bluuebunny/crossref_metadata_2025 huggingface dataset:
Ambient noise modeling for high fidelity acoustic simulation
Authors: Poulsen Andrew J. , Schmidt Henrik
Published: October 2011

A high fidelity acoustic simulator has been developed to enable realistic simulation of array time series in order to test sensing/processing algorithms. This simulator, capable of generating calibrated hydrophone or vector sensor array data, is fully integrated into a three-dimensional hydrodynamic array model, generating sensor time series for dynamically evolving array shape, location, and orientation. Furthermore, the simulator handles a changing number and configuration of acoustic sources, targets, and receivers while utilizing the legacy ray tracing code BELLHOP to account for ocean multipath effects. Properly modeling ambient noise is particularly important when determining the effect of noise on sensor/processing performance, e.g., array gain can vary significantly based on the directionality of ambient noise. Embedded in the simulator is the capability to efficiently generate broadband noise for an arbitrary noise intensity distribution as a function of depth and elevation angle (azimuthally symmetric ambient noise) using theoretical expressions for the array covariance structure. This approach is ideal for modeling surface noise in situations where the array covariance expressions need to be repeatedly recomputed to account for changing array shape. Results illustrate the advantages of the proposed approach for generating high fidelity time series to model real-world complexities in an efficient, elegant manner.
Application of the range dependent waveguide invariant distribution processor to unintentionally radiated broadband noise from surface ships in a range- and azimuthally dependent environment
Authors: Sell Alexander W. , Culver R. Lee
Published: October 2011

Waveguide invariant analysis is a useful tool for understanding spectral interference patterns from broadband sources in shallow water waveguides. These interference patterns (in the form of intensity striations) were observed in time-frequency plots of surface ships passing a horizontal line array located along the continental shelf off southeast Florida during a 2007 acoustical experiment. Previous work has shown that results from the Range Dependent Waveguide Invariant Distribution (RaDWID) method match well with simulations from parabolic equation acoustical models and require significantly less computation time; however, work to understand the processor's ability to recreate real data was incomplete. We will discuss how RaDWID processing can be applied to ship-radiated broadband noise to model spectral interference patterns. The implementation of the processor on these data including handling of environmental parameter uncertainty, broadband source power spectrum, and environmental features will also be discussed. [Work supported by ONR Undersea Signal Processing.]
Environmentally sensitive autonomous underwater vehicle (AUV) behavior design
Authors: LePage Kevin D.
Published: October 2011

The design of environmentally adaptive behaviors for AUVs conducting active ASW is discussed within the framework of the MOOS-IvP middleware. The control of a single or a group of autonomous, collaborative AUVs in the underwater environment requires the installation of on-board autonomy to enable the vehicles to optimize their trajectories and strategies as they prosecute underwater targets. As the underwater environment is harsh and large differences in performance can be anticipated as a function of lateral position, speed, and depth, a suite of environmentally sensitive behaviors has been developed to provide the required autonomy. Results from simulation and at-sea experiments will be shown.
Real-time sonar signal processing on-board an autonomous underwater vehicle
Authors: Hamilton Michael , Micheli Michele
Published: October 2011

An active, bistatic signal processing system has been implemented for use on-board autonomous underwater vehicles (AUVs) using towed arrays. The NATO Undersea Research Centre's (NURC) AUVs are programmed to maneuver in order to best track a target. To perform this action autonomously, the vehicle must be able to fully process and track targets via its towed array data in real time or faster. The processor implemented includes processing from the array hydrophone data, through beamforming, matched filtering, Doppler processing, and tracking. This system adapts many previously developed algorithms to function in real time. Research and algorithm adaptations in the areas of normalization, CFAR detection, and array navigation, have also been developed to deal with practical issues which have arisen in sea trials. The implementation, practical issues, and steps taken to address them will be presented. This research is supported by the NURC Consolidated Programme of Work, Cooperative ASW program.
A re-introduction of pre-stressed molded fiberglass isolation pads for floating floors
Authors: Golden Matthew
Published: October 2011

The pre-stressed molded fiberglass isolation pad has been available for over 50 years. In that time, no other material has been developed that exhibits the unique performance features of fiberglass. Fiberglass pads are a very non-linear spring. The dynamic stiffness of fiberglass pads also changes under load. Together these features allow them to provide consistent performance over a very wide load range. Recently, the next generation of pre-stressed molded fiberglass isolation pad has been introduced to the market. This talk will cover what has been improved with this new generation of pad along key performance dynamics of floating floors for acoustical and vibration isolation applications.
Acoustical performance of lightweight construction materials
Authors: Dugan Erin L.
Published: October 2011

Traditionally, acoustical privacy between spaces has been achieved by adding denser, heavier materials to the partition. Recently, several lightweight construction materials have been released into the construction market. Advances in material science have provided a new generation of lighter weight gypsum panels with multiple benefits to builders. Although lighter and significantly easier for contractors to install, the reduced mass of the gypsum panels raises concerns about its effects on the sound attenuation performance of these products. However, analyses have shown that these lightweight gypsum panels are able to provide nearly comparable levels of sound transmission performance as their heavier counterparts. An investigation of the intrinsic mechanical properties contributing to the overall acoustical performance and full-scale sound transmission results is presented comparing wall systems constructed with lightweight panels and standard-weight panels. Alternative assemblies used to increase the sound-attenuating performance are also discussed.
A computationally light method for simulating the physics and statistics of weak signals in spatially correlated random wave [and vibration] fields
Authors: Walker Shane
Published: October 2011

Ocean noise (natural plus man made) incident on an array has coherent and incoherent components. Simulations must accurately include both components so that the synthetic data are faithful to realistic scenarios wherein spatial correlations associated with random wave fields emerge over time. Indeed, noise simulations involving a large number of sensors over long time intervals can be quite computationally expensive. This talk introduces a computationally light method for simulating stochastic (time-domain) realizations of arbitrary duration of spatially correlated noise characteristic of the ocean soundscape. The method is well suited for studying the physics of weak signals in noise and provides an opportunity for studying the emergence of spatial correlations associated with random wave fields. While this talk focuses on passive SONAR simulations, the method can be generally applied to the study of random wave fields and vibrations in other environments such as seismics, helioseismics, and nondestrutive testing.
Comparison of three experimental methods for assessing the blocked electrical impedance of a moving-coil loudspeaker driver
Authors: Marquez Daniel R. , Leishman Timothy W. , Price Rex P.
Published: October 2011

In this paper, three methods are discussed for experimentally isolating the blocked electrical impedance of a loudspeaker driver. The first involves measurement of the voice-coil impedance in a vacuum, before and after an added mass is applied to its cone. The second involves the use of a scanning laser Doppler vibrometer in conjunction with frequency-dependent electrical measurements at the driver terminals. The third involves the traditional destructive method of potting the driver in a hard-drying compound to allow direct measurement of the blocked impedance. The advantages and disadvantages of each method are discussed. The impedances determined by the three methods are used to predict the frequency-dependent cone velocities of several drivers while under operation. Actual measured velocities are compared with the predictions to substantiate the accuracy of each method.
Grand Canyon National Park Overflights environmental impact statement (EIS): Backcountry impairment under the National Park Services' (NPS) noise standards
Authors: Hingson Dickson J
Published: October 2011

The longstanding Grand Canyon overflights noise pollution saga approaches a decision—public comment on the DEIS having concluded in June. Current, longstanding park impairment of soundscape and wilderness character, throughout the park's popular East end backcountry, is readily apparent from detailed quantitative “Location Point” analysis. Per cent time audible and sound level for these, by alternative, and season was displayed with an elegant technique, presented 2009 to INCE/ASA, by Nick Miller. Although the “NPS preferred” draft alternative did not represent significant improvement, the quieter “seasonal use,” Alternative “E” fared much better. This derives from seasonal closures, each year, alternating between the two currently used air tour loops. “E's” data indicate that more stringent daily limits on tour flight allocations will be required to avoid major adverse noise impacts continuance in park backcountry, even so. The core business of the park service being to prevent impairment in its wilderness backcountry, the stark findings afford the NPS a clear opportunity to adapt, with a more appropriate implementation alternative. This will be due by spring, 2012, to timely render a record of decision. An recent agreement between NPS and FAA as to relative roles was helpful in clarifying the applicable noise standards.
Engineering the band structure of one-dimensional hypersonic phononic crystals
Authors: Schneider Dirk , El Boudouti El Houssaine , Liaqat Faroha , Tremel Wolfgang , Butt Hans-Jürgen , Djafari-Rouhani Bahram , Fytas George
Published: October 2011

Phononic crystals—the mechanical analogues of photonic crystals—have attracted increasing interest and have been widely studied within the past decade. The phononic dispersion relation at hypersonic frequencies can be directly measured by the powerful non-destructive technique of high resolution spontaneous Brillouin-light-scattering (BLS) [W. Cheng et al., Nature Mater. 2006, 5, 830]. Due to the vector nature of the elastic wave propagation, theoretical phononic band structures can be uniquely verified at low dimensionality, and hence 1D phononic crystals constitute model systems for fundamental studies. Such hybrid Bragg stacks, composed of alternating layers of silica and poly(methyl methacrylate) (PMMA), respectively, exhibit clear hypersonic phononic band gaps [Gomopoulos et al., Nano Lett. 2010, 10, 980]. In this paper, we report on the fabrication, characterization, and both experimental and theoretical dispersion diagrams along and normal to the periodicity direction of silica/PMMA multilayers. The width of the gap, the phonon frequencies, and their intensities near the first Brillouin zone are sensitive probes of the longitudinal moduli and elasto-optic constants of the individual layers and structural parameters. Mixing with layer modes under oblique incidence conditions allows access to the shear moduli of the two layers.
Shaping the response of multi-degree-of-freedom mechanical systems
Authors: Ryaboy Vyacheslav M.
Published: October 2011

The paper pays homage to the outstanding contribution by Gideon Maidanik to studying synergic action of multiple add-on oscillators in reducing resonance response of a main structure. Methods and results of constructing multi-degree-of-freedom mechanical systems with required responses in frequency and time domains are presented with application to optimal vibration isolation, impedance matching and shock absorption. It is shown, in particular, that the limiting quality of instantaneous shock isolation, which was usually attributed to highly non-linear, heavily damped or active systems, can be achieved by linear low-damped multi-degree-of-freedom mechanical systems. Such systems can be synthesized as multiple vibration absorbers, stacked oscillators (chains), or more general structures including motion transformation elements.
Acoustic radiation pressure, torques, and scatterings: Insight for today from Gideon Maidanik's thesis research
Authors: Marston Philip L. , Zhang Likun , Thiessen David B.
Published: October 2011

Renewed interest in the identification of structural contributions to the scattering by complicated objects and the radiation forces and torques on simple objects in complicated acoustic beams makes it timely to review aspects of Maidanik's thesis research [J. Acoust. Soc. Am. 29, 738-742 (1957); 29, 936-940 (1957); 30, 620-623 (1958)]. Maidanik and Westervelt recognized the importance of King's earlier study of the low-frequency radiation forces on rigid movable spheres and extended that work to ka of 10. Hickling and Wang (1966) examined the properties of the scattering by such spheres and more recently Marston [J. Acoust. Soc. Am. 125, 3539-3547 (2009)] found that such a sphere approximates the low ka backscattering by an aluminum sphere in water. It was also found that negative radiation forces were possible for movable rigid spheres in a helicoidal Bessel beam. Recently, subtraction of complex amplitudes for movable semi-rigid targets has been used to isolate elastic contributions in finite-element based computations for finite cylinders [D. B. Thiessen et al., J. Acoust. Soc. Am. 129, 2686 (2011)]. Maidanik's analysis of radiation torques has recently been reconciled with other approaches [L. K. Zhang and P. L. Marston, J. Acoust. Soc. Am. 129, 1679-1680 (2011)]. [Work supported by ONR and NASA.]
Sound-structure interactions in a Japanese drum
Authors: Hwang Yun-Fan , Suzuki Hideo
Published: October 2011

Previous studies of the sound-structure interaction of a Japanese drum conducted by the authors were focused on the vibration of and the coupling between the two membranes attached at both ends of an air-filled hollow wood body which was treated as a rigid cylindrical shell. This is satisfactory for the lower modes where sound is produced primarily by the vibration of membranes. At higher frequencies, the vibration of the wood barrel cannot be ignored. In the current study, the wood barrel is modeled by using conical shell elements. Orthotropic conical shell finite-elements, which include the rotary inertia and transverse shear deformation, have been developed and coded in MATLAB. Experimental verification of the computed results and the effect of wood barrel vibrations on the acoustical characteristics of a drum are discussed. [This paper is dedicated to honor Dr. Gideon Maidanik for his monumental contributions in structural acoustics. The authors would like to thank Miyamoto Unosuke Shouten Co., Ltd., for providing the Japanese drum in this study.]
Finding schwa: Comparing the results of an automatic aligner with human judgments when identifying schwa in a corpus of spoken French
Authors: Milne Peter
Published: October 2011

This paper compares the results of an automatic aligner with human judgments when identifying schwa in a natural language corpus of spoken French. All word-final, postconsonantal possible schwa insertion sites in the standardized text portion of investigations conducted in both Qu'ebec and France were both hand coded for schwa and time aligned at the word and phone level by the Penn Phonetics Lab Forced Aligner, modified for use with French. The results of the two methods of coding were statistically compared to determine their level of agreement. Preliminary results show a strong correlation between the two methods. Possible effects due to dialect or phonetic context were investigated using a two-way, between subjects analysis of variance. A mixed design analysis of variance was also conducted. Initial results have found no significant effect due to dialect, but a possible effect due to context. This suggests that the results of automatic alignment are comparable with human judgments in both dialects of French, but results may differ for individual speakers in specific contexts. The advantages of using an automatic aligner that can aid in the collection of larger volumes of natural language data than is possible when working manually is discussed.
How knowledge of speech acoustics can improve the robustness of automatic speech recognition
Authors: Espy-Wilson Carol , Boyce Suzanne , Alwan Abeer
Published: October 2011

In this talk, we discuss the ways in which the parallel study of speech production and speech perception can help us develop better automatic speech recognition systems. The ultimate goal of speech recognition (recognition of spontaneous speech from any talker in any language) is still elusive due to a high degree of inter- and intra-speaker variability for production of a given sequence of sounds. While the acoustic information required for recognition may be present in the signal, its distribution, strength, and location are consistent and predictable only as a function of lawful changes in speech movements and/or listener perceptions. Understanding speech acoustics from this perspective is vitally important if we are going to achieve our ultimate goal. We will give several examples of lessons learned from studies of speech production and speech perception and how the knowledge gained can inform the engineering of robust ASR systems.
Recent progress in articulatory modeling for speech recognition
Authors: Livescu Karen
Published: October 2011

The automatic speech recognition research community has experimented with models of speech articulation for several decades, but such models have not yet made it into mainstream recognition systems. The difficulties of adopting articulatory models include their relative complexity and dearth of data, compared to traditional phone-based models and data. This talk will review the current state of articulatory models and will describe one particular approach to incorporating such models in modern speech recognition. In this approach, the articulatory variables are based on the vocal tract variables of articulatory phonology, and the models are represented using dynamic graphical models, a generalization of the more commonly used hidden Markov models. This approach allows the probabilistic modeling of asynchrony between articulators and reduction in articulatory gestures. Results will be presented showing improvements in lexical access using this type of articulatory model with automatically learned context-dependent articulatory feature distributions. Recent efforts to mitigate the data sparseness problem, including manual and automatic transcription, will also be presented.
Effect of subthalamic nucleus deep brain stimulation on tremor, rigidity, muscle strength, and movement
Authors: Corcos Daniel M.
Published: October 2011

The goal of this presentation is threefold. First, we will review studies in which we have shown the dramatic benefit of subthalamic nucleus (STN) deep brain stimulation (DBS) on bradykinesia, tremor, and rigidity. We will show that limb tremor is normalized, movement speed is increased, muscle activation patterns resemble those of healthy individuals, and rigidity is substantially reduced. Second, we will show that there is no difference between 90 min and greater than 3 months of STN stimulation for both the UPDRS or motor control measures. This finding confirms that the treatment efficacy that is derived from a short time course of stimulation generalizes to the longer time periods of STN stimulation that patients experience in their daily lives. Finally, we will conclude by presenting the effects of five years of continuous STN stimulation on muscle strength and movement speed. We will show that despite the fact that patients become more parkinsonian as measured by the UPDRS, they become stronger and faster at making simple movements. These results will be discussed in the context of models of therapeutic efficacy that are predicated on the idea that STN DBS reduces neuronal noise and thus both facilitates simple movements and the reduction of tremor.
Characterization of non-Gaussian, multi-static clutter from a mud volcano field
Authors: Preston John R. , Abraham Douglas A.
Published: October 2011

Sonar clutter is one of the primary limitations to active ASW. This work focuses on statistical analysis of clutter-like returns from some multi-static measurements. Non-Gaussian characterizations of multi-static clutter from a mud volcano field are presented. The received data are taken from either the Five Octave Research Array (FORA) or the NURC triplet array that have been used to collect extensive monostatic and bistatic data in a recent sea trial on the Malta Plateau off Sicily called Clutter 07. This work uses data from that sea trial to characterize non-Gaussian behavior of multi-static clutter from a mud volcano field using pulsed sources in the 800–3500 Hz band. Either the Page test or a maximum likelihood procedure is used to isolate the clutter-like returns before processing. K-distributions with their shape and scale parameters are used to describe non-Gaussian behavior together with the models of Abraham and Lyons to infer physical descriptors from the clutter. The ability to geo-reference key statistical measures of clutter allows CFAR processors to adaptively set thresholds and reduce false alarms. Examples are shown to demonstrate this. Also included are presentations of the shape parameter versus bistatic aspect angle and the cumulative density functions for this parameter. [Work supported by ONR code 321US.]
High frequency bottom loss database generation at the naval oceanographic office
Authors: George Jacob , Harvey David , Novarini Jorge
Published: October 2011

The Naval Oceanographic Office (NAVOCEANO) generates the low- and high-frequency bottom loss databases (LFBL and HFBL). In support of these upgrades, NAVOCEANO carries out survey operations to make acoustic and geophysical measurements. From these measurements, bottom loss parameters are extracted via numerical inversions. The HFBL database describes acoustic bottom loss over the range 1.5-4 kHz and is based on a set of nine bottom-loss curves derived from the Marine Geological Survey carried out by NAVOCEANO (1965–1968). The optimum curve at a given location is derived from a process of brute force inversion using measured transmission loss (TL) data. Curves are interpolated to the nearest 1/10th; they are then input to the CASS model to determine which curve optimizes the fit between the CASS prediction and the measured TL data. Optimal curves are determined independently at each of the 1/3 octave frequencies over the HFBL range. Studies of the derived curve values in a recent upgrade area have indicated very high variability. This variability does not tend to correlate with bottom sediment type, and the variability tends to be highest in the higher frequency bands. An implication is that scattering caused by roughness at the water/sediment interface may be driving variability.
Prediction of marine fine-grain sediment states: Determinants of mine burial and acoustic impedance
Authors: Bennett Richard H. , Curry Conrad W. , Meredith Roger W. , Faas Richard W.
Published: October 2011

The predicted depth of mines buried in marine muds is generally based on estimates of sediment shear strength (often unreliable). Conversely, sediment states of marine muds are water-dependent, defined empirically by the Atterberg Limits (liquid limit and plastic limit), and allow the sediment to be described as having fluid-like, plastic-like, or semi-solid consistency. When the natural water content and the liquid limit of normally and unconsolidated marine muds are approximately equal at depth below the seafloor, the mud at greater depth is considered to no longer behave as fluid-like, but plastic-like. This relationship provides a predictable conservative minimum mine burial penetration depth. Mine burial depths at two sites were shown to closely agree with predicted burial depths based on the natural water contents and the liquid limits (Bennett et al., SEAPROBE, Inc., Technical Report Number SI-0004-01, p., 89, 2004, funded by ONR). Prediction of selected sediment physical properties using acoustic impedance as a function of depth below seafloor may provide a method to estimate and evaluate sediment states. Comparison of subbottom natural water contents with a database showing known liquid limits for different types of marine muds should make possible prediction of conservative, minimum, mine burial depths.
Efficient parabolic equation modeling with shear (SCRAM)
Authors: Campbell Richard L. , Heaney Kevin D. , Duncan Alec J. , McCauley Robert D.
Published: October 2011

A novel parabolic equation model has been developed based upon Michael Collins RAM algorithm. By separating the PE solver from the fixed range-depth slice geometry of RAM, efficiency is significantly improved for full-field × propagation to points on a plan-view grid or along an arbitrary vessel track. The code is written in C with the ability to fully leverage modern many-core computers. In this paper, the SCRAM model is introduced, based on the PE propagator from Collins RAMS variant, extending CRAM to environments with sediments supporting shear wave propagation. Comparison with range-independent wave-integral solutions will be made. Specific application to the problem of propagation over continental shelves with calcerenite seabeds, such as those observed in the seas off the coast of Australia will be examined. Model-data comparisons for measurements taken near Dogan, Australia, will be made.
The depth dependence of earthquake T-phases at an ocean acoustic observatory
Authors: Stephen Ralph A. , Bolmer S. Thompson , Worcester Peter F. , Dzieciuch Matthew A. , Mercer James A. , Howe Bruce M.
Published: October 2011

T-phases are earthquake signals that have propagated, at least partially, in the ocean sound channel. T-phase hydrophone networks detect much smaller earthquakes over basin scales than land-based networks and they detect many more earthquakes than comparable regional scale seismic land networks. Furthermore, since T-phases travel at lower velocities than seismic phases, they result in much more precise locations of events given the same timing accuracy. T-phases are typically spread over 10's of seconds, and a common problem, however, is precisely identifying the arrival time of an event. T-phase stations usually consist of single hydrophones moored near the sound channel axis and the depth dependence of the T-phase envelope and frequency content is rarely studied. In the North Pacific Ocean, from 2004 to 2005, ambient noise and earthquakes were observed at an ocean acoustic observatory consisting of a vertical hydrophone array (from about 750 m above the seafloor to 375 m from the surface) and three co-located ocean bottom seismometers. This data set provides a unique opportunity to observe earthquake signals and their characteristics throughout the water column and to provide ground-truth to theoretical predictions on the excitation and propagation mechanisms of T-phases. In at least one case, a T-phases from a distant earthquake was readily observed even at the seafloor, well-below the conjugate depth.
A new active acoustics system for enhancing musician's environment on concert and recording stages
Authors: Woszczyk Wieslaw , Ko Doyuen , Hong Jonathan
Published: October 2011

The necessity of variable acoustics in modern performance spaces is widely acknowledged; particularly, there has been a growing interest in active acoustics enhancement systems. Many different systems have been developed and installed in concert halls, public venues, and research facilities worldwide. However, further improvements are required to provide musicians with a desirable acoustic on-stage support equal in quality to the best rooms. An innovative electro-acoustic enhancement system, based on measured high-resolution impulse responses, is developed at the Virtual Acoustics Technology (VAT) lab, in McGill University. The first model is installed in Multi-Media Room (MMR), a large rectangular space (80 ft. × 60 ft. × 50 ft.) designed as a film scoring stage. The system uses an array of omni-directional radiators and its signal processing includes 24-channel low-latency convolution at 24 bit/96 KHz, three separate stages of matrix mixing, equalization, and time variation. The objective measurement of the system adjusted to improve on-stage acoustics verifies the enhancement of parameters such as inter-aural cross-correlation coefficient (IACC), early stage support (ST1), and early decay time (EDT) without excessively increasing the overall acoustic energy in the room. The subjective evaluations collected from multiple recording sessions with professional musicians using the system will be presented. [Work supported by NSERC, JMP.]
Orchestra shell innovation: Vented shell case study
Authors: Giegold Carl , Pfeiffer Scott , Schuette Dawn , Norris Molly
Published: October 2011

The College Community School District music programs required a venue larger and more conducive to band and choral performance than their 1970s 400-seat theater. The new venue, located in Cedar Rapids, Iowa, seats 1000 in a space designed primarily for music but with theatrical capability as well. An adjustable orchestra shell and variable absorption tailor the room's acoustic response to speech, theater, jazz, symphonic band, choral, and orchestra. Though it must accommodate bands of up to 140 players for audiences of up to a thousand, the hall must also be responsive to small ensembles and intimate to audiences of only a few hundred. To control loudness for the largest bands, the orchestra shell can be vented to th flytower. The design will be presented, as well as measurement data and anecdotal impressions of the shell.
Active acoustics for concert stages
Authors: Schwenke Roger W.
Published: October 2011

Orchestra shells are often loud places. So much so that some orchestras have instituted noise monitoring and select their repertoire to limit noise exposure. Orchestra shells are loud places because they are surrounded on five out of six sides by nearby hard reflecting surfaces. This also means that the orchestra only experiences reverberation coming from the direction of the house. Active acoustics offers an alternative to physical orchestra shells, which is more light-weight, and offers more flexible acoustical performance including enveloping reverberation for performers.
A survey of selected 800 to 1800-seat multipurpose hall orchestra shells and eyebrows by McKay Conant Hoover Inc
Authors: Conant David A. , Chu William
Published: October 2011

New and renovated multipurpose halls by MCH Inc. are examined with focus on the room-acoustical design of sound to and among on-stage performers as well as, necessarily, acoustical considerations associated with direction of that sound to audience. Specifically, orchestra shell/recital screen design as well as integrated eyebrow/canopy design is addressed. Halls discussed include Kavli Theater (Thousand Oaks Civic Arts Plaza), Jackson Hall (Mondavi Center for Performing Arts), Ikeda Theater (Mesa Arts Center), Granada Theatre Restoration (Santa Barbara), Balboa Theatre Restoration (San Diego), Scottsdale Center for Performing Arts and the new Valley Performing Arts Center (Los Angeles).
Investigations of stage acoustics at the Sydney Opera House Concert Hall
Authors: Gulsrud Timothy E.
Published: October 2011

Improvements to onstage hearing conditions were made at the Sydney Opera House Concert Hall during a series of acoustics trials conducted during September 2009. During the acoustic trials, physical changes were made to reflective surfaces around the platform and an active acoustics system was demonstrated. Taken together, the temporary changes had a positive influence on hearing conditions during both rehearsals and performances by the Sydney Symphony Orchestra and Sydney Philharmonia. This paper reviews the strategies used to implement the improvements to stage acoustics, and discusses the unique techniques used to evaluate the stage acoustics both subjectively and objectively.
Passive acoustic methods for surveying visually cryptic frog species
Authors: Borchers David L. , Measey John G. , Altwegg Res
Published: October 2011

Passive acoustic survey methods have great potential for assessing cryptic species that are vocally active. The tiny Moss Frogs (genus Arthroleptella) that inhabit seepages on remote mountain tops in the Western Cape of South Africa are a case in point. Many species are restricted to individual mountains and most are on the IUCN Red List. Surveys are prohibitively expensive because each individual capture involves three to four person-hours of searching. However, males can be heard calling throughout the winter. Using a portable recorder, we gathered acoustic data from which abundance can be estimated and populations monitored. This involves estimation of both the spatial "footprint" of the acoustic array (i.e., what area it effectively surveys) and animal vocalization rates. Ideally both should be estimated as an integral part of the survey, rather than obtained from outside the survey. By combining recently developed mark-recapture methods that take explicit account of the spatial location of microphones, with data on acoustic signal strength and/or time-difference-of-arrival at different microphones, it is possible to do this. We describe the survey and estimation methods, which have many other potential applications. In the case of these frogs, acoustic survey is hundreds of times more efficient than methods involving physical capture.
Acoustics as a tool in sub-species and population identification for endangered fin whales, Balaenoptera physalus
Authors: Rankin Shannon , Barlow Jay , Archer Eric , Jones Benjamin
Published: October 2011

Identification of “stocks” (sub-species and independent populations) is important for understanding and mitigating potential sources of human-caused mortality. This is especially critical for endangered and protected species, such as the large whales. Stock identification for whales has typically been based on ecology, life history, morphology, and genetics. However, for many species, acoustic differences in whale call types may indicate population or sub-species structure. The potential role of acoustics in identifying species and sub-species has been identified in numerous publications; however, this role has yet to be realized for large whales. In an effort to include acoustic data in this process, we are contributing to current efforts to update the status of endangered fin whales, Balaenoptera physalus, in the North Pacific. An analysis of North Pacific fin whale populations based on identification of “song” provides hypotheses that can be tested with genetics. Strengths and limitations of acoustic methods will be presented, as will the potential for collaboration on the scale of ocean basins.
Vibro-acoustic doppler
Authors: Nabavizadeh Alireza , Urban Matthew W. , Fatemi Mostafa
Published: October 2011

This paper describes the principles and initial experimental results of a new Doppler method called vibro-acoustic Doppler (VAD). VAD uses acoustic response of a moving object to a highly localized dynamic radiation force of ultrasound to measure the velocity of the object. The low frequency radiation force is exerted by two co-focused ultrasound beams with slightly different frequencies. The acoustic response of the object is detected by a hydrophone. A formula that describes the relation between the Doppler frequency shift of the emitted acoustic field and the velocity of the moving object is reported. To verify the theory, experiments are conducted on a moving string and a fluid flow phantom. Results show that the error in velocity measurement is less than 9.1% for either phantom. An advantage of this method over the traditional ultrasound Doppler is that velocity measurement with VAD is almost independent of the angle between the ultrasound beam and motion direction. It is shows that in the worst case, the error is 10.3% for a ±30 deg angle variation. Potential biomedical applications of VAD will be discussed.
Young's modulus estimation of bovine lens ex-vivo using a laser-induced microbubble under impulsive acoustic radiation force
Authors: Yoon Sangpil , Aglyamov Salavat , Karpiouk Andrei , Emelianov Stanislav
Published: October 2011

According to the most widely accepted theory of presbyopia, the age-related loss of accommodation is attributed to Young's modulus changes in the lens. Previously, we have developed an approach to measure the mechanical properties of viscoelastic medium using microbubbles and acoustic radiation force. In this study, we tested this technique to assess the mechanical properties of bovine lenses ex-vivo. An impulsive acoustic radiation force was applied to laser-induced microbubbles created with nanosecond laser pulses at different locations in the lens. An acoustic radiation force with typical duration less than 150 μs was generated by a 3.5 MHz transducer. For accurate spatio-temporal measurements of the microbubble's displacement, a custom-made ultrasound system consisting of two 25 MHz transducers was built. The first transducer emitted a train of pulses and the other transducer received the train of echoes reflected from the microbubble. The developed system was operating at 400 kHz pulse repetition frequency. The results show good agreement between experimental measurements and the theoretical model of microbubble dynamics. Evaluation of the spatial distribution of elasticity demonstrates that the Young's modulus of the nucleus is higher than that of the cortex for bovine eye lenses of mature animals. [Work supported by NIH Grant EY018081.]
Measurement of elasticity of thin elastic layers with radiation force and wave propagation methods
Authors: Urban Matthew W. , Nenadic Ivan Z. , Bernal Miguel , Qiang Bo , Greenleaf James F. , Chen Shigao
Published: October 2011

In the field of tissue engineering, monitoring the elasticity of developing tissue cultures is important for evaluating their growth and maturation. In this work, we used wave propagation methods to measure the elasticity of thin tissue-mimicking layers to test the feasibility of measuring the elasticity of developing tissue cultures. We developed finite element and analytical models for investigating this problem and found good agreement between the results from both models. We used ultrasound radiation force to induce propagating waves, and the waves are measured using high frame rate ultrasound imaging at 10 kHz. The wave modes were identified and compared with an analytic model for Rayleigh wave propagation in a thin elastic layer bound to a solid substrate. The same gelatin mixture was used to make phantoms 1, 4, and 50 mm thick, where the phantom with 50 mm thickness was used as control and evaluated with shear wave imaging methods. The analytic model was used to fit data from experiments in the large block and thin layers of 1 and 4 mm thick, and the measured shear moduli were 22.7, 21.8, and 22.5 kPa, respectively. These results provide a validation for measurement of elasticity in thin elastic layers.
Modeling of the radiation force imparted on a spherical kidney stone by a focused beam of an ultrasound array
Authors: Sapozhnikov Oleg , Bailey Michael
Published: October 2011

Radiation force imparted on an elastic scatterer by a narrow ultrasound beam is different from that imparted by a plane wave, especially when the beam waist is comparable or smaller than the scatterer's diameter. Such a situation exists when a kidney stone is pushed by an acoustic wave emitted by a megahertz frequency ultrasound array. A spherical stone of several millimeters in diameter with elastic properties similar to calcium oxalate monohydrate kidney stones is considered. An acoustic wave is taken in a form of a continuous-wave 2.5 MHz focused ultrasound beam emitted by Philips HDI C4-2 imaging array. To study radiation force, the transducer field is created as a sum of plane waves of various inclinations, and scattering of each plane waves is modeled based on a known solution. Numerical calculations show that within some frequency range both the backscattering from and the radiation force on a kidney stone exceeds the values for absolutely soft or rigid spheres of the same diameter. A vector component of the radiation force can be created in a direction other than the ultrasound propagation by targeting off the stone center. [Work supported by NIH (DK43881, DK092197, and DK086371), RFBR, and NSBRI through NASA NCC 9-58.]
Determination of thresholds for renal injury in a porcine model by focused ultrasound
Authors: Simon Julianna C. , Wang Yak-Nam , Evan Andrew P. , Paun Marla , Starr Frank L. , Crum Lawrence A. , Bailey Michael R.
Published: October 2011

Recently, a system that uses focused ultrasound to expel renal stone fragments from the kidney by radiation force was developed by Shah etal. [Urol. Res. 38, 491–495 (2010)]. A worst-case treatment protocol using this system would require a total exposure time of 10 min, with a spatial peak pulse average intensity (I_SPPA) of 3600 W/cm2 in water (16 MPa peak positive pressure) and a 3% duty cycle. As the system operates above the FDA limits for diagnostic ultrasound, our goal is to verify the safety of the system by determining the threshold for renal injury. A 2-MHz annular array generating I_SPPA up to 29 000 W/cm2 in water was placed on the surface of in vivo porcine kidneys and focused in the proximal parenchyma. Exposures of 10 min duration with varying I_SPPAs and duty cycles were repeated at least 6 times. Mechanical tissue damage and cell viability were evaluated histologically using H&E, PAS, and NADH diaphorase stains. The proportion of samples showing injury was plotted versus duty cycle and I_SPPA. The results indicate that the system to expel renal stones operates below the threshold for kidney injury. [Work supported by NIH DK043881, DK086371, DK092197, and NSBRI through NASA NCC 9–58.]
Two-dimensional shear elasticity imaging using comb-push acoustic radiation force and algebraic direct inversion of the motion differential equation
Authors: Song Pengfei , Manduca Armando , Li Zhoubo , Zhao Heng , Urban Matthew W. , Greenleaf James F. , Chen Shigao
Published: October 2011

Tissue mechanical properties can be obtained by algebraic direct inversion (ADI) of the shear-wave motion differential equation, which is insensitive to reflection and geometry of the pushing beam. Shear waves normally generated by a focused ultrasound pushing beam have limited spatial extent in depth and are transient in time, leading to noisy and unstable ADI results. A comb-shape acoustic radiation force distribution can generate shear waves with longer spatial extent and time duration, facilitating more robust ADI. For 400 μs, a linear array transducer simultaneously transmitted four unfocused pushing beams (12 on elements for each pushing beam, 8 off elements between beams) into a tissue-mimicking phantom (∼1.5 kPa) with a cylindrical inclusion (∼4 kPa). The ultrasound system (Verasonics Inc.) then immediately switched to flash imaging mode (frame rate = 2 kHz, spatial resolution = 0.31 mm) to measure shear-wave displacements in a 38 mm by 30 mm domain that was used for ADI. The reconstructed 2D shear elasticity map provides accurate shear elasticity estimates (background = 1.5 kPa with 7% variance; inclusion = 3.9 kPa with 15% variance) and excellent contrast between the background and inclusion.
Recent progress toward a nanostructured piezoelectric microphone
Authors: Mathias Adam D. , Fox Jon R. , Cortes Jean P. , Horowitz Stephen B. , Sanghadasa Mohan , Ashley Paul
Published: October 2011

In an attempt to push the performance limits of piezoelectric MEMS microphones, several variations of micromachined acoustic sensors that contain piezoelectric zinc oxide nanorods embedded in a flexible polymer matrix were designed, fabricated, and characterized. The polymer matrix offers high compliance, high aspect ratio, ultrathin diaphragms, and low residual stress, while the zinc oxide nanorods provide high piezoelectric coupling. The devices, fabricated on a silicon substrate, consist of 100–800 μm diameter circular diaphragms composed of the piezoelectric polymer composite sandwiched between a circular gold bottom electrode and an annular gold top electrode. Electrical, mechanical, and acoustic characterization were performed on the fabricated sensors. Acoustic measurements included frequency response, sensitivity, linearity, and noise floor. Electrical properties such as resistance and capacitance, and piezoelectric properties, such as the effective piezoelectric coefficient, were also measured.
The effect of musical training on auditory perception
Authors: Kannyo Irene , DeLong Caroline M.
Published: October 2011

Previous research has shown that musical training affects the type of cues people use to discriminate between auditory stimuli. The current study investigated whether quantity of musical training and musical area of expertise (voice, percussion instrument, non-percussion instrument) affected musical feature perception. Participants with 0–4 yr of experience (13 non-musicians), 5–7 yr of experience (13 intermediate musicians), and 8 yr or more of experience (13 advanced musicians) were presented with pairs of 2.5 s novel music sequences that were identical (no change trials), differed by one musical feature (pitch change, timber change, or rhythm change), and differed by two musical features (pitch and timber change, pitch and rhythm change, or timber and rhythm change). In 64 trials, participants had to report whether they heard a change, as well as classify the specific type of change. Participants in the advanced group (M = 91.2%) and intermediate groups (M = 85.0%) performed significantly better than non-musicians (M = 70.0%). There was no effect of area of musical expertise (voice or instrument) on musical feature change detection. These results suggest that musical training in any area increases the ability to perceive changes in pitch, timber, and rhythm across unfamiliar auditory sequences.