bluuebunny/crossref_metadata_2025 huggingface dataset:
Information transfer of broadband sonar echoes
Authors: Gaumond Charles F.
Published: November 2013

The ability to compute information transfer of a broadband signal corrupted with additive noise is straightforward, but the case of signal corrupted by convolution with a stochastic, propagation impulse-response is more complicated. The known, integral solution is presented along with numerical methods for estimating differential entropy and mutual information using kernel density estimators. Numerical examples using simulations of echo and propagation responses are shown. Results are shown using echo data from Clutter09, an ocean experiment performed with an echo repeater. These echoes were generated with a known, modeled target response. The mutual information between the modeled target response and the echoes, which propagated through ocean environments, is also shown. These results are discussed with respect to developing a method of obtaining an information sonar equation that could be used to estimate the sonar parameters required to perform an information based task, such as signal classification. [Research funded by the Office of Naval Research.]
Clutter statistics of long-range wideband echoes from fish aggregations off the Oregon coast
Authors: Gauss Roger C. , Fialkowski Joseph M. , Love Richard H.
Published: November 2013

Echoes from fish can be the dominant source of reverberation over a range of important sonar frequencies and grazing angles. Moreover, fish echoes from broadband signals often retain coherent structure (generate clutter) after undergoing normalized match-filter processing. Coupled with their inherent spatiotemporal variability, fish can thus be a significant clutter problem for active sonars. Using a towed source and horizontal line-array receiver, measurements of mid-frequency (1.5-11 kHz) backscattering from aggregations of fish were made from the R/V New Horizon in five shallow-water and shelf-break areas off the coast of Oregon (Astoria Canyon to Heceta Bank) during July and August 2012. The experiment and the frequency-dependent echo statistics in relation to the observed distribution and behavior of the two primary resident fish species (Pacific hake and Pacific sardines) are discussed. For example, the short-time echo variability and spatial patchiness were characteristic of the mid-water (hake) and near-surface (sardine) fish observed concurrently on echosounder displays. Furthermore, the clutter’s probability density functions were found to be non-Rayleigh but well modeled by NRL’s Poisson-Rayleigh clutter model that provides a physical context for relating data distributions to scatterer attributes. [Work supported by the Office of Naval Research.]
Dual-channel orthogonal modulation differential pattern time delay shift coding underwater acoustic communication method
Authors: Han Xiao , Yin Jingwei , Zhang Xiao , Wang Chi
Published: November 2013

Information is carried by the time delay between adjacent code elements in differential pattern time delay shift coding system. It has an ability of anti inter-symbol interference and the Doppler effects. In order to obtain higher communication rate and reduce the interference between channels, this paper proposes a dual-channel orthogonal modulation differential pattern time delay shift coding underwater acoustic communication method and selects the balance Gold sequence as Patterns. At the transmitter end, divide input bits into two channels to differential pattern time delay shift encode and modulate orthogonally. Then add the encoded signal of two channels together to transmit. At the receiver end, demodulate the received signal orthogonally, search the correlation peak position of patterns. And estimate time delay to restore the original input information. Dual parallel channel transmission mode effectively improves communication rate of differential Pattern time delay shift coding and the orthogonal modulation method greatly reduces the interference between channels. Simulation research is carried on for the method, at transmission data 2x104bit and SNR -5dB, information is recovered at a communication rate 205 bit/s with very low bit error rate.
Propagation effects of surface waves in two unperturbed mode models
Authors: Henyey Frank S. , Thorsos Eric I.
Published: November 2013

Two unperturbed mode simulation models for acoustic propagation with a wavy surface have been developed. The first, LIN, is the first order in the surface elevation for a fixed number of modes. It is the model that provides the starting point for deriving transport equations, as the mode coupling spectra needed for transport theory are practical to evaluate. The second model, DAE, is more accurate for a larger number of modes, but the mode coupling spectra are very difficult to evaluate. The results are compared for an example propagation environment, and consequences to the accuracy of the transport theory are discussed.
Directionality of ambient noise measurements in Barrow Strait of the Canadian Arctic
Authors: Pelavas Nicos , Pecknold Sean , Lucas Carmen E. , Heard Garry J.
Published: November 2013

In August 2012, a field trial was carried out in Barrow Strait south of Gascoyne Inlet in the vicinity of 74.630 N 91.340 W. Underwater acoustic data was collected using a JASCO Autonomous Multichannel Acoustic Recorder (AMAR) and in-house designed sensor systems called Starfish Cubes. The Starfish Cubes were deployed twice, at different locations, each for one week duration and at depths of approximately 110 m. The Cubes consist of seven hydrophones with 1 m spacing and geometrically configured as three cross-dipoles with a central hydrophone, and have an operational frequency range of 5—750 Hz. During the trial 400 and 500 Hz tones were transmitted from discrete locations at various ranges. By using a beamforming method the tones were used to determine the orientation of the Starfish Cubes during their data collection periods. This enables investigation of the horizontal and vertical directionality of ambient noise. Unique localized sources contributing to the ambient noise are discussed such as a nearby grounded iceberg and a low frequency wandering tonal.
Eigenspace dynamics of sample covariance matrices
Authors: Quijano Jorge E. , Zurk Lisa M.
Published: November 2013

Estimation of the sample covariance matrix is a challenge in array processing, particularly with large-aperture arrays operating in dynamic environments affected by fast maneuvering interferers and background noise. Minimizing the impact of time-dependent variations in the underlying signal statistics requires short observation intervals, thereby reducing the number of snapshots available for covariance estimation. Distinguishing between true variations in the received signal statistics and artifacts introduced by insufficient samples is still an open field of research. Recent developments in random matrix theory (RMT) have provided mathematical foundations to understand the behavior of sample eigenvalues and eigenvectors, and how they deviate from their population counterparts due to the lack of snapshot support. Similarly, expressions have been obtained to describe the “distance” between an initial eigenspace (spanned by p eigenvectors), relative to a subsequent eigenspace (spanned by q eigenvectors). In this paper, simulations corresponding to a horizontal array operating in a realistic environment are used to investigate RMT-based metrics that quantify time-dependent eigenspace stability. This research develops mathematically justifiable methods for proper data segmentation into intervals that exhibit local stationarity, providing data-driven higher bounds for the number of snapshots available for the computation of sample covariance matrices.
The effects of source motion and bottom bathymetry on temporal coherence in shallow water propagation
Authors: Wylie Jennifer , DeFerrari Harry
Published: November 2013

Previous studies on coherence have been focused on the effects of water column fluctuations on temporal coherence with a stationary source/receiver setup. However, with focus being turned to moving source setups there has been documented a significant drop in temporal coherence. With a moving platform, the propagation path will change based on relative source/ receiver position, and hence the bathymetry along the path will vary. Here, we will examine the effects that this bathymetric variation and related ship speed contribute to coherence loss. A range dependent parabolic equation model will be used to predict the temporal coherence for individual mode arrivals. A slowly varying random bottom will be introduced to the model and the coherence calculated for different ship speeds and for both radial and tangential tracks. Results will be compared with stationary source/receiver setups in order to determine at what ship speed/ bottom bathymetry does source motion become the driving factor in loss of coherence versus water column fluctuations from a stationary setup. Preliminary results indicate that at a speed of 2 knots, there is remarked loss of coherence at all modes except the first with even small variations in bottom bathymetry, which is in agreement with experimental results.
Dual gate ultrasonic backscatter technique compared to x-ray microtomography parameters
Authors: Smathers Morgan , McPherson Joseph A. , Sellers Mark , Hoffmeister Brent K.
Published: November 2013

Over 52 million Americans suffer low bone mass and at least 10 million suffer from osteoporosis. This study seeks to develop a dual gate ultrasonic technique for predicting bone quality as well as bone quantity. Ultrasonic pulses from a 5 MHz transducer were propagated into regions of porous bone in 18 bone specimens from one bovine and four human donors. The dual gate technique considered the normalized mean of the backscatter difference (nMBD), which is the power difference between two gated regions of 2 μs each placed 1 μs apart over the returned signal. This ultrasonic parameter was compared to eight X-Ray MicroCT parameters describing bone quality and quantity. Among these are the Structural Model Index (SMI) and Relative Bone Volume (BV/TV). SMI grades the structure of a specimen based on its plate and rod characteristics, making it a bone quality characteristic. SMI produced an R value of 0.982 with nMBD. BV/TV, a bone quantity indicator, finds the ratio of bone volume in the total specimen volume, and showed an R value of 0.993 with nMBD.
Nonlinear propagation effects on measurement of backscatter coefficient of tissue-mimicking materials
Authors: Stiles Timothy
Published: November 2013

Measurement of the ultrasonic backscatter coefficient (BSC) holds great promise in providing quantitative diagnostic information on various diseases. Many clinical studies utilize the reference phantom method. In this method, the measured BSC is the ratio of the power spectrum of the scattered sound from the patient to the power spectrum from the reference phantom multiplied by the known BSC of the reference and an attenuation correction factor. In these studies, nonlinear propagation has been ignored. Nonlinear propagation causes changes in the power spectrum as incident energy is converted to harmonics and the acoustic signal undergoes nonlinear attenuation. This study characterized the effects of nonlinear propagation on reference phantom measurements of BSC from four tissue-mimicking samples in the frequency range from 2 to 20 MHz and incident pressure from 1 to 10 MPa (measured in water) using single element focused transducers. Samples consisted of glass microspheres suspended in a mixture of agar and concentrated milk. The resulting BSC varied by up to a factor of 30 depending on the incident pressure. Substantial changes in the overall shape of the BSC vs frequency were also observed. New methods of measurement of BSC that account for nonlinear propagation are explored.
An ultrasound technique for wireless power transmission through tissue to implanted medical devices
Authors: Radziemski Leon , Makin Inder R.
Published: November 2013

An ultrasound electrical recharging system (USERTM) is developed and tested, which wirelessly transmits significant amount of energy through animal tissue to charge implantable devices, batteries, or capacitors. The goal of this approach is wireless power transmission to active human implant devices. Experiments with transducers with resonant frequencies between 0.5 and 3.5 MHz led us to adopt 0.75 to 1.25 MHz as the range of optimum efficiency. In vitro experiments demonstrated significant charging of 4.1 V medically qualified Li-ion batteries across tissue depths of up to 5 cm. Charging currents close to 300 mA were achieved in vitro. Several in vivo tests confirmed the power delivery in a porcine model. In an in vivo survival test, tissue was exposed to 1 MHz ultrasound at an average intensity of 0.4 W/cm2 for 11.5 h. Histology of the exposed tissue showed tissue changes primarily attributable only to surgical implantation of the prototype device. Many traditional and developing implanted medical devices are targets for the introduction of this method of power delivery, to reduce the number of battery replacement operations, and improve performance compared to the existing electromagnetic method of wireless power delivery. [Work supported by the NIH/NIBIB R44EB007421.]
Integrated transmission-reflection quantitative ultrasound noninvasive prediction of trabecular bone principal structural orientation validated with mechanical testing
Authors: Lin Liangjun , Lin Wei , Qin Yi-Xian
Published: November 2013

Quantitative ultrasound (QUS) measurement was shown to have the ability to predict the principal structural orientation (PSO) with a spherical bone model. It is hypothesized that with a cubic bone model, integrated transmission-reflection QUS measurement can predict the PSO and therefore improved the correlation with the mechanical and structural parameters. Twelve trabecular bone cubes were harvested from bovine distal femur. Compression testing and µCT of 30 µm resolution were performed to obtain the mechanical and structural parameters. QUS measurement was performed on the transverse plane in a range of angles, from -30̊ to 30̊ to medial-lateral orientation at 5̊ increment. For each angle, reflection mode was used to measure the thickness of the sample in the specific scanning angle. Then, the sample thickness was used to normalize the transmission mode measurement in the same angle. The thickness measured by reflection mode QUS was highly correlated to the results measured by caliber (slope = 0.99, R2 = 0.85). Compared to the traditional transmission mode, the correlation coefficients (R2) between transmission-reflection mode ultrasound velocity versus mechanical and structural parameters were improved (elastic modulus, 0.62 to 0.73; SMI, 0.74 to 0.90; BV/TV, 0.75 to 0.85; Tb.N, 0.60 to 0.75; Tb.Sp, 0.66 to 0.73).
A piezoelectric micromachined ultrasonic transducer array for parametric loudspeakers
Authors: Je Yub , Lee Haksue , Moon Wonkyu
Published: November 2013

A parametric array is a nonlinear conversion process that can generate a highly directional sound beam with a small aperture. Since parametric sound generation requires high-intensity ultrasound for nonlinear interaction, efficient sound generation is an important issue in the practical use of parametric loudspeakers. In this study, a piezoelectric micromachined ultrasonic transducer array was investigated in order to generate directional audible sound with a parametric array. A piezoelectric micromachined ultrasonic transducer, with a micron-thick radiating plate, was verified to generate ultrasound with high-efficiency in air. Two types of unit transducers with different resonance frequencies (f1 = 100 kHz, and f2 = 110 kHz) were arranged in the transducer array to extend the frequency bandwidth. The electroacoustic efficiency of the transducer was measured to 71% at its resonance frequency. The ±3dB-frequency bandwidth of the transducer array was 17 kHz. The spatial distributions of the difference frequency wave were measured and compared with the computed data in the audible frequency range. The fabricated transducer array consumed 1 W of electric power while generating a 10 kHz-difference frequency wave with sound pressure level of 80 dB.
A micro-machined Tonpilz hydrophone for audible frequency sounds
Authors: Sung Min , Lee Haksue , Moon Wonkyu
Published: November 2013

A micro-machined Tonpilz hydrophone based on the piezoelectric thickness mode was designed for audible frequency range of 20 Hz~20kHz. The structure of the sensor was motivated by conventional Tonpilz transducers, but two different design approaches were adopted to enhance the sensitivity and to endure the high hydrostatic pressure in deep-sea. For improved sensitivity, the area ratio of the head-mass and the piezoelectric body was designed to be several hundreds to one, which amplifies the input of the transduction body due to acoustic pressure. Since this approach is adopted in order to develop a miniaturized hydrophone manufactured by a batch process, the size of the piezoelectric transduction body becomes too small to generate the amount of charge enough for detecting the signal using the conventional pre-amplifier at low frequencies below 500 Hz. We have developed and validated the lumped parameter model and used it to identify the requirements for the pre-amplifier circuits and the available sensitivity at low frequencies and to search for the appropriate design for miniaturized hydrophone. Then, the designed hydrophone was fabricated by micro-machining and assembled with the custom-made pre-amplifier inside with caster-oil filled rubber housing. The evaluation of the hydrophone will be presented. [Research supported by MRCnD.]
Hot topics in architectural acoustics: Classroom acoustics and archaeoacoustics
Authors: Lubman David
Published: November 2013

When ASA members discovered that typical American classrooms were too noisy or reverberant for serious learning in 1988 they began a successful grassroots movement to fix them. By 2002, ASA volunteers produced the first-ever ANSI standard for classroom acoustics. The effort was led by ASA’s TCAA and supported by three other TCs, the S12 Standards Committee, courageous ASA staffers, and elected officers. ANSI Standard S12.60 was adopted fully or partly by school districts, states, and architectural authorities including the Green Building Council. Classroom acoustics research reporting remains active at ASA meetings. We show how this standard helps to make a better world. The new fields of archaeoacoustics and historical acoustics are “hot”. They employ scientific acoustics to study the past. Their novel hypotheses and discoveries attract young investigators to acoustical careers. Sound was more important in the quiet ancient world. Many are fascinated by the 1988 discovery of strong correlation between the locations of Paleolithic cave paintings and cave resonance. Why? A pyramid at Chichen Itza, Mexico, chirps like a bird revered in Mesoamerican cultures. The chirp is explained by applying the convolution theorem to pyramid architecture. Was it intentionally designed? Other archaeoacoustic and historical acoustic examples are addressed.
Combining acoustical and fire-resistive design in separating assemblies
Authors: LoVerde John , Dong David W.
Published: November 2013

In most project types, separating assemblies must be fire rated, which means the assembly design and materials must be listed by one of the approved fire rating bodies. This can limit the acoustical design options to assemblies and materials that have previously been listed. For large developers, it can be advantageous to design new assemblies that are not currently listed that meet both the acoustical goals and the fire code requirements. Acoustical testing is performed on design iterations and with various products, in coordination with architectural elements and product manufacturers. The completed assembly is burn testing and agency listed. Examples and lessons of the process are shared.
Sensitivity analysis of an equivalent source model for a military jet aircraft
Authors: Neilsen Tracianne B. , Gee Kent L. , Hart David M. , James Michael M.
Published: November 2013

The noise from a tied-down F-22A Raptor is modeled with an equivalent source consisting of two line arrays of monopole sources and their image sources, to represent the interference from the ground. These arrays, one correlated and one uncorrelated, with Rayleigh-distributed amplitudes, mimic properties of fine and large-scale turbulent mixing noise. [Morgan et al., Noise Control Eng. J. 60, 435-449 (2012)]. The equivalent source modeling parameters (the distributions’ peak locations, amplitudes, widths, and the relative phase angle between correlated sources) are selected using Bayesian optimization implemented with simulated annealing and fast Gibbs sampler algorithms. The resulting equivalent source model reasonably predicts the radiated midfield up to 1250 Hz [Hart et al., POMA 19, 055094 (2013)]. In this study, the relationship between the correlated array’s peak location and its phase angle has been further analyzed. Although sensitivity analysis of the results reveals non-uniqueness of the model, it also yields additional physical insight in the form of bounds for the dominant aeroacoustic source region as a function of frequency. The far field sound radiation predicted by the equivalent source model for a wide range of frequencies will be compared to measured far-field directivities. [Sponsored by the Office of Naval Research.]
Unstructured large eddy simulations of heated supersonic twin jets
Authors: Brès Guillaume A. , Ham Frank E. , Lele Sanjiva K.
Published: November 2013

Unstructured large eddy simulations are performed with the compressible flow solver ”Charles” developed at Cascade Technologies, for heated supersonic over-expanded jets issued from a twin nozzle. The study focuses on the modeling of the internal flow and its effects on the flow-field in the jet plume and ultimately on the radiated noise. In this work, near-wall adaptive mesh refinement, synthetic inflow turbulence and wall modeling are used inside the nozzle. In addition to the converging-diverging nozzle geometry, the computational domain includes the Y-duct, S-ducts, and angle adapter upstream of the nozzles, to realistically reproduce the elements of the experimental configuration where the internal flow conditions and wall modeling can be expected to affect the external flow-field and sound-field predictions. Comparisons between the numerical predictions and experimental PIV and far-field noise measurements from NASA Glenn Research Center will be presented and discussed.
Frequency decorrelation of broadband acoustic signals in a turbulent atmosphere
Authors: Ostashev Vladimir E. , Wilson D. Keith , Vecherin Sergey N.
Published: November 2013

The impact of atmospheric turbulence on sound propagation is an important consideration for source localization with acoustic sensor arrays, studies of noise pollution, and the development of new remote sensing techniques. This paper takes as a starting point a set of recently derived, closed-form equations for the spatial-temporal coherence function of a broadband acoustic signal propagating in a refractive, turbulent atmosphere with spatial-temporal fluctuations in temperature and wind velocity. The theory is quite general and enables analysis of many statistical characteristics of the sound field. It has certain advantages in comparison with Monte-Carlo simulations and has already been used to study the spatial-temporal coherence of narrowband signals. In the present paper, this theory is employed to calculate and analyze the frequency decorrelation of broadband acoustic signals for typical regimes of the atmospheric boundary layer: mostly cloudy or sunny, with light, moderate, or strong wind. The results obtained are then used to study the effect of atmospheric turbulence on the temporal broadening of the intensity of an acoustic pulse.
A combined finite element/parabolic equation formulation for acoustic wave propagation over and within a rigid porous ground
Authors: Tao Hongdan , Li Kai Ming
Published: November 2013

This paper describes a finite-element (FEM) marching scheme for a standard wide-angle parabolic equation (PE) formulation for calculating the sound fields over and within a rigid porous ground. The study has an application for exploring the effect of snow cover on the propagation of horizontal acoustic waves under refractive atmospheric conditions. Instead of using the standard Crank Nicholson method to solve for the finite difference marching scheme, a FEM discretization approach has been advocated in the present study. By using this approach, the boundary conditions, i.e., the continuity of acoustic pressure and velocity, can be incorporated directly at the air/ground and ground/ground interfaces that facilitates the simultaneous calculations of the sound fields over and within the rigid porous ground. The FEM/PE formulation yields a complete set of information on the acoustic pressure and its spatial derivatives at any receiver locations. In addition, the perfectly matched layer (PML) technique has been adopted that simulates a dissipative layer especially designed to absorb sound waves without reflections from the uppermost layers. Numerical simulations have confirmed that the application of such impedance-matched PML has efficiently eliminated reflections and reduced the overall computational time.
High frequency guided ultrasonic waves for defect monitoring
Authors: Fromme Paul
Published: November 2013

High frequency guided ultrasonic waves offer a good compromise between area coverage and defect detection sensitivity for the health monitoring of critical sections of structures. Using standard ultrasonic transducers with single sided access to the structure, guided wave modes were generated that penetrate through the complete thickness of the structure. The wave propagation and interference of the guided wave modes depends on the frequency thickness product. Laboratory experiments were conducted using a laser interferometer and the wave propagation dependence on the wall thickness reduction verified against theoretical predictions. Measurements were conducted using accelerated corrosion in a salt water bath. From the measured signal changes due to the wave mode interference the wall thickness reduction due to corrosion was monitored. The energy transfer between the plate surfaces results in a good sensitivity for the detection of small defects on both surfaces. Experimentally the reflected wave was measured using standard pulse-echo equipment. Using a combination of evaluation in the time and frequency domain, the defect location and damaged plate side can be accurately determined. The high frequency guided waves have the potential for damage monitoring at critical and difficult to access locations from a stand-off distance.
Guided wave structural health monitoring using inductively coupled embedded sensors
Authors: Croxford Anthony , Zhong Chenghuan , Wilcox Paul
Published: November 2013

Conventional SHM systems typically rely on permanently attached sensor networks glued on to a structure. These add complexity and weight through either a wiring requirement or the use of wireless sensing nodes. This paper reports on an alternative approach whereby the wire between transducer and ultrasonic equipment is replaced by an inductive coupling. This allows a passive small sensor unit to be embedded into a composite component. Here a model is presented to describe the performance and optimization of such a coupling. The resulting sensors are embedded in a CFRP component and shown to exhibit excellent performance. Signal processing to account for the effects of misalignment is described. Finally, the ability of such a system to detect typical impact damage is demonstrated.
Effects of vowel duration and increasing dynamic spectral information on identification of center-only and edges-only syllables by cochlear-implant users and young normal-hearing listeners
Authors: Rogers Catherine L. , Donaldson Gail S. , Johnson Lindsay B. , Oh Soo Hee
Published: November 2013

In a previous study, cochlear implant (CI) users’ vowel-identification performance was compared to that of young normal-hearing (YNH) listeners. Stimuli included full syllables and two duration-neutralized conditions: center-only and edges-only (silent-center). CI users performed more poorly than YNH listeners overall and showed proportionately larger decrements in performance for partial syllables. Error analyses suggested that at least some CI users rely more heavily on vowel-duration cues than YNH listeners. The present study was designed to test this hypothesis and to determine whether increasing duration of dynamic cues in the edges-only conditions would improve performance, particularly among poorer-performing CI users. Ten YNH listeners and ten adult CI users heard /dVd/ syllables recorded from three talkers. Full syllables were edited to create center-only and edges-only stimuli in which vowel duration cues were or were not preserved, plus edges-only stimuli with different durations of dynamic information. Performance of both groups improved in the duration-preserved condition for center-only, but not edges-only, stimuli. The center-only duration benefit was larger for the CI than for the YNH group. Increasing the duration of dynamic information in the silent-center stimuli improved vowel-identification performance for both groups. Individual differences among CI users and implications for listener-training programs will be discussed.
Feature divergence of pathological speech
Authors: Sandoval Steven , Utianski Rene , Berisha Visar , Liss Julie , Spanias Andreas
Published: November 2013

Many state of the art speaker verification systems are implemented by modeling the probability distribution of a feature set using Gaussian mixture models. In these systems, a decision is made by comparing a likelihood of an observation using both a Gaussian mixture model corresponding to an individual, and a Gaussian mixture model universal back ground model. In this study we propose to use a similar framework to instead characterize the divergence of the feature set distribution between healthy and pathological speech. We accomplish this by determining the difference between a universal background model trained on healthy speech and model of an individual's pathological speech. There are several known methods to evaluate the difference between two probability distributions, one example being the Kullback-Leibler divergence. By building a universal background model using healthy speech, we hope to capture the expected distribution of our feature space. Then by computing a difference between a dysathric individual's feature distribution, and the universal background model, we can determine the features that are most likely to capture the effects of a specific motor speech disorder.
SoundMap: A mobile app for optimizing room acoustics and speaker placement
Authors: Bodon K. J. , Jensen Zachary
Published: November 2013

Improving room acoustics can be expensive and time consuming, even for the most experienced acousticians. SoundMap ™ is a user friendly app that can be used to easily model rooms based upon acoustic properties. A combination of the method of images, ray tracing, and modal analysis will be used to calculate steady state levels for different frequency bands in a room. The modeling will also take several other factors into account, including the room impulse response, absorption coefficients of boundary materials, furniture, and other room elements. The model will incorporate generic loudspeaker systems, with the future design goal of integrating specific loudspeaker systems. Through a contour plot, the user will be able to test the effects of loudspeaker location, loudspeaker type, room layout, and room materials, with the aim of optimizing the listening experience.
“Tone deaf”— The touch based ear-training game
Authors: Pyzdek Andrew T.
Published: November 2013

Inspired by the color matching game “Colorblind” by ChewSoft, Tone Deaf is the new game that challenges players to match the pitch and timbre of a note by touching the screen to draw a single cycle of the waveform. The shape of the waveform is then used to determine the appropriate harmonics and their phases, while the length of the cycle determines the frequency. Players will progress through multiple levels of difficulty, starting with simple waveforms such as sine waves, sawtooth waves, and square waves, and finally emulating the complex patterns of instruments such as the piano, trumpet, and violin.
Acoustical Society of America Silver Medal in Musical Acoustics
Authors: Strong William J.
Published: November 2013

The Silver Medal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.
From pole to pole: Soundscapes of the Atlantic Ocean
Authors: Klinck Holger , Miksis-Olds Jennifer L. , Nieukirk Sharon L. , Matsumoto Haruyoshi , Dziak Robert P.
Published: November 2013

Between July 2009 and December 2010, two identical calibrated hydrophone packages were deployed and continuously operated (2,000 Hz sampling rate) in the Fram Strait (79°N, 5.5°E) and the Bransfield Strait (62°S, 55.5°W). Analysis of these recordings were combined with a data set collected during the same time period by the Comprehensive Nuclear-Test-Ban Treaty Organization International Monitoring System (CTBTO IMS) hydroacoustic station HA10 (250 Hz sampling rate) at Ascension Island (8°S, 14.4°W). The combination of these datasets allowed a comparison of low-frequency noise levels in polar and tropic areas of the Atlantic Ocean. The recordings were analyzed for major natural (e.g., marine mammals, ice) and anthropogenic (e.g., shipping, seismic) contributors to the ambient sound field and their seasonal variability. Preliminary results indicate (1) a higher seasonal variability of ambient noise levels in polar regions compared to the tropics, (2) the seasonal variability of ambient noise levels in the Arctic and Antarctic were driven by different contributors, and (3) highest noise levels were observed in the Arctic in association with seismic oil and gas exploration. [Partial funding from NOAA/PMEL and the Korea Polar Research Institute.]
Nonlinear time series analysis of snapping shrimp sounds
Authors: Hee Wai Tyler , Allen John S. , Gebbie John , Siderius Martin
Published: November 2013

Snapping shrimp produce sounds through cavitation bubbles generated by the rapid closing of their claws. These sounds are a primary source of ambient noise in sub-tropical, shallow water environments. Though seasonal and daily variations of snapping shrimp sound levels have been reported, comprehensive studies of short time series have been limited. We investigate the respective spectral characteristics from acoustic arrays recordings at various locations in Oahu, HI, over hourly, daily and weekly periods. Nonlinear time series analysis methods encompassing recurrence plots are used to investigate the acoustic time series together with bivariate and cross recurrence plot analysis with that of tidal and sunlight cycles. Signal entropy and determinism are investigated and transient acoustic ship sounds are located
Comparison of soundscapes across the Bering Sea shelf, a biological perspective
Authors: Miksis-Olds Jennifer L.
Published: November 2013

Selectively decomposing and visualizing different aspects of an acoustic time series provides a greater understanding of the sources and environmental dynamics contributing to and shaping the temporal and spatial patterns of the measured sound. Source contributions to the overall soundscape vary in space and time, and the biological component is highly dependent on temporal, geographic, and oceanographic factors. The biological contributions to soundscapes along the eastern Bering Sea shelf are tightly coupled to the presence of sea ice and have strong annual patterns. The differences between locations reflect the relative contribution of different species to the soundscape. Using soundscape plots to display the acoustic environment during the overlap of peak vocal activity by different marine mammal species in the winter/spring season produces a visual representation of acoustic niche partitioning by Arctic species.
Larval settlement in response to estuarine soundscapes
Authors: Eggleston David , Lillis Ashlee , Bohnenstiehl Del
Published: November 2013

Ambient underwater sound has the potential to be an important orientation and settlement cue for marine invertebrate larvae, yet larval responses to relevant sound patterns are largely unknown. In estuaries of the Southeastern United States, oyster reefs are patchy productive habitats that harbor many soniferous fish and invertebrates, creating distinct sound characteristics. This habitat-related sound could provide a useful cue for the planktonic larvae of obligate reef dwellers and facilitate encounter with suitable settlement substrate. To investigate sound as a settlement cue in this system, larval settlement responses to oyster reef and soft-bottom sounds, as well as a no-sound control were tested for the Eastern oyster, Crassostrea virginica. Laboratory and field experiments suggest that sound has a significant effect on oyster settlement rates: higher numbers of larvae settled in the presence of oyster reef sounds than in soft-bottom sound or silent control treatments. Improved understanding of the relationship between habitat sound fields and subsequent larval recruitment is central to bio-physical studies of larval connectivity and recruitment in marine systems.
On the feasibility of estimating attenuation from the coherence of ambient noise
Authors: Menon Ravi , Gerstoft Peter
Published: November 2013

There has been a long standing interest, especially in seismology, to be able to reliably retrieve attenuation information from ambient noise. While theoretical work has shown that it is possible to retrieve attenuation from noise, in practice, several factors such as anisotropy of noise distribution and intensity, site amplification factors, etc., make it an extremely challenging task. By assuming a sufficiently uniform noise distribution, researchers have obtained estimates of attenuation by fitting the theoretical noise coherence function modified by an exponentially decaying term, to the observed coherence. In this talk, we present results from analyzing seismic data from the Southern California seismic network in the microseism band (0.05–0.2 Hz) and discuss the feasibility of estimating attenuation from coherence. Specifically, we demonstrate that the assumption of a single wavespeed at each frequency is not valid at certain frequencies. Such variations in wavespeed are often due to inhomogenities in the medium and scattering effects, and it is very likely that interactions between these waves results in a reduction in amplitude due to phase cancellations, which might be erroneously perceived as attenuation. While it might still be possible to estimate attenuation if these interaction effects are accounted for, it raises questions on the validity of the simple exponential decay model.
Offshore impact pile driving as a source of opportunity for geoacoustic investigations
Authors: Potty Gopu R. , Miller James H. , Kim Huikwan
Published: November 2013

Noise generated by offshore impact pile driving can radiate into and propagate through the air, water, and sediment. Most of the recent studies have focused on predicting acoustic pressure field in water to assess environmental impacts. In this study, we focus on the propagation of acoustic energy along the interface between water and ocean bottom. We modeled the interface wave propagation using the commercial Finite Element (FE) code, Abaqus 6.11. A field test is planned for this summer using a scaled model impact pile driving off the dock in the Bay Campus University of Rhode Island (URI). Interface data (particle velocities at the water-sediment interface) will be collected using the Shear Measurement System. Our efforts will focus on identifying the arrivals corresponding to various wave types using data-model comparison. In addition to the interface waves, we will also model the Mach wave front arrival angle. We will explore the possibility of utilizing the arrival times and angles corresponding to these wave types for setting up an inverse problem. This test will also verify the possibility calculating compressional wave speed using a single three-axis geophone by measuring arrival angle of Mach wave front at the interface generated by impact pile driving. [Work sponsored by the Link Foundation Ocean Engineering and Instrumentation PhD Fellowship program.]
Geoacoustic inversion of noise radiated by surface ships
Authors: Knobles David P. , Koch Robert A. , Sagers Jason D. , Stotts Steven A.
Published: November 2013

Addressed is the issue of determining physical properties of the seabed in shallow water using ambient noise from surface ships of opportunity. Both the amplitude and phase of the source spectrum are unknown. The coherent modal interference structure in the received spectra is sensitive to parameters such as the sound speed in the seabed, the speed of the ship, the source-receiver range, the water depth, etc. Such sensitivity allows in some cases for information on these parameters to be extracted from a statistical information approach such as maximum entropy. In shallow water, the rate of decay with propagation range of the received incoherent levels is sensitive to the intrinsic seabed attenuation. For ship of opportunity data, estimating values for the attenuation is complicated by the ambiguity existing between source level and attenuation. This work explores various methods that attempt to resolve the source level and attenuation ambiguity using experimental data taken in the Gulf of Mexico and the New Jersey continental shelf. One approach is to use short-range data to give a prior distribution for the source levels and to then estimate the marginal distributions of the attenuation with longer-range data. [Work supported by ONR.]
The effect of seawater attenuation on the directionality and spatial coherence of surface-generated ambient noise
Authors: Buckingham Michael J.
Published: November 2013

Acoustic attenuation in seawater is sufficiently weak that it usually has little effect on the spatial characteristics of ambient noise. However, at frequencies above 10 kHz and depths below 6 km, seawater attenuation may influence the directionality of surface-generated ambient noise. In a semi-infinite, homogeneous ocean, all the noise is downward-traveling, since there are no bottom reflections, and, in the absence of attenuation, the directional density function varies as the cosine of the polar angle measured from the zenith. When attenuation is present, the angular width of this noise lobe becomes narrower, because sound from distant surface sources is attenuated more than acoustic arrivals from overhead. This narrowing effect increases as frequency rises, since the attenuation is a rapidly increasing function of frequency. The spatial coherence of the noise is also modified by the attenuation. For a pair of horizontally (vertically) aligned sensors, the zeroes in the spatial coherence function are shifted to higher (lower) frequencies. These effects of attenuation on the noise field are sufficiently large to be detectable using the recently developed, deep diving instrument platform Deep Sound, which is capable of measuring broadband ambient noise on multiple hydrophones to depths of 11 km. [Research supported by ONR.]
Standards development and execution for therapeutic ultrasound applications
Authors: Schafer Mark E.
Published: November 2013

Therapeutic ultrasound holds great promise in the treatment of a number of different disease states and patient conditions. In bringing these devices to market, the two main considerations are naturally safety and efficacy. Central to the safety evaluation of such devices is the determination of potential hazards through the use of international standards. The International Electrotechnical Commission (IEC), has several standards and initiatives in the area of therapeutic ultrasound, both in the measurement of ultrasonic fields and in safety characterization. To be effective, these standards must not only be technically accurate, but also sufficiently practical that their primary users, namely manufacturers, can properly implement them. This talk reviews the development of standards related to therapeutic ultrasound and also discusses the implementation approaches among different manufacturers. For instance, while diagnostic ultrasound systems can be safely managed with only type-testing, the energy levels from therapeutic systems require that every system be evaluated or calibrated before patient use. Typically, systems undergo detailed sub-system testing, with only limited testing performed on the final product at full energy levels. Assumptions with regard to output linearity are also used to further minimize the difficulties implicit in measurements at high ultrasonic energies.
Just doing our DUTy!—An international project on dosimetry for ultrasound therapy
Authors: Shaw Adam
Published: November 2013

This presentation will describe a large international project which aims to develop the metrological infrastructure for the determination of ultrasound exposure and dose to tissue. Ultimately this will improve treatment planning and risk assessment. The 3-year project started in June 2012. It is co-ordinated by the UK National Physical Laboratory and is funded in part by the European Metrology Research Programme of the European Union. The other project partners are INRIM (IT), PTB (DE), UME (TR), CSIC (ES), ICR (UK), Moscow State University (RU), NIM (CN), and University of Merseburg (DE). The scientific work is divided into six Work Packages: —Quantities and definitions will review dose and in situ exposure quantities proposing alternatives where necessary; —Laboratory dosimetry standards will develop reference methods for thermal and non-thermal therapeutic dose parameters; —Dose modeling and validation will develop theoretical and computer modelling procedures to calculate acoustic and thermal dose quantities with well understood uncertainties; —Intercomparison of methods will formally compare measurement methods and models developed; —Dosimetry Transfer Standards will develop phantoms and test systems for the assessment of clinical ultrasound equipment, transferring laboratory standards to end-users; —Application to clinical treatment will provide a direct link between the methods developed and the clinical use of therapeutic ultrasound with the long-term aim of improving treatment planning.
Dosimetry for therapy ultrasound
Authors: ter Haar Gail
Published: November 2013

Ultrasound is probably the only clinical therapy modality that does not as yet have a well established dosimetric parameter. There are a number of reasons for this. Unlike other energy forms, ultrasound produces cell killing by two distinct principle mechanisms: cavitation and heating. While dose parameters have been proposed for each mechanism, there has been no attempt to combine these into a single unit. Existing dosimetric methods will be reviewed and put into the context of other therapeutic methods. Biological and physical end points will be discussed.