bluuebunny/crossref_metadata_2025 huggingface dataset:
Automatic classification of humpback whale social calls
Authors: Tolkova Irina , Bauer Lisa , Wilby Antonella , Kastner Ryan , Seger Kerri
Published: June 2017

Acoustic methods are an established technique to monitor marine mammal populations and behavior, but developments in computer science can expand the current capabilities. A central aim of these methods is the automated detection and classification of marine mammal vocalizations. While many studies have applied bioacoustic methods to cetacean calls, there has been limited success with humpback whale (Megaptera novaeangliae) social call classification, which has largely remained a manual task in the bioacoustics community. In this project, we automated this process by analyzing spectrograms of calls using PCA-based and connected-component-based methods, and derived features from relative power in the frequency bins of these spectrograms. These features were used to train and test a supervised Hidden Markov Model (HMM) algorithm to investigate classification feasibility. We varied the number of features used in this analysis by varying the sizes of frequency bins. Generally, we saw an increase in precision, recall, and accuracy for all three classified groups, across the individual data sets, as the number of features decreased. We will present the classification rates of our algorithm across multiple model parameters. Since this method is not specific to humpback whale vocalizations, we hope it will prove useful in other acoustic applications.
Cepstral analysis of vocal tract resonance from Tree Swallow (Tachycineta bicolor) songs during learning
Authors: Taft Benjamin N.
Published: June 2017

Bird vocalizations range in spectral composition from pure-tone whistles through resonant bugles to noisy squawks. Birds differ from mammals in the vibratory source of their vocalizations. Individuals in both groups use muscular control of the resonances of their vocal tracts to affect the resulting acoustic signal. Sensorimotor learning about this process plays an important role in the learning of both human speech and avian song. It is hypothesized that vocal tract resonances, as measured by cepstrum-based formant detectors, will show more variation both among and within calls early in the learning process. This should be particularly true for birds whose songs consist of rapidly frequency-modulated pure tones. Field recordings of multiple wild tree swallows (Tachycineta bicolor) are analyzed over the course of the breeding season. The consistency of vocal tract resonances are compared among birds of different ages and between newly- and previously-learned song units.
Evaluating autonomous underwater vehicles as platforms for animal population density estimation
Authors: Harris Danielle , Fregosi Selene , Klinck Holger , Mellinger David K. , Barlow Jay , Thomas Len
Published: June 2017

AFFOGATO (A Framework For Ocean Glider-based Acoustic density estimation) is a multi-year project (2015—2018) funded by the Office of Naval Research. Its main goal is to investigate the utility of slow-moving marine vehicles, particularly ocean gliders and profiling floats, for animal density or abundance estimation, using the passive acoustic data that these vehicles can collect. In this presentation, we will (1) provide a project overview and (2) share results from the initial stages of the project. As part of one task, existing deployments in the Gulf of Alaska, Hawaii, and the Mariana Islands have been used to investigate the capability of gliders to adhere to planned survey tracks. Simulations were also conducted to assess whether realized glider survey track lines could produce unbiased density estimates using two hypothetical animal distributions and assuming so-called design-based analysis methods (the standard, and also simplest, approach). Five deployments were assessed and deviances of up to 20 km from the planned survey track line were found. Under the specific simulated conditions, density estimates showed biases up to 9%. Next stages of the project will also be discussed, including ongoing work to estimate the probability of detecting different cetacean species using AUVs.
Low-frequency active acoustic response of underwater bubble plumes
Authors: Isakson Marcia J. , Hurewitz Zel J. , Abkowitz Paul M.
Published: June 2017

Active, low frequency acoustics may provide a method of locating and identifying methane bubble plumes over a large area by exciting radial and column resonances. In this work, a proof of concept experiment was conducted by measuring the active, low frequency response of an air bubble plume at the Lake Travis Test Station at the University of Texas at Austin. Several flow rates, bubble sizes, and plume widths were investigated. The test consisted of insonifying the plumes at two different standoff distances using a low-frequency chirp from 300-2500 Hz. The plume response was much longer in time than originally expected due to resonant ringing. The long-time response was modeled with a finite element model, which predicted the column resonance. This behavior may be able to be exploited for long-range bubble plume identification. [Work supported by ExxonMobil.]
What can we learn from breaking wave noise?
Authors: Deane Grant B.
Published: June 2017

Breaking waves are an important process at the air-sea interface: they limit the growth of waves, transfer momentum between the atmosphere and ocean, generate marine aerosols, change ocean albedo, and enhance the transport of greenhouse gases across the air-sea interface. However, they are a challenging phenomenon to study in the field and much is yet to be learnt about the transient, two phase flow inside whitecaps. Acoustical oceanography has much to offer as a remote sensing tool for studying wave breaking, and has been exploited to great effect by David Farmer and his colleagues over the past 3 decades. I will cover some of the highlights of this fascinating subject, including recent developments to study air entrainment and turbulence in breaking waves using radiated wave noise. [Work supported by ONR,Ocean Acoustics Division, and NSF.]
Insights from acoustical oceanography: A personal assessment
Authors: Farmer David
Published: June 2017

New ways of looking at the natural environment often lead to new insights. It is true of the ocean and especially so in the rapidly developing field of acoustical oceanography. This will be illustrated with examples drawn from personal experience over the past 3-4 decades, having application to a range of phenomena from coastal processes to air-sea interaction, from stratified flow over topography to sea ice behavior. Much is owed to the Acoustical Society’s welcoming approach to oceanographers, to the skill and enthusiasm of our students, colleagues, and staff, and to the invaluable support of our sponsors.
Fast compressive pulse-echo ultrasound imaging using random incident sound fields
Authors: Schiffner Martin F. , Schmitz Georg
Published: June 2017

In fast pulse-echo ultrasound imaging (UI), the image quality is traded off against the image acquisition rate by reducing the number of sequential wave emissions per image. To alleviate this tradeoff, the concept of compressed sensing (CS) was proposed by the authors in previous studies. CS regularizes the linear inverse scattering problem (ISP) associated with fast pulse-echo UI by postulating the existence of a nearly-sparse representation of the object to be imaged. This representation is obtained by a known linear transform, e.g., the Fourier or a wavelet transform. A central degree of freedom in the regularized ISP is the choice of the incident sound fields. Previous studies focused exclusively on steered plane waves. In this study, we investigate the usage of random incident sound fields to improve the relevant mathematical properties of the scattering operator governing the linear ISP. These sound fields are synthesized by a linear transducer array whose physical elements are excited applying combinations of random time delays and random apodization weights. Using simulated and experimentally obtained radio frequency signals, we demonstrate that these sound fields significantly reduce the recovery errors and improve the rate of convergence for low signal-to-noise ratios.
Reverberation suppression and enhanced sensitivity by coherence-based beamforming
Authors: Dahl Jeremy J.
Published: June 2017

Diffuse acoustic reverberation is often present in poor quality ultrasound images and can mask organs and anatomical structure. In addition, imaging methods such as blood flow and targeted microbubble imaging can be problematic in the presence of reverberation and thermal noise. We present a beamforming method that is based on the spatial coherence of backscattered ultrasound waves. The method differentiates signal from noise based on the spatial coherence of the signal and small spatial differences (or lags), and is therefore called the Short-Lag Spatial Coherence (SLSC) beamformer. Because diffuse reverberation and thermal noise are spatially incoherent, they can easily be distinguished from tissue, blood, and other signals of interest. We present SLSC beamforming and its applications to cardiac and other imaging targets, tissue harmonic imaging, flow imaging, and molecular imaging. We show that the technique improves the visibility of organ structures and the sensitivity of flow and molecular imaging targets by suppression of noise signals. We demonstrate a real-time SLSC beamforming prototype system that achieves upwards of 35 fps in cardiac imaging and 50 fps in molecular imaging. The system demonstrates high-quality, stable images of in vivo organs and targets using the SLSC beamformer.
Ultrafast ultrasound imaging temporal resolution enhancement with filtered delay multiply and sum (FDMAS) beamforming
Authors: Moubark Asraf , Alomari Zainab , Harput Sevan , Cowell David , Freear Steven
Published: June 2017

FDMAS beamforming technique have been employed with low number of steering angles and smaller lateral steps in order to improve the image quality for better cyst classification. Taking advantage of the autocorrelation process in FDMAS, lateral steps were reduced in order to calculate the time delay for the RF signal more accurately. The new beamforming technique has been tested on CIRS phantoms experimentally with the ultrasound array research platform version 2 (UARP II) using a 3-8 MHz 128 element clinical transducer. The point spread function (PSF) main lobes lateral resolution measured at 20 dB shows an improvement of 65.8% for lateral steps λ to λ/5. Meanwhile, the contrast ratio (CR) obtained for an anechoic cyst size 1 mm in diameter located at 15 mm depth with lateral steps of λ and λ/5 are -11.7 dB and -18.36 dB, respectively. The contrast to noise ratio (CNR) also shows improvement of 17.6% for the same lateral steps reduction. In conclusion, reducing lateral steps in FDMAS beamforming technique with low number of steering angles outperforms DAS with a high number of steering angles in laboratory experiments by narrowing its main lobes and increasing the image contrast thus improve the temporal resolution.
Non-invasive carotid artery elastography using multi-element synthetic aperture and plane wave imaging: Phantom and in vivo evaluation
Authors: Nayak Rohit , Schifitto Giovanni , Doyley Marvin M.
Published: June 2017

Vascular elastography can visualize the strain distribution in the carotid artery, which governs plaque rupture. In this study, we hypothesize that multi-element synthetic aperture (MSA) imaging, which produces divergent transmit beams can overcome the grating lobes issues associated with compounded plane wave (CPW) imaging, and produce more reliable strain elastograms. To corroborate this hypothesis, we conducted phantom and in vivo studies using both the techniques, and determined the most optimal imaging configuration for carotid elastography. The phantom studies were conducted using cryogel vessel phantoms. We validated the phantom study results in vivo, on healthy volunteers. These studies were performed using a commercially ultrasound scanner (Sonix RP, Ultrasonix Medical Corp., Richmond, BC, Canada), operating at a transmit frequency of 5 MHz. The phantom results demonstrated that the plaque was visible in elastograms from both techniques; however, MSA elastograms had fewer artifacts, with a 12 dB improvement in elastographic contrast to noise ratio relative to CPW imaging. Further, the results from the in vivo study agreed with the phantom results. These results suggest that MSA imaging can produce useful strain elastograms. Our future work will involve further development and more in vivo validation.
Experimental implementation of a synthesized two-dimensional phased array for transcranial imaging with aberration correction
Authors: Tsysar Sergey , Svet Victor D. , Yuldashev Petr V. , Khokhlova Vera , Sapozhnikov Oleg
Published: June 2017

Ultrasound (US) imaging of brain structures is a challenging, but highly promising diagnostic technology in medical ultrasound. Recent advances in transcranial US therapy suggest the potential to implement diagnostic US at higher frequencies, ideally for full brain imaging. In this work. we present experimental results of ultrasound imaging of spherical and tubular scatterers placed behind a skull phantom. The phantom was produced from a casting compound with acoustic properties matching those of skull. Phantom shape was defined from CT data of a human skull and 3D printing of a mold. A two-dimensional ultrasound array was simulated by mechanical translation of the focal spot of a broadband single-element 2 MHz transducer over the phantom surface. This synthesized array mimicked a 2D flexible phased array placed on the top of the patient's head. A pulse-echo technique was used for reconstructing the thickness of the skull phantom and detecting backscattered signals from the test objects. Transcranial image reconstruction was performed using a delay-and-sum technique that accounts for refraction and absorption inside the phantom. It was demonstrated that aberration correction using either straight rays or more accurate refracted raytracing yields significant improvement of image quality. [Work supported by RSF-14-15-00665.]
Investigation of the effect of neglecting reflections in Power-based sound in ducts
Authors: Nashed Mina W. , Elnady Tamer , Åbom Mats
Published: June 2017

In high frequency sound propagation inside ducts, the modal density is very high that the sound starts to propagate in rays. The acoustic performance of a duct network can be simulated using power-based models. The application of such situations is for HVAC systems and large silencers for power generation. Several standards are available for the analysis of HVAC systems using the same technique, such as ASHRAE and VDI. For each element, the flow-generated sound power inside the element is added to the input sound power and the output sound power is calculated by subtracting the Insertion Loss of the element. The attenuated sound energy can be either dissipated inside the element or reflected back to the system. Standards always assume that no energy is reflected and all the attenuation happens inside the element. This assumption is investigated in this paper. Several standard HVAC elements are considered, calculating the amount of energy dissipated inside the element and that reflected back. It was found that if all the reflected energy is considered, this will affect the output power from the system, especially in the highly reflective elements. The investigation was done using the Finite Element Method with the ray tracing technique.
Linear sound amplification and absorption in a corrugated pipe
Authors: Dai Xiwen , Golliard Joachim , Aurégan Yves
Published: June 2017

Linear sound propagation in an axisymmetric corrugated pipe with shear flow is studied numerically and experimentally. The acoustic and hydrodynamic perturbations are described by the linearized Euler equations (LEEs) in a parallel shear flow. Wave propagation and scattering are computed by means of a multimodal method where the disturbances are expressed as a linear combination of acoustic modes and hydrodynamic modes. The Floquet-Bloch approach is used to calculate the wavenumber in the periodic system. Both sound amplification and absorption, depending on the Strouhal number, are well predicted compared to experiments, which means that the flow-acoustic coupling in the system is effectively described by the present model. It is also shown that the corrugated pipe can amplify the sound even if the shear layer over the cavities is stable everywhere.
Dose-response model comparison of recent sonic boom community annoyance data
Authors: Rathsam Jonathan , Gille Laure-Anne
Published: June 2017

To enable quiet supersonic passenger flight overland, NASA is providing national and international noise regulators with a low-noise sonic boom database. The database will consist of dose-response curves, which quantify the relationship between low-noise sonic boom exposure and community annoyance. The recently-updated international standard for environmental noise assessment, ISO 1996-1:2016, references two fitting methods for dose-response analysis. Fidell’s community tolerance method is based on theoretical assumptions that fix the slope of the curve, allowing only the intercept to vary. By contrast, Miedema and Oudshoorn’s method is based on multilevel grouped regression. These fitting methods are applied to an existing pilot sonic boom community annoyance data set from 2011 with a small sample size. The purpose of this exercise is to develop data collection and analysis recommendations for future sonic boom community annoyance surveys.
A multiple-criteria decision analysis to evaluate sonic boom noise metrics
Authors: DeGolia Joe , Loubeau Alexandra
Published: June 2017

A statistical analysis was performed to select which noise metrics are best at explaining human annoyance to sonic boom noise. This follows previous work to downselect these metrics, but offers a more robust argument. The analysis began with calculation of a set of thirteen noise metrics and collected information about their explanatory powers (r2 between annoyance rating and noise metric) in five laboratory dose-response studies performed at different sonic boom simulation facilities. In these studies, indoor and outdoor human responses were gathered under various experimental conditions—booms alone, booms with rattle indoors, and booms with indoor vibration. This input data was then passed through two stages of multiple-criteria decision-making algorithms. In the first step, a Pareto efficiency analysis was conducted to objectively group metrics and eliminate poor contenders. The second step involved an Analytic Hierarchy Process to rank the remaining metrics, with an option to subjectively weight the studies by perceived importance. The result of this downselection is the ranking of five metrics that were selected as top contenders: BSEL, ESEL, ISBAP, PL, and DSEL. [ISBAP = PL + 0.4201(CSEL-ASEL)].
A study of reflected sonic booms using airborne measurements
Authors: Kantor Samuel R. , Cliatt Larry J.
Published: June 2017

In support of ongoing efforts to bring commercial supersonic flight to the public, the Sonic Booms in Atmospheric Turbulence (SonicBAT) flight test was conducted at NASA Armstrong Flight Research Center. During this test, airborne sonic boom measurements were made using an instrumented TG-14 motor glider, called the Airborne Acoustic Measurement Platform (AAMP). During the flight program, the AAMP was consistently able to measure the sonic boom wave that was reflected off of the ground, in addition to the incident wave, resulting in the creation of a completely unique data set of airborne sonic boom reflection measurements. This paper focuses on using this unique data set to investigate the ability of sonic boom modelling software to calculate sonic boom reflections. Because the algorithms used to model sonic boom reflections are also used to model the secondary carpet and over the top booms, the use of actual flight data is vital to improving the understanding of the effects of sonic booms outside of the primary carpet. Understanding these effects becomes especially important as the return of commercial supersonic approaches, as well as ensuring the accuracy of mission planning for future experiments.
The minimum number of ground measurements required for narrow sonic boom metric confidence intervals
Authors: Doebler William , Sparrow Victor
Published: June 2017

In subsonic civilian flight, the FAA’s permissible noise standard sets a limit on average aircraft loudness and requires that the loudness is known to within an adequately narrow 90% confidence interval. The FAA and international partners are developing a certification standard for the enroute regime of overland civil supersonic flight. In support of developing this standard, it may be useful to identify the number, location, and frequency of ground measurements to ensure that metrics' 90% confidence intervals for a supersonic flyover are acceptably narrow. Using NASA’s Superboom Caustic Analysis and Measurement Program (SCAMP) database where an F-18 jet flew above a linear 3048 m long 81-microphone array, confidence intervals of array-averaged metric values were calculated for six steady speed, level altitude flights. Microphones were selectively removed from the metric averaging process using various techniques to identify the effect of microphone number on confidence interval size. Preliminary results indicate ten measurements yield sufficiently narrow confidence intervals compared to a large number of measurements. [Work supported by the FAA. The opinions, findings, conclusions, and recommendations expressed in this material are those of the authors and do not necessarily reflect the views of ASCENT FAA Center of Excellence sponsor organizations.]
Infrasound scattering from stochastic gravity wave packets
Authors: MILLET Christophe , RIBSTEIN Bruno , LOTT Francois
Published: June 2017

Long-range infrasound propagation problems are characterized by a large number of length scales and a large number of propagating modes. In the atmosphere, these modes are confined within waveguides causing the sound to propagate through multiple paths to the receiver. In most infrasound modeling studies, the small scale fluctuations are represented as a “frozen” gravity wave field that is superimposed on a given average background state, and the normal modes are obtained using a single calculation. Direct observations in the lower stratosphere show, however, that the gravity wave field is very intermittent, and is often dominated by rather well defined large-amplitude wave packets. In the present work, we use a few proper modes to describe both the gravity wave field and the acoustic field. Owing to the disparity of the gravity and acoustic length scales, the acoustic field can be constructed in terms of asymptotic expansions using the method of multiple scales. The amplitude evolution equation involves random terms that can be related to vertically distributed gravity wave sources. To test the validity of the theory, numerical results are compared with recorded signals. It is shown that the present stochastic theory offers significant improvements over current semi-empirical approaches.
Simulating global atmospheric microbaroms from 2010 onward
Authors: Smets Pieter , Assink Jelle , Evers Läslo
Published: June 2017

Microbaroms are atmospheric pressure oscillations radiated from non-linear ocean surface wave interactions. Large regions of interacting high-energetic ocean waves, e.g., ocean swell and marine storms, radiate almost continuously acoustic energy. Microbaroms dominate the infrasound ambient noise field, which makes them a preferred source for passive atmospheric probing. Microbarom are simulated using a two-fluid model, representing an atmosphere over a finite-depth ocean and a coupled ocean-wave model providing the sea state. Air-sea coupling is crucial due to the two-way interaction between surface winds and ocean waves. In this study, a detailed overview is given on how global microbarom simulations are obtained, including a sensitivity analysis of the various model input data and parameterizations. Simulations are validated by infrasound array observations of the International Monitoring Systems (IMS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). An brief demonstration is given on the added value of global microbarom simulationsfor infrasound studies and how to obtain these source simulations.
Infrasound sensing on Mars: Wind noise predictions for a porous dome geometry
Authors: Pitre Kevin , Petculescu Andi
Published: June 2017

Infrasound sensing will play an important role in future Mars exploration. Applications include quantifying bolide impacts, monitoring subsurface activity, storm and dust-devil dynamics, as well as characterizing the planetary boundary layer. As on Earth, infrasonic measurements are likely to be hampered by wind-generated noise at the frequencies of interest. Instead of the rosette-type filter geometry commonly used at Earth monitoring stations, porous hemispherical domes could be more easily deployed in an ``inverted-umbrella'' configuration, with the sensor at the apex. By adapting previous work (Noble et al., Proc. Meet. Acoust. 21, 045005 (2014)) to the conditions in the Martian surface layer, we predict the infrasonic wind noise at the center of a porous dome placed at the locations of various Mars landers (Viking 1 and 2, Pathfinder, Mars Science Laboratory, and Phoenix). The predictions include the turbulence-turbulence, turbulence-shear, and stagnation-pressure contributions, obtained for different dome porosities and Martian wind speeds. Measurements at Mars' surface as well as interpolated data from the Mars Climate Database (www-mars.lmd.jussieu.fr), a detailed Mars circulation model, are used as inputs to the model. The work was funded by a grant from the Louisiana Space Consortium.
Simulation model for interaural time difference discrimination for tones
Authors: Hartmann William M. , Brughera Andrew
Published: June 2017

Difference limens for the interaural time difference (ITD) can be measured with a 2-interval, 2-alternative forced-choice staircase using the ITD as the staircase variable. Experimental results can be predicted by a computational model that simulates the experiment protocol in every important detail, as applied to human listeners, but the computer can tolerate hundreds of times more runs. At the core of the simulation is a decision process based on an opponency model for the two medial superior olives (MSO). MSO firing rates as functions of ITD are initially determined by a stochastically driven Hodgkin-Huxley cell model and represented in the simulation by a four-parameter fitted function. A corresponding noise function is estimated from multiple runs of the cell model. Left-right symmetry in both the model and the experiment protocol simplifies the calculations. Simulations have practical value in relating staircase thresholds to the underlying parameterized firing rate functions for given staircase variables, especially the initial ITD and the step size. Understanding this relationship is critical for the design and evaluation of experiments at low tone frequencies where thresholds grow to span a wide range. [Work supported by the AFOSR and ARCLP.]
Resource sharing in a collaborative study on cochlear synaptopathy and suprathreshold-hearing deficits
Authors: Bharadwaj Hari M. , Simpson Jennifer M. , Heinz Michael G.
Published: June 2017

Evidence from animal models of substantial noise-induced cochlear synaptopathy even in the absence of measurable audiometric changes has led to an active debate over whether such damage occurs in humans, and whether it contributes to suprathreshold-hearing deficits. Addressing these fundamental and translational questions requires multi-disciplinary approaches that integrate widely ranging forms of data and analyses, e.g., animal/human/model, evoked/single-unit/behavioral, and lab/clinical. Furthermore, connecting results across research groups around the world working on various species requires a systematic approach to resource sharing that will promote rigor and reproducibility. Here, we describe our efforts and plans to share resources from a large-scale collaborative project on noise-induced synaptopathy that links single-unit, evoked, and behavioral data from chinchillas with evoked, behavioral, and imaging data from humans studied in the laboratory and in the clinic. In addition to using modular implementations of stimulation paradigms, computational models, and analysis tools in high-level languages, we adopt open-access resource repositories and integrated platform-independent tools for version control, distributed development, documentation, and testing. Such resource sharing will help expedite answering the question of whether the anatomical/physiological effects seen in smaller animal models are present and perceptually significant in humans.
Identifying a perceptually relevant estimation method of the inter-aural time delay
Authors: Andreopoulou Areti , Katz Brian F.
Published: June 2017

The Inter-aural Time Difference (ITD) is a fundamental cue for human sound localization. Over the past decades, several methods have been proposed for its estimation from measured Head-Related Impulse Response (HRIR) data. Nevertheless, inter-method variations in ITD calculation have been found to exceed the known Just Noticeable Differences (JNDs), hence leading to possible perceptible artifacts in virtual binaural auditory scenes, even for cases when personalized HRIRs are being used. In the absence of an objective means for validating ITD estimations, this paper evaluates which methods lead to the most perceptually relevant results. A subjective lateralization study compared objective ITDs to perceptually driven inter-aural pure delay offsets. Results clearly indicate the first-onset Threshold detection method, using a low relative threshold of -30 dB, applied on 3 kHz low-pass filtered HRIRs as the most perceptually relevant procedure across various metrics. Alternative threshold values and methods based on the maximum or centroid of the Inter-Aural Cross Correlation of similarly filtered HRIRs or HRIR envelopes also provided reasonable results. On the contrary, phase-based methods employing the Integrated Relative Group Delay were not found to perform as well.
Vertical sound source localization when listeners and sounds rotate: The Wallach vertical illusion
Authors: Pastore M. Torben , Yost William
Published: June 2017

In addition to testing his prediction that listeners would use changes in binaural cues relative to listeners’ self-induced head movements to disambiguate front-back confusions, Wallach (1939) also tested his calculations that the relative rate at which these binaural cues change could be used by listeners to determine the elevation of the sound source. Wallach was able to induce the illusion that a sound source rotating along the azimuth plane was perceived as though it were above the listener. We sought to replicate and expand upon Wallach’s study. We rotated listeners in a specialized chair at constant velocity. We presented filtered Gaussian noises at bandwidths of one-tenth octave, two octaves, and broadband, using center frequencies of 500 Hz and 4 kHz from a ring of 24 azimuthal loudspeakers located at pinna height. Sounds could also be presented from loudspeakers elevated relative to pinna level. The relative rates of sound and listener rotation around the azimuth plane were varied according to the relationship established by Wallach (1939) and listeners made judgments about the perceived elevation and rotation of the sounds. [Partially supported by a grant from the National Institute on Deafness and Other Communication Disorders, NIDCD.]
Free-field sound localization on the horizontal plane as a function of stimulus level with an electronic, level-dependent hearing protection device
Authors: Thompson Eric R. , Ennis Zachariah N.
Published: June 2017

Electronic, level-dependent hearing protection devices (HPD) provide different levels of attenuation as a function of the input sound pressure level, so that loud sounds are attenuated for protection, but soft and moderate sound levels may be presented with little or no attenuation, or even with a small positive gain. While previous experiments have investigated sound localization with HPDs and moderate stimulus levels, it is important to understand the impact of level-dependent HPDs on the localization of both low- and high-level sounds. In this experiment, horizontal-plane sound localization judgments were obtained from human listeners with and without an earplug-type electronic, level-dependent HPD at several stimulus levels from 20 to 80 dB SPL. The data were analyzed in terms of the proportion of front/back reversals, and the mean absolute lateral error after correcting for front/back reversals. There were very few front/back reversals in the open-ear conditions at any level, and the mean absolute lateral error was less than 5 degrees. With the HPD, there were more front/back reversals than with open ear and the mean lateral error was greater, particularly for the loudest sounds where amplitude compression may have had an influence on performance.
Source-blind localization and segregation model featuring head movement and reflection removal
Authors: Deshpande Nikhil , Braasch Jonas
Published: June 2017

This model takes two simultaneous speech signals, spatialized to unique azimuth positions and convolved with a simple multi-tap stereo impulse response. The model first identifies reflections and generates an inversion filter for the left and right channels. It then localizes the sources and virtually rotates its head to a known orientation for the best resulting segregation of the sources. Next, the model segments the input signals in time and frequency, applies the inverse filter, and searches for residual energy in each bin to compensate the target signal from the mixture. From the residual non-canceled energy, it generates a binary masking map and overlays this on the mixed signal’s spectrogram to extract only the target signal. Improvement in SNR from head rotation approaches over 30 dB.
The source and effects of binaural cue ambiguity in free-field stereo sound localization—Behavioral testing
Authors: Clayton Colton , Balderas Leslie , Zhou Yi
Published: June 2017

Horizontal sound localization in free field requires integration of interaural time (ITD) and level (ILD) differences, in making accurate spatial judgments. Recently, we showed that listeners demonstrated great variability in localizing a stereo sound source (Montagne and Zhou, JASA, 2016). We hypothesized that this variability might arise from conflicting sidedness between ITDs and ILDs within and/or across frequency bands. To test this hypothesis, here we generated a new set of stimuli with variable spatial congruence between ITDs and ILDs by adding a constant inter-channel level cue ( + /- 5 dB) either aligned with or opposed to the inter-channel timing cue (from -1 to 1 msec). In Experiment 1 listeners responded to 15-ms broadband noise bursts. Response variability decreased when the inter-channel timing and level cues were spatially congruent and increased when they were not. In Experiment 2 listeners responded to low- and high-pass filtered noise (1.5 kHz cutoff) for the spatially incongruent stimuli only. Response variability was much reduced but the perceived source location consistently pointed to the “wrong side,” favoring the level cue. Together, the new results suggest a significant weighting role for ILDs (generated from level-based stereophony) in determining the lateral position of a stereo image.
The source and effects of binaural cue ambiguity in free-field stereo sound localization—Modeling simulation
Authors: Zhou Yi , Montagne Christopher
Published: June 2017

Our recent study (Montagne and Zhou, JASA 2016) showed that binaural localization cues—interaural time (ITD) and level (ILD) differences—were more variably distributed when stimuli were presented stereophonically instead of from single speakers. We hypothesized that variability in listeners’ responses is directly related to variability in the binaural cues imposed by the stimulus. Here, we investigate the validity of this hypothesis by examining the distribution of ITDs and ILDs using a simulated binaural neural network. The peripheral component of this model includes an updated auditory-nerve model (Zilany et al., 2014) and the central component of this model incorporated binaural correlation and level difference analysis. The decision variable was made based on combined ITD and ILD distributions across frequencies. The modeled data were analyzed and interpreted with regard to results from a parallel behavioral test. The model results suggest that low-frequency ITDs are a major cue for sound source localization even they are ambiguously distributed with multiple peaks. On the other hand, the ILD cue can strongly modulate which ITD peak dominates the perceived source location. The network analysis further investigates potential neural mechanisms by examining decision-making based on an ILD-modulated ITD network vs. separate ITD and ILD networks.
A discussion of macroscopic properties for acoustic metamaterials: Models and measurements
Authors: Sieck Caleb F. , Alu Andrea , Haberman Michael R.
Published: June 2017

Macroscopic material properties are useful to describe long wavelength dynamics of inhomogeneous media. Analytically, these properties are often determined by weighted field averages, which define the effective fields of a representative unit cell. The relations between these effective fields provide macroscopic properties. In addition to traditional properties (wavenumber, impedance, density, and compressibility), recent research has shown that inhomogeneous media require coupling parameters between effective volume-strain and momentum fields, known as Willis coupling or bianisotropy. However in the absence of embedded sources, metamaterial properties are non-unique allowing for macroscopic descriptions which only include traditional properties or traditional properties and coupling parameters. Many acoustic metamaterial measurements extract macroscopic properties using reflection and transmission coefficients of finite samples. Unfortunately, this widely used technique returns properties which relate boundary fields, not effective fields as usually assumed. Even though boundary fields may well approximate effective fields for very long wavelengths, the extracted properties are at best Bloch properties of a periodic medium and in general only apply to the exact measurement setup. The aim of this talk is to provide discussion on the issues of non-uniqueness and measurements of macroscopic properties in light of the importance of physically meaningful properties.
Vibration damping materials with enhanced loss due to microstructural nonlinearity
Authors: Konarski Stephanie G. , Hamilton Mark F. , Haberman Michael R.
Published: June 2017

One conventional approach to attenuating structure-borne waves or reduce the ringdown time of modes in structural elements is to attach damping layers or patches to vibrating components. Common patch and layer materials are specially formulated polymers or engineered polymeric composites that demonstrate elevated viscoelastic loss factors in the frequency range of interest. Recent research has shown that small volume fractions of negative stiffness inclusions embedded in a lossy material generate effective loss factors that exceed that of the host material. The ability to generate negative stiffness behavior, however, is often the result of nonlinear inclusion material response. Presented here is a multiscale model of a particulate composite material consisting of a nearly incompressible host material containing small-scale heterogeneities with a nonlinear elastic stress-strain response. We investigate the nonlinear dynamic behavior of the heterogeneous medium for small harmonic perturbations about several pre-strain states to demonstrate the influence of the microscale dynamic response on the macroscopically observable mechanical loss. Of primary interest is the energy dissipation capabilities of the composite which can be tuned using inclusion pre-strain. Loss for composites with nonlinear inclusions is compared to conventional composites containing air voids or steel inclusions. [Work supported by ONR.]
Analysis of one-dimensional wave phenomena in Willis materials
Authors: Muhlestein Michael B. , Haberman Michael R.
Published: June 2017

The primary benefit of treating a complicated acoustic system as an acoustic metamaterial (AMM) is that once the effective material properties are determined, well-established mathematical analyses may be used to describe wave propagation within the system. However, many standard analyses are not well understood for the class of materials known as Willis materials. Willis materials are characterized by constitutive relations that couple both the pressure and momentum density to both the particle velocity and the volume strain. This work presents the mathematical analysis of the propagation of a velocity pulse of finite duration within a one-dimensional Willis material in the time-domain. In particular, the propagation of the pulse is described in the context of (i) an infinite Willis material, (ii) two half-spaces where one or both display Willis coupling, and (iii) a thin coupled partition in an uncoupled background. Willis coupling is shown to affect the relationship between incident and scattered waves via a convolution rather than a simple multiplication, as is the case with uncoupled media.
Versatile hybrid sandwich composite combining large stiffness and high damping: spatial patterning of the viscoelastic core layer
Authors: Gallo Marta , Rinaldi Renaud G. , Chazeau Laurent , Chenal Jean-Marc , Ganachaud François , Leclerc Quentin , Ege Kerem , Totaro Nicolas
Published: June 2017

With the aim of decreasing CO2 emissions, car producers’ efforts are focused, among others, on reducing the weight of vehicles yet preserving the overall vibrational comfort. To do so, new lightweight materials combining high stiffness and high (passive) damping are sought. For panels essentially loaded in bending, sandwich composites made of two external metallic stiff layers and an inner polymeric (i.e. absorbing) core are broadly used. In the present work, the performances of such sandwich structures are enhanced by optimizing their damping behavior according to their use. More precisely, spatial patterning through selective UV irradiation of the viscoelastic properties of the silicone elastomeric layer is obtained based on a recently published UV irradiation selective technique [1]. Initially developed to modulate the elastic property gradient in Liquid Silicone Rubber (LSR) membranes, the procedure is now generalized to control the viscoelastic behavior of Room Temperature Vulcanization (RTV) silicone. Since the Young’s modulus and damping factor of the polymeric material are triggered by the UV irradiation dose, the resulting vibration response of the sandwich composite, made of aluminum skins and RTV silicone core, can be accordingly tuned. [1] Stricheret al. (2016). “Light-Induced Bulk Architecturation of PDMS Membranes,” Macromol. Mater. Eng. 301(10), 1151-1157.
Design and closed-loop control of an electroactive polymer-based tunable Helmholtz resonator
Authors: ABBAD Ahmed , Rabenorosoa kanty , Ouisse Morvan , Atalla Noureddine
Published: June 2017

A Helmholtz resonator is a passive acoustic resonator used to control a single frequency resulting from the cavity volume and the resonator neck size. The aim of the proposed study is to present a new concept and strategy of tunable Helmholtz resonator in order to enhance acoustic performances in lower frequencies (<500 Hz). The proposed concept consists in replacing the resonator rigid front plate by an electroactive polymer (EAP) membrane. When an electric field is applied, a change is made in the mechanical properties of the EAP membrane which induce a resonance frequency shift. A closed-loop control algorithm is developed to allow a real-time adaptability. Experimental measurements are performed on the developed prototype to determine the potential of this concept in term of acoustic absorption and Transmission Loss for low-frequency.
Integrating optical coherence tomography with laryngeal videostroboscopy
Authors: Mehta Daryush , Maguluri Gopi , Park Jesung , Kobler James B. , Chang Ernest , Iftimia Nicusor
Published: June 2017

During clinical voice assessment, laryngologists and speech-language pathologists rely heavily on laryngeal endoscopy with videostroboscopy to evaluate pathology and dysfunction of the vocal folds. The cost effectiveness, ease of use, and synchronized audio and visual feedback provided by videostroboscopic assessment serve to maintain its predominant clinical role in laryngeal imaging. However, significant drawbacks include only two-dimensional spatial imaging and the lack of subsurface morphological information. A novel endoscope will be presented that integrates optical coherence tomography that is spatially and temporally co-registered with laryngeal videoendoscopic technology through a common path probe. Optical coherence tomography is a non-contact, micron-resolution imaging technology that acts as a visual ultrasound that employs a scanning laser to measure reflectance properties at air-tissue and tissue-tissue boundaries. Results obtained from excised larynx experiments demonstrate enhanced visualization of three-dimensional vocal fold tissue kinematics and subsurface morphological changes during phonation. Real-time, calibrated three-dimensional imaging of the mucosal wave and subsurface layered microstructure of vocal fold tissue is expected to benefit in-office evaluation of benign and malignant tissue lesions. Future work calls for the in vivo evaluation of the technology in patients before and after surgical management of these types of lesions.
Recent results in silent speech interfaces
Authors: Denby Bruce , Chen Shicheng , Zheng Yifeng , Xu Kele , Yang Yin , Leboullenger Clemence , Roussel Pierre
Published: June 2017

Silent Speech Interfaces (SSI) are sensor-based communication systems in which a speaker articulates normally but does not activate their vocal chords, creating a natural user interface that does not disturb the ambient audio environment or compromise private content, and may also be used in noisy environments where a clean audio signal is not available. The SSI field was launched 2010 in a special issue of Speech Communications, where systems based on ultrasound tongue imaging, electromyography, and electromagnetic articulography were proposed. Today, although ultrasound-based SSIs can achieve Word Error Rate scores rivaling those of acoustic speech recognition, they have yet to reach the marketplace due to performance stability problems. In recent years, numerous approaches have been proposed to address this issue, including better acquisition hardware; improved tongue contour tracking; Deep Learning analysis; and the association of ultrasound data with a real time 3D model of the tongue. After outlining the history and basics of SSIs, the talk will present a summary of recent advances aimed at bringing SSIs out of the laboratory and into real world applications.