bluuebunny/crossref_metadata_2025 huggingface dataset:
The first order statistics of backscatter from the fractal branching vasculature
Authors: Parker Kevin J.
Published: November 2019

The issue of speckle statistics from ultrasound images of soft tissues such as the liver has a long and rich history. A number of theoretical distributions, some related to random scatterers or fades in optics and radar, have been formulated for pulse-echo interference patterns. This work proposes an alternative framework in which the dominant echoes are presumed to result from Born scattering from fluid-filled vessels that permeate the tissue parenchyma. These are modeled as a branching, fractal, self-similar, multiscale collection of cylindrical scatterers governed by a power law distribution relating to the number of branches at each radius. A deterministic accounting of the echo envelopes across the scales from small to large is undertaken, leading to a closed form theoretical formula for the histogram of the envelope of the echoes. The normalized histogram is found to be related to the classical Burr distribution, with the key power law parameter directly related to that of the number density of vessels vs diameter, frequently reported in the range of 2 to 4. Examples are given from liver scans to demonstrate the applicability of the theory.
In-air and underwater auditory evoked cortical responses in the dolphin
Authors: Schalles Matt , Mulsow Jason , Houser Dorian S. , Finneran James J. , Shinn-Cunningham Barbara
Published: November 2019

Auditory signal processing in dolphins is of special interest because these animals echolocate and possess high upper-cutoffs of hearing (∼140 kHz). The few previous measurements of auditory cortical responses (ACRs) in dolphins have been performed in air or with a restrained dolphin half submerged in water. Our goal was to record ACRs from an unrestrained dolphin fully submerged in water utilizing far-field sound stimulation. We performed a series of experiments in air and under water manipulating stimulus presentation rate and level. An increasing stimulus rate from 2 to 4 Hz showed only a nominal decrease in ACR potential; a greater decrease in ACR amplitude occurred with an 8-Hz rate. Decreasing stimulus sound pressure level (SPL) decreased the ACR in a manner consistent with auditory brainstem responses to similar SPLs. Taken together, these findings support the idea that valid cortical potentials can be obtained in air and underwater, though differences in ACR amplitude and polarity require further investigation. Brainstem responses are consistent between both environments; however, the cortical response is attenuated underwater, and a polarity reversal along the anterior-posterior axis observed in air is not present underwater.
Overview of Quiet Supersonic Flights 2018 (QSF18) in Galveston, Texas
Authors: Rathsam Jonathan , Cliatt Larry J.
Published: November 2019

NASA and partners planned and executed the Quiet Supersonic Flights 2018 (QSF18) test program in Galveston, TX. The primary goal was to successfully engage a community, unaccustomed to hearing sonic booms, in a multiweek test of quiet supersonic flights. Secondary goals included assessing community survey methods and methods for sonic boom exposure determination. This presentation provides an overview of test planning, test execution, data analysis methods, dose-response results, and lessons learned. All of these elements inform future community response testing with NASA's X-59 Quiet Supersonic Technology (QueSST) aircraft.
Acoustics of a piezo inkjet channel with an entrained air bubble
Authors: Segers Tim , Fraters Arjan , Reinten Hans , de Loore Youri , Lohse Detlef , Versluis Michel
Published: November 2019

Piezo-acoustic drop-on-demand (DOD) inkjet printing is widely applied in high-end digital printing due to its unprecedented precision and reproducibility. However, the stability of piezo-DOD inkjet printing can sometimes be compromised through the stochastic entrainment of bubbles within the ink channel. The acoustically driven air bubble modifies the ink channel acoustics, and conversely, the modified ink channel acoustics influences the bubble dynamics. Here, we measure the acoustic eigenfrequency of a MEMS based silicon ink channel as a function of the bubble size. The eigenfrequency was measured using a pulse-echo system and the bubble size using a short-wave infrared imaging setup. We show that the measured eigenfrequency increases when an air bubble is entrained. Surprisingly, the ink channel resonance frequency plateaus at total bubble volumes larger than 10 pl. Moreover, it was found that at a constant total bubble volume, the resonance frequency increases with the number of entrained bubbles. We show that both experimental observations can be quantitatively explained from a simple lumped element model (LEM) comprising the ink channel Helmholtz resonator coupled to the bubble mass-spring system. The results of the LEM model were validated using a full numerical model of the coupled ink channel—bubble system.
Evaluation of optoacoustic response with a combined Monte Carlo optical and acoustic simulation approach
Authors: Urban Matthew W. , Rose James A. , Buhrow Benjamin , Haider Clifton
Published: November 2019

Optoacoustic, or photoacoustic, imaging combines the penetration capabilities of ultrasound imaging with the contrast mechanism of optical absorption related to the photoacoustic effect. To enable modeling of photoacoustic measurements and imaging applications, the problem can be divided into modeling of the optical photon propagation and the resulting acoustic wave propagation. In highly scattering media such as soft tissues, Monte Carlo (MC) methods are used to evaluate photon propagation, absorption and the subsequent generation of a heat source that produces the photoacoustic effect. Acoustic wave equations are then used to model the propagation of the sound in the medium. However, if the appropriate physics could be modeled with a single tool, there would be advantages of consistency in spatial and temporal domains as well as easier integration of the optical and acoustic simulations. We propose using MC methods for optical photon propagation and for the acoustic wave propagation. The simulations are split into two stages for the optical photon propagation and the acoustic phonon propagation. We describe how the same MC framework is used to model photon propagation and acoustic phonon propagation. We will then demonstrate this new combined MC framework in models of photoacoustic problems in homogeneous and heterogeneous cases. These results will be compared with results from using k-Wave models for the acoustic wave propagation. The correspondence between k-Wave the acoustic MC model are shown to be in good agreement.
Acoustics education through digital fabrication
Authors: Granzow John
Published: November 2019

The integration of makerspaces in academic settings presents an opportunity to apply principles of musical acoustics to the rapid production of sounding objects. Digital fabrication accelerates the design cycle and alters what can be accomplished in the scope of such educational labs. Acoustic principles motivate parametric 3-D designs using open-source CAD software. These models can then be materialized through digital fabrication to empirically test numerical predictions; they also serve as prototypes for new instrument design and sound art. This paper reviews such a course offered at the University of Michigan in the Performing Arts Technology program. Machine and software requirements are discussed as well as methods to combine acoustic problem-sets with contemporary fabrication methods.
Speech perception frameworks revisited using the complex auditory brainstem response
Authors: Zhao Tian , Kuhl Patricia K.
Published: November 2019

Speech perception and experience-related effects have been theorized and experimentally tested through a wealth of behavioral measures as well as neural measurements focusing on cortical processes. Recently, the complex auditory brainstem response, targeting neural processes at a much earlier stage, has allowed us to generate and test new research questions from existing theoretical frameworks and can potentially expand these frameworks. We will present results from two recent studies examining different components of complex auditory brainstem responses to test hypotheses regarding universal as well as experiential effects in speech perception. In the first study (Zhao and Kuhl, 2018), the onset latency of the complex auditory brainstem response was found to predict perception of stop consonant and that both onset latency and perception are modulated by language background. In the second study (Zhao et al., 2019), the frequency-following component of the complex auditory response (FFR) was found to show directional asymmetry for the neural discrimination of an English vs. French prototypical /u/, supporting the Natural Reference Vowel framework. Implications and future directions will be discussed regarding using complex auditory response to test speech perception frameworks.
Underwater acoustic communication performance by signal to noise plus interference ratio in BLAC18
Authors: Kim Hyeonsu , Choi Jee Woong , Bae Ho Seuk
Published: November 2019

In underwater acoustic communications, inter-symbol interference (ISI) caused by multipath propagation of underwater channel degrades communication performance significantly. Various techniques, such as time reversal combining and decision feedback equalization, have been developed to eliminate the influence of the interference. However, few studies have assessed the performance with the signal-to-noise (SNR) of received communication signals. In practical underwater acoustic systems, the channel must be accurately estimated for the channel equalization and the SNR is involved in the accuracy of the channel estimation. The effect of interference is dominant at short distances, but the effect of noise becomes dominant as distance increases. In this study, SNR, signal-to-interference ratio, and signal-to-noise plus interference ratio (SINR) are estimated as a function of the distance, and communication performances are examined. Communication data from BLAC18, conducted in East Sea of Korea in 2018, are used to analyze the communication performances. In the experiment, communication signals with a carrier frequency of 2.5 kHz were transmitted and received at horizontal distances of 30, 60, and 90 km. Data analysis results shows that communication performance is most correlated with SINR. [Work supported by the ADD(UD170022DD).]
Vector communication by moving source during KOREX-17
Authors: Choi Kang-Hoon , Kim Hyeonsu , Choi Jee Woong , Kim Sunhyo , Dahl Peter H.
Published: November 2019

In underwater acoustic communication, a time reversal technique with spatially separated large-size receiver array has been used to overcome delay spread caused by multipath channel and obtain spatial diversity gain. This technique is difficult to be accommodated in space-constraint environments due to the size of receiver array. Since an acoustic vector sensor has capability to simultaneously measure x, y, and z-components of particle velocities as well as acoustic pressure at a single point, it can provide better communication performances than a system using hydrophones only. In this study, acoustic communication performance using a vector sensor is demonstrated using communication data collected during Korea Reverberation Experiment (KOREX-17) conducted in shallow water located at 34°43′N, 128°39′E on May 25, 2017. The channel characteristics and communication performances extracted using the acoustic pressure and particle velocity components are shown in this talk, and the performance variation is discussed as a function of distance. [Work supported by the Ministry of Oceans and Fisheries, Korea (PMS4110).]
Measurement of low frequency impact insulation
Authors: Dong David W. , LoVerde John
Published: November 2019

The authors have proposed a dual-rating method for measuring impact insulation in which the high and low-frequency components of impact noise are evaluated independently [LoVerde and Dong, J. Acoust. Soc. Am. 141, 428–440 (2017)]. The measurement of low frequency impact sound in rooms is critical to determining human response and acceptability of floor ceilings. In this paper we discuss issues related to low frequency measurements in residential applications. The paper will include analysis of the suitability of the standard tapping machine as a source for low frequency impact noise for typical assemblies within North America. The authors will review the uncertainty of low frequency measurements in typical receiving rooms. The paper will discuss the measurement methodology as a requirement for adoption of a measurement standard.
In-line syntactic-foam device for control of water hammer and fluid-borne noise
Authors: Cunefare Kenneth , Ramsey David N. , Pedigo Nathaniel
Published: November 2019

Water hammer, a common problem in plumbing, is characterized by an impulsive increase in pressure. The pressure rise and associated momentum transfer may cause plumbing noise and vibration, and, potentially, catastrophic plumbing component failures. Water hammer arresters are required in building codes to be proximate to fast-acting valves, such as present in washing machines and other appliances. Commercially available water hammer arresters introduce compliance with a free-piston air spring as the means to limit the peak pressure during water hammer. Syntactic foam, comprising microspheres within a host polymer matrix, may be suitable for application in a water hammer arrester device. Foam-based arresters also enable flow-through designs, which may reduce other fluid-borne noise in addition to controlling water hammer. A prototype flow-through, in-line syntactic water hammer arrester device has been designed and tested. The flow-through design demonstrates adequate performance for service as a water hammer arrester, as well as significant insertion loss against fluid-borne noise.
In-air hearing in Hawaiian monk seals: Implications for understanding the auditory biology of monachid seals
Authors: Ruscher-Hill Brandi , Sills Jillian , Reichmuth Colleen
Published: November 2019

Despite its critically endangered status, little is known about the sensory biology of the Hawaiian monk seal (Neomonachus schauinslandi), a member of the Monachinae subfamily of phocid seals. While previous research has suggested that at least one monachid species exhibits reduced sensitivity to airborne sounds, no comparable hearing data are available for other species. Our aim in this study was to measure an in-air auditory sensitivity profile for a Hawaiian monk seal using a psychophysical paradigm. One adult male seal was trained to participate in a go/no-go procedure in an acoustic chamber, which enabled measurement of absolute detection thresholds for narrowband signals at frequencies spanning the range of hearing in air. The resulting behavioral audiogram for this individual reveals poor hearing sensitivity. The lowest threshold of 40 dB re 20 μPa at 0.8 kHz occurs within a + 20-bandwidth of best hearing extending more than seven octaves. The apparently elevated in-air hearing thresholds for two monachid seals—compared to the highly sensitive true seals in the Phocinae subfamily—suggest that auditory adaptations may differ between these groups. Additional research is needed to confirm this finding, which has implications for understanding the evolution of hearing in amphibious marine mammals.
The genesis of giants: Behavioral, social, and vocal development of northern elephant seals
Authors: Casey Caroline B. , Charrier Isabelle , Mathevon Nicolas , Nasr Claire , Forman Parker , Reichmuth Colleen
Published: November 2019

To identify the conditions that support the development of hierarchical relationships within networks of familiar competitive rivals, we consider the ontogeny of area use, social relationships, and communicative behavior among male northern elephant seals (Mirounga angustirostris). We cross-sectionally sampled the behavior of 207 males during reproductive development on the breeding colony at Año Nuevo, CA to determine (1) whether space utilization changes as a function of age, (2) how social relationships vary across different age classes, and (3) the structural development of their ritualized acoustic displays. As males mature, space use within the breeding colony decreases, creating a more predictable social environment in which repeated interactions promote greater connectivity between individuals. Additionally, the vocalizations of sub-adult males transition from highly variable and unstructured to stable adult calls that reliably convey individual identity. The emergence of these acoustic signatures during a profound period of physical development—along with concurrent changes in movement patterns—coincides with the establishment of stable relationships between mature competitors. These findings indicate that ontogenetic changes in male behavior can be important determinants of adult position within structured hierarchies and provide insight into the role of behavioral development in species that exhibit intense competition for access to resources.
Propagation distances and sound properties of the antennal rasps produced by spiny lobsters (Palinurus elephas) in European coastal waters
Authors: Jézéquel Youenn , Bonnel Julien , Coston-Guarini Jennifer , Chauvaud Laurent
Published: November 2019

Spiny lobsters (Palinurus elephas) have been overfished in European waters, and adult breeders are now scarce. Our recent study highlighted the high acoustic potential of this species, which can emit loud broadband pulse trains, called “antennal rasps,” with peak-to-peak source levels (estimated at 1 m from the source) above 160 dB re 1 μPa² [Jézéquel et al., Marine Ecology Progress Series 615 (2019)]. These acoustic properties imply that these sounds could be detected during in situ passive acoustic monitoring. However, before using a such tool, we need to understand how antennal rasps propagate in situ and at what distance they could be detected above the ambient noise. To answer these questions, we recorded spiny lobster antennal rasps in the Iroise Sea (Brittany, France). We used a linear array of 8 hydrophones, with distances between animals and receivers ranging from 0.5 m to 100 m. We recorded antennal rasps from 38 individuals of various sizes. Our results demonstrate that large spiny lobsters can be detected at 100 m, and that sound properties might be directly influenced by the size of the individuals.
Passive acoustic beaked whale surveys using gliders off Southern California
Authors: Mellinger David K. , Nieukirk Sharon L. , Fregosi Selene
Published: November 2019

A passive acoustic survey off Southern California is being conducted in summer–fall 2019 to estimate the distribution of beaked whale species. Two gliders are being flown to estimate the occurrence of Cuvier's, Blainville's, Stejneger's, Hubbs', and Baird's beaked whales in several regions: (1) near the Navy's Southern California Offshore Range (SCORE), in particular near fixed passive recorders there; (2) over the farther reaches of the continental shelf and shelf slope; and (3) over deep (>3000 m) waters offshore of the shelf slope up to 350 km from shore. The gliders collect passive acoustic data up to ca. 90 kHz, which should enable differentiation of these species of beaked whales in situations of reasonably high signal-to-noise ratios. Preliminary results of the glider flights and data analysis will be presented. [Funding from Navy NAVFAC.]
Annular and spiral bubble nets: A simulation-focused analysis of humpback whale feeding strategies
Authors: Bryngelson Spencer H. , Colonius Tim
Published: November 2019

Humpback whales can generate bubbly regions (called bubble nets) via their blowholes, which they appear to exploit via loud vocalizations for feeding purposes. We model this phenomenon as the acoustic excitation of an dilute bubble net of radially varying void fraction. A fully coupled phase-averaging approach is used to compute the bubble response and corresponding acoustics. We first assess the possibility of a sophisticated wave-guidance behavior of high-frequency whale vocalizations within the bubble net. For a small range of flow parameters, the reflections associated with the bubbly region result in an observable wave-guidance behavior, though even then these reflections disperse rapidly. In light of this, we also consider multiple whales surrounding the bubble net, each vocalizing towards its center. We show that for physically realistic configurations, including variations in the bubble net void fraction and number of whales, the bubble net can keep its core region substantially quieter than the exterior. Finally, we investigate the ability of spiral, rather than annular, geometries for keeping the bubble-free region quiet.
Application of an embedded general-purpose computing platform to passive acoustic monitoring
Authors: Martin Bruce , Cole Art , Hillis Craig , Gaudet Briand , Moloney John , Kowarski Katie , Hannay David E. , Maxner Emily
Published: November 2019

JASCO Applied Sciences has developed a novel passive acoustic monitoring system, the OceanObserverTM, that has been fielded in undersea and surface AUVs as well as on buoys and sub-sea observatories. The hardware is based on the Zynq system-on-a-chip (SoC), which features a large field-programmable gate array (FPGA) and two ARM processing cores. The FPGA is used to implement real-time filtering for the analog-to-digital converters and a real-time detector for odontocete clicks. JASCO’s PAMlab JAVA software has been adapted to run in the ARM processors. This allows for the detector algorithms to be tested and proven using recorded data sets, and the deployment of algorithms in the real-time hardware using the same proven software baseline. The advantages of this approach for rapidly adapting generic hardware to diverse monitoring projects will be highlighted.
A physical model to investigate the acoustic behaviour of microbubbles and nanodroplets within a bone fracture
Authors: Ferri Sara , Polydorou Anastasia , May Jonathan , Wu Qiang , Stride Eleanor P. , Evans Nicholas D. , Carugo Dario
Published: November 2019

Impaired fracture healing is a major financial burden for healthcare services; 5%–10% of bone fractures result in non-unions, and there is no clinically approved systemic therapy. This study characterises acoustically stimulated microbubbles (MBs) and nanodroplets (NDs) as non-invasive ultrasound responsive vehicles for the targeted delivery of osteogenic compounds. A microscope-compatible water-tank incorporating a passive cavitation detector was developed to study the acoustic behaviour of MBs and NDs within physical models of bone fractures (gap: 3.5–5.5 mm, angles: 0 deg and 90 deg). The device was designed using COMSOL Multiphysics (Burlington, MA) and tested in-vitro. The bone was simulated using a material with comparable acoustic impedance (Sawbones, WA). Numerical simulations showed that the developed experimental set-up generated a relatively uniform acoustic field at a target plane. It could be operated at either 1 or 2 MHz US frequency, at an acoustic pressure in the range 0–1 MPa. The inclusion of a fracture model caused perturbations to the acoustic field, which were dependent on the architecture of the fracture (i.e., relative to the incident US field). Ongoing studies are investigating how these perturbations affect ND/MB response in-vitro. Further studies will investigate the relationship between MB/ND acoustic response and the release of biologically active compounds.
Using microbubbles to transduce ultrasound into mechanical deformations capable of activating neurons genetically sensitized to membrane stretch
Authors: Ibsen Stuart , Tong Ada , Schutt Carolyn , Esener Sadik , Chalasani Sreekanth
Published: November 2019

Ultrasound is an ideal modality to stimulate neurons due to its ability to focus through deep tissue. To facilitate the selective ultrasound activation of neurons within a dense network, we have developed a new method called sonogenetics where we genetically sensitize individual neurons to respond to the mechanical deformations created by an ultrasound pulse. This was done by misexpressing the TRP4 mechanotransduction ion channel in select neurons. As a model system, we used Caenorhabditis elegans nematodes which were allowed to freely move on the surface of an agar gel. We found that ultrasound alone did not create enough mechanical deformation at the surface of the agar to activate the TRP4 channels. To overcome this challenge, we introduced stabilized microbubbles to the system by plating them on the gel surface where they naturally surrounded the worms. The interaction between the microbubbles and the ultrasound created mechanical deformations that propagated into the body of the worm and successfully activated the expressed TRP4 causing subsequent neural activation. Activation was confirmed using calcium dependent fluorescent dyes and by quantifying whole worm behavioral changes. This technique can be a valuable tool for future applications in mammalian neural systems aimed at understanding complex neural circuits.
Improvements and implementation of code for propagating sonic booms in complex urban environments
Authors: Riegel Kimberly A. , Seaton George , Costa William
Published: November 2019

Sonic booms around buildings still require further study for them to be well understood. Previously, a combined ray tracing/radiosity program was created in FORTRAN to simulate the behavior of sonic booms around structures. The program was validated against the 2009 SonicBOBS data and some simple urban geometries. The original program produced good agreement, however, substantial drawbacks to the code were evident. It was not user friendly and creating new geometries was very difficult. The code was ported to Python in order make the user experience better which sacrificed the speed benefits of FORTRAN. Substantial modifications to the code were made to improve the speed and it has been validated with the original Fortran simulations and now runs at a comparable computation time to the original. In addition, the method for creating and importing geometries has been updated so complicated geometries can be incorporated into the simulation more easily by the user. The new program will be discussed in detail. In order to test the new software, several input booms were propagated through an urban environment. The characteristics for the boom before it interacted with the city were then compared to see how the urban environment changes the boom. These updates will allow for the future integration of additional functionality including non-homogeneous atmosphere, turbulence, edge diffraction and other factors that are expected to have a significant impact on the resulting booms.
Preliminary analysis of the PCBoom software for calculating secondary sonic booms
Authors: Riegel Kimberly A. , Sparrow Victor , Stout Trevor A.
Published: November 2019

Secondary sonic booms, also known as over-the-top sonic booms, are created during every supersonic aircraft flight, but they only reach the ground some of the time depending on atmospheric conditions. They represent the booms that either initially travel upward from the aircraft and refract to the ground or booms that initially travel downwards, reflect from the ground, and then travel upward and back down again to the ground a second time. Historically secondary booms have not been given as much widespread attention as the primary boom which is loudest, but secondary booms limited Concorde’s operations near the coast lines and could be important for planned future supersonic aircraft. The purpose of this paper is to provide an overview of an ongoing study to assess the current capabilities of calculating secondary sonic booms using the PCBoom software. Preliminary results will be presented. [Work supported by the FAA. The opinions, findings, conclusions and recommendations expressed in this material are those of the authors and do not necessarily reflect the views of ASCENT FAA Center of Excellence sponsor organizations.]
Capillary pore pressure effects on acoustic to seismic coupling detection of buried containers
Authors: Sabatier James
Published: November 2019

The effects of rainfall on one type of buried container has been investigated at a test site near the University of Mississippi. Simulated and natural rainfall experiments were carried out over a three-year time period. The measurements allow for weathering effects on the buried container seismic to acoustic ratio detection contrast. The container was a filled 20 l plastic fuel container buried 30 cm in the natural loess soil. Six containers were buried, two were controls, two were exposed to the natural weather and two were used for simulated rainfall experiments. A loudspeaker was used to excite vibrations in the ground and a co-located vertical component geophone and a microphone measured the out of plane seismic/acoustic ratio in the vicinity of the containers. The rain induced wetting phase causes the container’s acoustic-to-seismic coupling contrast to increase and resonant frequency to decrease. The water drying phase restores the original frequency responses of smaller amplitude and higher resonant frequency. The phenomenon is cyclical. The capillary pressure in the pore spaces of soil grains reduces with wetting and increases with drying. These pore pressure changes are controlling the soil stiffness and acoustic response of the buried container.
Nonlinear acoustic landmine detection experiment: Cylindrical drumlike landmine simulant buried in wetted or unwetted pea gravel
Authors: Furman Mikaela M. , Korman Murray S.
Published: November 2019

A laboratory experiment for studying acoustic landmine detection involves an 8 in. diameter, 4 in. tall drumlike landmine simulant buried two inches beneath the surface of a pea gravel medium in a cylindrical tank (9 in. O.D., 2 in. thick, 24 in. tall). The cylindrical column of gravel is supported on the sides by the concrete wall, and underneath by the thin circular acrylic top plate of the simulant (which has a thick aluminum bottom plate). Above the surface, a fine spraying mister is controlled to wet the gravel at regular intervals. A porous system near the bottom of the tank drains off excess water. For airborne acoustic excitation two loud speakers are driven by an amplified swept tone (50–850 Hz). A laser Doppler vibrometer connected to a spectrum analyzer measures the particle velocity response across the surface. Nonlinear tuning curve responses were measured on the surface to compare the characteristic frequency shift of the resonant peak with amplitude for nonwetted or wetted gravel. Then, at fixed drive amplitude, the tuning curve response was measured at discrete scan locations across the gravel. Therefore, at any specific resonant frequency, the mode shape response of the coupled simulant-gravel system can be measured.
Directionality of ground-based exploding balloons
Authors: Ostergaard Sarah A. , Neilsen Traci , Escobedo Julio A.
Published: November 2019

The directionality of an explosion should be accounted for when estimating sound power. Our goal is to estimate the directionality of explosions from measurements on an arc not concentric with the origin of the explosion. To learn how to interpret such data, a test was conducted in a grass-covered field using exploding balloons. The balloons were filled with a stoichiometric mixture of oxy-acetylene and when ignited produced acoustic shock waves. The gas-filled balloons were placed in the ground in preformed “craters.” The craters were different shapes to hopefully produce different directionalities. Measurements were taken using both circular microphone arrays centered on each of the four crater locations and a single semi-circle array that was not concentric with any of the craters. The goal is to connect the two measurements by including the effective flow resistivity of the ground and determine how to interpret the directionality from data collected from the semicircle setup. This study was in preparation for a later volcano hazards workshop with buried explosives.
Acoustic wave confinement by chiral waveguide made of Helmholtz resonators
Authors: Zhou Yun , Bandaru Prabhakar R. , Sievenpiper Daniel F.
Published: November 2019

Confining sound and controlling acoustic wave propagation is of significant importance for efficient energy harvesting. We propose an acoustic waveguide that exists at the interface between two metamaterials consist of unit cells based on Helmholtz resonators arranged in opposite chirality, which gives good confinement of sound wave in the air for frequencies within the bulk band gap of the metamaterial. The amplitude of pressure attenuates by 3 dB within 1/3 of the lattice constant. This waveguide is shown to be robust to frequency and spatial disorders in the system, as long as the edge mode is situated in the bandgap. An acoustic circuit was formed by introducing disorders at sharp corners. Our simulations demonstrate that the acoustic impedance at the interface, as defined by the ratio of the local pressure to the sound velocity, is 3 orders of magnitude smaller than the bulk impedance of the metamaterial for the frequency of interest, giving rise to confinement of the sound wave.
A single-detector acoustic camera based on space-coiling anisotropic metamaterial
Authors: Jiang Tianxi , He Qingbo
Published: November 2019

Acoustic imaging is important in diverse applications but is limited by hardware complexity, as an acoustic camera relies on a group of detectors to image sound sources. This study uses spatially encoded structures to solve the problem of single-detector planar acoustic imaging at audio frequencies: a space-coiling metamaterial with high anisotropy is proposed to realize a single-detector acoustic camera. This design outperforms the conventional acoustic camera in terms of dimensions, bandwidth, and cost, and is expected to have real impact on engineering in single-detector acoustic imaging.
Perception precedes production in native Mandarin speakers of English
Authors: Yu Madeleine , Mizrahi Reina , Creel Sarah
Published: November 2019

Nonnative accents are commonplace, but why? Ample research shows that perceptual representations of second-language speakers are shaped by their first language. But is production also affected? If perceptual representations perfectly control motor production, then second-language speakers should understand their own speech accurately. To test this, we recorded 48 native Mandarin speakers labeling pictures in English. We then played back their own recorded productions (e.g., “lock”) as they chose one of four pictures (lock, log, shape, and ship). They also heard a paired native English speaker. Words contained contrasts challenging for Mandarin speakers, principally coda voicing (lock, log) and similar-vowel (shape, ship) pairs. Listeners achieved 89% accuracy on both their own productions and native speakers,’ suggesting good matching between perception and production. However, errors were unevenly distributed: Mandarin speakers heard their own voiced codas (log) as voiceless (lock) more often than the reverse (10% vs. 5%, p = 0.002). This mirrors a similar but larger voiceless bias in native-English listeners hearing accented stimuli, suggesting that Mandarin speakers’ coda voicing perception is more nativelike than their production. Ongoing work attempts to differentiate interlanguage intelligibility effects from learning of idiosyncratic speech patterns, and we are exploring which acoustic features predict recognition.
Performance comparison of various strategies in 24-channel versatile sound field reproduction system
Authors: Omoto Akira , Kashiwazaki Hiroshi
Published: November 2019

A sound field reproducing system which consists of a hedgehog-shaped 24-channel narrow directional microphone and the speakers of the same number is currently proposed. The system is aimed for the versatile usage, for example, the reproduction of the sound field in a concert hall, and also applicable to various simulation for noise control engineering. The basic reproduction technique is intuitive and straightforward, in which a signal recorded by a particular microphone would be emitted from a loudspeaker located at the almost same direction. To compensate for the insufficient directional characteristics in the low-frequency range, some kinds of signal processing are necessary. So far, several methods, such as the inverse filtering based on the boundary surface control principle, the ambisonics, the beamforming, are attempted. The processed low-frequency components are integrated with the directly assigned high-frequency components. In addition to the procedure that uses 24 recorded signals, the alternative method which reproduces the directional information by convolving the measured directional impulse responses with the signal of the fewer channel, such as monaural or stereo format, could be used. The performance of these various reproduction methods is compared with each other.
Limited duration integral equation method
Authors: Richards Edward , Song Hee-Chun , Hodgkiss William S.
Published: November 2019

This talk describes the limited duration integral equation method (DIEM), a reference solution for time domain scatter from one-dimensional surfaces. The DIEM approximates the exact Helmholtz integral equation by truncating this spatially infinite integral. The DIEM truncation causes error in its solution, which is mitigated using arrival time predictions from the analytically simpler Helmholtz-Kirchhoff approximation (HKA). The HKA is additionally shown to effectively replace much of the DIEM convergence analysis, leading to efficient DIEM solutions. The exact Rayleigh-Fourier method (RFM) is used to validate the DIEM result for a sinusoidal scattering surface scenario. While the HKA yields significant error in this scenario, it predicts the truncation behaviors of the DIEM correctly. Unlike the RFM that is specific to periodic surfaces, however, the DIEM is not restricted to any specific surface geometry. The DIEM therefore proposed as an efficient reference solution for future line source scattering studies with general scattering surfaces.
Interactive rendering of dynamic virtual audio-visual environments for "subject-in-the-loop" experiments
Authors: Grimm Giso , Hendrikse Maartje M. , Hohmann Volker
Published: November 2019

The benefit from hearing devices with directional filtering algorithms, e.g., hearing aids with fixed beamformers, may depend on the user’s head movement behavior. Traditional evaluation methods for hearing devices often do not allow for head movements, or present stimuli in tasks which do not result in natural movement behavior of the participants. To overcome these limitations, virtual audio-visual environments are increasingly used to reproduce listening environments. Here, we present a software tool for interactive real-time simulation of audio-visual virtual environments. Simulation methods for time-domain rendering of direct sounds and early reflections in a geometric image source model in combination with a simple method of rendering diffuse sound fields from first-order Ambisonics recordings as well as diffuse reverberation from recorded first-order Ambisonics impulse responses are presented. A set of five typical and difficult listening environments was created in the lab with loudspeaker reproduction, and the movement behavior of 40 young and elderly normal hearing listeners was recorded in these environments. Furthermore, the influence of this individual head movement data on the performance of various signal enhancement algorithms was simulated. Data show that the application of virtual acoustic environments may contribute to a higher ecological validity of lab-based hearing-device evaluation methods.
Computations of sound power and level components in symphony orchestra
Authors: Skalevik Magne
Published: November 2019

A symphony orchestra and its members are both sources and receivers. The individual musician in an orchestra hears a combination of direct sound from own instrument, a mix of direct sounds from co-musicians, and reverberant sound from the whole orchestra. The delicate balance between these three components is assumed to have big impact on playing conditions, hearing of self and others, masking of self and others, ensemble, self-reinforcing feedback loops that cause escalating sound power, and excessive noise exposure, to mention a few. Of course the result will affect the audience. Different models for computing the three sound components, and results will be presented.
Timing is everything: Drivers of interannual variability in blue whale migration
Authors: Szesciorka Angela R. , Ballance Lisa T. , Rice Ally , Hildebrand John , Širović Ana , Franks Peter J.
Published: November 2019

The growth and survival of large-bodied marine predators depend on temporal synchrony with resource availability. Baleen whales migrating long distances must therefore respond to interannual variability to avoid a predator-prey mismatch. Highly migratory and acoustically active, blue whales are a model species for investigating the drivers and timing of migration. Using passive acoustic recordings collected from 2007 to 2017, we examined the relationship among migration timing (inferred from blue whale “D” and “B” calls), environmental indices, and measured krill abundance. Arrival to Southern California feeding grounds was correlated with sea surface temperatures (SST) on Costa Rica breeding grounds (r = 0.81, <0.01). Colder SSTs in both regions resulted in early arrival and correlated with greater krill abundance in Southern California (r2 = 0.47, p = 0.03). The correlation between krill abundance and the transition from D to B calls (r2 = 0.55, <0.01) suggested that in high-krill-abundance years, whales switched earlier from social to reproductive-related behavior on their feeding grounds. This phenotypic plasticity may allow blue whales to accommodate environmental variability while balancing important biological needs. However, D call onset dates increased significantly over the 11-year study (r = 0.68, p = 0.03), shifting arrival two months earlier. Longer time on the feeding grounds may increase ship-strike and entanglement risk for this endangered species.
High-frequency quantitative ultrasound and B-mode analysis for characterization of peripheral nerves including carpal tunnel syndrome
Authors: Byra Michal , Wong Jonathan , Shah Sameer , Han Aiguo , O'Brien, W. D. , Du Jiang , Chang Eric , Andre Michael P.
Published: November 2019

We investigated the use of high-frequency quantitative ultrasound (QUS) and B-mode texture features to characterize ulnar and median nerve fascicles using a clinical scanner (Vevo MD) and a 30-MHz center-frequency probe. US correlation with histology was first investigated in the ulnar nerve in situ in cadaveric specimens. 85 fascicles were matched in B-mode images and the histology sections. Collagen and myelin concentrations were quantified from trichrome labeling, and backscatter coefficient (-24.89 ± 8.31 dB), attenuation coefficient (0.92 ± 0.04 dB/cm MHz), Nakagami parameter (1.01 ± 0.18) and entropy (6.92 ± 0.83) were calculated from ultrasound data. B-mode texture features were obtained via the gray-level co-occurrence matrix algorithm. Combined collagen and myelin concentration were significantly correlated with the backscatter coefficient (R = -0.68), entropy (R = -0.51), and several texture features. For the median nerve, we measured backscatter and morphology in 10 patients with carpal tunnel syndrome and 21 healthy volunteers. Significant differences (<0.01) between patients and controls and AUC 0.89–0.94 for QUS biomarkers were observed. Our study indicates that QUS may potentially provide useful information on structural components of even very small nerves (2 × 4 mm) and fascicles for diagnosing and monitoring injury, and surgical planning.
Tissue characterization using backscatter and attenuation coefficients: theoretical developments and in vivo applications
Authors: Lavarello Roberto J.
Published: November 2019

Conventional echographic imaging depicts anatomical structure by displaying the magnitude of backscattered ultrasound echoes. However, ultrasonic radiofrequency data contains a richer information content that can be exploited for constructing images of intrinsic tissue properties. In particular, spectral-based ultrasonic tissue characterization techniques allow imaging parameters such as the backscatter (BSC) and attenuation (AC) coefficients. Even though this type of analysis has been explored for decades, several challenges ranging from technical algorithmic issues to the lack of widely validated, successful clinical applications have limited efforts directed towards these imaging modalities. The formulation of BSC and AC estimation as a 2-D inverse problem in combination with regularization methods is discussed, and this approach is shown to significantly extend the trade-off between estimation precision and spatial resolution. Recent applications of BSC and AC estimation in vivo are also discussed, including the assessment of interstitial fibrosis and tubular atrophy (IFTA) and inflammation in renal allografts, the diagnosis of cervical lymph nodes, and the high frequency characterization of skin.
Moving ultra
Authors: Brooks Bennett M.
Published: November 2019

The Ultra Music Festival is an international electronic dance music (EDM) franchise. Ultra started in Miami Beach but has been in downtown Miami for over a decade. In 2018, the attendance at the 3-day Ultra fest in the public Bayfront Park was about 200K. The venue is surrounded by high-rise apartment buildings. During the week of sound checks prior to the event, many residents are seen pulling suitcases to taxis/ubers to escape the onslaught. The buildings literally shake. A coalition of residents in downtown Miami sought to monitor the event and to reduce its negative impact on the neighborhood. Bass levels (40 to 125 Hz) approached 120 dB at an adjacent residence. In this frequency range, the Cavanaugh criteria metric (L1—L90) for the impact of outdoor entertainment facilities on residential neighbors was close to 50 dB. The Miami City Commission voted to not renew the Ultra contract for Bayfront Park. In 2019, the festival was moved to the nearby island of Virginia Key, where it generated numerous complaints. As of this writing, Ultra is in political limbo, with its future location yet to be determined. Measured sound data from the event and Ultra’s current status will be presented.
Practical realisation of an active acoustic metamaterial building block
Authors: Tan Joe , Cheer Jordan , Daley Stephen
Published: November 2019

Acoustic metamaterials (AMMs) have been demonstrated as an alternative approach to achieving high levels of noise control using an array of subwavelength unit cells, exhibiting behaviour not seen in conventional materials. Specifically, active AMMs offer the potential for greater levels of broadband wave manipulation, tunability and adaptability. However, determining the control source strengths that achieve broadband negative effective material properties is not straightforward. This study presents a practical method of designing an active system that directly minimises the effective material properties. The source strengths required for both single monopole and dipole control sources to minimise the effective bulk modulus and the effective density respectively have been calculated via an optimisation procedure in the frequency domain. A finite impulse response (FIR) filter has then been designed in each case to match the optimised frequency responses and enable real-time implementation. The performance of the designed FIR filters has been tested by implementation using the two different control sources in a one-dimensional duct and the ability of the proposed active AMM building blocks to achieve broadband negative effective material properties is tested. Interestingly, by combining the two optimised control sources, double negativity can be achieved, offering the potential for negative refraction.