bluuebunny/crossref_metadata_2025 huggingface dataset:
Sparse Bayesian learning for time-varying DOA estimation
Authors: Park Yongsung , Meyer Florian , Gerstoft Peter
Published: December 2020

Sparse Bayesian learning (SBL) provides sparse direction-of-arrival (DOA) estimation performance, and an SBL scheme with sequential processing is proposed for time-varying DOA estimation. SBL employs a Gaussian prior for the source signals and models variances of the source amplitudes as a hyperparameter. For sequential processing, the Gaussian-distributed source signals are modeled as Gaussian processes, and we consider the variances of the source amplitudes as the parameter of the covariance function in the Gaussian process. The sequential SBL estimates the variance parameter that evolves sequentially over time based on a state-space model. The suggested SBL with the sequential processing provides high-resolution capabilities for time-varying DOAs with varying source strengths or moving sources over time. The present method is evaluated by using simulated and real data (SWellEx-96 Event S5).
An acoustic remote sensing method for high-precision speed estimation of micro-UUVs
Authors: Railey Kristen , Dibiaso Dino , Schmidt Henrik
Published: December 2020

Understanding the dominant sources of acoustic noise in unmanned underwater vehicles (UUVs) is important for passively tracking UUVs and for designing quieter propulsion systems. This work describes how the speed of a vehicle can be passively measured by the unique high frequency acoustic signature of a brushless DC motor propulsion system. First, the causes of high frequency tones were determined through direct measurements of two micro-UUVs and an isolated thruster. From this analysis, the vehicle noise was mapped to speed and the common and dominant features of noise were established: strong tones at the motor's pulse-width modulated frequency and its second harmonic, each of which is a carrier with sidebands at frequency intervals equivalent to the propeller rotation frequency multiplied by the poles of the motor. Field experiments were performed where the speed of two micro-UUVs was predicted by measuring the sidebands of the two dominant tones. When the mapping of rotational to translational speed of the UUV was known, this method produced speed predictions with 0.004 m/s accuracy. These findings are applicable to many off-the-shelf vehicles available today which rely on brushless DC motors and can be easily integrated into passive acoustic security systems for target motion analysis. [Work supported by the Department of Defense NDSEG program, ONR, and Draper.]
Acoustic source localization in imperfectly known environments using frequency-differencing techniques
Authors: Dowling David R.
Published: December 2020

Remote unknown sound-source localization is a challenging task with applications in a variety of fields, such as underwater acoustics, atmospheric acoustics, structural acoustics, bio-medical ultrasound, animal bio-acoustics, and seismology. In nearly all cases, the localization algorithm is only successful when there is good cross correlation between remotely measured and predicted acoustic fields, a possibility that exits at low frequencies and/or short ranges in imperfectly known environments. However, at sufficiently high frequency and/or long range, the requisite measured-to-predicted-field correlation might never be high enough for successful source localization. However, recent investigations of the frequency-difference autoproduct, a quadratic product of two complex field amplitudes having different frequencies, suggest that it may have the phase structure of an acoustic field at the difference frequency. Thus, using sufficiently low difference frequencies, unknown sources may be localized at ranges where conventional techniques are unsuccessful by correlating measured and predicted (ideal) autoproducts. The underlying formulation of frequency-differencing techniques is presented along with examples drawn from simulations, laboratory experiments, and ocean propagation measurements that involve frequencies from fractions of a Hertz to more than 100 kHz, and propagation distances from tens of centimeters to hundreds of kilometers. [Sponsored by ONR, NAVSEA, and NSF.]
Blind localization of early room reflections from reverberant speech using phase aligned spatial correlation
Authors: Shlomo Tom , Rafaely Boaz
Published: December 2020

Blind estimation of the direction of arrival (DOA) and delay of room reflections from reverberant sound may be useful for a wide range of applications. However, the high temporal and spatial density of early room reflections limit existing methods to the detection of only a small number of reflections. This paper presents a novel method for blind estimation of the DOA and delay of early reflections that overcomes the limitations of existing solutions. The method is based on a signal model in which the reflection signals are explicitly modeled as delayed and scaled copies of the direct sound. A phase alignment transform of the spatial correlation matrices is proposed; this transform can separate reflections with different delays, enabling the detection and localization of reflections with similar DOAs. It is shown that the DOAs and delays of the early reflections can be estimated by separately analysing the left and right singular vectors of the transformed matrices. A simulation study of a speaker in a room recorded by a spherical array demonstrates the effectiveness of the proposed method for accurately localizing a large number of reflections.
Cognitive sampling: The power of harnessing sampling strategies with machine learning techniques for enhanced machine classification and machine interpretation of acoustic datasets
Authors: Sen Gupta Ananya
Published: December 2020

Machine learning has received increased popularity in the acoustical community for its ability to interpret, classify and predict information autonomously from large-scale datasets. Beyond traditional supervised and semi-supervised learning architectures such as deep learning, and ensemble approaches, unsupervised learning networks such as autoencoders are being used to discover efficient data codings that enable hitherto unforeseen feature spaces. Unrelated yet deeply significant to the success of these myriad approaches is the spectral resolution of the signal itself as it has implications on the richness of information used by the learning architecture. Furthermore, much remains to be done in interpreting machine-learnt feature representations by domain experts and linking the domain knowledge to the machine-learnt knowledge. This talk will introduce a new way of enabling this link, by harnessing the power of compressive sampling and more generally, non-uniform sampling strategies and information theory to popular machine learning techniques. Specific applications will include a variety of acoustical applications involving spectral feature generation and interpretation.
The connection between grain size, porosity, and Biot model parameters
Authors: Chotiros Nicholas P.
Published: December 2020

The seabed is a porous acoustic medium, consisting of solid grains permeated by pore water. The Biot model for acoustic propagation in a porous medium is often regarded as a complex model that has an excessive number of input parameters, particularly permeability, pore size and tortuosity. Furthermore, the relationship between these parameters and the sediment classification, which is based on the mean grain size, is unclear. Borrowing from the geophysics and civil engineering communities, a relationship between grainsize and the Biot parameters was developed. This opens the way to predicting the acoustic properties of the seabed from geophysical seabed classifications. The relationship for well-sorted, unconsolidated sands and silts is well established. The transition from sand/silt to clay is where the problem becomes complicated for the following reasons: Because, in clay, a significant fraction of the fluid is attached to the solid platelets by electrostatic forces, and a significant proportion of the clay platelets may be suspended in the pore fluid, the boundary between pore water and skeletal frame needs to be clearly defined. The skeletal frame is sparse and supported by electrostatic forces, and therefore behaves differently to a mechanical packing of grains. [Work supported by ONR, Ocean Acoustics Program.]
Sound transmission in mass timber floor-ceiling assemblies
Authors: Way Evelyn , Holmgreen Erik , Ameen Jason , McLain Ricky
Published: December 2020

As mass timber structures become more commonly used in the United States, laboratory acoustical data is needed to guide the design of these buildings. In the fall of 2019, a laboratory test program of airborne isolation per ASTM E90 and impact isolation per ASTM E492 of mass timber floor-ceiling assemblies was undertaken. Cross Laminated Timber (CLT), Dowel Laminated Timber (DLT) and Mass Plywood Panel (MPP) panel types were tested with ceiling conditions selected based on 2021 IBC fire code requirements. Comparisons will be made between panel types and other contemporary building types using broadband, low, and high frequency metrics.
Acoustic discrimination of fine surface textures by echolocating free-tailed bats
Authors: Smotherman Michael , Odunsi Stephen , Hobbs Mikayla , Croft Thomas
Published: December 2020

Surface texture is an integral cue used by echolocating mammals for characterizing and forming a mental representation of an ensonified target. Bats need to be able to recognize and discriminate between different target surface textures. Previous work showed that bats rely on spectral cues embedded in echoes to resolve textures, but the resolution limits for this behavior are unknown. Mexican free-tailed bats (Tadarida brasiliensis) are fast, high-flying insectivorous bats that emit broadband FM multi-harmonic sonar pulses. We trained three bats to perform a two-alternative forced-choice assay in which they compared and selected the coarser of two sandpaper samples of different grit size. Commercial sandpaper grits decrease in mean particle size following an exponential function. We tested the bats ability to discriminate between 10 different grit sizes varying from 40 to 240 grit, corresponding to mean particles diameters varying from 425 to 50 μm. Bats discriminated all grits from a smooth plexiglass control and almost all grits from each other up to 180versus 220 grit (82 vs 68 μm) but not 220 vs 240 (68 vs 54 μm), indicating an extraordinary minimum difference threshold of about 14 μm, which rivals human performance using tactile active sensing by finger touch.
The nonlinear field produced by 1-D and 2-D imaging arrays with plane and diverging wave modes for ultrafast imaging
Authors: Lai Ting-Yu , Averkiou Michalakis A.
Published: December 2020

Combining plane and diverging wave imaging (PWI/DWI) with tissue harmonic imaging (THI) may offer improvements in image quality in applications requiring very high frame rates (ultrafast). The beam shape and magnitude of the 2nd harmonic in tissue are important design considerations. We developed a numerical model based on the KZK equation and modeled three 1-D diagnostic arrays, L11-4v linear array, P4-2v phased array, and C5-2 convex array operating in PWI/DWI. Our numerical code predicts the nonlinear field of nonaxisymmetric sources and source configurations with elevation and no azimuthal foci (plane/diverging fields), which have not been modeled before. We showed that the second harmonic produced by ultrafast THI is 2-16 dB lower than that of focused beams for the imaging arrays considered when operated at the same maximum MI. This moderate difference of the second harmonic between PWI/DWI and focused ultrasound suggests that it is feasible to combine PWI/DWI and THI. We have also investigated harmonic generation produced by diagnostic 2-D arrays for 4-D THI. From our predictions for the second harmonic field we propose beamforming approaches for 4-D cardiac THI with focused ultrasound, PWI, and DWI that would result in frame rates of 10, 81, and 1275 Hz, respectively.
Keeping the grid size under control: Nyquist sampling in the Iterative nonlinear contrast source method
Authors: Verweij Martin D.
Published: December 2020

Nonlinear propagation of ultrasound is applied in medical imaging and therapy, as well as in nondestructive testing. Development of dedicated equipment and protocols, and interpretation of results, is facilitated by reliable simulation of nonlinear ultrasound fields. Typical applications require accurate representation of higher harmonics with amplitudes 120 dB below the fundamental, over spatiotemporal domains that span several hundreds of wavelengths/periods of the fundamental. Finite-element and finite-difference schemes usually require 10–20 points per wavelength/period of the highest harmonic, without a way to restrict the number of harmonics involved in the solution. Solving the nonlinear wave equation with these methods may therefore require a prohibitively large computational grid. Alternatively, the nonlinear wave problem may be cast into an integral equation, which can be solved iteratively. This is the basis of our ever-expanding Iterative Nonlinear Contrast Source method. Most importantly, this approach allows to explicitly limit the wavenumber/frequency range included in the solution, and hence enables sampling at the Nyquist rate set by the highest desired frequency. As a consequence, the computational grid can be relatively small without introducing aliasing. This presentation elucidates how this is achieved by an appropriate combination of numerical filtering and windowing operations during each iteration.
Comparison between experimental and computational methods for the acoustic and thermal characterization of therapeutic ultrasound fields
Authors: Maruvada Subha , Soneson Joshua , Liu Yunbo
Published: December 2020

For high intensity therapeutic ultrasound (HITU) devices, pre-clinical testing can include measurement of power, pressure/intensity and temperature distribution, acoustic and thermal simulations, and assessment of targeting accuracy and treatment monitoring. Though relevant standards are available, technical challenges remain because of the often focused, large amplitude pressure fields encountered. Measurement and modeling issues include using hydrophones and radiation force balances at HITU power levels, validation of simulation models, and a suitable tissue-mimicking material (TMM) for temperature measurements. To better understand these issues, a comparison study was undertaken between simulations and measurements of the HITU acoustic field distribution in water and TMM, and temperature rise in TMM. For the specific conditions of this study, the following results were obtained. In water, the simulated values for p + and p- were 3% lower and 10% higher, respectively, than those measured by hydrophone. In TMM, the simulated values for p + and p- were 2% and 10% higher than those measured by hydrophone, respectively. The simulated spatial-peak temporal-average intensity values in water and TMM were greater than those obtained by hydrophone by 3%. Simulated and measured end-of-sonication temperatures agreed to within their respective uncertainties (coefficients of variation of approximately 20% and 10%, respectively).
Ultrasonic bone assessment: backscatter difference measurements of the femoral neck in vivo
Authors: Downey Kiera L. , Delahunt Sarah I. , Georgiou Loukas A. , Gray Aubrey J. , Thomas Doni M. , Pirro Gia , Newman Will R. , Main Evan N. , Moore Joshua T. , Hoffmeister Brent K.
Published: December 2020

Introduction: Ultrasonic backscatter techniques are being developed to detect changes in bone caused by osteoporosis. The goal of this study was to evaluate the clinical utility of backscatter difference measurements at the femoral neck. Methods: Backscatter signals were acquired from the left and right femoral necks of 97 human volunteers using an ultrasonic imaging system (Terason T3000). The signals were analyzed to measure the normalized mean of the backscatter difference (nMBD), a quantity that represents the power difference between two portions of the same backscatter signal. Also, a bone sonometer (GE Achilles EXPII) was used to measure the stiffness index (SI) of the left and right heel bones. Results: Linear regression analysis was used to compare nMBD measurement at the femoral neck to SI measurements at the heel. A statistically significant (R ≥ 0.2) correlation was observed between nMBD and SI. Conclusion: These results suggest that nMBD is sensitive to naturally occurring variations in bone tissue, and thus may be able to detect larger changes in bone caused by osteoporosis.
Study of ultrasonic scattering mechanisms in nonalcoholic fatty liver disease using liver histopathological slides
Authors: Wu Yashuo , Lopez Leonardo , Andre Michael P. , Loomba Rohit , Sirlin Claude B. , Valasek Mark A. , Wallig Matthew A. , O'Brien William D. , Han Aiguo
Published: December 2020

Quantitative ultrasound (QUS) techniques are emerging to be useful for assessing nonalcoholic fatty liver disease (NAFLD), the accumulation of fat droplets in the liver without alcohol intake. Several QUS parameters, such as the backscatter coefficient (BSC), are known to be correlated with liver fat content. However, the underlining ultrasonic scattering mechanisms are not fully understood. Understanding these mechanisms may yield better QUS models for improved diagnostics. This study's purpose is to test the following hypothesized mechanism: hepatocyte nuclei are acoustic scattering sites and the accumulation of fat droplets changes the spatial distribution of hepatocyte nuclei, leading to the change of the structure function (SF), a component of the BSC. Hematoxylin and eosin-stained liver histopathological slides from 48 participants were digitized. Hepatocyte nuclei and fat droplets were automatically recognized. For each participant, the SF versus frequency was calculated from the nuclear distribution. The fat fraction (FF) was determined by the fractional surface area of fat droplets. The SF was positively correlated with the FF (Pearson's r ∼ 0.4, p < 10-4) between frequencies 1 and 30 MHz, supporting the hypothesized mechanism. Other potential mechanisms, such as the additional scattering caused by fat droplets, will also be discussed. [Work supported by R01DK106419 and R01CA226528-01A1.]
New views of tissue scattering
Authors: Parker Kevin J.
Published: December 2020

What causes scattering of ultrasound from normal soft tissues such as the liver, thyroid, and prostate? Commonly, the answer is formulated around the properties of spherical scatterers, related to cellular shapes and sizes. However an alternative view is that the closely packed cells forming the tissue parenchyma create the reference media, and the long cylindrical-shaped fluid vessels serve as the scattering sites. Under a weak scattering or Born approximation for the extracellular fluid in the vessels, and assuming an isotropic distribution of cylindrical channels across a wide range of diameters, consistent with a fractal branching pattern, some theoretical predictions can be made. Our model predicts that backscatter increases as a power law of frequency, where the power law is determined by the fractal dimension. These results are consistent with the pioneering measurements of Campbell and Waag. Furthermore, the normalized histogram of echo amplitudes is found to be related to the classical Burr distribution, with the key power law parameter directly related to the fractal dimension, expected in the range of 2 to 3 for normal vasculature. Thus, the first and second order statistics of backscatter from soft vascularized tissues appear to be determined by fractal branching cylindrical vessels.
Wavefront tracing for undersea acoustic propagation
Authors: Pate David J.
Published: December 2020

An acoustic wavefront tracing algorithm and corresponding computational implementation is presented. Similar to ray tracing and beam tracing, wavefront tracing casts independent rays that refract through the medium and reflect from boundaries. However, with wavefront tracing these rays step congruously and are connected as a triangulated surface. As this triangulated surface moves through space and time it contacts boundaries, receivers, or other points of interest, thereby providing all possible paths from the source. As each triangle steps forward, three space-filling tetrahedra are formed and acoustic properties are then linearly interpolated via barycentric coordinates. This interpolation also applies at a boundary surface, allowing for both specular reflection and diffuse scattering. The algorithm is derived from the wavefront construction method, in which the triangulated surface is adaptively modified to maintain a desired level of detail. However, by keeping the wavefront topology fixed, along with an efficient encoding of the algorithm, highly detailed simulations with millions of triangles are achievable. Borrowing from the computer graphics community, a bounding volume hierarchy is used to accelerate the computation of ray–boundary intersections. An example simulation of a synthetic aperture sonar ping is provided, in which the wavefront comprises 21 million triangles and a rippled seafloor comprises five hundred thousand triangles.
Laboratory measurements of conical reed woodwinds in a Physics of Music class
Authors: Worland Randy
Published: December 2020

In our Physics of Music class for non-science majors, wind instruments are initially modeled by studying resonances of open and closed (i.e., one end closed) cylindrical tubes. Among the woodwinds, flutes and clarinets fit the open and closed cylinder models quite well. However, the acoustical properties of closed (i.e., reed driven) conical woodwinds, such as oboes, bassoons, and saxophones, are less intuitive and more difficult to motivate in a course for non-science majors. The laboratory exercise described here employs a straightforward analysis of simple dimensional measurements of bore profile and tone-hole location to verify a few of these properties, and to illustrate some of the acoustical differences between flutes, clarinets, and conical woodwinds. For pedagogical reasons described in this presentation, a straight soprano saxophone provides an ideal prototype for this study, although more commonly available alto and tenor saxes can also be used.
Statistical assessment of traffic noise patterns and COVID-19 effects
Authors: Dong Wayland , Lo Verde John , Rawlings Samantha
Published: December 2020

Road traffic noise assessments are based on noise indicators, including, at a minimum, average noise indicators like equivalent sound level (Leq) and single-event noise indicators like maximum sound level (Lmax). In the absence of guidance from regulatory agencies as to how these indicators should be defined and measured, previous work has included proposed definitions and methods for estimating the noise indicators and determining the uncertainty and reliability of the estimates. The analyses were based on statistical analyses of time history noise levels recorded at various cities across Connecticut and California as well as Dublin, Ireland [King et al., Noise-con (2016)]. Previous work suggested that the observed patterns and methods were broadly applicable across a wide variety of road types and cities, based on measurements performed at different locations. The dramatic changes in traffic due to the COVID-19 pandemic allowed analysis of the effect of changing traffic volumes and diurnal patterns on the time history levels at given locations. This paper describes the effect of the pandemic on traffic patterns and what this demonstrates about the variability and robustness of the statistical estimation methods.
Free-field schlieren measurements of laser-induced breakdown shock propagation
Authors: Hart Carl R. , Lyons Gregory W. , Muhlestein Michael B.
Published: December 2020

Measurements of free-field shock propagation are fundamental to understanding source characteristics, and for transfer functions through complex environments. Probe interference and undesirable high-frequency response plague typical approaches with acoustic microphones, which are also limited to resolving the pressure field at a single position. Measurements made with optical methods do not have such drawbacks, and schlieren measurements are particularly well suited to measuring both the spatial and temporal evolution of nonlinear pulse propagation. A laser induced breakdown source is used to generate spherically symmetric weak shockwaves. A z-type schlieren instrument and high-speed framing camera are used to measure schlieren images of passing shock waves. Quantitative measurements relate schlieren image intensity values to light refraction angles, and by the inverse Abel transform the density (and pressure) fields induced by the shockwave are recovered. Comparisons of analytical predictions, assuming spherically symmetric and inviscid propagation, with experimentally measured shockwaves are presented.
Weakly nonlinear acoustic theory on pressure propagation in bubbly flows with different cases of nonuniform distribution of initial flow velocities of gas and liquid phases
Authors: Maeda Taiki , Kanagawa Tetsuya , Ayukai Takahiro
Published: December 2020

Three cases of weakly nonlinear propagation of plane progressive pressure waves in flowing water containing many uniformly separated spherical microbubbles are theoretically investigated, with a particular focus on different cases of initial flow patterns. The gas and liquid phases initially have a high velocity with uniform distribution, and a low velocity with nonuniform distribution for each phase. Basic conservation laws based on a two-fluid model are employed to govern different velocity distributions for gas and liquid phases. From the method of multiple scales with perturbation expansions, we derive three cases of nonlinear wave equation describing the long-range propagation of waves: (i) the KdVB (Korteweg–de Vries–Burgers) equation for a long wave, (ii) the NLS (nonlinear Schrödinger)-I equation for a short wave in slow nonuniform flow, (iii) the NLS-II equation for a short wave in fast nonuniform flow. As a result, all the initial velocities contribute to an advection effect of waves, initial nonuniform flow distribution induces a variable coefficient of advection term into the KdVB, NLS-I, and NLS-II equations, and an important role of relative velocity between the gas and liquid phases is clarified.
Theoretical Improvement of a KZK equation for focused ultrasound in bubbly liquids with thermal effects
Authors: Kagami Shunsuke , Kanagawa Tetsuya , Ayukai Takahiro
Published: December 2020

Toward medical applications such as HIFU treatment, weakly nonlinear evolution of focused ultrasound in initially quiescent bubbly liquids is theoretically investigated with a special attention to the consideration of a thermal effect. Although our group (Kanagawa, JASA, 2015) was derived a Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation for quasi-plane progressive ultrasound with initially nonuniform number density of microbubbles, thermal effects such as thermal conduction were completely neglected. In this paper, we modify our previous KZK equation by incorporating thermal effects, i.e., the thermal conduction and thermodynamics inside bubble, and the liquid viscous damping in bulk liquid. By using the method of multiple scales to basic equations for bubbly liquids introducing an energy equation proposed by Prosperetti (JFM, 1991), a revised KZK equation incorporating all the thermal effects was derived. Although a newly discovered dissipation term without differentiation corresponds to the thermal conduction, the coefficient of original dissipation term was expressed by the liquid viscosity and liquid compressibility (i.e., acoustic radiation damping). Hence, the physics of dissipation by thermal conduction differs that by liquid viscosity and compressibility. Furthermore, we emphasize that a thermal effect contributes the nonlinear effect, that is, nonlinear coefficient include the ratio of specific heats of the gas inside the bubble.
Processing of tonal sequences and assessing user perception of audio products
Authors: Guzman Sandra J.
Published: December 2020

This talk will highlight how lessons learned from Bill Yost during my time at the Parmly Hearing Institute influenced both my past academic research and more recent efforts in commercial product development. Two primary subject areas will be points of focus, (1) discussion of my psychoacoustic research on the processing of tonal sequences, and (2) application of academic research methods to business concerns. The psychoacoustic study of tonal sequences evaluated involvement of musical training and working memory in the processing of tonal sequences defined by both pitch contour and sequence rhythm. To evaluate involvement of musical training in task performance, subjects were recruited from both music and audio-arts academic programs. Subjects reconstructed four-element tonal sequences by focusing on pitch only, rhythm only, or on both pitch and rhythm. Findings suggested that rhythm reconstruction was generally more difficult than pitch reconstruction, with effect of musical training primarily on processing sequences defined by pitch and effect of working memory on rhythmic sequences. Additionally, an overview of product development research will be presented, focusing on the assessment of end-user perception and understanding of audio products. The process, core challenges, and strengths and limitations of product development research will be examined.
“Auxauralities” : Ears-on 3-D-printed acoustics metamaterials for sound art
Authors: Roussel Georges , Dall'Ara-Majek Ana , Proulx Franc¸ois , Gauthier Philippe-Aubert , Bernier Nicolas
Published: December 2020

Due to unique acoustic properties, acoustic metamaterials (AMMs) find many engineering applications in industrial or military sectors. However, as a result of their complex behavior and since they are generally unknown to the non-scientists, AMMs are not integrated into the thinking of daily auditory culture and sound environments. AMMs' potentially speculative effects on sound environments and audio cultures could be communicated and investigated through art. To fully seize this opportunity, there is a need for Arts and Sciences sympoiesis as a way of thinking, creating, designing and experientially testing audible-range AMMs. Since engineering AMMs require considerable expertise in physics and additive manufacturing, it is not easy for non-acousticians to explore such materials. Therefore, an “ears-on” audible experiential approach was developed. To do so, the presented work is a co-creation process for developing tools for sound art. Two approaches were investigated as sound art prototyping tools. First, an auralization process is presented to perform acoustic simulations and virtually hear the results beforehand. A second approach uses modular 3-D-printed resonators and crystals for the rapid improvement of the hands-on and “ears-on” iterative design of a sound art installation: “Auxauralities” [Work supported by Fonds Recherche Québec Audace, 2020-AUDC271071].
Elastic wave propagation in self-similar and non-self-similar hierarchical two-dimensional square lattices
Authors: Ignacy Muthu Refugine Nirmal , Carrillo-Munoz Maria , Sharma Bhisham
Published: December 2020

In this talk, we examine the elastic wave propagation behavior of infinite two-dimensional self-similar and non-self-similar hierarchical square periodic lattices. Using finite element analysis, we calculate the dispersion curves of different hierarchical lattice structures along their irreducible Brillouin zone (IBZ) paths. The effects of similarity, geometrical symmetry, and material symmetry on bandgap generation are studied. The mechanisms responsible for bandgap generation are explained by studying the mode shapes for different characteristic length ratios. We show that material symmetry can help induce wave attenuation bandgaps at low frequencies. Further, we classify the P- and S-wave propagation modes and study the effect of similarity on the generation of polarized bandgaps. We demonstrate that controlling the hierarchical similarity provides a robust method for tailoring the dispersion characteristics of periodic lattice structures.
High-frequency spectral shaping enhances glimpsing speech in noise for younger adults with normal hearing
Authors: Madorskiy Rachel , Fogerty Daniel , Dubno Judy R.
Published: December 2020

Amplification is necessary to restore audibility to individuals with hearing impairment. However, frequency-specific amplification alters the spectrum of speech in addition to increasing the speech level. The current study investigated the effects of spectrum and speech level on speech recognition by younger adults with normal hearing. Sentence recognition was measured in quiet, speech-modulated noise, and steady-state noise. In addition, acoustic metrics were utilized to quantify the alterations resulting from spectral shaping. Acoustic metrics included (1) the Hearing Aid Speech Perception Index, in order to investigate changes to the temporal envelope, and (2) glimpse analyses, to quantify the proportion of time-frequency units that were glimpsed in a sentence. Results demonstrated that at high speech levels in quiet, spectral shaping was associated with lower sentence recognition. However, in all other conditions, and particularly in noise, spectral shaping enhanced sentence recognition. Acoustic metrics indicated that this enhancement in noise is associated with increases in the proportion and signal-to-noise ratio of glimpses, which resulted in improved preservation of the envelope and temporal fine structure of sentences in comparison to unshaped stimuli. Thus, spectral shaping is beneficial for speech recognition in noise for normal hearing participants due to enhanced speech glimpses.
Alveolar stops exhibit greater coarticulatory resistance than retroflexes and dentals in Malayalam
Authors: Krishnaswamy Meghavarshini , Dutta Indranil , Bhaumik Maumita
Published: December 2020

Tight coronal contrasts in Malayalam geminates (V1t̪:V2 vs. V1t:V2 vs. V1t:V2) are examined in an Ultrasound study of tongue contours to understand the nature of coarticulatory resistance and aggressiveness. Degree of Articulatory Constraint (DAC) predicts that articulatory complexity mitigates the nature of coarticulatory resistance (CR) cross-linguistically. Findings from our study of Ultrasound tongue contours are contrary to the predictions of the DAC, where the expectation is that the directionality of CR and aggressiveness will be Vt̪:V < Vt:V < Vt:V. We find that the order of CR is Vt:V < Vt̪:V < Vt:V. Greater variability in tongue constriction location in retroflex and dentals is found compared to alveolars. Low neighborhood density alveolars exhibit low contextual adjustments even at the constriction. This is a consequence of greater articulatory complexity. Malayalam alveolars are distributionally restrictive compared to dental and retroflex places of articulation. Alveolars in Malayalam have low neighborhood densities which may indeed govern coarticulatory resistance and aggressiveness of this place of articulation. These findings have been corroborated in an acoustic study of Malayalam stops (Dutta et al., 2019). We discuss the implications of our findings for DAC and propose that sparse lexical representation coerces coarticulatory resistance in tight coronal place contrasts.
Are there any differences between the tongue and posterior pharyngeal wall movement patterns during normal and Masako swallow?—An ultrasound analysis
Authors: Wang Emily Q. , Perlman Alison , Maxwell Adam , Verhagen Metman Leonard A.
Published: December 2020

Parkinson's disease (PD) is a neurodegenerative movement disorder affecting volitional movement due to Dopamine-producing neuron death in the substantia nigra. Impaired swallow function is highly prevalent with nearly 100% involvement in PD during the disease course and involves all three phases of swallowing. The oral stage of swallowing is impaired first. Reduced bolus control and reduced interior-to-posterior movement of the bolus transfer lead to delayed swallowing response, premature spillage, decreased base of tongue (BOT) retraction and strength, decreased hyolaryngeal elevation and excursion, and reduced action of pharyngeal constrictors. Together, these result in bolus retention, residue throughout the pharynx, and reduced airway protection leading to significant aspiration. To target these deficits we have designed an exercise regime to teach early to mid-stage PD patients to do the Masako swallow maneuver of saliva (swallow with tongue-tip held between teeth), with high intensity and frequency (i.e., 120 repetitions per day) in one month. The preliminary results are very promising. All participants demonstrated positive changes. To understand the underlying mechanism, we used Ultrasound and recorded 20 normal subjects while they did three normal swallows and 3 Masako swallow maneuvers. The initial observations indicated the tongue and pharyngeal movement patterns differ between the two maneuvers.
Quantifying the performance of ray-based Blind Deconvolution (RBD) algorithm for long-range shipping sources
Authors: Touret Richard X. , Durofchalk Nicholas C. , Sabra Karim G.
Published: December 2020

The ray-based Blind Deconvolution (RBD) can provide an estimate of the relative arrival-times of the channel impulse responses (CIRs) between a shipping source (acting as a shallow source of opportunity) and a remote receiver array (e.g., a short bottom-mounted vertical line array (VLA)) [Durofchalk and Sabra, JASA 147(3), 1927–1938 (2020)]. Previous RBD studies primarily rely on beamforming on the (most energetic) direct path to estimate the phase of the unknown source; but in typical downward refracting environments the direct path is only observable at short ranges for a (very shallow) shipping source. Alternatively, the overall performance of the RBD algorithm when treating long range sources of opportunity remains to be evaluated in similar settings when only bottom-interacting multipath arrivals can reach the VLA, i.e., beyond the range when the direct path is observable. In this study, a combination of numerical simulations and experimental validation (using the SBCEx16 experiment conducted in the Santa Barbara shipping channel with short, bottom-mounted VLAs) is used to investigate the maximum detection range of shipping sources of opportunity via multipath arrivals as a function of frequency, bathymetry effects and anisotropy of the shipping source and the implications for estimating the CIRs using the RBD method.
Acoustically measured transmission loss improves effectiveness of sonar search
Authors: Wiseman Charles H.
Published: December 2020

The Sonar Equation is the heart of the process for predicting the effectiveness of an Antisubmarine Warfare (ASW) ship's sonar in the underwater detection of submarines. The equation's determination of Ranges associated with probabilities of detection and false alarms is the fundamental input for the selection of the most effective sonar modes in an individual ship and, at the broader tactical scale, in the selection of ASW search plans. The Sonar Equation's predictions of sonar performance, however, are subject to considerable error when employed tactically at sea in ASW operations. A major source of the error is the input, Transmission Loss, usually derived from XBT “snapshots” of temperature versus water depth. The resulting predictions of sonar performance are projected uniformly over space and time, leading to predictions that are stale and inaccurate. Accuracy of the Sonar Equation's output, however, can be improved by measuring Transmission Loss acoustically and continuously. A stream of pulses, periodically broadcast from a specially designed expendable sound source, is measured at the front end of the ship's sonar. A large population of Transmission Loss values is built up from which strong statistical inferences regarding detection can be drawn. The power of a continuously updated population of Transmission Loss values leads to more accurate inferences of the local acoustic environment.
Study of low frequency flight recorder detection
Authors: Su I Yun , Liu Wen-Yang , Chuang Li-Chang , Fang Kai-Hong , Chen Chi-Fang
Published: December 2020

A flight recorder is installed in every aircraft to record the flight status. When the plane crashes into the ocean, the underwater locater beacon (ULB) inside the flight recorder will be triggered and make a pulse sound at least 30 days. In order to find it as soon as possible, it is important to fully understand the signal of the ULB and how it propagation underwater. Recently, low frequency flight recorder is developed to improve the detection range. The signal frequency of the ULB is not only 37.5 kHz, but also can be 8.8 kHz. For the 8.8 kHz signal has longer detection ranges due to lower transmission loss than the 37.5 kHz signal has. This study will show the simulation based on Gaussian Beam Model, the experiment results of the 8.8 kHz beacon, and the comparison of simulation and experiment results between the two different frequencies. Analysis of the detection range prediction of the 8.8 kHz beacon is also carried out in the seas surrounding Taiwan, which can be used to assist search planning of the flight recorder. [This study was sponsored by Taiwan Transportation Safety Board under Project No. NTUUAL-2020-01.]
Finding consensus among rheological models for shear waves in soft tissues
Authors: Szabo Thomas L. , Parker Kevin J. , Holm Sverre
Published: December 2020

Shear wave viscoelastic properties of tissue are now measured by a wide variety of methods including elastography, imaging scanners, rheological shear viscometers, and a variety of calibrated stress-strain analyzers. Because absorption and sound speed can be strong functions of frequency, fitting the data to an viscoelastic model which best describes observed behavior is a common step in understanding and comparing data sets among tissues and disease states. Because the same data can be represented by different model constants, there is a need to reach consistency and consensus on the most effective models among different sub-fields in acoustics, biomechanics, and elastography. To this end, we examined many established rheological models as well as data sets. We argue that the long history of biomechanics, including the concept of the extended relaxation spectrum, and the theoretical framework of multiple relaxation models which model the multi-scale nature of physical tissues, consistent with power law data extending over several decades of frequency and time, all lead to the conclusion that fractional derivative models represent the most succinct and meaningful models of soft tissue viscoelastic behavior.
Large-scale gradient-based optimization in acoustics applications
Authors: Walsh Timothy
Published: December 2020

Engineering applications in acoustics and structural acoustics commonly require optimization with a large, high-dimensional space of parameters. Examples include inverse problems, design, and control, especially in cases where the parameters to be optimized are spatially and/or temporally dependent. In these scenarios the dimension of the search space precludes the use of global-based optimization algorithms, due to the rapidly growing number of required numerical evaluations of the partial differential equation (PDE) (e.g., wave equation). In such cases, gradient-based optimization with adjoint methods provides an attractive strategy wherein the cost of evaluating sensitivities is independent of the number of optimizable parameters. In this talk, we will present an overview of adjoint-based PDE-constrained optimization in Sandia's Sierra Mechanics software, with a focus on acoustic and structural acoustics applications. We will derive a general mathematical framework and then specialize to acoustics applications. Examples will be given in inverse, design, and control that involve spatially or temporally dependent variables with high-dimensionality. [Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy's National Nuclear Security Administration under Contract No. DE-NA0003525.]
Optimization approach for designing diffuse acoustic fields on demand
Authors: Aquino Wilkins , Rouse Jerry
Published: December 2020

Reverberation chambers are used for design, optimization and qualification of structures. The low frequency limit (Schroeder frequency) of applicability is dependent upon the chamber size. We have developed a source optimization methodology which can decrease this cut-on frequency. The target diffuse field is represented by plane waves having uniformly distributed direction and phase. The corresponding cross-spectral density can be shown to be a Bessel function of the first kind in 2-D and a sinc function in 3-D. The construction of the diffuse field at a given frequency (or set of frequencies) is then cast as a constrained optimization problem. To this end, the goal is to find the cross-spectral density of a set of point sources that closely approximates (in some sense) the target diffuse field cross-spectral density (e.g., sinc or Bessel function). To enforce positive definiteness of the solution, we use a matrix factorization approach in which the matrix factors become the design variables. We demonstrate that we can construct diffuse fields on demand in arbitrary enclosures with known wall impedance. Furthermore, we demonstrate that there exist source configurations that can generate near diffuse fields at frequencies below the Schroeder frequency.
The microphone engineering lab notebooks of Ben Bauer
Authors: Pettersen Michael S.
Published: December 2020

Benjamin B. Bauer (1913–1979) was an ASA Fellow and awarded the ASA Silver Medal (1978). He held over 100 patents for acoustical/audio technology, with his first patent being arguably the most significant: the invention of the Uniphase principle integral to the Shure Unidyne model 55 microphone. Introduced in 1939 and still manufactured today, the Shure Unidyne was the first unidirectional microphone using a single dynamic element. Today, the Uniphase principle is employed in the vast majority of directional microphones. In September 2016, Bauer's microphone engineering lab notebooks, dating from 1936 to 1944, were found in offsite storage; they had not been seen for over 50 years. The presentation provides a peek into these Bauer notebooks as he discovers and refines the Uniphase principle, as well as numerous other electro-acoustical concepts—some decades ahead of their time.
Novel functional microphones created using 3D printing for rapid development
Authors: Windmill James , Reid Andrew
Published: December 2020

The ability to detect sound is a sense found across multiple animals in the natural world. Hearing in the insects has, for example, evolved independently approximately nineteen times. This has produced a huge variety of different miniature acoustic sensory structures, with many different characteristics and novel features. Many different researchers have attempted to take inspiration from biological hearing systems, with the most well-known being the miniature directional ear of the Ormia ochracea. However, from an engineering point of view there are specific problems involved. Firstly, the acoustic structures found in the natural world are three dimensional, and composed of softer biological materials. Secondly, the development cycle for researchers working on MEMS based microphones depends on their ability to access fabrication facilities. Whilst the use of multi-user fabricators reduces costs, particularly for academic research, the turnaround time is measured in months. This talk will present recent work to utilise digital light processing 3-D printing techniques as a method to rapidly create novel microphone designs. The initial development of acoustic devices that utilise 3-D structures will be illustrated, and the use of multiple materials in single 3-D prints to create functional microphones capable of producing an electrical output signal will be discussed.