bluuebunny/crossref_metadata_2025 huggingface dataset:
Strain differences in song and hearing in canaries (Sernius canarius)
Authors: Dooling Robert , brown Jane , Brittan-Powell Beth , Ball Gregory F. , Conte Matt , Carleton Karen , Madison Farrah
Published: November 2019

Breeders have bred canaries either for specific song characteristics (song canaries) or morphology/plumage (type canaries) for centuries. Type canaries (e.g., Border and Gloster strains) retain song characteristics that are typically quite similar to those of wild canaries. By contrast, song canaries (e.g., Belgian Waterslager and Roller strains) have been selected for song types pleasing to the human ear, resulting in songs that, in most cases, are less complex, lower pitched, and narrower in a frequency range than songs from wild canaries. We now suspect that song selection in the Belgian Waterslager song canary has either directly or indirectly resulted in high-frequency hearing loss associated with hair cell abnormalities. Here, we compare hearing in the Belgian Waterslager and several other type and song canaries including the American Singer Canary. Though bred only since the 1930s, American Singer canaries also have a high-frequency hearing loss that looks very similar to that of the Belgian Waterslager and may have similar pathologies. Illumina whole genome sequencing has preliminarily identified a number of high-impact SnpEff variants in Belgian Waterslager and American Singer Canaries, some of which are related to deafness genes in mammals.
Alpha male Guyanan red howler monkey responses to nocturnal and diurnal loud calls
Authors: Do Nascimento Leandro A. , Beard Karen
Published: November 2019

Our understanding of the communication system of howler monkeys is hampered by our ability to collect acoustic and behavioral data across their entire period of activity. It is not surprising that most studies are restricted to the daylight period despite knowledge that this species is also active at night. Our goal was to describe vocalization patterns, call structure, and test the function of diurnal and nocturnal loud calls of the Guyanan red howler monkey. To be able to study 24-h cycle call emissions, we used 20 passive acoustic monitoring devices deployed in the territory of four different troops of howlers. To test the function of diurnal and nocturnal loud calls, we set up a broadcast experiment and recorded the behavioral response of alpha males to the playbacks. There is a significant difference between some spectral properties of nocturnal and diurnal howls (duration, standard deviation, median frequency, skewness, kurtosis, and flatness). The alpha males responded differently to nocturnal and diurnal playbacks. They approached more often, vocalized more, and never evaded when presented with nocturnal call playbacks. We found significant differences between approach latency, evade latency, and soft call latency. Howler monkeys responded differently to the playbacks, which suggest that nocturnal and diurnal loud calls serve different functions. We found that nocturnal calls triggered more aggressive responses than diurnal calls.
Applications for marine mammal studies using passive acoustic data from the Coastal Endurance array off Newport, Oregon
Authors: Ferguson Elizabeth
Published: November 2019

The National Science Foundation-funded Ocean Observatories Initiative (OOI) maintains a series of coastal and oceanic monitoring sites that consists of a multitude of physical and biological sensors. As part of this program, OOI has collected continuous, broadband passive acoustic data along the continental shelf and slope off Newport, Oregon since 2016. The Coastal Endurance cabled array consists of two mooring lines that straddle the Columbia River plume, and capture data from this nutrient rich upwelling site along the northeast Pacific coast. In addition to this instrumentation, underwater gliders conduct regular transects to provide better spatial resolution of coastal ocean parameters in the region. Representative data from the continental slope and seamount recording sites of the Coastal Endurance Array were reviewed for vocally active marine mammals. Physical oceanographic variables collected concurrently from the mooring line instrumentation and coastal gliders were used to spatially and temporally characterize the regional marine mammal habitat. This effort demonstrates applications for use of OOI’s accessible, multi-instrument platform for conducting marine mammal ecosystem studies.
Investigation of acoustic navigation strategy of bats based on spatial learning by a mathematical model
Authors: Mibe Yurina , Yamda Yasufumi , Ito Kentaro , Kobayasi Kohta I. , Hiryu Shizuko
Published: November 2019

Echolocating bats achieve minimal design ultrasonic sensing using one transmitter and two receivers. We have previously found that the bats adaptively change avoidance routes and number and direction of broadcasts as they learn obstacle space by repeatedly flight. In this research, we propose a mathematical model that represents changes in flight path and pulse emission during spatial learning of bats based on these behavioral data. Specifically, by using the psychological effect of alertness to obstacles as a parameter, we confirmed that a simple mathematical model can express the changes in acoustic navigation as the bats learn the space. Furthermore, we flied the bats in spaces where either acoustically clear (chain trains) or poorly permeability obstacles (acrylic boards) were placed in the same layout. As a result, differences in flight speed and pulse direction were found between those two conditions. By comparing the simulation result from mathematical model with behavioral results, we discuss psychological effects on unknown and known space due to differences in acoustic permeability and utilization of spatial memory during navigation. [Work supported by JSPS KAKENHI Grant Nos. JP18H03786 and JP16H06542 and JST PESTO Grant No. JPMJPR14D8.]
Teledyne RD instruments engineering developments to increase acoustic measurement range
Authors: Wanis Paul
Published: November 2019

Acoustic sensors are commonly used for marine measurement and navigation purposes. Acoustic Doppler Current Profilers (ADCPs) measure ocean currents and waves and Doppler Velocity Logs (DVLs) measure instrument motion relative to the sea bed. Both types of instruments perform their measurements by emitting an acoustic signal and measuring the Doppler shift of the return echoes. The maximum sensing range of these instruments is determined by many factors including directivity of the acoustic transducer, spreading losses, frequency-dependent absorption losses, backscatter intensity, and noise in the environment. Users always wish to maximize the range performance in a given application, but there is typically a trade-off between range performance and other parameters such as system size, power, measurement uncertainty, and susceptibility to fading effects. In this presentation, we provide an overview of some of the newest technologies created by Teledyne RD Instruments to improve the achievable range of these instruments. These new technologies include new signal processing algorithms to enhance bandwidth performance while remaining robust against fades and new transducer array technologies to improve the range that can be achieved with a given transducer aperture. These technologies enable greater range performance with a minimal impact to other system parameters.
Integrative passive acoustic monitoring in Monterey Bay National Marine Sanctuary
Authors: Ryan John P. , Cline Danelle E. , Benoit-Bird Kelly J. , Chavez Francisco , Raanan Ben Y. , Urmy Samuel S. , Zhang Yanwu , Oestreich William K. , Goldbogen Jeremy , Joseph John E. , Margolina Tetyana , DeVogelaere Andrew , Forney Karin , Kudela Raphael M. , Santora Jarrod A.
Published: November 2019

Monterey Bay National Marine Sanctuary, in the highly productive California Current System, is vital habitat for many marine mammal species. Passive acoustic monitoring (PAM) is an effective means to detect species’ presence and acoustic behavior. Using the infrastructure of a cabled observatory and detection and classification of sound sources, we examine applications of PAM as an essential part of ecosystem-based research and management. The first case study integrates PAM with multidisciplinary data—whale sighting rates, forage species’ abundances, levels of primary production, concentrations of a neurotoxic algal compound, and acoustic modeling results—to examine how occurrence patterns of humpback whale song reflect ecosystem variations. The second case study takes a similar approach to examine blue whale call occurrence, with emphasis on varying detection and classification methods for different call types. The third case study examines an anthropogenic sound source: explosives intended to deter interference of pinnipeds in fishing operations. Toward new developments that are proving insightful, we consider three further approaches: (1) application of unsupervised machine learning methods to advance characterization of humpback whale song structure; (2) integration of PAM and active acoustic sensing to examine predator-prey relationships; and (3) integration of PAM time-series analyses with data from animal tags.
Acoustic determination of CO2 bubble rise heights during a controlled release experiment
Authors: Blomberg Ann E. , Loranger Scott , Pedersen Geir , Waarum Ivar Kristian , Eek Espen , Totland Christian
Published: November 2019

Carbon capture and storage (CCS), where CO2 is captured from industrial sources and stored in geological formations, has emerged as a promising method for reducing the amount of CO2 released into the atmosphere. Current regulations require monitoring the water column above a storage site to verify that there are no indications of leakage. Determining the rise height of CO2 bubbles is important in order to understand the environmental consequences of a potential CO2 leak, as well as to establish an efficient monitoring strategy. The rapid dissolution of CO2 in seawater is likely to limit the rise height of CO2 bubbles. However, few quantitative studies have been published. During a controlled release experiment in the Oslo Fjord, we simulated a CO2 leak at a water depth of 60 m. CO2 bubbles were released at rates of 0.575 l/min and 1.15 l/min, from a 3 mm orifice. Rise heights were determined using multiple echo sounders and sonars mounted on the Simrad Echo R/V. We observed consistent scattering from bubbles as high as 50 m above the leak point. We also experienced that it is challenging to locate the top of the plume using most echo sounders, due to the imaging geometry of the system.
Acoustic droplet vaporization threshold of perfluorocarbon droplets as a function of frequency: Effects of droplet cores and size
Authors: Aliabouzar Mitra , Kumar Krishna N. , Sarkar Kausik
Published: November 2019

Phase shift liquid perfluorocarbon (PFC) droplets vaporizable by ultrasound can be used for many therapeutic and diagnostic applications. The ultrasound activation pressure required for the phase change of these droplets into echogenic microbubbles is termed acoustic droplet vaporization (ADV) threshold. We have studied the ADV and IC (inertial cavitation) thresholds in a tubeless setup using an acoustic means varying frequency of the excitation, the droplet core and their average size. The ADV threshold was found to increase with the increasing frequency for the lowest boiling point liquid, perfluoropentane (PFP), for both large and small average size droplets. For higher boiling point liquids, perfluorohexane (PFH) and perfluorooctyle bromide (PFOB), this study did not detect vaporization for small size droplets at the excitation levels (maximum 4 MPa peak negative) studied here. The large PFOB droplets experienced ADV only at the highest excitation frequency 15 MHz. For large PFH droplets, ADV threshold decreases with frequency that could possibly be due to the superharmonic focusing being a significant effect at larger sizes and the higher excitation pressures. ADV thresholds at all the frequencies studied here occurred at lower rarefactional pressures than IC thresholds indicating that phase transition precedes inertial cavitation.
Standing wave assisted acoustic droplet vaporization for dual payload release from acoustically responsive scaffolds
Authors: Aliabouzar Mitra , Jivani Aniket , Lu Xiaofang , Kripfgans Oliver , Fowlkes Jeffrey B. , Fabiilli Mario L.
Published: November 2019

Ultrasound standing waves have been utilized for many biomedical applications. Here, we demonstrate how standing waves can enhance drug release using acoustic droplet vaporization (ADV), which is the phase-transitioning of perfluorocarbon (PFC) emulsions via ultrasound. These experiments utilized acoustically-responsive scaffolds (ARSs), which are composite fibrin hydrogels containing payload-carrying, monodispersed PFC emulsions. Single- and bi-layer ARSs were generated with dextran-loaded emulsions (diameter: 6 mm) containing either perfluorohexane, or perfluorooctane in each layer. First, we studied the influence of standing waves on payload release from single-layer ARSs. At 4 MPa peak rarefactional pressure, elevated amplitudes due to constructive superposition in the standing wave field enhanced payload release up to 35% at 2.5 MHz in a seven-day longitudinal study. Second, the effect of standing waves was combined with the frequency-dependent ADV to enhance dual payload release from bi-layer ARSs. We demonstrated the sequential release of two dextran payloads from ARSs, which were, respectively, contained within each emulsion, using temporally staggered ADV at 3 MHz (day 0) and 8.8 MHz (day 4). These results will also be discussed in the context of practical strategies for achieving similar conditions for in vivo applications
Possible role of ultrasound research platforms in measuring endogenous decompression bubble nuclei
Authors: Papadopoulou Virginie , Le David Q. , Dayton Paul A.
Published: November 2019

Venous gas emboli (VGE), of the order of several tens of micrometers, can be detected with ultrasound imaging after scuba diving and are a marker of physiological decompression stress. Higher VGE post-dive are associated with a higher risk of decompression sickness, but these bubbles can also be observed after shallow, conservative and completely asymptomatic dives. The risk of decompression sickness, but also the amount of VGE observed post-dive, have been shown to exhibit a significant amount of yet unexplained inter- and intra-subject variability, even for an identical, controlled diving exposure. Importantly, the precise location and formation mechanism of VGE both remain largely unknown. In this talk, we describe the development of ultrasound techniques that overcome barriers to effective imaging of these bubbles in humans. A focus is on optimizing the assessment of post-dive bubble loads by refining their evaluation on echocardiograms to facilitate a more dynamic assessment. Emphasis will then be given to the adaptation of biomedical ultrasound contrast-specific imaging schemes to investigate the infamous "micronuclei" hypothesized to be at the origin of the gas bubbles observed in divers.
The journey of the Thai musical instruction collection at the University of California, Los Angeles
Authors: Adler Supeena I.
Published: November 2019

An ensemble of Thai classical instruments was first brought to UCLA by Dr. David Morton who taught in the Ethnomusicology Department. After he left UCLA, the instruments were disused for decades. In 2015, the author was hired to examine and restore the collection to a playable condition, and subsequently to re-establish the Music of Thailand ensemble class. With financial support from the Thai consulate and the Center for Southeast Asian Studies, the course is now offered regularly and the instrument collection has expanded further. The oldest of the instruments at UCLA originated from the family of a prominent teacher and are highly regarded by their descendants and considered spiritually powerful. These connections were honored with a wai khruu (‘honoring the teachers’) ceremony held at UCLA featuring a professional ensemble of musicians from Thailand. In this paper, the author will introduce the classical instruments of Thailand, their basic construction and tuning, and the process of restoring the collection at UCLA.
Atmospheric vertical wind effects and their impact on sonic boom
Authors: Rallabhandi Sriram
Published: November 2019

The one-dimensional augmented Burgers' equation has been generally used for nonlinear lossy sonic boom propagation. This equation models the effects of nonlinearities, loss mechanisms such as absorption and dispersion due to molecular relaxation and thermoviscous dissipation, and geometric spreading through ray tube areas including Blokhintzev scaling as well as atmospheric stratification. Traditionally, atmospheric winds are accounted for by using horizontal wind components varying in magnitude as the sonic boom pressure waveform propagates from near the aircraft toward the ground. Vertical wind components, though present in the real atmosphere, are generally ignored because they are usually much weaker compared to the horizontal components. However, for long propagation distances, such as in the case of secondary booms or speeds at or slightly below Mach cut-off, vertical winds could play a role in changing the location and intensity of sonic booms. This work will update sBOOM, an augmented Burgers' equation solver, to include the vertical component of atmospheric winds. The sonic boom ground signatures and other relevant data will be compared against those obtained ignoring vertical wind components. Such differences will be discussed and documented for cases which may include shaped low-boom as well as strong shock signatures.
Field test comparison of various acoustic drone detection methods
Authors: Sedunov Alexander , Salloum Hady , Haddad Darren , Sutin Alexander , Sedunov Nikolay , Yakubovskiy Alexander
Published: November 2019

Acoustics methods for Unmanned Aerial Systems (UAS) detection have several advantages. They are low cost and passive, do not radiate any RF signals, and can provide UAS classification. The disadvantages of acoustic methods include shorter detection distances and susceptibility to acoustic noise. We present the results of field tests of several acoustic UAS detection methods. The tested systems included the Drone Acoustic Detection System (DADS) that was developed by Stevens Institute of Technology, a 16 microphone cross two-tier acoustic array, directional acoustic microphones (parabolic and shotgun microphones), and the OptiNav ACAM 120 acoustic array. The field tests were conducted to investigate the performance of various acoustic systems for UAS detection and tracking ability of various DJI models. Directional microphones and systems with many microphones did not demonstrate a significant advantage over the lower cost DADS that consists of three nodes, with each node having four microphones. Cross-correlation of signals between various microphone pairs is used for finding the acoustic signal direction of arrival. This system provides acoustic target detection and tracking. Classification software discriminates between a UAS and other possible targets, such as airplanes, helicopters, and ground vehicles. [Work supported by Air Force Research Laboratory under Contract No. FA8750-17-C-0190.]
Optimization of acoustic drone detection based on tests with linear acoustic array
Authors: Haddad Darren , Sedunov Alexander , Salloum Hady , Sutin Alexander , Sedunov Nikolay , Yakubovskiy Alexander
Published: November 2019

In a number of field tests for Unmanned Aerial Systems (UAS) acoustic detection, we used several detection systems including a 16 microphone cross two-tier acoustic array, directional acoustic microphones (parabolic microphones and shotgun microphones), and the OptiNav ACAM 120 acoustic array. The improvement of the detection distance using direction microphones and microphone arrays was less than what was estimated based on the system directivity index. A possible limitation of the directional system performance can be due to wind noise, presence of various noise sources and atmospheric turbulence conditions. The turbulence leads to decorrelation of the acoustic signal received by various elements of a microphone array. The UAS and noise signals recorded by the cross two-tier AFRL acoustic array was used for estimation of external noise and UAS signal correlation depending of the distances between microphones. The array is shaped like a two-tier cross, with each tier spanning 3 m and pseudo-logarithmic spacing between the elements. The coherence measurements between various microphone pairs were used for the estimation of the optimal size of a microphone array for UAS detection and optimal sensor separation for the Stevens Drone Acoustic Detection System (DADS). [Work supported by Air Force Research Laboratory under Contract No. FA8750-17-C-0190.]
Running with speedster superheroes: What they hear, and practical applications regarding observers travelling at supersonic speeds
Authors: Jerome Trevor W.
Published: November 2019

In 1842, Christian Doppler provided the well-known descriptions of frequency shifts perceived by an observer in motion. These fundamental relationships show that listeners moving relative to a sound source at subsonic speeds perceive a shift in frequency that depends on the direction of relative travel. About one hundred years later, the first speedsters (characters with superhuman speed) emerged in fiction media. Since then, dozens of speedsters have come to life in comic books, television, and cinema. The acoustical content hypothetically perceived by such superheroes at supersonic speeds is investigated. Specifically, the implications of an observer passing through a sound wave—with high and low molecular density regions of a fluid medium—under various atmospheric conditions are explored, assuming turbulence could be sufficiently mitigated. Both transonic and extremely hypersonic (>10 times the speed of sound) regimes are considered. Finally, possible practical applications for supersonic travel are examined.
Human heel-contact and toe-off times measured with an in-air 40 kHz Doppler ultrasound
Authors: Timsina Sabin , Sabatier James
Published: November 2019

In-air Doppler ultrasound is used to measure human gait parameters as a person walks in a hallway. Single element, 10 mm diameter transmit and receive transducers are used for a walk range from 2–10 m in a continuous wave mode at 40 kHz. The person’s foot heel-contact and toe-off times are needed to determine the leg’s swing phase and double stance times as well as asymmetries between the left and right legs. At the times, the foot velocity is zero, and the other body segments continue to move with non-zero velocities causing Doppler frequency shifts that mask the smaller foot velocity of interest. We currently use an algorithm to fit the measured foot velocity in the Doppler data to a model in order to estimate these times. This model was developed from simultaneously measured video motion capture and Doppler ultrasonic data for walking persons. Less than desirable results are achieved when the ultrasonic measured times are compared to those from commercially available pressure sensitive gait mats. We will present a comparison of the heel-contact and toe-off times measured using beamed transducer arrays and a foot plate sensor made from a pressure sensitive material.
Performance mechanisms and stability criteria for highly sub-wavelength, broadband nonreciprocal non-local acoustic metamaterials
Authors: Geib Nate , Sasmal Aritra , Wang Zhuzhu , Zhai Yuxin , Popa Bogdan Ioan , Grosh Karl
Published: November 2019

Active acoustic metamaterials have received considerable attention recently due in large part to their ability to generate nonreciprocal wave transmission. We have shown previously how the spatial separation of acoustic sensors and sources can be leveraged to generate highly sub-wavelength, broadband nonreciprocal behavior in an acoustic waveguide. We showed that by transmitting pressure signals from one location along the waveguide to a loudspeaker at another location, we could achieve a peak isolation of 35 dB with a Q10dB factor of just over 0.25. Here, we discuss the mechanisms by which this nonreciprocity is achieved and the conditions required for the system to be stable. We show how conclusions regarding the performance and stability characteristics of an idealized plane wave acoustic model of our system must be adjusted when accounting for the controlling electronics and loudspeaker dynamics used in the experimental testing.
Stabilization of bianisotropic fluid models for time domain simulation
Authors: Wallen Samuel P. , Goldsberry Benjamin M. , Haberman Michael R.
Published: November 2019

Willis fluids are characterized by constitutive relations that couple the pressure and momentum density to both the particle velocity and the volume strain. This effective dynamic response coupling may arise due to microstructural asymmetry, long range order, or time-varying material properties and has been shown to be analogous to electromagnetic bianisotropy [Phys. Rev. B 96, 104303 (2017)]. Recent work has shown that, when wavevectors exceed a critical magnitude, the currently employed model for passive Willis fluids possesses a linear instability stemming from the truncation of higher-order coupling terms in the derivation of the constitutive relationships [J. Acoust. Soc. Am. 144(3), 1832 (2018)]. While this instability can be avoided when using frequency domain methods, it poses significant problems for time domain simulations, as short-wavelength numerical noise may grow exponentially. In the present work, we report on methods of stabilizing the Willis fluid model. Specifically, we consider mathematical manipulations of the wave equation derived from the lowest-order constitutive equations, similar to methods that have been explored in continuum approximations of nonlinear spring-mass chains, as well as higher-order coupling terms. Physical interpretations and implications for time domain finite difference and finite element simulations are discussed. [Work supported by the postdoctoral program at ARL:UT.]
A feasibility study on achieving mode coalescence in acoustic waveguides
Authors: Kelsten Matthew , Norris Andrew
Published: November 2019

In a previous talk at ASA it was shown that the double root, commonly referred to as an exceptional point (EP), for modal frequencies in a 2-D or 3-D waveguide can exhibit almost perfect absorption over a relatively broad frequency range. The key to the phenomenon is that the wall impedance is such that modes coalesce at a complex-valued frequency. In this talk, we consider how to feasibly achieve the aforementioned wall impedance with the use of simple resonators. Within the frequency ranges supporting scale separation, it can be shown that a wall aligned with resonators can be modelled as an effective surface with a unique admittance. It is with this concept that we arrive at results showing distinct frequencies at which mode coalescence can occur. Strategies capable of deriving the necessary resonators parameters, and therefore, its dimensions are given. Numerical results are shown for reflection and transmission from a waveguide with the tuned effective surface composed of resonators in addition to the theoretical impedance boundary associated with constant EP behavior. Computer simulations and preliminary experimentation of the phenomena are referenced. Future attempts of utilizing more complicated metasurface designs are discussed for next iterations. [Work supported by NSF.]
Effective impedance of a locally resonant metasurface
Authors: Lott Martin , Roux Philippe
Published: November 2019

We study here a mesoscopic metasurface made of a randomly distributed set of long vertical metallic rods attached to a thin elastic plate. The A0 Lamb wave mode is strongly affected by the low-quality factor forced resonance of the rods. At such resonance, the rods modify the apparent stiffness of the plate. At the corresponding anti-resonance, the rods clamp the plate in the metamaterial region, which induces eigenfrequency band gaps. Between these two resonant and anti-resonant frequencies, the continuum in the values of the effective rigidity change the reflectivity, and thus the corresponding complex impedance of the metasurface in terms of amplitude and phase. In the present study, experimental data are presented to estimate the effective impedance of such a locally resonant metasurface, in agreement with theory and numerical simulation.
A causal role of superior temporal gyrus in auditory-motor control of vocal production
Authors: Liu Hanjun , Liu Dongxu
Published: November 2019

Accumulating evidence has shown that the superior temporal gyrus (STG) plays an important role in auditory feedback control of vocal production. The precise role of this region in auditory-vocal integration, however, remains unclear. The present event-related potential study applied a transcranial magnetic stimulation (TMS) protocol, continuous theta-burst stimulation (c-TBS), to depress activity in the left STG as young adults produced sustained vowels while their voice was unexpectedly pitch-shifted downwards by 50 or 200 cents. The behavioral results showed significantly larger vocal compensations for pitch perturbations in the c-TBS condition as compared to the sham condition. At the cortical level, c-TBS over left STG led to significantly smaller cortical P2 responses than the sham condition. These findings provide the first causal evidence for linking the STG to auditory feedback control of vocal production. Enhanced vocal compensations for pitch perturbations as a result of disrupting the STG activity lend support to the idea that the STG may be critically involved in top-down inhibitory mechanisms of speech motor control, through which vocal motor behaviors can be appropriately regulated without being excessively influenced by auditory feedback.
Changes in L2 production variability associated with visual biofeedback training
Authors: Li Joanne Jingwen , Ayala Samantha , Harel Daphna , Shiller Douglas , Niziolek Caroline A. , McAllister Tara
Published: November 2019

Previous research suggests that acoustic variability across repeated productions of a phoneme could index the robustness of speech motor plans. Variability at onset is thought to reflect robustness in feedforward control [1,2], while variability at midpoint may reflect the narrowness of sensory targets and/or speakers’ capacity for feedback correction [3]. In L2 production, speakers may show elevated variability at onset because of unfamiliar motor plans and at midpoint due to weak sensory targets [2]. This study investigated variability in L2 vowel production before and after a brief training incorporating visual biofeedback. We hypothesized that midpoint variability would decrease after training, reflecting refinement of the auditory target, whereas onset variability may remain unchanged because the limited training might not be sufficient to establish a robust feedforward plan. Sixty native English speakers received 1 h of biofeedback training to produce two Mandarin vowels (/y, u/). After training, both vowels showed decreased midpoint variability, but only /y/ showed reduced onset variability. In addition, for /u/ only, higher pre-training midpoint variability was correlated with greater improvement in accuracy (distance from native-speaker target). These results are discussed in connection with the differing relationships of Mandarin /y/ and /u/ to the English vowel inventory.
Time reversal focusing of high amplitude sound in a reverberation chamber: Optimizing the placement of transducers
Authors: Patchett Brian D. , Anderson Brian E.
Published: November 2019

Time reversal (TR) is a signal processing technique that may be used to intentionally generate high amplitude focusing of sound. The use of time reversal in room acoustics has been studied previously, but an analysis of the dependence of spatial positioning of the transducers in the room, and its effect on high amplitude focus signals has not previously been explored. Experiments are carried out in two reverberation chambers of differing size with eight compression drivers. Using these drivers, the impulse response is found and reversed in time. The spatial dependence of the transducers position is measured by calculating the time reversed impulse response at various transducer positions and then measuring the peak focal amplitude generated when the time reversed signal is broadcast to those positions. Multiple measurements suggest that the amplitude of the focus signal changes with both room size and proximity to a reflecting surface in the chambers.
The spectral structure of acoustic time series can predict the perceptual assessment of urban soundscapes
Authors: Mitchell Andrew , Kang Jian
Published: November 2019

The field of soundscape studies considers sound environments as perceived, in context, and has recently focussed on understanding the potential of physical acoustical features, including temporal characteristics, for predicting human perception. This study investigates the presence of a 1/f structure in the power spectrum slope of six (psycho)acoustical parameters of 30-s recordings of urban acoustic environments. The acoustical parameters were calculated as time series throughout the recording period, then the power spectrum of the time series was calculated and plotted on a log-log scale, with the x-axis ranging from 30 s/10-1.5 Hz to 0.01 s/102 Hz. The slope of the best-fitted straight line through the power spectrum was calculated and compared to the corresponding perceptual attribute ratings of the soundscape collected on site during the recording. The dataset includes 300 + recording-response pairs. An overall 1/f structure was not found for any of the parameters. Differences in temporal behaviour are indicated at different time scales, with a deviation in slope typically occurring at ∼2 s/0.5 Hz, reflecting differences in temporal behaviour among within-sound-event time scales and between-sound-event time scales. An ordinal logistic regression model is developed which predicts the perceptual attributes of urban soundscapes based on the spectral slopes of the acoustic time series.
Application of lp-norm regularisation techniques in the synthesis of indoor tyre pass-by noise with the inverse method
Authors: Papaioannou Athanasios , Elliott Stephen , Cheer Jordan
Published: November 2019

The indoor pass-by noise measurement can nowadays be realised in a laboratory environment with a far field microphone array and a stationary vehicle on a rolling road, according to ISO-362-1:2016. Within this indoor testing procedure, there exists the ability to quantify the contributions from the various noise sources in a car to gain further insight into the total noise disturbance. The tyre noise contribution can be estimated by using an additional set of microphones close to the tyre and performing an inverse method. This work assumes measured near field pressure data close to a rolling tyre at different car speeds. The inverse method is utilised to find the corresponding source strength estimates which are then used to synthesise the far field tyre noise contribution and compare it with the one measured directly at the far field microphone array. A combination of novel l1 regularisation and conventional l2 regularisation methods is finally investigated to further optimise the equivalent source strength estimates and, subsequently, the far field pass-by noise pressure estimates through the frequency range of interest.
Using the frequency-difference autoproduct to regain coherence in rough surface scattering
Authors: Joslyn Nicholas J. , Dowling David R.
Published: November 2019

Incident and reflected acoustic waves, with wavenumber k, are coherent in an ideal Lloyd’s mirror environment. However, a random rough surface, characterized by its rms roughness height h, reduces this coherence as kh increases. This presentation describes the ability of the frequency-difference autoproduct to recover reflected-field coherence, albeit at a lower frequency, even in the presence of high kh values. The frequency-difference autoproduct is a quadratic product of complex field amplitudes at different frequencies within the signal bandwidth. Prior work has shown that the frequency-difference autoproduct can mimic a below-band field at the difference frequency. Thus, by choosing a sufficiently-low difference frequency, the apparent surface roughness can be reduced so that a rough-surface scattered field resembles a flat-surface reflected one. For the theory and simulation results presented here, the surface roughness is Gaussian distributed and isotropic, and the Kirchhoff (tangent plane) approximation is used to determine the reflected sound. For 1 < kh < 6, theoretical and numerically simulated autoproducts in a rough-surface environment are compared to acoustic fields at the difference frequency in an ideal Lloyd’s mirror environment. Accompanying experimental results may be provided as well, if available. [Work supported by ONR.]
High-frequency backscattering enhancements from elastic cylindrical shells in water: Observations and ray theory
Authors: Hall Bernard R. , Marston Philip L.
Published: November 2019

Sometimes elastic features for acoustically illuminated targets in water are relegated primarily to low frequency bands. For empty spherical shells however, a pronounced high-frequency backscattering elastic-enhancement was observed and modeled using ray-theory [G. Kaduchak, D. H. Hughes, and P. L. Marston, J. Acoust. Soc. Am. 96, 3704–3714 (1994)]. That phenomenon was termed a backwards wave enhancement because the wave phase and group velocities guided on the shell move in opposite directions and required a modified ray diagram. In the present research, this type of backscattering enhancement is demonstrated and modeled for empty cylindrical elastic shells in water. While the full ray-theory requires solving for complex roots descriptive of elastic waves on fluid-loaded shells, it was found helpful to first consider the properties of ordinary Lamb waves on plates whose thickness was selected to be that of the shell of interest. A search for different roots of Lamb’s Equation confirms that a root exists that exhibits opposing phase and group velocities in the frequency region of interest. As expected from the model, the associated backscattering enhancements are localized in frequency though they can be easily identified using tone bursts. [Work supported by Office of Naval Research.]
Study on phase of reflection coefficient of the medium with gradient change of acoustic impedance
Authors: Hu Bo
Published: November 2019

Medium with gradient change of acoustic impedance is a new type acoustic structure which composed of several materials and has a continuous gradient composition and structure whose specific acoustic impedance varies smoothly across the layer. It has been used in various practical situations such as acoustic rectifiers, medical devices, weakening vibration and reducing noise. The purpose of this paper is to investigate the phase characteristics of reflection coefficient of medium with gradient change of impedance to make use of the sound pressure and vibration velocity of the wave. Exact solutions of the Helmholtz equation are derived for a typical density profile and sound-speed profile. The solutions in the medium are matched with solutions in the homogeneous upper and lower layers to derive analytical expressions for the phase of the reflection coefficient of a plane wave which incident from the upper medium. The phase of reflection coefficient in a variety of cases that of different frequencies and incident angles are examined. A number of simulation results are presented and comparison is made with computed results. The phase data can be used in the subsequent vector signal processing.
Experimental analysis of the effects of bistatic target scattering on synthetic aperture sonar imagery
Authors: Blanford Thomas E. , Johnson Shawn , Brown Daniel C.
Published: November 2019

Downward looking synthetic aperture sonar (SAS) systems, such as those used to detect surficial and buried unexploded ordinance, may use arrays with large spatial extent compared to the depth of the targets they are imaging. With such systems the targets are in the nearfield of the physical array formed by the projector and receiver. Beamforming algorithms, data representation schemes, and automated target recognition algorithms can benefit from considering the bistatic scattering patterns of targets in this geometry. This presentation will describe experimental analysis of the effects on SAS imagery due to bistatic scattering from cylindrical targets. A set of field measurements of elastic and inelastic acoustic scattering from open and closed ended cylinders was collected in a lake environment in less than 3 m of water. These data will be compared to analogous, in-air laboratory measurements. Finally, possible methods for automatically detecting elastic scattering behavior from bistatic collection geometries will be discussed.
Comparison of sparse Bayesian learning and atomic norm minimization in detecting passive tonal signals
Authors: Shin Myoungin , Choo Youngmin , Lee Keunhwa , Hong Wooyoung
Published: November 2019

The frequency estimation of tonal signals in passive sonar systems is crucial to the identification of the marine object. In this study, we introduce the frequency estimation of tonal signals using the multiple measurement vector atomic norm minimization(MMV-ANM) technique based on compressive sensing (CS) and sparse Bayesian learning (SBL) technique based on Bayesian Inference. CS techniques have been employed in identifying the tonal frequency components. It is now well-known from the theory of CS that a high-dimensional signal can be recovered from a relatively small number of measurements as long as the desired signal is sparsely represented. MMV-ANM, an extended version of CS technique for solving the basis mismatch problem, has been proposed and shown better performance in terms of resolution and stability. On the other hand, tonal signals at passive sonar systems are also estimated with sparse Bayesian learning (SBL) using MMV. The prior source amplitudes are assumed independent zero-mean complex Gaussian distribution with the unknown variances (hyperparameters). The hyperparameters are derived by maximizing the probability of given passive data, which leads to sparse tonal signal frequencies. We compare performance of SBL and MMV-ANM in estimation of passive tonal signals with synthetic and in situ data. [*corresponding author Youngmin Choo]
Examination of active target detector using in situ data
Authors: Choo Youngmin , Kang Mingu , Hong Wooyoung , Lee Keunhwa
Published: November 2019

When operating active sonar systems, target-like signals including clutter are detrimental to detecting target signals and induce an increment of false alarms. In this work, various approaches including machine learning and deep learning techniques are applied to in-situ data to investigate their performance. First, one of conventional schemes, constant false alarm rate (CFAR) detector is used to find target signals in acoustic data. It detects target signals with high SNR, but it also captures high-intensity clutter signals, which leads to many false alarms. Subsequently, data-driven decision rules from machine learning of support vector machine (SVM) and deep learning of convolutional neural network (CNN) are applied. Both of SVM using aural features and CNN with spectrogram show better accuracy. In particular, false alarms from the CFAR detector are extremely decreased owing to the data-driven decision rules not exploiting the signal intensity for target detection.
Acoustic behavior of snapping shrimp in east china sea
Authors: Lee DaeHyeok , Ko Myungkwon , Choi Jee Woong
Published: November 2019

Ambient noise in shallow water is typically more complicated than that in deep sea. The snapping shrimp, which is a major source of ambient noise in shallow water, produces impulsive-shape noise. During the period of 14–28 May 2015, the Shallow-water Acoustic Variability Experiment (SAVEX15) was performed in the East China Sea (ECS) at a shallow water off the southwest of Jeju Island, Korea. In the study area, snapping shrimp noise was recorded continuously with dominant frequencies higher than 3 kHz. Envelope correlation method combined with the threshold detection was used to extract the snapping events from the received ambient noise data. Although many previous research studies have reported that the diurnal variation of snapping shrimp noise is mainly due to water temperature variation controlled by light availability, the observed snap rates in our experimental site showed unusual sinusoidal pattern and seemed to be positively correlated with the phase of the tidal current. [Work supported by the Development of Civil Military Technology Program (No. 18-SN-RB-01) from the Institute of Civil Military Technology Cooperation (ICMTC) of the Republic of Korea.]
Time-frequency characteristics estimation of underwater moving objects using memory-dependent derivative method
Authors: Sun Weitao , Wang Huigang , Gu Qingyue , Xu Yifeng , Rong Shaowei
Published: November 2019

The line-spectra changes of the radiated noise of underwater moving object is observed as the form of narrow-band time varying signal due to the Doppler effect. The modulation law of the time varying signal contains a large number of feature information of moving targets, which can be used for detection and classification. The goal of time-frequency analysis is to extract subtle changes the function relationship of frequency over time. In this research, a memory-dependent derivative methodology is proposed to deal with accurate time–frequency representation of time varying signals under strong background noise. Memory-dependent derivative is a convolution of a common derivative by the time-varying signals with a dynamic weighted function in the past period time. Considering the stated methodology, it is derived that the discrete data from previous times to estimate signal value at current time and reduce the effects of the noise. Using the Fourier transformation with different scales and delays transformation as the kernel function, the energy concentrated time-frequency curve is obtained with higher resolution and without frequency leakage. The simulated results demonstrate that given method is immune to background noise and estimate the main frequencies with high accuracy, specially the rapid change of the modulated frequency.
An archival database of high-resolution directivities
Authors: Edelman Rachel C. , Bellows Samuel , Leishman Timothy W.
Published: November 2019

Having easily accessible and accurate directivity patterns of sound sources is valuable for many applications, including architectural acoustics modeling and spatial audio. To provide this information to other researchers, the authors of this presentation are creating an online directivity database for live human speech, played musical instruments, and other sources of sound. The results are derived from recordings of the sources over their useful bandwidths at 2522 unique microphone positions over a surrounding sphere (i.e., with 5-deg resolution in both the polar and azimuthal angles). Processing of the recordings has led to frequency-dependent spherical-harmonic expansions. The expansion coefficients, as well as broad-band tabulated attenuation results (commonly used in architectural acoustics simulation packages), are freely available in the ASCII format. The database also contains figures and animations of the directivity patterns, allowing for quick visualization. The collections should help improve modeling of various acoustic spaces, microphone placements for recordings, and general understanding of source radiation characteristics.