable final position. Additionally, speakers of both dialects have been observed to hypervoice voiced plosives word-initially. The current experiment explores the boundary characteristics of a trading relations model within the plosive system of both dialect groups. The specific question addressed by the paper is whether the range of plosive variation suggests a shared property of nonstandard dialects, or whether the relation among acoustic measures is dialect specific. Results are discussed in light of acoustic, perceptual and categorical stability.
Development of assisting system for learning Chinese aspirated sounds
Authors: Hoshino Akemi , Dang Jianwu , Yasuda Akio
Published: May 2008

Chinese aspirates are generally difficult for Japanese to pronounce and perceive. In order to assist Japanese students to learn Chinese, the authors attempt to build a system to automatically evaluate the pronunciation of Chinese aspirates by Japanese students. To do so, this study analyzed 21 single-vowel syllables of six different Chinese aspirates, bilabial, alveolar, velar, palatal, retroflex, and dental using two evaluation parameters: the voice onset time (VOT) and mean breathing power during VOT. The speech materials were uttered by nine Japanese students and nine native Chinese speakers. It is found that for a give aspirate, the longer the VOT is, the better the score is, as is generally said. But we found that an aspirate with a larger breathing power acquires good mark even with a shorter VOT in a certain range of VOT. The testing results showed that a combination of these two parameters can distinguish aspirated and unaspirated sounds quite well. To achieve an assisting system, we developed a method to automatically detect the VOT. To detect the burst of an aspirate, a filter bank was used to measure signal energy in frequency domain, and the burst timing was determined.
The production of Mandarin and American English vowels by Mandarin-speakers
Authors: Liao Jia-Shiou
Published: May 2008

This study examines whether there is any correspondence between how Mandarin-speakers pronounce Mandarin vowels and how they pronounce those vowels' English equivalents and non-equivalents. Twenty Mandarin graduate students, who spoke English as a second language and had stayed continuously in America for at least two years, produced a series of American English vowels in /hVd/ contexts from a randomly ordered list. To approximate English syllable structure, they also read a list of /hVdV/ syllables containing Mandarin vowels in the first syllable. The vowel in the second syllable is always a schwa. First- (F1) and second-formant (F2) values of each Mandarin and English vowel were analyzed. The statistical results suggest that the distances between the Mandarin corner vowels in the vowel space are similar to those between the English ones. The acoustic characteristics of the English vowels with Mandarin equivalents do not differ significantly from those equivalents. For the other English vowels, the formant values most often differ from those of their closest Mandarin equivalents in only one formant or in neither. For instance, Mandarin subjects do not distinguish English /u/ from the near-close near-back vowel in either formant - attributable to the absence of the near-close near-back vowel in Mandarin.
Syllable production rate in conversational speech
Authors: Raphael Lawrence J.
Published: May 2008

Most acoustic analyses of speech are based on samples obtained from carefully constructed corpora that are read or recited by subjects in a laboratory setting. Recently, speech scientists have attempted to obtain speech samples that are representative of a more casual, conversational style than might be obtained in the laboratory. One available and plentiful source of such speech samples can be found in "talkradio" shows in which listeners engage in phone conversations with radio hosts. Phone-in programs receive calls from thousands of callers each day across the continental United States. Moreover, the listeners who call generally speak in an essentially natural, unself-conscious manner, exhibiting a broad range of rates and emotional states. This paper reports the results of a study of syllable production rate from samples of speech obtained from a variety of types of phone-in programs, including those focusing on sports, politics and the arts. The data reveal that syllable production rates (in syllables per second) range from 3.05 to 7.50. Subjective judgements of speech rate by naive subjects were found to correlate only moderately with actual rates of syllable production.
A temporally stable representation of power spectra of periodic signals and its application to F0 and periodicity estimation
Authors: Kawahara Hideki , Morise Masanori , Takahashi Toru , Nisimura Ryuichi , Banno Hideki , Irino Toshio
Published: May 2008

A unified framework for extracting F0 and periodicity is proposed based on a new formulation of STRAIGHT. Averaging power spectra, they are calculated using two time windows a half pitch period apart, yields a temporally stable power spectrum for periodic signals (TANDEM spectrum). Applying consistent sampling theory also yields computationally efficient implementaiton of spectral envelope estimation used in STRAIGHT (STRAIGHT spectrum). Normalized TANDEM spectrum by STRAIGHT spectrum only represents periodicity information and can be used to detect periodicity both in the base-band (for F0 extraction) and other frequency bands (for mixed mode excitation). This unified framework provides a basis to represent the complex modes of voice excitation and enables greatly realistic remaking of extreme vocal expressions. [Supported by Grant in aids for scientific research and CrestMuse project.]
Perception of two English front vowels by L1 Dutch speakers with different regional accents
Authors: Escudero Paola , Simon Ellen
Published: May 2008

This paper reports the results of a categorization task of the English vowels "epsilon" and "ash" by native speakers of Dutch. Dutch has only one member of the contrast ("epsilon"), the acoustic realization of which is subject to considerable regional variation (Adank et al., 2007). Previous research has shown that that there is asymmetrical lexical competition between English words containing "epsilon" and "ash" for native speakers of Dutch (Weber & Cutler, 2004; Escudero et al., in press). Weber & Cutler (2004) argue that "epsilon" is the dominant category for native speakers of Dutch, because it is phonetically closer to the L1 Dutch sound. The present study investigates whether the dominant category may vary depending on the speakers' L1 dialect by examining how two groups of Dutch-speaking participants from different dialect regions (the Randstad region in the Netherlands and East-Flanders in Belgium) perceive the English vowels "epsilon" and "ash." Preliminary results indicate that participants from these two area's do indeed categorize English "epsilon" and "ash" differently as the result of the acoustic properties of their L1 vowel "epsilon" (F1, F2 and duration).
Motor equivalent strategies in the production of /u/ in perturbed speech
Authors: Brunner Jana , Hoole Phil , Perrier Pascal
Published: May 2008

Several articulatory strategies are available during the production of /u/, all resulting in a similar acoustic output. For example, speakers can protrude the lips and compensate for that by widening the velar constriction. This study investigates whether speakers use this relation under perturbation. Five speakers were provided with palatal prostheses which were worn for two weeks. Speakers were instructed to make a serious attempt to produce normal speech. Their speech was recorded via EMA and acoustics several times over the adaptation period. Formant values of /u/-productions were measured. Velar constriction width and lip protrusion were estimated. For four speakers a correlation between constriction width and lip protrusion was found. A correlation between lip protrusion and F1 or F2 was rare and no correlation occurred between constriction size and either of the formants. The acoustic output was thus constant. The results show that under perturbation speakers use motor equivalent strategies. The correlation between constriction size and lip protrusion is stronger than in studies investigating unperturbed speech (e.g., Perkell et al., 1993). This could be because under perturbation speakers are inclined to try out several strategies in order to reach the acoustic target and the co-variability might thus be greater.
Articulatory exaggerations during infant directed speech
Authors: Green Jordan R. , Nip Ignatius , Wilson Erin , Mefferd Antje
Published: May 2008

Although a growing body of literature suggests a principal role for observational learning in the acquisition of speech, the facial movements of infant directed speech (IDS) have rarely been studied. Identifying both the auditory and visual features of IDS is an essential step toward understanding the contribution of environmental stimulation to the development of speech and language. The current project uses three-dimensional motion capture technology to describe how parents modify their articulatory movements when communicating with their infants. The following three experimental questions will be addressed: (1) Do parents exaggerate articulatory gestures during IDS?; (2) If so, are there individual differences among parents in the degree of IDS?; and (3) Is there a strong association between acoustic and movement characteristics of IDS? Mouth movements were recorded from twenty-four mothers while speaking to their infants and to an unfamiliar adult. Mouth shapes during four target vowels were measured for differences in maximum vertical separation, maximum horizontal spread, and duration across speaking conditions. The result indicated that the majority of mothers exaggerated their lip movements when speaking to their infants. Speculation is made regarding the potential role of articulatory exaggerations in early speech learning.
Word-initial voiceless geminate stops: production and perception
Authors: Ridouane Rachid , Halle Pierre
Published: May 2008

Quantity contrasts (i.e., singleton vs geminate consonants, short vs long vowels) are common in the languages of the world. Yet, most singleton-geminate contrasts occur in word-medial position. Languages that allow gemination in other than word-medial position (word-initially or word-finally) are quite few. Even less frequent is the occurrence in the languages of the world of word-initial voiceless geminate stops. Pattani Malay (Abramson, 1986), Turgovian Swiss German (Kraehenmann, 2003), Tashlhiyt Berber (Ridouane, 2007), are the only documented languages that allow singleton-geminate contrasts word-initially for all native consonants, including both voiced and voiceless plosives. In this work we deal with word-initial voiceless geminate stops in Tashlhiyt Berber and present results from 3 experiments: 1) a production study including acoustic and electropalatographic measurements 2) a native-listener experiment with labelling and discrimination, and 3) a cross-language perceptual experiment, with listeners of two languages differing in germination: Italian (in which gemination only occurs word-medially) and French (in which gemination only occurs between words in continuous speech).
Soundscape source extraction using wavelet-based sparse representations
Authors: Bunting Oliver , Chesmore David
Published: May 2008

As part of the EPSRC Instrument for Soundscape Recognition, Identification and Evaluation (ISRIE) project, the work described here aims to extract sources from a soundscape, with the aim of improving the signal to interference ratio to aid automatic identification and classification. The paper will describe the project's background and aim. Results using directional audio coding (dirAC) to separate sparse signals will be presented. This method has been shown to have successfully separated two speakers at known positions from a virtual B-format soundscape. An extension of this method using the dual-tree complex wavelet transform will also be presented, which improves the sparsity of the time-frequency representation. Initial results for spatially known sources will be presented. It is expected that some results from current work on localising and tracking sources in a B-format soundscape will be presented.
Investigation of damage mechanisms of composite materials: multivariable analysis based on temporal and wavelet features extracted from acoustic emission signals
Authors: Marec Anne , Thomas Jean-Hugh , El Guerjouma Rachid
Published: May 2008

The aim of this work is the analysis of damage development and time-to-failure mechanisms within fibre-matrix composite materials in order to assess their remaining lifetime using in situ ultrasonic sensors. Thus Acoustic Emission (AE), which represents the generation of transient ultrasonic waves in a material under load, is used to discriminate the different damage mechanisms in composite materials. In this work, unsupervised pattern recognition analyses (fuzzy c-means) associated with a principal component analysis are used for classifying the AE events. A cluster analysis of AE data is achieved and the resulting clusters are correlated to the damage mechanisms of the material under investigation. This method gives good results on complex composite materials such as glass fibre/polyester cross-ply composites, sheet molding compound (SMC), concretes. Furthermore, AE signals of heterogeneous materials are not stationary. Thus, time-scale or time-frequency methods (continuous and discrete wavelet transforms) are used to determine new relevant descriptors from AE signals. These new descriptors are introduced in the clustering process to provide a better characterization and discrimination of the different damage mechanisms.
Image processing and wavelets transform for sizing of weld defects using ultrasonic TOFD images
Authors: Kechida Ahmed , Drai Redouane , Benammar Abdelsaalam
Published: May 2008

Ultrasonic time-of-flight diffraction (TOFD) is rapidly gaining prominence as a reliable nondestructive testing technique for weld inspection in steel structures, providing highly accurate positioning and sizing of flaws. A number of signal and image processing tools have been specifically developed for use with TOFD data and adapted to function autonomously without the need for continuous intervention, configuring automatically according to the nature of the data and the data acquisition settings. This paper presents the results of several innovative procedures based on Multiresolution analysis such as wavelet transforms and texture analysis for detecting edges of planar defects. The approach is based on the decomposition by packets of wavelets of the image while taking into account of the underimage content textural after each level of decomposition. The reconstruction of the image is done by eliminating the underimages of poor textural information and at the end the segmented image is got by a binarisation operation done on the image rebuilt histogram. The automation of sizing and positioning of weld flaws in TOFD data as an essential stage of a comprehensive TOFD inspection and interpretation aid is developed and implemented. Key words: Ultrasonic Time-Of-Flight Diffraction., Texture Analysis, Wavelet Transform.
Mid-frequency bottom interaction measurements off the New Jersey continental shelf
Authors: Choi Jee Woong , Dahl Peter H.
Published: May 2008

Two kinds of bottom interaction measurements conducted in waters 80 m deep off the North American continental shelf as part of Shallow Water 06 (August, 2006) are discussed. In each, acoustic signals were recorded on two, colocated vertical line arrays of length 1.4 m, one at depth 25 m, and other at depth 50 m. The source was deployed at depth 40 m from the R/V Knorr that could either be positioned or towed at rate 0.1 m/s. The first, "bottom reflection" is interpreted as a measure of the modulus of the plane wave reflection coefficient as functions of frequency (1-20 kHz) and grazing angle associated with the discrete set of ranges (50-300 m). The second represents a "move-out" type measurement with source towed away from the receiver, and reflection at continuous angles associated with the 50-300 m range. Frequency range was 1-2 kHz, and as the source was 5 m off the bottom, spherical wave effects are investigated. Both measurements were carried out over the same four directions originating from the receiver, each separated by 90 degrees. Physical processes responsible for the observations in each case are discussed and modeled. [Supported by ONR, with partial support from Hanyang University.]
Analysis of acoustic backscattering from the ocean bottom using radiative transfer theory
Authors: Quijano Jorge E. , Zurk Lisa M.
Published: May 2008

Radiative Transfer (RT) theory is a heuristic formulation for analysis of wave propagation in random media based on the principle of conservation of energy rather than on the solution of the wave equation. The theory has been applied to electromagnetics and more recently to ultrasound and seismics, and it has the advantage of being computationally tractable for complex random environments. In this paper the RT formulation is proposed for the problem of layered ocean bottom sediment with random scatterers. The volume backscattering level from tenuous media is obtained by solving the RT equation at each individual layer and by applying the corresponding reflection and transmission coefficients at the rough boundaries. Simulations of the backscattered acoustic intensity from a finite layer with elastic spherical scatterers are presented. The results obtained from the RT equation are compared to those based on the wave equation. Single frequency steady state solutions are considered for different cases of sediment attenuation and layer thickness. The flexibility of the RT method is demonstrated by showing the individual effect of propagating longitudinal and shear waves in the elastic sediment. It is proved that the contribution of shear waves in consolidated sediments is considerable.
Determination of seabed scattering law from long range reverberation
Authors: Harrison Christopher H.
Published: May 2008

Reverberation degrades sonar performance, and often the dominant cause in shallow water is scattering from the seabed. Usually scattering is weaker at low angles than at high whereas, in contrast, sound propagates better at low angles than at high. This, in turn, affects the range-dependence of signal-to-reverberation which influences the choice of source level. A better understanding of this scattering angle dependence (or scattering law) offers the potential of improved discrimination of targets against this reverberation background. This paper will discuss an experimental technique for deducing the scattering angle dependence and backscattering strength from long range reverberation (out to 25 km) measured on a vertical line array (VLA). Well-sampled near simultaneous angle-dependent propagation measurements out to comparable ranges are used to separate the propagation effects without the need for any modeling. Applying the technique to the Malta Plateau (during BOUNDARY2003 and BOUNDARY2004), first the method appears to work, and second it suggests that the scattering law is close to Lambert when the seabed is flat.
Quasi-deterministic forward scattering from the sea surface
Authors: Deane Grant , Preisig James , Tindle Chris T.
Published: May 2008

Gravity waves create focal regions and caustics in sound forward-scattered from the sea surface. Focal regions are associated with rapid variations in amplitude and Doppler shift, which can impact the performance of underwater communications systems and sonars operated near the shore. Single-bounce focal regions consist of a superposition of up to 3 micro-paths, each of which is associated with its own amplitude, time delay, and Doppler shift. Focal regions move systematically through the water column as the wave propagates. Studies of these effects in near-shore ocean experiments and a laboratory flume have shown that a quasi-deterministic analysis of wave scattering can lead to valuable insights about the underlying scattering process. [Work supported by ONR.]
Observations and modeling of angular compression and vertical spatial coherence in sea surface forward scattering
Authors: Dahl Peter H.
Published: May 2008

Measurements and modeling of vertical spatial coherence and related angular spreading associated with forward scattering from the sea surface are presented. The van Cittert-Zernike theorem is used in the modeling. The measurements were conducted in waters 80 m deep off the North American continental shelf (Shallow Water 06, Aug. 2006). Acoustic signals were recorded on a moored array system (MORAY) consisting of three arrays (each 1.4 m): two vertical line arrays at depth 25 m and 50 m, and one horizontal array at depth 27 m. The source (1-20 kHz) was deployed at depth 40 m from the R/V Knorr, at ranges 50-500 m from the MORAY. Conditions were characterized by a downward-refracting profile, e.g., sound speed going from 1530 m/s at the surface to 1490 m/s at depth 25 m. Refraction modifies the vertical angular vertical spread due to scattering, which can understood from Snell's law. The Snell mapping is smooth, and a Taylor expansion around the mean grazing angle provides a functional relation between the angular variance near the surface and that at the receiver associated with scattering. The latter is measurably compressed owing to refraction, an effect mirrored in the spatial coherence data. [Research support from ONR.]
Objective and subjective analysis of acoustical response in newly renovated Palais Moncalm, Quebec City, Canada
Authors: Migneron Jean-Philippe , Migneron Jean-Gabriel , Hardy Jean-François
Published: May 2008

To celebrate the 75th anniversary of Palais Montcalm, the building has been almost entirely rebuilt to convert it into the House of Music. The main room, named Salle Raoul-Jobin, has been designed specifically for the resident chamber orchestra: Les Violons du Roy. Collaboration between acoustical consultant, Larry S. King, and architect Jacques Plante of MUSE consortium results in a 979 seats concert hall with variable acoustic to accommodate different kinds of musical events. Since reopening in March 2007, the general acoustic has been enthusiastically acclaimed by professionals, by world known musicians, and by the public. The principal objective of this study is to characterize acoustical response of the room with various adjustments of wall curtains and motorized canopy. This important reflective area is software-controlled in a range of 3 meters depending on musical needs. Acoustical objective parameters, such as reverberation time, early decay time, impulse response or C80 factor will be analyzed and compared to musical subjective perception of a few instruments played at multiple positions on stage and for different listening locations.
Applications of a plane wave based room correction system for low frequencies using multiple loudspeakers
Authors: Celestinos Adrian , Nielsen Sofus Birkedal
Published: May 2008

When low frequency sound is radiated inside small listening spaces by loudspeakers, large uniformities occur over the sound field. This is due to the multiple reflection and diffraction of sound on the walls and different objects in the room. A developed system named Controlled Acoustically Bass System (CABS) produces uniform sound field at low frequencies. This is performed by utilizing loudspeakers at the front wall and extra loudspeakers at the opposite wall, processed to remove the rear-wall reflection of a rectangular room. Effectiveness of CABS on different room scenarios has been evaluated by using a computer simulation program based on the Finite Difference Time Domain Method (FDTD). CABS has been simulated in a small car cabin and in an irregular room. Non-ideal placement of loudspeakers in CABS have been evaluated. The influence of utilizing CABS with different types of loudspeakers has been evaluated by simulations and measurements.
Acoustics in a small control room
Authors: Beristain Sergio
Published: May 2008

Acoustics in small rooms is allways a problem, particularly at the low frequency range, because of their size and the fact that there is very limited space to install all the acoustic materials needed in order to obtain the desired acoustic response, but when an electroacoustic system has to be employed as it is the case in a small Control Room for a small recording studio, matters become even worse. First of all, the space is further reduced in order to accomodate the required sound system, and with the presence of hard to control low resonant frecuencies, which can be excited at any moment during any recording session, it can be produced highly different sound presure levels at those frequencies, changing the timbre of sounds. Some measurement results are presented.
Developing acoustical policies around in EU countries
Authors: Bergmark Katrin , Janssen Marc R.
Published: May 2008

According to research, noise levels in hospitals worldwide have increased. At the same time, the awareness of the negative effects of noise on patients and healthcare staff has grown. To manage or eliminate noise in hospitals, standards and policies are a great help. An overview of international standards will be presented, showing various parameters and differences in values and angles of approach, e.g based on activity or room type. To further optimize the content, and stimulate the use of the standards, some countries have even defined healthcare specific standards. These can support the planning and the evaluation of the sound environment in those premises. New insights from research and case studies, as well as emerging laws, provide opportunities or even force us to extend the existing content of standards to meet future demands. Suggestions for that include extension of the amount of parameters, such as decrease of sound pressure level (ΔSPL) and parameters addressing privacy (PI, AC). Finally, revision of standards provides opportunities for end users to increase their understanding and interest in acoustic and to supply possibilities to define the desired quality of the sound environment.
Experimental study on applicability of sound masking system in medical examination room
Authors: Ueno Kanako , Lee Hyojin , Sakamoto Shinichi , Ito Atsuko , Fujiwara Mai , Shimizu Yasushi
Published: May 2008

Recently, speech privacy to avoid oral information leakage in healthcare facilities has become an important issue. This study investigated effectiveness of sound masking system in regard to masking efficiency, annoyance and its influence on speech conversation for medical examination rooms in an experimental approach. Considering actual application, two adjacent medical examination rooms partitioned by a low sound insulation wall in a typical healthcare facility were selected as an experimental field and sound masking system was temporally installed. In the rooms, acoustic environment was measured and reproduced in an anechoic room with a 3-D sound field simulation system using a 6-ch sound recording/reproduction technique. In the simulated acoustic condition, subjective tests were designed to quantify the masking efficiency and annoyance caused by the masking sound. The annoyance test was conducted in listening condition (with high attention to the sound) and in talking condition (with low attention). As a result, mixed maskers composed by water stream, synthesized speech signals, and steady state noise showed high performance in both aspect of masking efficiency and annoyance.
Automatic detection of short time periodic bird calls in realistic monitoring scenarios
Authors: Wolff Daniel , Tauchert Klaus H. , Frommolt Karl H. , Bardeli Rolf , Kurth Frank , Clausen Michael
Published: May 2008

In this contribution, we propose a method for the automatic detection and localisation of bird calls featuring simple as well as highly repetitive structures. Reporting from a research project focused at computer aided acoustical monitoring, a detector for Locustella luscinoides (Savi's Warbler) is presented, performing reliably even on highly distorted recordings. In cooperation with the Animal Sound Archive at the Humboldt University, Berlin, this detector was incorporated into a multimodal censusing method combining GPS-data and automatically annotated audio recordings to perform line mapping. An evaluation of the proposed techniques for unsupervised monitoring purposes was also performed on 20 hours of multichannel recordings from Lake Parstein, a cane brake area in Germany. Finally, exemplifying the discriminative potential of the underlying features, we will point out the application to other members of the Warbler family as well as the detection of cricket and toad sounds.
Species identification and measurement of activity in odontocete species of Palmyra Atoll by acoustic monitoring
Authors: Baumann Simone , Hildebrand John A. , Wiggins Sean M. , Schnitzler Hans-Ulrich
Published: May 2008

Acoustic monitoring has been used to study odontocete presence at Palmyra Atoll, a remote island in the Northern Line Islands chain. Long-term recordings of high-frequency, broadband acoustic data have become possible with recent technological advances. A High-frequency Autonomous Recording Package (HARP) has been developed which samples at 200 kHz with a duty cycle of 1/4 for up to seven months. This instrument has recorded since October 2006 at Palmyra Atoll. Visual and acoustic surveys were conducted around Palmyra Atoll using a four-element towed hydrophone array sampling real-time at 200 kHz to obtain species-specific acoustic data. These data are used as reference for automatic detection algorithms applied on the long-term recordings. To date, acoustically and visually detected odontocetes include bottlenose dolphins (Tursiops truncatus), spinner dolphins (Stenella longirostris), melon-headed whales (Peponocephala electra) and beaked whales of the genus Mesoplodon. The long-term HARP data reveal acoustic activity primarily at night time and predominantely odontocete clicks. Both the beaked as well as the melon-headed whales are present year round and show a distinct daily acoustic activity cycle.
Distribution patterns of delphinids in the California Current Ecosystem observed through acoustic monitoring of species-specific echolocation clicks
Authors: Oleson Erin M. , Soldevilla Melissa S. , Calambokidis John , Collins Curtis , Wiggins Sean M. , Hildebrand John A.
Published: May 2008

Visual surveys along the U.S. west coast conducted in the 1980s-90s suggested that Pacific white-sided and Risso's dolphins likely undergo annual movement between California during winter-spring, and Oregon-Washington in the summer-fall. Using high-frequency autonomous acoustic recordings within the southern California, central California, and Washington regions of the California Current System, we evaluated the seasonal occurrence of these dolphin species through detection of their echolocation clicks. The clicks of Pacific white-sided and Risso's dolphins are characterized by a unique combination of local frequency peaks for each species, providing a statistically robust means of identification from autonomous acoustic records. Based on these unique spectral characters, we extracted periods of clicking by each species from concurrently sampled coastal and shelf/slope locations off southern California and Washington, and a single offshore site off central California. The number of hours that each species was heard per day was quantified and compared among seasons and regions. Both species were heard year-round at shelf/slope sites off southern California and Washington; however their patterns of occurrence at coastal sites differed somewhat. Our results indicate year-round presence of Pacific white-sided and Risso's dolphins in some regions, suggesting that the seasonal distribution of these species may have recently changed.
Nearest-neighbor techniques for automated monitoring of nocturnal flight calls
Authors: Figueroa Harold , Farnsworth Andrew
Published: May 2008

Flight-calls are short vocalizations used primarily during nocturnal flight. Their observation provides a means for studying the timing, location, and composition of nocturnal migrations. As part of a three-year study the Cornell Lab of Ornithology is using autonomous recorders to sample flight-calls of nocturnal migrants in the Northeastern US. The resulting tens of thousands of hours of recording, make software-assisted detection and classification essential. Automatic processing and human evaluation have yielded a considerable collection of flight-calls, 5-1000 examples for ̃100 species. The many-class classification problem, along with the availability of many examples from most of the classes, and established (condensation and editing) and recent (metric-trees) techniques used in prototype-based classification nearest-neighbor techniques, have led us to develop nearest-neighbor based techniques and software to assist in the analysis of this data. We will present classification results on two examples, a set of thrushes (genera Catharus and Hylocichla, family Turdidae) consisting of six species and wood-warblers (family Parulidae) consisting of 48 species. The thrush flight-calls are visually and aurally distinctive, usually 100-400 ms in duration and occupy and the 2-5 kHz band. Wood-warbler flight-calls are typically between 20-100 ms in duration and occupy the 5-10 kHz, and are difficult for many experienced observers to distinguish.
Bayesian model parameterization selection for seabed reflection-coefficient inversion
Authors: Dettmer Jan , Dosso Stan E. , Holland Charles W.
Published: May 2008

This paper considers Bayesian inversion of seabed reflection-coefficient data for multi-layer geoacoustic models; in particular, the important issue of determining appropriate model parameterizations (e.g., number of layers, sound speed and density variations within layers). A poor model parameterization can lead to unreasonable inversion results. In particular, under-parameterization can introduce theory error in the inversion, causing biased results. However, more complex models always fit the data better. Therefore, parameterization quality cannot be quantified only in terms of data misfit, and Occam's razor is commonly applied to prefer simple parameterizations. In a Bayesian framework, Occam's razor is inherently included through Bayesian evidence. Bayesian inversion can be associated with two levels of inference. The first level assumes a specific model parameterization, and quantifies the data information content. This paper focuses on the second level: using Bayesian evidence to compare different model parameterizations. To this end, Gibbs sampling is applied, including full error covariance estimation, to sample the posterior probability density (PPD) for various parameterizations. Bayesian evidence is then computed from the PPD samples by numerical integration (reverse importance sampling).
Local bottom characterization using an autonomous underwater vehicle
Authors: Nielsen Peter Louring , Holland Charles W.
Published: May 2008

In the past decade the usage of autonomous underwater vehicles (AUV) to sample properties of the underwater environment has increased. The advantages of using platforms are their autonomy and that operations can be performed covertly. In 2007, the CLUTTER'07 experiment was conducted on the Malta Plateau with the main aim of characterizing the underwater environment. An AUV was deployed at a particular site on the Plateau to demonstrate the feasibility to infer bottom properties using such an autonomous platform. The AUV was equipped with 2 sound sources covering a frequency band 800-3500 Hz, and the transmitted signals were acquired on a bottom moored vertical array. The mission of the AUV was to perform a linear track of ̃1000 m passing the vertical array as close as possible while transmitting every second from the sound sources. This experimental configuration is similar to the move-out or wide-angle reflection measurements. The received signals are inverted for geoacoustic properties using both matched-field techniques and processed for direct bottom reflection properties. The results obtained are compared to independent findings from different experiments using various types of equipment at different seasons in the same area. [Research sponsored by NURC, ONR OA321 and the CLUTTER Partners]
Echogenic liposomes for image-guided drug delivery
Authors: Holland Christy K. , McPherson David D.
Published: May 2008

Echogenic liposomes (ELIP) are under development to enable ultrasound-controlled drug delivery. Ultrasound-triggered release of hydrophilic and lipophilic agents was assessed from circulating ELIP in vitro using color Doppler ultrasound (6 MHz). Calcein, or recombinant tissue plasminogen activator (rt-PA), both hydrophilic agents, or papaverine, a lipophilic agent, were each loaded into ELIP and diluted in 0.5% bovine serum albumin. Ultrasound-triggered release of calcein, rt-PA or papaverine from ELIP was determined relative to detergent and untreated controls. Calcein concentration was measured by fluorimetry and release of rt-PA was assayed with a chromogenic substrate and a spectrophotometric method. Papaverine concentration was quantified by absorbance spectrophotometry and the amount of papaverine associated with P-ELIP was determined using a spin column filtration technique. Dynamic changes in echogenicity were assessed with low output B-mode ultrasound (0.04 MI) as mean digital intensity. Treatment with color Doppler ultrasound resulted in a statistically significant amount of calcein and rt-PA release from liposomes (p < 0.01), but did not induce papaverine release (p > 0.05). The differential efficiency of ultrasound-mediated pharmaceutical release from ELIP for water-soluble and lipid-soluble compounds suggests that water-soluble drugs are better candidates for the design and development of ultrasound-controlled drug delivery systems.
Nonlinear propagation in microbubble cloud, does it make the distal myocardium appear brighter or darker
Authors: Tang Meng-Xing , Eckersley Robert
Published: May 2008

A number of questions remain in contrast ultrasound imaging regarding the complex interaction between bubbles, US and tissue. E.g. in contrast echocardiography for perfusion imaging, it is sometimes difficult to interpret the images for the myocardium distal to the probe. Due to US nonlinear propagation through the bubble-filled chamber, the distal part can appear artefactually brighter or darker in e.g. Pulse Inversion images. Although tissue at target is likely to increase in brightness in contrast specific images when nonlinear propagation happens, it is less clear for microbubbles. This work tries to gain better understanding of this by investigating how nonlinear propagation of ultrasound pulses can change the appearance of microbubbles and tissues in Pulse Inversion images by altering their acoustic response. A series of specifically designed simulations and experiments were performed. The results show that nonlinear propagation can have a significant impact on the appearance of tissue containing bubbles, and this varies with insonating frequency and pressure. These results suggest the mechanism involves a balance between a reduction in nonlinear bubble scattering after propagation against an increase in the nonlinear tissue scattering. Consequently the deeper tissues containing bubbles may appear brighter or darker depending on the relative contribution of these two effects.
Acoustic array interactions in the time domain
Authors: Benthien George W.
Published: May 2008

In this paper I discuss the computation of acoustic array interactions in the time domain. Acoustic array interactions in the time domain are expressed in terms of mutual impulse response functions. The mutual impulse response between a pair of array elements is the acoustic force on the first element of the pair due to an acceleration impulse of the second with all other elements held rigid. The mutual response functions are calculated in the frequency domain using the boundary element program CHIEF and then Fourier transformed to the time domain. As the convergence in the frequency domain can be very slow, I introduce modified impulse response functions that converge much faster in the frequency domain and are simply related to the desired impulse response functions. This approach reduces the range of frequencies required in the CHIEF computations and gives better accuracy in the initial time period. Transient results are presented for an array of simple transducer elements. The mutual impulse response functions are combined with the transducer element equations to yield a system of differential-integral equations of delay type. A solution procedure for equations of this type is presented.
Finite element analysis simulations of a piezoelectric cymbal actuator using atila software
Authors: Tremper Thomas , Vazquez Carazo Alfredo , Uchino Kenji
Published: May 2008

The piezoelectric ultrasonic cymbal actuator is a well known flextensional type actuator. Because of the actuator's geometry, the small movements of the piezoelectric ceramic are amplified by the flextensional structure. Simulation of this device was performed using Atila finite element software, which is specially suited for piezoelectric devices. This study will focus on some of the necessary parameters to accurately simulate cymbal actuators and other piezoelectric actuators. The simulations discussed will be compared to actual experimental data. Based on the experimental results the simulations will be reexamined and modifications will be made to increase the models accuracy. Employing this iterative process will promote increased accuracy in future simulations, which would therefore decrease development time and increase productivity.
Nonlinear multifrequency transmitter for seafloor characterization
Authors: Di Marcoberardino Lucilla , Marchal Jacques , Cervenka Pierre
Published: May 2008

In the underwater context, it is known that the frequency diversity provides essential information to derive the nature of the seafloor. This presentation deals with a new concept based on a transmitter that generates simultaneously several harmonic frequencies. Our final objective is to assert the feasibility of a multi-frequency tool whose desirable characteristics could be specified for applications such as detection of sunken oil slicks, sediment characterization, or surveys before cable or pipe laying. The acoustic beams are generated through the harmonic components of a shock wave radiated by an antenna driven at a high level. The source is unique in time and space so that the multi-frequency responses are inherently perfectly matched. A numerical model based on a generalized KZK equation has been developed to estimate the saturated fields. Measurements of the first harmonic fields obtained in our outdoor tank facility are compared with simulations.
Modeling the acoustic radiation force in piezoelectrically driven micro fluidic chambers using ATILA
Authors: Fisher Karl
Published: May 2008

A procedure is demonstrated to quantitatively evaluate the acoustic radiation forces in micro fluidic particle manipulation chambers. Typical estimates of the acoustic pressure and the acoustic radiation force are based on an analytical solution for a simple 1-dimensional standing wave pattern. The complexities of a typical micro fluidic channel limit the usefulness of this approach. By leveraging finite element approaches, and a generalized equation for the acoustic radiation force, channel designs can be investigated in two- and three-dimensions. Calculations and experimental observations are in good agreement. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.
Equivalent circuit models derived from finite element models using structural dynamics techniques
Authors: Bernard Julien
Published: May 2008

Electroacoustic transducers can be divided into an active part, the driver, and a passive part, the structure. The driver ensures electromechanical transduction, while the structure performs various mechanical and acoustical functions, such as support, shock and pressure protection, and impedance transformation. For design purposes, one often needs an equivalent circuit model which gives a relationship between the acoustic characteristics of the overall device and that of its components. Transducer equivalent circuits are usually either physical or modal. Physical equivalent circuits lend themselves to the treatment of a transducer as an assembly, but in general yield frequency dependant parameters. Modal equivalent circuits are more adequate for resonant transducers, but describe transducers as a whole. This works shows how these two types of equivalent circuits can be obtained from a full finite element model by using common structural dynamics techniques: substructuring and modal expansion. It also shows that a third, hybrid type of equivalent circuit can be obtained by using a component mode synthesis technique derived from the Craig-Bampton method. This hybrid equivalent circuit combines the advantages of physical and modal equivalent circuits, enabling to express transducer modal parameters in terms of driver and structure modal parameters.
Acoustic field calculation for a compact barrel-stave flextensional transducer array
Authors: He Zhengyao , Sun Chao
Published: May 2008

The boundary element method together with the finite element method is used to calculate the radiated acoustic field of a compact array of barrel-stave flextensional transducers. At first, the surface vibration displacement distribution of one barrel-stave transducer is obtained by the finite element method using the commercial software ANSYS. The calculation results are then imported into the boundary element calculation software SYSNOISE. At the frequency of 1400Hz, the radiated acoustic field and radiation impedance are calculated by the boundary element method for a planar array which is composed of three identical barrel-stave flextensional transducers uniformly distributed on a circle with spacing much less than half wavelength. The calculation results show that the mutual interactions among elements are significant for the compact array. The mutual radiation resistance between two transducers is close to the self-radiation resistance of the transducers. And the transmitting source level of the 3-element array is 8.7dB higher than that of one transducer if the surface vibration velocities of the transducers in the array are the same as that of one transducer. The proposed technique can be used to predict the performance of a transmitting transducer array at the stage of preliminary design.