bluuebunny/crossref_metadata_2025 huggingface dataset:
Research into the human response to vibration in residential environments.
Authors: Waddington David C. , Moorhouse Andrew T. , Brown Phil A.
Published: October 2013

This paper describes work being carried out at the Univ. of Salford to develop a method by which human annoyance to vibration in residential environments can be assessed. The objective of this study is to yield a robust relationship between vibration exposure and human response; therefore, providing a reliable basis for the development of standards and guidance for the assessment of vibration in residential buildings. The vibration sources to be considered are those affecting residents that are outside their control, such as construction, road, and rail activities. The protocol involves the measurement of vibration outside and inside residences and a social study questionnaire based on face-to-face interviews with adults. The project is expected to capture a wide-scale study of 2000 case studies, and examples of early field measurements and results are presented. This work is likely to be of interest to planners and practitioners involved in the design of buildings and environmental health officers involved in the assessment of vibration complaints. [Work funded by the Dept. for Environment, Food, and Rural Affairs (Defra) UK.]
Comparison of tapping machines for impact insulation class (IIC) measurement accuracy.
Authors: Farbo Aaron M.
Published: October 2013

This study compares tapping machines from different manufacturers and age for impact insulation class (IIC) measurement accuracy. In addition to the IIC measurement accuracy, the study also compares the impact frequency and effect of different impact surfaces (steel and rubber). The tapping machines were tested in a model condo unit in accordance with impact insulation class testing standards ASTM E1007-04 and ISO 140-6. These standards clearly state the impact frequency and type of impact surface to be used (hardened steel). Previous testing standards did not specify the material type for impact surfaces and many older tapping machines included both steel and rubber feet. The results of this study will be presented to show the effect of age, impact frequency, and impact surface on the resulting IIC measurement for the tapping machines.
Vertical profile of community noise in high-rise built environment.
Authors: Mahbub Alam Sheikh , Eang Lee Siew , Johnny W. L. H.
Published: October 2013

High-rise public housing apartments in Singapore are often subjected to different types of community noise sources in close proximity. Community noise in housing estates comprises noise sources such as food center noise, children playground noise, soccer court noise, basketball court noise, waste disposal truck noise, etc. It was found as one of the major noise source categories in residential environment. With the enhanced performance quality in many aspects of public housing in recent years, it is imperative that the acoustics performance of the apartments can be enhanced to match overall quality of public housing environment through appropriate characterization of these noise sources. A scientific and reliable approach for characterizing noise propagation from these sources is vital in the implementation of projects. Software modeling and simulation were carried out to study noise propagation characteristics of five types of community noise sources. Five 16-storey residential buildings were investigated with noise measurement from these sources, conducted on each level of the buildings. The predicted results were verified with field measured data. This study observes that noise level from these sources reduces between 3.7 and 12.8 dBA at a height between 43 and 46.5 m above the ground with the increase in building height.
Prediction of sound propagation in rectangular ducts by a ray-tracing model with phase.
Authors: Yousefzadeh Behrooz , Hodgson Murray
Published: October 2013

A ray-tracing model which includes phase changes due to distance traveled and surface reflection has previously been developed for predicting sound field in rectangular rooms. Including phase has removed the limitation associated with energy-based models, that room dimensions must be larger than the sound wavelength. The model has been applied to a rectangular room with dimensions not large compared to the wavelength. The room dimensions are that of a real-world ventilation duct, with the boundary conditions idealized as a point source at one end and anechoic termination at the other end. Predictions have been made of the pressure field inside the duct and the results have been compared with analytical solutions. The model is found to be capable of predicting the modal characteristics of the duct.
Assessing the origin of tonal sound emanating from refrigerant piping in the historic Mattress Factory project at the University of Washington Tacoma Campus.
Authors: Bogomolov Elizabeth , Wiebusch Julie A.
Published: October 2013

UW Tacoma campus is located in the Union Depot Warehouse National Historic District. Siting the campus in this area and renovating rather than demolishing some of the remaining historic, industrial buildings as campus classrooms and offices has stimulated the city’s urban renewal. Mattress Factory was one of these historic structures, regulated by the Tacoma Landmarks Commission. The new chilled water system in Mattress Factory consists of two 70-ton chillers located in a mechanical room on the lowest level of the four-story building. Air-cooled condensing units, located on the roof, connect to the chiller compressors. The refrigerant piping was required to be incorporated within the building envelope so as not to alter the appearance of the historic exterior. The piping path between the compressors and condensers was somewhat circuitous due to existing structural elements. A discernable, tonal whine was exhibited in spaces on the second and third floors when the chiller was running. The sound corresponded with the location of the refrigerant piping within the wall cavity, with the dominant sound level at the second floor in the area of an existing beam. This paper outlines the process of identifying the cause of the sound and the ultimate mitigation treatment.
Noise from rooftop mechanical equipment in residential buildings.
Authors: Nash Anthony
Published: October 2013

Community planning codes restrict building heights with the intent that the building is in general conformance with the character of the neighborhood’s built environment. Although these codes prescribe the maximum height, they do permit a limited amount of rooftop space to be used for elevator penthouses, exhaust fans, cooling towers, and miscellaneous other rotating mechanical equipment. Thus, the stage is set for a potential acoustical conflict between the need for building mechanical services on the rooftop above and the expectations of people occupying residences below (ironically, the most expensive space in the building). This paper discusses a number of design and retrofit projects involving rooftop equipment installations over noise-sensitive spaces. The cases include rooftop equipment such as small corridor exhaust fans, rotary chillers, traction elevators, etc. The paper describes both the noise generating mechanisms and transmission paths as well as techniques for mitigating mechanical equipment noise into occupied spaces.
Gesture controlled synthetic speech and song.
Authors: Fels Sidney , Pritchard Bob , Vatikiotis-Bateson Eric ,   The Visual Voice Team
Published: October 2013

We describe progress on creating digital ventriloquized actors (DIVAs). DIVAs use hand gestures to synthesize audiovisual speech and song by means of an intermediate conversion of hand gestures to articulator (e.g., tongue, jaw, lip, and vocal chords) parameters of a computational three-dimensional vocal tract model. Our parallel-formant speech synthesizer is modified to fit within the MAX/MSP visual programming language. We added spatial sound and various voice excitation parameters in an easy-to-use environment suitable for musicians. The musician’s gesture style is learned from examples. DIVAs will be used in three composed stage works of increasing complexity performed internationally, starting with one performer initially and culminating in three performers simultaneously using their natural voices as well as the hand-based synthesizer. Training performances will be used to study the processes associated with skill acquisition, the coordination of multiple “voices” within and among performers, and the intelligibility and realism of this new form of audio/visual speech production. We are also building a robotic face and computer graphics face that will be gesture controlled and synchronized with the speech and song. [This project is funded by the Canada Council for the Arts and Natural Sciences and Engineering Research Council, Canada. More information is at: www.magic.ubc.ca/VisualVoice.htm]
Synthesizing vowel transitions with an analog vocal tract.
Authors: Brady Michael C.
Published: October 2013

A mechanical vocal tract with a pneumatic sound source, silicone tongue, and lip rounding mechanism is introduced. The tract is designed to make controlled transitions between static articulatory vowel configurations. The focus on transitions is important because many argue that it is the change between steady-state sounds that the nervous system is tuned for in extracting information from the speech signal. I draw on examples and experimental results as I review this steady state versus transition distinction. The notion of articulatory transitions as the motor control targets of robotic speech production is then discussed. Video demonstrations of the mechanical tract helps to illustrate how transitions as control targets may be implemented. In conclusion, I argue for why an analog vocal tract with its true aerodynamics (as opposed to synthesis using a cascade of digital filters) is called for in generating articulator-transition-based speech sounds.
Effects of the airway surface liquid on vocal fold vibration.
Authors: Daily David , Lo Forte Dan , Thomson Scott L.
Published: October 2013

A two-layer airway surface liquid (ASL), comprised of a Newtonian sublayer and a non-Newtonian surface layer, lines the laryngeal lumen. During phonation the layers on opposing vocal folds experience merging, squeezing, stretching, and rupture. Various aspects of the ASL have been studied, but its role in vocal fold vibration remains largely understudied. This presentation describes the results of experiments and computational simulations aimed at improving our understanding of the role of the ASL, in particular the non-Newtonian layer, in phonation. The experimental setup for measuring the liquid properties is described, and results are presented. The measured liquid properties are input into a finite element model of the vocal folds, which includes a simulated non-Newtonian layer, using the software package ADINA. The non-Newtonian liquid is also incorporated into a two-mass vocal fold model, which includes the effects of the ASL during collision and separation. The finite element and two-mass models are compared with each other and with experimental results to assess the influence of the non-Newtonian component of the ASL on vocal fold vibration.
Recovering area functions from acoustics and midsagittal profiles.
Authors: McGowan Richard S. , McGowan Rebecca W.
Published: October 2013

Simultaneously recorded midsagittal pellet positions and acoustic output for several subjects comprise the Wisconsin X-Ray Microbeam Speech Production Database (XRMB-SPD). An articulatory synthesizer, EASY, was used to help recover area function parameters corresponding to the production of vowels by subjects in the XRMB-SPD by means of analysis-by-synthesis. Specifically, for each subject, an initial personalized midsagittal profile was created based on the pellet positions, pellet trace, and pharyngeal wall trace during neutral vowel production. Based on the scales of this initial profile for a subject, subsequent midsagittal profiles were generated from the pellet data during various vowel productions. Each midsagittal profile and the corresponding first three formant frequencies were used to optimize the parameters of an area function in the EASY for closest acoustic match. The optimization was performed with a genetic algorithm. The results are examined in terms of consistency within a subject for different vowels and consistency within vowel for different subjects. Synthesized examples of vowel production will also be presented. [Work partially supported by Grant DC-001247 to CReSS LLC.]
Wave refraction at an interface: Snell’s law versus Chapman’s law.
Authors: Godin Oleg A.
Published: October 2013

Wave energy streamlines determine the paths along which energy is transported from a wave source. The energy streamlines provide insights into mechanisms of wave propagation and scattering and are often utilized to visualize wave fields. In contrast to rays, which are essentially an asymptotic, short-wave concept, energy streamlines adequately represent arbitrary wave fields. However, usefulness of energy streamlines in studies of wave fields is limited by the fact that, unlike rays, no general laws governing energy streamline refraction are known. Here a simple refraction law is derived for energy streamlines of acoustic and linearly polarized electromagnetic waves. The refraction law is an extension of a result recently established by D. M. F. Chapman for sound refraction at plane interfaces of homogeneous media. While Snell's law of ray refraction at an interface is formulated in terms of the ratio of sound speeds in media in contact in the case of acoustic waves, Chapman's law implies that refraction of acoustic energy streamlines is controlled by the ratio of mass densities. Similarities and differences between Snell's and Chapman's refraction laws are discussed. It is shown that analysis of energy streamlines provides a new, helpful perspective on wave transmission through an interface.
A two-dimensional coupled mode model for acoustic propagation in a range-dependent waveguide.
Authors: Luo Wenyu , Schmidt Henrik
Published: October 2013

A two-dimensional, two-way coupled mode model is presented in this work. By combining a forward marching and a backward marching, this model is valid for problems where backscattering is significant. This two-way solution provides great accuracy, and it also features in efficiency, which is achieved by applying the single-scatter approximation. In addition, this model is stable with appropriately normalized range solutions in the formulation. This model is capable of handling two-dimensional problems with either a point source in cylindrical geometry or a line source in plane geometry. The computer code CSNAP is adopted to provide the fundamental model solutions and their associate coupling matrices in this model. This two-dimensional model can be easily extended to a three-dimensional model with the feasibility to solve large-scale realistic three-dimensional problems. Numerical examples are presented to demonstrate the accuracy, efficiency, and stability of this two-dimensional, two-way coupled mode model. [Work supported by the Office of Naval Research.]
Shallow water tomography: Ray theory vs travel-time sensitivity kernels.
Authors: Iturbe I. , Roux P. , Nicolas B. , Virieux J. , Mars J.
Published: October 2013

In underwater acoustics, ray tomography is the classical method used to estimate velocity variations, but recently. Travel-Time Sensitivity Kernels (TSK) approaches have been developed. In this paper, we deal with TSK for two source-receive arrays in an acoustic waveguide for shallow water tomography. As a first step, we show that separation of the different raypaths is improved by using a recently proposed new array processing [time-delay double beamforming (DBF) algorithm]. DBF consists of changing the 3-D data space from source depth, receiver depth and time into a new 3-D space related to ray propagation expressed by the beamformed variables, source angle, receive angle and time. As a consequence, each eigenray of the multipath propagation for a source-receiver couple can be identified and separated through DBF. In this context of DBF, the TSK is no longer point-to-point as usual, but relies on all source-receiver time series. Kernels are computed using the fact that the processed signal is a linear combination of time-delayed signals between all sources and receivers. Results in simulated data and in real datasets recorded in an ultrasonic tank prove that combination of TSK and DBF increases the resolution and robustness performance of shallow-water acoustic tomography.
A finite element model for acoustic propagation in shallow water waveguides.
Authors: Isakson Marcia
Published: October 2013

A finite element model is developed using a commercial code to calculate the backscattering of acoustic waves in a two-dimensional shallow water waveguide with rough interfaces. Finite elements approach an exact solution to the Helmholtz equation as the discretization density increases. A time series for the backscattering is computed from time harmonic computations using Fourier synthesis. A parametric study of the roughness parameters for the sediment/water interface and the air/water interface will be presented in order to assess the range of validity of approximate methods. [Work sponsored by Internal Research and Development, Applied Research Laboratories.]
National Academy of Engineering “Technology for a quieter America” project—impact on “green acoustics”?
Authors: Davies Patricia , Maling George C. , Tocci Gregory C.
Published: October 2013

In 2006, the National Academy of Engineering (NAE) initiated an investigation of the potential benefits of a focused effort to control noise in the workplace, communities, and homes that may be of interest to professionals engaged in “green” acoustics. It covered three initiatives: (1) applications of current technology; (2) research and development initiatives for noise control technology; and (3) intragovernmental and public relations programs. Several workshops were held in the 2005–2008 period with representatives from industry, academia, professional societies, private consultants, and government agencies who examined existing and potential solutions along with policies that would help to develop and deploy solutions. Members of the committee were George C. Maling, Jr., Robert J. Bernhard, Robert Bruce, Elizabeth A. Cooper, Patricia Davies, Carl Hanson, Robert Hellweg, Gerald Lauchle, Richard Lyon, Gregory Tocci, Ian Waitz, and others. In mid-2009, a consensus report will be issued that: (a) summarizes the state of current noise control engineering practice; (b) recommends how existing knowledge can address current challenges; (c) presents a research and education agenda that promotes the generation of new knowledge that can provide the greatest benefit to society; and (d) recommends policies that government agencies can develop to further improve the American soundscape.
The Human Factor: Healthcare, sustainability, and acoustics.
Authors: Rohde Jane
Published: October 2013

There are several areas of concern within healthcare environments, which include staff turnover, infection control, patient satisfaction, and constant increase in costs with diminishing reimbursements. The healthcare systems used are under tremendous scrutiny and those that understand the necessity of creating sustainable care models are headed for future success. Sustainable care models are supported by the physical environment, which has to be based upon evidence-based design principles. This presentation will discuss a case study that is seeking to demonstrate the connection between the person, the place, and the product, resulting in improved patient and resident outcomes. Acoustics, both in the general population and the neonatal/pediatric population, is addressed. Examples of how noise causes disruption to sleep and negative patient and resident outcomes will be provided. Higher stress levels and other issues related to noise will be discussed regarding impacts on staff and performance. The sense of place and how this information can be impacted by design will then be reviewed. Many design professionals know little about acoustics or how to handle mitigating noise in the physical environment. The discussion will then turn to the discussion of products and how products tie into potential multi-faceted solutions.
Balancing acoustical performance with sustainability in LEED 2009 (Leadership in Energy and Environmental Design).
Authors: Bischel Marsha , Costello Amy
Published: October 2013

USGBC’s LEED 2009 rating system provides minimal guidance for achieving optimal acoustical performance in sustainable spaces; however, there are opportunities within the rating systems to combine acoustics with other performance attributes to create spaces with optimal indoor environmental properties. Many acoustical finishes are composed of materials that can help achieve LEED points in several categories and can be critical differentiators in determining total building performance and occupant comfort. Strategies to be discussed will include highly light reflectant surfaces, high recycled content, passive energy reduction, and others. By employing such strategies, the acoustical performance of the building may be enhanced while meeting the sustainability objectives.
Application of acoustic materials for comfort and safety.
Authors: Matheson Robert , King Joseph , Levit Natalia
Published: October 2013

This work presents an overview of two high performance acoustic products from DuPont™ with various case studies on lowering low frequency noise transmission using DuPont™ LoWave™, low-weight thin blanket with enhanced low frequency performance, and lowering noise with cleanable, dust free sound absorptive panels protected by DuPont™ Tyvek®, a distinctive flash spun plexifilamentary film-fibril sheet, combining excellent barrier properties and characteristic porous structure to make it acoustically transparent in the voice frequency range.
Building ventilation and acoustics for people who don’t know much about building ventilation.
Authors: Ermann Michael
Published: October 2013

The architectural composition required for building ventilation, used both for low energy cooling and improved air quality, can be anathema to acoustical goals of speech privacy and noise control. This paper presents a short tutorial on the basics of cross ventilation, stack ventilation, comfort ventilation, and indoor air quality as it relates to climate, building type, and indoor pollutants. It is geared to those without significant prior knowledge and follows a similar tutorial on geothermal systems, presented at the Miami ASA conference.
Peripheral neural coding strategies for spectral analysis and sound source location in the nonteleost bony fish, Acipenser fulvescens.
Authors: Meyer Michaela , Popper Arthur N. , Fay Richard R.
Published: October 2013

Coding mechanisms for spectral analysis and sound source location were investigated in Acipenser fulvescens, the lake sturgeon. A. fulvescens belongs to one of the few extant nonteleost ray-finned fishes, with a phylogenetic history that dates back about 200 million years. A shaker system was used to simulate the particle motion component of sound during electrophysiological recordings of isolated single units from the eighth nerve. Data were compared to teleosts and land vertebrates. Peripheral coding strategies for spectral analysis and sound source location in A. fulvescens resembled those found in teleosts. Frequency characteristics generally resembled that of low-frequency afferents of other fishes and land vertebrates and the auditory periphery in A. fulvescens appears to be well suited to encode the intensity of sound. Eighth nerve afferents responded to directional stimuli in a cosinelike manner (as in teleosts). However, differences from teleosts were found that may have implications for the mechanisms for sound source location in azimuth. The common physiological characteristics among A. fulvescens, teleosts, and land vertebrates may reflect important functions of the auditory system that have been conserved throughout the evolution of vertebrates.
Ontogeny of auditory saccular tuning in the plainfin midshipman fish, Porichthys notatus.
Authors: Alderks Peter W. , Sisneros Joseph A.
Published: October 2013

Sensory systems are important throughout an animal’s life history, allowing it to detect and respond to biologically relevant stimuli important for survival and reproduction. The auditory system of the plainfin midshipman fish (Porichthys notatus) plays an important sensory receiving role for encoding vocal-acoustic communication signals produced by adults, but the response properties and function of this receiver system during ontogeny are less understood. Here, we examine the response properties of evoked saccular potentials in two size classes of juveniles [small = 1.9–3.0 cm standard length (SL) and large = 5.0–8.0 cm SL] and in nonreproductive adults (> 9.0 cm SL) to determine the auditory sensitivity of saccular hair cells during ontogeny. Saccular potentials, maximally evoked at twice the stimulus frequency, were recorded in vivo using a lock-in amplifier while playing pure tone stimuli via an underwater speaker. Results indicate an ontogenetic retention of saccular tuning sensitivity with size/age with peak sensitivity ranging from 75 Hz (lowest frequency tested) to 185 Hz. In addition, maximum detectable frequency of the saccule also increased with size/age. These results suggest that the midshipman saccule is best suited to detect low frequency components (< 105 Hz) of conspecific vocalizations throughout ontogeny.
Otolith crystallization in salmonid fishes: Possible causes and consequences for the fish.
Authors: Coffin Allison B.
Published: October 2013

The primary hearing organ in most fishes is the saccule, which contains a calcareous otolith composed of aragonite and its associated sensory epithelium. In some fish populations, particularly salmonids, the aragonite in the saccular otolith is partially or mostly replaced by vaterite, a phenomenon known as otolith crystallization. Despite the relatively common occurrence of otolith crystallization, the cause of this switch in calcium carbonate type and the consequences for the fish are not understood. The present study looks at both proximal and distal mechanisms that may contribute to otolith crystallization in various salmonid species, particularly with regard to environmental stress and physiological consequences of that stress. Structural and functional data on the ears of salmonids with crystallized otoliths will also be presented. Auditory evoked potential recordings from juvenile chinook salmon demonstrated that fish with at least one vaterite otolith have significantly increased hearing thresholds compared to conspecifics with two aragonite otoliths. These findings suggest that otolith crystallization can have potential negative consequences for the animal.
FM echolocating bats avoid pulse-echo ambiguity by shifting broadcast frequencies.
Authors: Hiryu Shizuko , Bates Mary , Simmons James A. , Riquimaroux Hiroshi
Published: October 2013

Big brown bats pursue flying insects in open areas, but they also hunt for prey near vegetation. The proximity of obstacles requires emission of sounds at short interpulse intervals (IPIs) to guide collision-avoidance maneuvers, yet the bat has to locate obstacles distributed in depth for path planning, which requires longer IPIs. If IPIs are too short, the stream of echoes for one sound will still be arriving when the second sound is emitted, creating ambiguity about matching echoes to broadcasts. We investigated how bats cope with pulse-echo ambiguity by recording sounds with a miniature radio microphone (Telemike) carried during flights through a dense array of obstacles (vertically hanging chains) that were distributed in depth. Array density forced bats to emit FM sounds at short intervals (strobe groups) with consequent pulse-echo ambiguity. We found that when ambiguity occurred, bats shifted the FM sounds in strobe groups upward and downward in frequency by several kiloHertz to distinguish each broadcast’s echoes. Overlap of echo streams from the bat’s own FM broadcasts causes extreme clutter interference, and bats react by slightly shifting FM frequencies to distinguish one sound’s echo stream from another sound’s. [Research supported by an ONR grant.]
Spatial and temporal coherence of scattered field from large fish groups instantaneously imaged with ocean acoustics waveguide remote sensing (OAWRS).
Authors: Ratilal Purnima , Andrews Mark , Gong Zheng , Makris Nicholas
Published: October 2013

Wide area sonar system, such as OAWRS (ocean acoustics waveguide remote sensing), can instantaneously image large shoals of fish spanning tens of kilometers from long ranges in an ocean waveguide. An analytic and numerical model is developed for the spatial and temporal coherence of the scattered field from a large group of fish in a shallow water waveguide. The temporal coherence of the received signal depends on both the temporal coherence of the random waveguide through the medium Green’s function and the correlation time scale for fish group distribution. The spatial coherence of the received signal depends on both the spatial correlation scale of the random waveguide inhomogeneities and that for the imaged fish group distribution. The temporal and spatial correlation scale for the fish group distribution are determined from experimental data acquired in the Gulf of Maine during the 2006 Ocean Acoustics Waveguide Remote Sensing (OAWRS) Experiment. The effect of temporal and spatial coherence of the scattered field on subsequent coherent array processing and matched-filtering is discussed.
Extension of path-integral theory to shallow-water coherence.
Authors: Mignerey Peter C.
Published: October 2013

A path-integral approach to the mutual coherence function of acoustic signals propagating in deep water was developed in the late 1970’s. This theory requires a single dominant ray path that interacts weakly with the boundaries, a restriction which has precluded direct application to acoustic propagation in shallow water. Here, path-integral theory is extended to the mutual coherence of mode amplitudes defined over the horizontal plane. In this domain, the mode amplitudes follow a principal ray that has no interaction with lateral boundaries. The mutual coherence is found to be related to the spectrum of sound-speed fluctuations via a Fourier transform along a direction transverse to the acoustic propagation path. For sound-speed fluctuations generated by a linear internal-wave field, solutions are obtained that predict the mutual coherence with no free parameters. Such solutions were computed for a winter environment existent during an experiment that took place on the New Jersey shelf in December 2003. Comparison between theoretical and measured coherence is encouraging with respect to both the power-law behavior at short separations, and the transition to saturation at large separations. [Work supported by the Office of Naval Research.]
Effect of the internal tide on midfrequency transmission loss in the Shallow Water 2006 Experiment.
Authors: Yang Jie , Rouseff Daniel , Tang Dajun , Henyey Frank S.
Published: October 2013

Nonlinear internal waves depress the high-gradient region of the thermocline. After the waves have passed, it may take several hours for the thermocline to rise to its prewave level. To examine consequent acoustic effects, two acoustic data sets collected 18–19 August in SW06 were analyzed with one at a fixed range of 550 m and the other along a tow track out to 8.1 km. Both data sets allow the effects of the rising thermocline on acoustic propagation to be examined over a range of temporal and spatial scales. Signals transmitted are in the midfrequency band 1.5–10.5 kHz. The gradual rising of the thermocline is shown to change acoustic intensity by 5 and 2 dB for the fixed and towed source data, respectively. Using nearby oceanographic moorings, a simple plane wave ocean model is developed to provide time-dependent environmental input to broadband acoustic modeling assuming range-independency. Modeling results are shown to produce mean transmission loss results consistent with experimental observations at both the short and the long ranges. The results suggest that the rising thermocline effect of nonlinear internal waves on mean transmission loss is observable, significant, and predictable. The result has implications on geoacoustic inversion. [Work supported by ONR.]
Exploiting correlation in passive sonar Bayesian localization techniques.
Authors: Jemmott Colin W. , Culver R. Lee , Bose N. K. , Bissinger B. E.
Published: October 2013

Low frequency acoustic signals in shallow water are strongly affected by interference between multiple paths resulting from boundary interactions. As the acoustic source moves through this interference pattern, the spatial variation in transmission loss can result in strong temporal modulation of the received signal, which can be used to localize the source. Acoustic propagation models can produce accurate transmission loss field predictions, but are sensitive to ocean environmental parameters such as bottom composition, bathymetry, and sound speed profile. If the uncertainty in the undersea environment can be described by probability density functions of these parameters, Monte Carlo forward models can be used to produce an ensemble of possible transmission loss realizations. A probabilistic model representing this ensemble must include a density function of transmission loss at each location, as well as correlation of transmission loss between locations. In addition, the choice of probabilistic model has a large impact on the form of the resulting Bayesian localization algorithm. Previous results have shown that including spatial correlation of transmission loss can result in improved localization. This talk will introduce a non-Gaussian probabilistic model for representing uncertainty in transmission loss predictions that includes correlation, and discuss the resulting recursive Bayesian localization algorithm.
Effect of noise sources motion on the performance of passive imaging from ambient noise cross-correlation.
Authors: Sabra Karim G.
Published: October 2013

It has been demonstrated theoretically and experimentally that an estimate of the Green’s function between two receivers can be obtained from the long-time average of the cross-correlation of ambient noise at these two receivers in various environments and frequency ranges of interest: ultrasonics, underwater acoustics, and seismology. The coherent wavefronts emerge from a correlation process that accumulates contributions over time from noise sources whose propagation path passes through both receivers. Previous theoretical studies of the performance of this noise-based passive imaging technique assumed that the noise sources remain stationary. The influence of the motion of the noise sources (Doppler effect) on this passive imaging technique was investigated theoretically in both free spaces using a stationary phase approximation and extended to waveguide environments. Although the Doppler effect typically degrades the performance of standard wideband coherent processing schemes, such as time-delay beamforming of fast moving sources, it was found that the Green’s function estimates extracted from ambient noise cross-correlations are not affected by the Doppler effect. Practical implications for at-sea passive tomography experiments using shipping noise will be discussed. [Work supported by ONR, Code 321.]
Improvements in compression of coded excitation echoes by using a spatially varying Wiener filter.
Authors: Sanchez Jose R. , Oelze Michael L.
Published: October 2013

Coded excitation schemes require compression of echoes to restore pulse resolution after transmission of an elongated signal. Compression schemes are often performed using a Wiener filter, which contains a smoothing parameter that controls the trade off of gain in echo signal-to-noise ratio (eSNR), sidelobe levels, and axial resolution. A Wiener filter that takes into consideration the spatially varying nature of the pulse-echo impulse response of the ultrasound imaging system within the depth of field was explored. This spatially varying Wiener filter (SVWF) generates numerous compressed outputs within the depth of field that are compounded into one final output, i.e., one final image. The final image using the SVWF has improved sidelobe levels and eSNR when compared to not using the SVWF for compression. Experimental measurements were conducted with a 2.25 MHz weakly focused (f/3) single-element transducer (−6-dB bandwidth of 75%). The imaging targets evaluated consist of planar reflectors, wire targets in water, and wire targets in urethane rubber (ATS 539 multipurpose tissue-mimicking phantom). To evaluate the performance of the SVWF, the spatial resolution, eSNR, and sidelobe-to-mainlobe ratio were evaluated from the images. Preliminary results suggest that compressing at each spatial location within the depth of field improved sidelobe levels leading to improved imaging performance. [Work supported by NIH-R21-EB006741.]
Shear wave elastography of cetacean tissues.
Authors: Gray Michael , Martin James , Rogers Peter
Published: October 2013

An ultrasound-based elastography system is being developed to noninvasively measure the complex shear speed in cetacean head tissues, including brain, jaw fat, and melon. The system instrumentation features a pair of dual-element confocal ultrasound transducers, one of which is used to remotely generate low frequency shear waves in soft tissues via radiation force, while the other is used as a vibrometer to measure the resulting shear wave displacements. Results are presented for in situ measurements on formalin fixed tissues from a bottlenose dolphin (tursiops truncatus). [Work supported by ONR.]
Tissue shear elasticity assesment using time reversal.
Authors: Thomas Gallot , Stefan Catheline , Nicolas Benech , Carlos Negreira , Javier Brum
Published: October 2013

Shear waves in a soft solid can be focalized using time-reversal (TR) methods. The wavelength depending on the elasticity of the medium is related to the focal spot width through the Rayleigh critera. This study proposes to quantitatively estimate the mechanical properties inside a 3-D soft solid cavity from one channel TR experiments. Shear waves are created with an external low-frequency (<300 Hz) mechanical excitation. The first step of the TR experiment consists in the observation of the forward reverberant elastic field; in a second step the backward field is computed in order to refocus the shear waves. Then the wavelength is deduced from the TR focus spot. Two methods for the observation step have been tested, the first one measuring one component of the vectorial field inside the solid by ultrasonic techniques developed in elastography. This method takes advantage of the ultrasound spatial accuracy and its robustness as regard to shear wave source allows to think about many applications in the medical field, including deep or moving organs. The second one is based on the surface wave measurement by acoustic sensors. This low-cost method could be useful in food industry.
Towards predicting intracranial pressure using transcranial Doppler and arterial blood pressure data.
Authors: Mourad Pierre D. , Marzban Caren , Kliot Michel
Published: October 2013

Pressure within the cranium (intracranial pressure, or “ICP”) represents a vital clinical variable whose assessment—currently via invasive means—and integration into a clinical exam constitutes a necessary step for adequate medical care for those patients with injured brains. In the present work we sought to develop a non-invasive way of predicting this variable and its corollary–cerebral perfusion pressure (CPP), which equals ICP minus arterial blood pressure (ABP). We collected transcranial Doppler (TCD), invasive ICP and ABP data from patients at a variety of hospitals. We developed a series of regression-based statistical algorithms for subsets of those patients sorted by etiology with the goal of predicting ICP and CPP. We could discriminate between high and low values of ICP (above/below 20 mmHg) with sensitivities and specificities generally greater than 70 percent, and predict CPP within ±5 percent, for patients with traumatic brain injury. TCD and invasive ABP data can be translated into useful measures of ICP and CPP. Future work will target use of non-invasive ABP data, automation of TCD data acquisition, and improvement in algorithm performance.
Micro flexible ultrasound imaging array systems.
Authors: Lee Michael , Singh Rahul S. , Culjat Martin O. , Brown Elliott R. , Grundfest Warren S. , Lee Hua
Published: October 2013

Medical ultrasonography has continued to be an important biomedical imaging modality for its various advantages. Conventional medical ultrasound systems typically utilize a rigid transceiver phase array, with a relatively small transceiver contact area. A micro conformal system increases observation aperture by using a large, flexible transducer array that conforms to curved body surfaces, providing increased angular coverage and 3-D imagery. In addition, the frequency-modulated continuous wave (FMCW) signaling format requires lower peak power than pulse-echo systems and exhibit more favorable receiver noise characteristics. This paper provides an overview of the hardware development of the micro flexible ultrasound array system. The image formation procedure is first presented in the form of pulse-echo imaging modality. Subsequently, image reconstruction algorithms are formulated for the FMCW imaging format. In addition, the equivalence between the pulse-echo and FMCW imaging modes is developed. This enables us to conduct image reconstruction process in both space as well as spatial-frequency domain. The presentation includes theoretical analysis, image formation algorithms, and laboratory experiments. [This research project was supported by the Telemedicine and Advanced Technology Research Center (TATRC), Department of Defense under award numbers W81XWH-07-1-0672 and W81XWH-07-1-0668.]
Real-time guitar radiation sound synthesis of forced string and body eigenfrequency vibrations using microphone array techniques.
Authors: Bader Rolf
Published: October 2013

A guitar top plate vibration is investigated for different frequency regions taking string driving point dependencies into consideration using a microphone array of 128 microphones and back-propagating the recording to the top plate positions. These radiation patterns are integrated in space at arbitrary virtual microphone positions. A guitar tone or piece is then synthesized using these radiation patterns where the microphone positions can be changed as in a real recording situation. The synthesis process takes the pressure and phase relations of more than 100 positions on the top plate and the sound hole into consideration for two cases of waves, the traveling waves of forced top plate vibration of the string frequencies and the eigenfrequencies of the guitar body appearing mostly during the initial transient phase. These eigenfrequencies are integrated using the much more simple mode shapes of the top plate eigenmodes. The amplitude behavior of these frequencies, appearing and decaying during the initial transient, is calculated by integrating the energy which is supplied by the string acting with a force on the top plate as an impulse train.
Acoustic holography measurements in comparison with a three-dimensional finite element method modulation of the body of a classical guitar.
Authors: Richter Jan
Published: October 2013

The body of a classical guitar (consiting of the rib, back plate, top plate with bridge and fan bracing, soundhole and wooden block) which had been performed by 3-D finite element method (FEM) was presented at the 151st meeting of the ASA (session 3aMU3 in Providence, RI). As a submittal, a real guitar was used whose geometrical parameters had precisely been modeled using a computer. The resulting computation has subsequently been matched to the measurements of an acoustical holography taken from the same guitar body. This time the aim was to demonstrate how closely the FEM model resembles the “real” sound radiation of the guitar. Acoustic holography graphically displays the characteristics of sound radiation from a given body. Again the mode-shapes are of interest, but this time the characteristics of the sound in relation to the frequencies are of greater importance. They demonstrate how realistic the modulation is compared to the actual acoustics of the guitar.
Normal modes of a circular drum head under nonuniform applied tension: Mode splitting with respect to perturbation symmetry.
Authors: Worland Randy
Published: October 2013

The effect of nonuniform tension on the normal modes of single headed musical drums is examined. Using the common (m,n) designation, ideal circular membrane modes with m>0 are doubly degenerate. This degeneracy may be lifted by a perturbation to the circular symmetry. Of practical interest to drummers are perturbations caused by nonuniform tension applied at the rim of the drum in the tuning process, leading in some cases to audible frequency splitting. The symmetry of the perturbation determines which of the various two-fold degenerate modes will split, and to what degree the two resulting frequencies will differ. A selection rule taken from group theory is used, along with principles of perturbation theory, to describe a general model of the frequency splitting of drum modes under the influence of nonuniform applied tension. This model is compared with results of finite element modeling of the membrane normal modes. Experimental results obtained using electronic speckle pattern interferometry (ESPI) are also compared with the model.
Predicting the effects of masking noise on communication distance in birds.
Authors: Dooling Robert J. , Leek Marjorie , West Ed
Published: October 2013

Anthropogenic noise (e.g., highway noise) that exceeds natural ambient sound levels potentially can mask important acoustic signals used by birds during communication. Signals degraded by masking can in turn adversely affect critical behaviors such as mate attraction, territorial defense, parent-offspring communication, predator avoidance, and prey detection. The amount of masking depends not only on the physical characteristics of the noise (intensity, frequency, temporal pattern, etc.) but also the auditory capacity of the species, the acoustic structure of their vocal signals, the proximity of the birds to the noise source and each other, and the sound attenuation properties of the habitat. Here we present a quantitative model for predicting effective communication distances between birds subject to different levels and types of anthropogenic noise. Cross-species analysis shows that communication distances are largely context/environment dependent and species specific. Extrapolation of noise impact distance estimates even within groups of similar species should be exercised with caution. This model should be useful in environmental impact analysis of anthropogenic noise on birds and other wildlife, particularly species of conservation concern.