bluuebunny/crossref_metadata_2025 huggingface dataset:
It’s time to collaborate: What human linguists can learn from machine linguists
Authors: Fry Michael D.
Published: October 2018

For decades, one of the primary goals of machine learning has been to emulate human performance by learning from human behavioural data. However, machine learning has now matured to a point where humans are learning from machines—for example, consider playstyles of Go (Silver, D., et al., "Mastering the game of go without human knowledge," Nature 550.7676(2017):354). Drawing on this idea, this project considers what speech scientists might be able to learn from considering how machines analyze the speech signal. One goal in phonetics is to break down the speech signal into units such as phonemes, syllables, and tones. Machines are also able to break down the speech signal in either a supervised or unsupervised manner. In supervised learning, the machine is trained to classify phonemes, tones, etc., using previously known labels. In unsupervised learning, the machine learns a lower-dimensional, latent representation of the speech signal and then identifies meaningful clusters in the latent space. This project takes an unsupervised approach to lexical tone identification in Mandarin. Specifically, an adversarial autoencoder and density-based clustering are used to identify the tones of Mandarin. Results contrast Mandarin lexical tones as determined by linguists and by machine learning.
Underwater source localization using a fleet of three gliders
Authors: Jiang Yong-Min
Published: October 2018

The NATO Centre for Maritime Research and Experimentation has been exploring the potentials of passive acoustic payload equipped underwater gliders for maritime intelligence, surveillance and reconnaissance missions. During the CMRE Glider Sensors and Payloads for Tactical Characterization of the Environment 2015 sea trial, it was successfully demonstrated that a fleet of three passive acoustic payload equipped gliders simultaneously detected the ‘anomalous’ sound in shallow water and reported back to the glider control center. This work studies the feasibility of localizing the source (the coordinates and the depth) using the information provided by the glider fleet. The results of three different source localization approaches are compared. The impact of the errors in conventional glider time and location data, as well as insufficient/incorrect knowledge of the ocean environment on underwater source localization is discussed. (Work funded by NATO-Allied Command Transformation.)
Effects of reverberation on estimates of synthetic aperture sonar multi-look coherence
Authors: Lyons Anthony P. , King Jonathan L. , Brown Daniel C.
Published: October 2018

Multi-look coherence makes use of phase information for target detection and classification by splitting the angle and frequency spectral bandwidth contained in a complex synthetic aperture sonar image into sub-bands and then estimating the coherence between the images formed from these sub-bands. Based on experimental results, it appears to be possible to separate man-made targets from interfering reverberation and clutter using coherence, as targets have features that scatter coherently as a function of angle or frequency. Characteristics of a target object may also be inferred, as sub-band coherence is a sensitive function of both angle and frequency. The expectation operation performed to obtain estimates of the complex correlation coefficient is evaluated using a spatial average, which lowers the spatial resolution of the resulting coherence map. The final resolution of a coherence image will be a function of the original image resolution, the number of sub-look images formed from the original image and the number of samples used in the expectation. In this work, we explore the effects of signal, reverberation, and noise levels on estimates of coherence using experimental data. Trade-offs in terms of signal-to-reverberation, expectation window size, and the number of sub-looks will be presented.
Analysis and interpretation of underwater acoustic data originated from the vicinity of the last known location of the Argentinian submarine ARA San Juan
Authors: Nielsen Peter L. , Zampolli Mario , Le Bras Ronan , Mialle Pierrick , Bittner Paulina , Poplavskiy Alexander , Rozhkov Mikhail , Haralabus Georgios , Tomuta Elena , Bell Randy , Grenard Patrick
Published: October 2018

The CTBT International Monitoring System (IMS) is a world-wide network of seismic, infrasound, hydroacoustic, and radionuclide stations designed and deployed to detect nuclear explosions. Two of the IMS hydrophone stations, one in the Atlantic Ocean and one in the southern Indian Ocean, recorded signals of unknown nature which originated from the vicinity of the last known location of the San Juan submarine on 15 November 2017. To verify the accuracy of this hydroacoustic event localization, the Argentinian Navy successively deployed a controlled depth charge to the North of the last known position of the submarine. The signals from this source were also detected on the same two IMS hydrophone stations. Several techniques were employed to compare hydroacoustic features in the signals from the 15 November event and the controlled depth charge, including an assessment of spectral energy levels, cepstral analysis, azimuth and arrival time estimation of direct and reflected signals. This presentation compares the received signals, examines their main characteristics, and, through the use of acoustic modelling, identifies possible propagation paths between the source and receiver, including a plausible explanation of early arrivals hypothesized to follow propagation paths through the Antarctic ice sheet.
In situ demonstrator of a method to track in three dimensions cetaceans with passive acoustics in the context of close interactions impacts with marine renewable energy devices
Authors: Lossent Julie , Medjber Bouzidi , Gervaise Cédric , Drira Achraf , Souami Yanis , Iorio Lucia D.
Published: October 2018

Collision risk and close interactions of cetacean with marine renewable energy (MRE) devices are among the main concerns and the least documented of the list of potential impacts of MRE. In this study, we developed a method to track in three dimensions click trains emitted by cetaceans in a close vicinity to MRE devices. We deployed two synchronized directional recording arrays 150 m apart from each other near Cherbourg (France). With an acoustic tag VEMCO© placed at several depths we performed transects with several trajectories simulating the potential behaviors (diving, surfacing, avoidance, and attraction) and click production of delphinidae. Thanks to the directional recording arrays and by crossing the direction of arrival of the same sounds calculated on each array, we build 3D maps of the synthetic clicks. We manage to reconstruct the trajectories (absolute positions x, y, and z in meters) of the emitter. In the areas located 100 m upstream and downstream of the two recording arrays, the location accuracy is maximum. This method could also be used to prove the departure and the non-return of cetacean from an exclusion zone. Moreover, this approach has been designed to be operational for the monitoring of cetaceans in environmental impact assessment studies.
Controlled source level measurements of whale watch boats and other small vessels
Authors: Wladichuk Jennifer L. , Hannay David E. , Li Zizheng , MacGillivray Alexander O. , Thornton Sheila
Published: October 2018

The Vancouver Fraser Port Authority’s Enhancing Cetacean Habitat and Observation (ECHO) program sponsored deployment of two autonomous marine acoustic recorders (AMAR) in Haro Strait (BC), from July to October 2017, to measure sound levels produced by commercial vessels transiting the strait. Fisheries and Oceans Canada (DFO), a partner in ECHO, supported an additional study using these same recorders to systematically measure underwater noise emissions (0.01-64 kHz) of whale watch boats and other small vessels that operate near Southern Resident Killer Whale (SRKW) summer feeding habitat. During this period, 20 different small vessels were measured operating at a range of speeds (nominally 5 knots, 9 knots, and cruising speed). The measured vessels were categorized into six different types based primarily on hull shape: ridged-hull inflatable boats (RHIBs), monohulls, catamarans, sail boats, landing craft, and one small boat (9.9 horsepower outboard). Acoustic data were analyzed using JASCO's PortListen® software system, which automatically calculates source levels from calibrated hydrophone data and vessel position logs, according to the ANSI S12.64-2009 standard for ship noise measurements. We found clear positive correlations of source levels with speed for all of these vessels; however, the speed trends were not as strong as those of large commercial vessels.
Characterization and modeling of typhoon-generated noise in South China Sea
Authors: Wang Jingyan , Li Fenghua
Published: October 2018

Ocean noise recorded during a typhoon is dominated by wind-generated noise sources, and can be used to monitor the typhoon and investigate the mechanism of the wind-generated noise. An analytical expression for the typhoon-generated noise intensity is derived as a function of wind speed. A “bi-peak” structure was observed in an experiment in South China Sea during which typhoon-generated noise was recorded. Strong wind speed dependence and frequency dependence were also observed in the frequency range of hundreds to thousands of Hertz. The model/data comparison shows that results of the present model are in reasonable agreement with the experimental data, and the typhoon-generated noise intensity has a dependence on frequency and a power-law dependence on wind speed.
Scattering from multiple elastic targets using the coupled finite element/boundary element method
Authors: Abawi Ahmad T. , Kirsteins Ivars P. , Marston Philip L. , Daniel Timothy D.
Published: October 2018

The fluid-structure interaction technique provides a paradigm for solving scattering from elastic targets embedded in a fluid by a combination of finite and boundary element methods. In this technique, the finite element method is used to compute the target’s elastic response and the boundary element method with the appropriate Green’s function is used to compute the field in the exterior medium. The two methods are coupled at the surface of the target by imposing the continuity of pressure and normal displacement. This results in a self-consistent boundary element method that can be used to compute the scattered field anywhere in the surrounding environment. The method reduces a finite element problem to a boundary element one with drastic reduction in the number of unknowns, which translates to a significant reduction in numerical cost. In this talk, the method is extended to compute scattering from multiple targets by self-consistently accounting for all interactions between them. The model allows to identify block matrices responsible for the interaction between targets, which proves useful in many applications. The model is tested by comparing its results with those measured involving two aluminum cylinders one of which is excited by modulated radiation pressure.
Seismic profile processing to identify sediment layering structure in shallow water
Authors: Wang Wenbo , Ren Qunyan , Li Jun , Ma Li
Published: October 2018

The equivalent layering structure of surface sediment is a key parameter for sound propagation modelling and geoacoustic inversion in shallow waters. Previously, the structure identification is manually performed through identifying these horizontal lines as shown in the profiling image, which represent the interfaces with strong acoustical impedance contrast. In this paper, a hybrid image processing method (statistical equalization, multi-scale line filtering, and wavelet decomposition) is adapted to automatically identify these interfaces, afterwards, an image-binary threshold and a dislocation phase subtraction approach are successively applied to determine sediment layer number and relative thickness. The data from dozens lines of surveys as collected in 2016 are processed. Through integrating the processing results with GPS data, 2D distributions of sediment layer number and thickness of the first and second sediment layer are constructed. The spatial distributions of sediment layer number and thickness demonstrate certain trends, which are in accordance with expected sedimentary process in this region and should be carefully treated in 3D sound propagation modelling and geoacoustic inversion.
The study on dispersion characteristics of Scholte wave in elastic media with variable parameters
Authors: Liu Ya-Qin , Zhang Hai-Gang , Yang Shi-E
Published: October 2018

In the real ocean environment, due to the reflection of the water-sediment interface, the elastic sediment will generate inhomogeneous compressional wave and inhomogeneous shear wave, and the interaction between them will form the Scholte wave. Besides, the compressional and shear wave velocities in an elastic sediment layer are changing with depth leading to the coupling of compressional and shear waves. As the dispersion characteristics of the Scholte wave is affected by the coupling effect, in this paper, a study on the dispersion characteristics of Scholte wave in an environment with variable parameters elastic sediment layer is given. Specific environmental examples are simulated and the dispersion curves are compared with the KRAKENC program. In addition, the influence of the parameters of elastic sediment layer on the Scholte wave dispersion curves is analyzed. Comparing the dispersion curve of the Scholte wave in the uniform sediment layer and in elastic medium with variable parameters, it is found that some characteristics of the dispersion curve in the uniform layer will no longer fit the elastic layer with variable parameters.
An investigation of laboratory sound transmission loss testing for steel-framed partitions
Authors: Shafer Benjamin
Published: October 2018

Laboratory sound transmission loss (STL) test reports and research publications may be used to validate partition designs as valid and code-compliant sound isolation treatments in buildings. However, longitudinal and cross-laboratory analyses of the sound transmission loss of steel-framed building partitions have revealed such a wide variation in experimental results and calculated ratings that design validation is impossible. There are multiple possible explanations for this variation in results. Steel manufacturers list a variety of mil-thicknesses under the same “gauge” specification, for example. This research study investigates laboratory testing parameters and material components such as the repeated use of the same steel framing for varying panel configurations, screw length and spacing, and steel mil-thickness, regarding the effect that each of these aspects of sample assembly design and testing have on the sound transmission loss of steel-framed partitions.
Acoustic characteristics comparison for glasses and windows by laboratory measurement
Authors: Li Hui , Wang Jianghua , Yan Xiang , Guo Jing
Published: October 2018

Windows are usually with a much lower sound insulation index comparing to walls. Integrated sound insulation of building components is decided by the weakest element. So, windows are the key of indoor quietness. The Rw of 3 structures of glass and 5 structures of windows are measured in laboratory. By comparing the results, the influence of thickness of glass, thickness of air layer, thickness and material of lamination and frame are shown. Rw + Ctr of the glasses are between 34 dB and 39 dB. Rw + Ctr of the windows are between 27 dB and 41 dB.
Parameters determining the suitability of bat species for acoustic monitoring
Authors: Koblitz Jens C. , Scharf Anne , Stilz Peter , Malinka Chloe , Macaulay Jamie D.
Published: October 2018

Acoustic monitoring of bats is increasingly used in biodiversity assessments, population monitoring, and environmental impact assessments. In addition to accurate species identification, additional factors make it challenging to derive population trends or better sizes based on acoustic monitoring. Inter- and intra-species- as well as individual variation of acoustic parameters and acoustic activity result in varying detection probabilities. Changes in environmental conditions result in large changes in the volume monitored by the device. Differences in the devices used for acoustic monitoring make it inherently difficult to compare data collected with different devices. The single call monitoring volume is modelled for bats belonging to different guilds under consideration of the different call parameters such as call intensity, frequency, and directionality. By broadcasting bat echolocation calls from various distances to monitoring devices, the acoustic parameters influencing the successful detection of a call were examined. A microphone array was used to track bats in the vicinity of monitoring devices and the distance between device and bat was measured for each call based on the time of arrival difference. The acoustic detection function, the probability of detecting calls as a function of distance, was then derived for multiple detector types.
Estimating density of fin whales and beaked whales with a mix distance sampling and spatially explicit capture recapture design
Authors: Marques Tiago A. , Thomas Len , Moretti Dave
Published: October 2018

Dedicated passive acoustic density estimation studies with reliable survey design are still rare. We will present one such project: DECAF-TEA (Density Estimation for Cetaceans from Acoustic Fixed sensors in Testing and Evaluation Areas), which aims to estimate the density of beaked and fin whales on the SCORE US Navy range. We consider a mixed design that can deal with both species that produce acoustics signals with relatively short propagation distances (e.g., beaked whales) and those that produce signals with long propagation distances (e.g., fin whales), via distance sampling (DS) for the former and spatially explicit capture recapture (SECR) for the later. For beaked whales, we consider pairs of 3D bearing sensors to provide estimates of 3D localizations of detected whales, and from such data estimate detectability via distance sampling. At the same time, single units might provide a way to estimate density of fin whales via SECR. In either case, cue rates will be obtained from independent sources. In the context of DS we explore the impact of measurement error on the 3D bearing estimates and how this error propagates via errors in localization all the way through to potential bias in density estimation.
Song variability and change in the Australian pygmy blue whale song—Implications for passive acoustic abundance estimation
Authors: Beck Capri D. , Gavrilov Alexander , McCauley Robert , Jenner Curt , Jenner Micheline
Published: October 2018

Blue whales were heavily exploited throughout the early 20th century with many populations hunted to near extinction. Today, several known sub populations of blue whale exist, separated by geographic range and the acoustic signals they produce. The eastern Indian Ocean subpopulation of pygmy blue whales is easily identified by the production of a characteristic Australian song type. Long term collection of passive acoustic data from the Perth Canyon, Western Australia and Portland, Victoria, have revealed unprecedented levels of variability in the vocal behaviour of Australian pygmy blue whales. These levels of variability have significant implications for any attempts to assess the abundance of this population with acoustic techniques. Further, these findings may indicate higher levels of cognitive capability than previously expected in blue whales. The mechanisms behind variability in song production are unclear, though there is research to suggest that changes in vocal behaviour may be culturally driven or caused by changes in the ambient noise and environmental conditions. These findings highlight shortfalls in the current methods for measuring acoustic abundance, as well as indicate that higher than expected levels of variability may exist in the vocal behaviour of other pygmy blue whale subpopulations.
Learning deep features of spectrogram to estimate acoustic density of a fish species inhabitatingPosidonia oceanica seagrasses
Authors: Lefèvre Lucas , Hermand Jean-Pierre , Debeir Olivier
Published: October 2018

In field acoustic investigations on seagrass ecology, characteristic /kwa/ sound production of a fish species systematically present in meadows constituted by Posidonia oceanicaspecies were recorded (Mediterranean, since 1995). Machine learning is investigated to automate estimation of acoustic density of the /kwa/ species. A multi-model deep neural network is implemented that directly inputs the spectrograms of signals recorded on hydrophones above and within the canopy. The network is a combination of 1D convolutional neural networks and a recurrent neural network with long short-term memory units and fully connected networks. Such architecture is able to process spectral information in the convolutional network and temporal information in the recurrent network, thereby making the best use of information in both time and frequency domains. In spite of high background noise level, the true-positive detection rate is shown to be excellent. With respect to human expert supervision, false-positive detections were, for the major part, faint sounds produced by distant fishes of the same species, as verified through careful re-listening. The apparent error rate is 8.4 ×10−2 on a partially mislabeled dataset of three days (7-10 pm). The true error rate, after label correction, is estimated at 1×10−2.
Short-term fluctuations in the ambient noise field at an Arctic chokepoint horizontal line array
Authors: Thomson Dugald , Barclay David R. , Dosso Stan E. , Heard Garry J.
Published: October 2018

The Arctic is a region known for high variance in both ambient noise levels and local sound propagation conditions, and is currently experiencing an historic increase in shipping traffic, resulting in an acoustic environmental that is changing so rapidly that the sparse ambient noise data available from decades-old studies have been rendered obsolete. Renewed interest in Arctic acoustics have provided fresh noise data at northern sites, and in the summer of 2015 Defence R&D Canada collected a continuous two-week recording of the 48-hydrophone Northern Watch horizontal line array at Gascoyne Inlet. Over the ice-free study period, numerous ship passes, weather events, and anomalies were observed in the high-quality acoustic recordings. In this paper, spectral fluctuations, directionality, and correlation with ship tracks and weather observations in the noise data are analyzed to help improve the applicability of operational arctic noise models supporting sonar performance.
Inferring first-year sea ice thickness using broadband echosounders
Authors: Bassett Christopher , Lavery Andone C. , Wilkinson Jeremy P. , Maksym Ted , Courville Zoe R.
Published: October 2018

Sea ice thickness is sparsely observed in situ. Under-ice acoustic techniques are a useful, but are generally used measure ice draft as a proxy for ice thickness. Using measurements of broadband acoustic backscattering (75–130 kHz) from laboratory-grown sea ice up to 80 cm thick, individual echoes from the water-ice and ice-air interfaces were isolated. Using the time delay between the echoes and a sound speed profile in the ice, total thicknesses were inferred and agree well with lengths of ice cores. This approach requires no ancillary data (i.e., water sound speed or pressure measurements). A temporal-domain model combining backscattering from both interfaces and from bubbles suspended within the brine channels also compares favorably with the measurements. This model is used to study the feasibility of applying the technique to first-year sea ice and to identify the bandwidths that best balance the constraints imposed by the scattering physics and practical considerations.
Persistent Pests: The role of gas diffusion in histotripsy bubble longevity
Authors: Bader Kenneth B. , Bollen Viktor
Published: October 2018

Histotripsy is a focused ultrasound therapy under development for tissue ablation via the mechanical action of bubble clouds. While strong bubble activity is a hallmark of histotripsy, persistent bubble clouds shield the focal zone from subsequent pulses and prevent complete liquefaction of the target tissues. The diffusion of gas into the bubble during histotripsy exposure may be a contributing factor to the longevity of histotripsy-induced cavitation. To investigate the role of gas diffusion in bubble persistence, the oscillations of a single nanoscale nucleus exposed to a histotripsy pulse were computed in parallel with a first-order diffusion equation. The bubble gas content increased more than five orders of magnitude during the expansion phase, inflating the equilibrium bubble diameter by more than a factor of 50. The inertial collapse of the gas-filled bubble was arrested significantly in comparison to computations neglecting diffusion, as indicated by the minimum bubble size and maximum bubble wall speed during the collapse. The residual gas bubble required more than 15 ms for passive dissolution post excitation, consistent with experimental observation. These results indicate gas diffusion does not influence the bubble dynamics during the excitation, but is a contributing factor to bubble persistence between histotripsy pulses.
Prototypical madness: Design and demonstration of a magnetic-acoustic targeted drug delivery system
Authors: Gray Michael , Beguin Estelle , Stride Eleanor P. , Nesbitt Heather , Logan Keiran , Kamila Sukanta , McHale Anthony , Callan John , Barnsley Lester
Published: October 2018

Ultrasound, microbubbles, and magnetic nanoparticles have been used both separately and in varying combinations for targeted drug delivery. Recent studies have demonstrated the therapeutic benefit of magnetic microbubble (MMB) retention and acoustic targeting using separate devices. As a developmental step towards clinical implementation, a magnetic-acoustic device (MAD) was designed for the purpose of generating co-aligned magnetic and acoustic fields with a single hand-held enclosure. This paper presents in vitro characterization and in vivo demonstration of a targeted therapeutic system wherein the MAD non-invasively retains and activates drug-loaded MMBs. Free field experiments were conducted in order to characterize the magnetic field and its gradient for MMB capture, and to quantify acoustic field strength and directivity. Flow phantom experiments were used to quantify MMB retention and illustrate the resulting enhancement of cavitation activity. Murine experiments then demonstrated therapeutic efficacy in a pancreatic cancer model, showing a significant benefit in comparison to the use of separate magnetic and ultrasonic devices.
Multi-source passive acoustic source localisation
Authors: Paverd Catherine , Lyka Erasmia , Coussios Constantin
Published: October 2018

Accurate acoustic source localisation (ASL) has significant potential to improve diagnostic ultrasound imaging of small vessel structures. Recently, super-resolution imaging techniques for both active and passive source mapping have been developed; however, these approaches assume the presence of a single source within the point spread function (PSF) of the system. In reality, multiple sources may be present, for example, when high concentrations of contrast agent are used. We use a two-step approach to localise multiple sources within the PSF of a clinically relevant passive cavitation detection system. First, we apply a Blind Source Separation (BSS) technique known as Independent Component Analysis, which relies on higher-order statistics to separate and reconstruct signals originating from independent sources. Second, we determine the time-difference-of-arrival of the separated signals on each receiver, and perform ASL by fitting a polynomial using least squares regression. Simulation and experimental results demonstrate that with the BSS-ASL combination, multiple sources aligned axially within the PSF of a single array located 70 mm from the focus can be localised with sub-millimetre resolution. We verify sources as distinct using Passive Acoustic Maps generated from a perpendicular linear array. Further work is necessary to ascertain performance limits and to validate the technique in vivo.
The state of percussion research in musical acoustics: How we got here and where it is going
Authors: Morrison Andrew C.
Published: October 2018

Drums are among the most ancient of all musical instruments and have been found in nearly all cultures across the world. This work covers a selection of major investigations of the acoustics of percussion instruments by a variety of scientists throughout history. Ernst Chladni’s efforts to characterize the vibration of plates are well known in acoustics and often replicated by students in the laboratory. Other scientists who made early contributions to the understanding of percussion instruments include Lord Rayleigh and C. V. Raman. Rayleigh’s observations of the acoustics of the kettledrum and bells represented only a fraction of his contributions to acoustics. Raman, who is remembered more for his work in spectroscopy, made detailed studies of the traditional Indian drum, the tabla. Modal analysis techniques used to investigate the acoustics of percussion instrument have evolved significantly in recent years. A brief review of current modal analysis techniques for studying percussion instruments is presented in this work. In addition, suggestions for future directions of percussion research is described here.
Preliminary modal analysis of the Alo Gong
Authors: Onwubiko Stephen G. , Neilsen Tracianne B. , Keke Maria T.
Published: October 2018

The Alo is a percussion instrument found predominantly in the eastern parts of Nigeria with the Igbo’s and plays an important role in the Igbo musical culture and settings. Being a bass gong with tones of three pitches, the Alo produces a very distinct sound and a sustained reverberation rendering a background beat to music of an African instrument ensemble or a mixed ensemble. This paper discusses the acoustical output characteristics of this instrument. The spectral characteristics of the sustained reverberation is presented, along with the dynamics responses of the structure to an excitation. These analyses not only provide an understanding of the distinct sound of the Alo instrument but may also be used by African instrument acoustician to re-model, or create more instruments with resonance frequencies.
Developments in continuous unattended monitoring systems
Authors: Manvell Douglas , Anderson Ken , Docker Bryce
Published: October 2018

Continuous, unattended noise monitoring systems can immediately alert you should noise levels exceed defined criteria. Once alerted to an exceedance, operators can act to return levels to compliance. This approach has two significant limitations. First, the operator can only take action after the breach has occurred and therefore systems are only able to inform owners about problems that have occurred in the past, rather than allowing them to maintain compliance. Second, the noise limit exceedances might not be due to specific noise from the operator but from unrelated, residual noise in the often-complex noise climates around the particular site and will then be the cause for a false positive. Compliance breaches are frequently triggered by aircraft overflights, road traffic or community sources. Modern monitoring systems enable users to view noise characteristics and listen to the noise breach to determine the source and act if necessary. However, this approach can create a significant number of false positives each taking up operator time to address. A previous paper by the authors described how airport noise management systems have addressed this problem by combining data from other systems, and how different techniques are required in urban & industrial noise management. This paper describes developments in these techniques and gives examples of techniques that allow operators to take action before a compliance breach occurs, and to reduce the number of false positive alerts.
Rotorcraft and unmanned aerial system noise measurement technology development and challenges
Authors: Stephenson James H. , Scudder Keith , Greenwood Eric
Published: October 2018

Rotorcraft and Unmanned Aerial Systems (UAS) produce undesired noise that propagates into the community. Significant research has been dedicated over the years to accurately predict the acoustic field of these vehicles from first principles. Despite significant advances in predictive capability, (semi)empirical predictions incorporating acoustic flight test measurements remain the most accurate way to model their noise. However, flight test measurements present significant challenges that must be mitigated. Examples include ground and atmospheric attenuation, inclement weather, and the need to ensure a low background noise condition at the test location. Background noise requirements typically limit testing to remote areas where facility power is not natively available. In order to help mitigate these challenges, a radio-controlled and ground-based measurement system with low space, weight, and power requirements was developed. This system, called Wireless Acoustic Measurement System II (WAMS II), is remotely activated, can record local weather and acoustic measurements with 24-bit accuracy, and has an extended battery life. These capabilities are an improvement on the first generation system and allow for the easy deployment of the multiple systems required to capture the full vehicle acoustic directivity patterns. The design, development, and effectiveness of these systems will be discussed.
A broadband impulsive signal detection filter for unknown acoustic sources in outdoor environments using non-coplanar microphone arrays
Authors: Bunkley Steven , White Michael J. , Blevins Matthew G. , Netchaev Anton , Klein Jordan D. , Lyons Gregory W. , haskins richard
Published: October 2018

This paper describes a method for non-coplanar microphone arrays that temporally isolates and cleans unknown broadband acoustic impulses for detection, classification, and scene analysis. Possible events are initially identified using a sliding statistical time window. Then the authors posit that most of the false triggers due to environmental noise can be filtered by using generalized cross correlation to phase align the microphone channels and reject implausible velocities. Finally, the phase aligned signals are calibrated and averaged across the microphones. With appropriate hyperparameter tuning, this method appears robust to ambient noise, wind noise and physical interaction. Performance is measured using a simulation and a real historic dataset of over 2 hours of curated acoustic recordings containing 559 gunshots, 120 blasts, and 747 other various weather and non-impulsive events recorded with no prior information under normal operating conditions. Events were found and validated using human listeners with a tool to visualize the waveform and the spectrogram. For this dataset, the model accurately found over 95% of the gunshots with 92% temporal separation and 100% of the blasts identified by the listeners. These results show the method to be a viable solution for impulsive outdoor broadband acoustic signal detection.
Supervised machine learning for crowd noise classification at collegiate basketball games
Authors: Nottingham Kolby T. , Pedersen Katrina , Zhao Xin , Butler Brooks A. , Wadsworth Spencer , Smith Blake , Transtrum Mark K. , Gee Kent L. , Warnick Sean
Published: October 2018

Acoustical monitoring combined with machine learning (ML) may help in understanding crowd dynamics. While ML has been applied in numerous audio applications, the aim is usually to distinguish events from noise, rather than trying to characterize the noise itself. This paper comprises an initial study using ML to characterize crowd dynamics during collegiate basketball games. High-fidelity crowd noise recordings from several men’s and women’s games were synchronized with game video and used to produce a training dataset for supervised ML by linking game events (e.g., baskets, fouls) with acoustic labels (e.g., cheering, silence, and applause). Using the training dataset, a ML classifier was built to identify causal game events from acoustic crowd responses. Findings, potential improvements, and additional crowd noise applications are discussed.
Wave propagation in 1D piezoelectric crystal coupled with 2D infinite network of capacitors
Authors: Kutsenko Anton A.
Published: October 2018

For 1D piezoelectric crystal, the dispersion equation is a simple linear dependence between the frequency and the wave number. After connecting the crystal to the 2D electrical network of variable capacitors, we can obtain very unusual and tunable dispersion diagrams. We present analytic results describing dispersion equations for surface and volume acousto-electric waves and show the corresponding wave simulations. The talk is based on the papers: 1) A. A. Kutsenko, A. L. Shuvalov, and O. Poncelet, “Dispersion spectrum of acoustoelectric waves in 1D piezoelectric crystal coupled with 2D infinite network of capacitors,” J. Appl. Phys. 123, 044902 (2018); 2) A. A. Kutsenko, A. L. Shuvalov, O. Poncelet, and A. N. Darinskii, “Tunable effective constants of the one-dimensional piezoelectric phononic crystal with internal connected electrodes,” J. Acoust. Soc. Am. 137(2), 606–616 (2015).
Acoustic bianisotropy in effective fluids of finite domain
Authors: Sieck Caleb F. , Guild Matthew D. , Alù Andrea , Haberman Michael R. , Orris Gregory
Published: October 2018

Recent research has shown that subwavelength asymmetry and/or nonlocal effects in heterogeneous acoustic media can be described as a dynamic effective fluid displaying acoustic bianisotropic properties. Theoretical homogenization schemes have demonstrated emergent acoustic bianisotropy for an infinite array of subwavelength inhomogeneities in a fluid matrix, and experimental studies have demonstrated individual asymmetric microstructures and single layer metasurfaces exhibiting bianisotropy. However, metamaterials research has shown that a finite domain effective fluid behaves unlike an infinite domain or a surface, and the effective properties of the domain tend to depend on the chosen boundaries and on the position within the domain, even when the microstructure is periodic. This work presents the use of multiple scattering homogenization to discuss the dependence of bianisotropic properties of finite effective fluids on the choice of boundaries and domain size in order to inform future experimental studies on acoustic bianisotropy. [Work supported by the Office of Naval Research and the NRC Research Associateship Program.]
Acoustic focusing via guided waves in bianisotropic fluid layers
Authors: Wallen Samuel P. , Lawrence Andrew J. , Goldsberry Benjamin M. , Haberman Michael R.
Published: October 2018

Willis fluids display a complex, effective dynamic response stemming from microstructural asymmetry, long range order, and/or time-varying material properties. These materials are characterized by constitutive relations that couple the pressure and momentum density to both the particle velocity and the volume strain. This coupling has been shown to be analogous to electromagnetic bianisotropic media, which exhibit coupled electric and magnetic fields [Phys. Rev. B 96, 104303 (2017)]. In a recent study, an acoustic lens composed of an array of Willis fluid layers was demonstrated, where the pressure phase imparted by each array element was tuned by varying the direction of Willis polarization and was determined using finite element analysis. In this work, we report on analytical solutions for guided waves in layers of fluid displaying Willis coupling and derive dispersion relations for layers with rigid and pressure-release boundary conditions. Special cases highlighting the effect of Willis polarization direction are presented via numerical examples. The acoustic lens is revisited with array phases obtained from analytical solutions, eliminating the need for finite element methods. Lenses designed for focusing and steering incident pressure waves are demonstrated using fully analytical models. [Work supported by NSF, ONR, and ARL:UT.]
Discrimination of band-limited rippled spectra of various central frequencies in cochlear implant users
Authors: Nechaev Dmitry , Goykhburg Marina , Bakhshinyan Vigen , Supin Alexander , Tavartkiladze George
Published: October 2018

Sound signals with wide-band rippled spectra were used for the frequency resolving power measurements in cochlear implant users. In the present study, resolution of band-limited ripple spectra of various central frequencies and speech discrimination test (Russian language) were compared. The rippled spectra had 2-oct cosine envelope with ripples equally spaced on the logarithmic scale. The central frequencies of the rippled spectra were 1, 2, or 4 kHz. Ripple resolution was measured with a three-alternative forced-choice procedure using a paradigm of discrimination of a test signal with ripple phase reversals from a reference signals with a constant-phase ripples. The average ripple discrimination thresholds were 1.9 ripples/octave (RPO) for 1 kHz; 2.3 for 2 kHz; and 2.3 for 4 kHz. The lowest correlation between ripple discrimination limits and speech discrimination results was about 0.2 at a central frequency of 4 kHz, the highest correlation was 0.6 at 1 kHz. In all the cases, the relation between the ripple spectrum resolution and speech discrimination test had positive trends. Band-limited rippled-spectrum tests allow to reveal informative frequency bands for speech discrimination in cochlear implant users. [Work supported by the Russian Science Foundation, Grant No. 16-15-10046.]
Perceiving phonemes with simulated variable cochlear implant insertion depths
Authors: Smith Michael L. , Winn Matthew
Published: October 2018

Cochlear implant (CI) patients have difficulty encoding spectral aspects of a speech signal, and are at a severe disadvantage compared to normal hearing listeners in distinguishing consonants that differ by place of articulation (PoA). One reason for this difficulty could be due to a shifting of spectral energy that occurs with a shallow insertion depth of the electrode array. The present study aimed to measure the effects of spectral shifting on phoneme categorization and PoA perception specifically. Speech was vocoded and then shifted by 0, 2, 4, and 6 mm in cochlear space to simulate shallow CI insertion depth in normal hearing listeners. Stimuli included a /b-d/ and /s-ʃ/ continua that differed by PoA, as well as /ra/ and /la/, to create a six-alternative forced choice paradigm. Results show phoneme categorization became less categorical, with a biased perception of /b-d/ and /s-ʃ/ continuum towards /d/ and /s/ respectively, consistent with higher-frequency energy in those consonants. Some participants were better at recalibrating to the spectrally shifted stimuli than others, as their perception of each continua remained somewhat balanced with increased amounts of spectral shifting. This study showcases the potential consequences and individual differences resulting from shallow insertion depth of a CI.
Wideband transient otoacoustic emissions in ears with normal hearing and sensorineural hearing loss
Authors: Schairer Kim , Keefe Douglas H. , Fitzpatrick Denis , Putterman Daniel , Kolberg Elizabeth , Garinis Angie , Kurth Michael , McGregor Kara , Light Ashley , Feeney M. P.
Published: October 2018

Otoacoustic emissions (OAEs) are generated in the cochlea in response to sound and are used clinically to separate ears with normal hearing from sensorineural hearing loss (SNHL). OAEs were elicited at ambient pressure by clicks (CEOAE) and wideband chirps (TEOAE) sweeping from low-to-high frequency with a sweep rate of either 187.6 Hz/ms (short chirps) or 58.2 Hz/ms (long chirps) and a bandwidth extending to 8 kHz. Chirps were presented at the same sound exposure level (SEL) as clicks, or + 6 dB relative to clicks. A total of 288 OAE waveforms were averaged for short chirps in ~1 minute compared to 120 waveforms for long chirps. Compared to clicks, the chirp has a lower crest factor, which allows it to be presented at an overall higher SEL without distortion. OAEs were elicited in 79 adults with normal hearing and 51 adults with mild-to-moderate SNHL. One-sixth octave OAE signal-to-noise ratios from 0.7 to 8.0 kHz were compared across stimulus types and conditions. The area under the receiver operating curve (AUC) was used to assess the accuracy of detecting SNHL. Average AUCs across 1/6th octave frequencies ranged from 0.90 to 0.89 for TEOAEs and were 0.87 for the CEOAE suggesting excellent test performance.
Irrelevant sound effects with locally time-reversed speech: Native vs. non-native language
Authors: Ueda Kazuo , Nakajima Yoshitaka , Ellermeier Wolfgang , Kattner Florian
Published: October 2018

To disentangle the contributions of local and global temporal characteristics of irrelevant speech in native and non-native language, irrelevant speech/sound effects (ISEs) of normal speech, reversed speech, locally time-reversed speech [Ueda et al. (2017). Sci. Rep. 7:1782] and its reversal on serial-recall of visually presented series of digits were examined. ISE experiments were performed with German native listeners (n= 79) and with Japanese native listeners (n= 81), employing both German and Japanese speech with either sample. All conditions involving speech significantly impaired memory performance when compared to a pink-noise control condition. When the native language of each group of listeners was presented, locally time-reversed speech with the shortest segment duration (20 ms), which was highly intelligible, was as equally disruptive as normal speech to the memory task, whereas locally time-reversed speech with longer segment durations (70 or 120 ms) was less disruptive. The effect of segment duration totally disappeared when the locally time-reversed speech was played backward. When the non-native language was presented, locally time-reversed speech showed the same pattern of results in each language group, irrespective of the direction of playback. Thus, the irrelevant sound effect worked differently for one’s native and non-native languages.
Notches in sentence spectra bias subsequent phoneme categorization
Authors: Stilp Christian
Published: October 2018

Spectral differences across earlier (context) and later (target) sounds are perceptually magnified, resulting in spectral contrast effects (SCEs) that bias categorization of later sounds. Most studies added spectral peaks to context sounds in order to produce SCEs, but noise contexts with spectral notches at speech frequencies biased phoneme categorization in a complementary manner (Coady et al., 2003 JASA). We tested whether this approach generalized to speech contexts with spectral notches. On each trial, a context sentence preceded the target phoneme (Experiment 1: /ɪ/-/ɛ/; Experiment 2: /d/-/g/). Sentences were processed by notch filters that attenuated energy in the same frequency regions that, when amplified to add spectral peaks, produced SCEs (Experiment 1: 100–400/550–850 Hz, as in Stilp et al., 2015 JASA; Experiment 2: 1700–2700/2700–3700 Hz, as in Stilp & Assgari, 2017 JASA). Notch depths ranged from −5 to −20 dB in 5-dB steps. In both experiments, notch-filtered sentences biased phoneme categorization in complementary directions to SCEs, with bias magnitudes increasing at larger notch depths. Whether earlier sounds have spectral peaks or notches, speech categorization is highly sensitive to the magnitudes of spectral differences across context and target sounds.