bluuebunny/crossref_metadata_2025 huggingface dataset:
Measuring guitar top plate resonances at stages of fabrication
Authors: Horne Max , Hoffman Kurt R.
Published: November 2021

This project investigates how the shape, quality, and boundary conditions of an object affect its normal modes of vibration. Here we report the results of electronic speckle pattern interferometry (ESPI) measurements on several potential guitar top plates in moving from a solid rectangle shape to the final top plate shape with a sound hole and bracing. The measured nodal patterns were similar for two distinct top plates as they were cut and sanded into final form. The measured frequencies of each normal mode were similar with typical variations of less than 10%. The experimental data was compared to theoretical data modeled in COMSOL to test the accuracy of the input parameters characterizing the wood. We found that the model results agree with the experimental data well at low frequencies, but the accuracy of the model decreases when higher frequency modes are considered.
On the possibility of nonlinear reflections in shock-containing noise near a high-performance military aircraft
Authors: Vaughn Aaron B. , Leete Kevin M. , Gee Kent L. , Adams Bradley R. , Downing J. M.
Published: November 2021

The skewness of the pressure time derivative, or derivative skewness, is a useful indicator of crackle perception in jet noise. Near a military aircraft, derivative skewness values are greater at ground-based measurements relative to nearby off-ground locations. As proposed in Vaughn et al. [J. Acoust. Soc. Am. 149(4), 2403–2414 (2021)], nonlinear reflections are a possible explanation for the increased derivative skewness values at the ground. For an ensemble of windowed shock events, the propagation angle, apparent source location, and angle of incidence relative to the ground are estimated using a two-point cross correlation. The shocks are then classified into shock reflection regimes based on their combination of angle of incidence and measured shock strength. A significant number of shocks measured along the ground array fall in the nonlinear reflection regime. A nonlinear shock reflection results in a pressure increase at the shock greater than twice the free-field pressure, which causes an increase in the derivative skewness value. Therefore, measurements at the ground may overpredict the crackle perception of a standing observer.
Physics-based filtering of irrotational wavepackets from high-speed Schlieren
Authors: Prasad Chitrarth , Gaitonde Datta
Published: November 2021

The eduction of acoustically efficient wavepacket structures from experimental measurements or high-fidelity numerical data aids in understanding different noise generation mechanisms in jets. This is often achieved by employing either signal processing techniques or modal decompositions. The former often require some user-defined thresholds that must be adjusted for each operating condition whereas the latter are more robust and can be applied to any jet flow-field irrespective of the operating conditions. The application of physics-based decompositions requires time-accurate spatio-temporally resolved data of the type obtained from well-validated numerical databases, which require substantial computational resources. There is an inherent advantage in extending decomposition-based approaches to experimental measurements, which can provide a substantially longer time series of data compared to numerical simulations. This investigation explores the application of Doak's Momentum Potential Theory to high-speed schlieren imaging, which is a widely used flow visualization tool in jet noise research. The procedure is applied to different test-cases, selected based on the availability of high-quality experimental measurements and numerical data. The coherent wavepackets obtained exhibit superior spatio-temporal coherence and radiative efficiency that capture the noise radiation mechanisms in the flow.
Seismoacoustic modeling of a below-ground explosion using finite element analysis
Authors: Blom Philip S.
Published: November 2021

The generation of seismic and acoustic energy by below-ground explosions is a complicated, inelastic process in which damage and failure dynamics near the source and at the rock-air interface have a significant impact on the resulting seismoacoustic wavefield. Recent investigations by Blom et al. (2020) have demonstrated that combining the Rayleigh integral with a parametric spall model describing the ground motion characteristics for a given emplacement (i.e., depth, yield, and geology characteristics) results in accurate predictions for acoustic signals produced by below-ground explosions. In order to supplement this parametric, physics-based model, numerical simulations have been used to investigate the seismic and acoustic signals produced by a below-ground explosion using finite element methods including material crush at the source and tensile failure at the surface. The aim of these simulations is to enhance our understanding of the seismoacoustic signal generation by this complicated spatially and temporally extended source and investigate how acoustic and seismic observations can be leveraged to characterize below-ground explosions. An overview of the finite element simulations and the various challenges involved in their execution will be presented along with preliminary results.
Atmospheric parabolic equation with Galerkin discretization and boundary fitted grid for modeling infrasound propagation over topography
Authors: Ochi Gordon M. , Swearingen Michelle E.
Published: November 2021

Studies utilizing the parabolic equation (PE) to model infrasound propagation over topography have traditionally implemented them as 2D or Nx2D PE models. These methods, to one extent or another, trade-off accuracy for enhanced computational speed. Three-dimensional parabolic equation (3DPE) models are seldom seen in atmospheric acoustic propagation studies compared to their 2D and Nx2D counterparts, despite the fact that theta coupling and proper modeling of horizontal refraction and diffraction in a 3DPE model should enable greater accuracy. In this work a 3DPE in cylindrical coordinates is developed under the alternating direction implicit scheme, with a Galerkin discretization and boundary fitted grid, such that the PE is capable of handling arbitrary and irregular topography features. Finally, 2D, Nx2D, and 3D implementations of the aforementioned PE model are examined for cases of propagation over a simple hill in homogeneous, downward refracting, and upward refracting atmospheres. Insights are drawn with regards to the accuracy at a variety of positions and ranges, and the computational speeds of the various methods.
How, when, and where predictions combine with speech in auditory cortexd
Authors: Sohoglu Ediz
Published: November 2021

Human speech perception is rapid, accurate and robust to noise. These characteristics are enabled by top-down predictive computations that combine bottom-up sensory input with prior expectations. Here, I distinguish between two accounts of how predictions combine with speech signals in auditory cortex. Is expected speech content enhanced to leave a “sharpened” version of the sensory input? Or is expected content subtracted away to leave only those parts that are unexpected, i.e., “prediction error”? Based on fMRI and MEG data, I show that neural representations of spoken words are suppressed when listeners have strong predictions based on long-term lexical knowledge. This neural signature is uniquely consistent with the prediction error account, occurs in superior temporal cortex within 400 ms of speech input and in the delta/theta frequency band. These results provide a comprehensive window into predictive processing of speech, showing how, when and where predictions combine with sensory signals.
Ultrasonic characterization of cold sintered ZnO components with varying relative densities
Authors: Arguelles Andrea P. , Trolier-McKinstry Susan , Trautman Elizabeth
Published: November 2021

The cold sintering process is a low temperature processing technique used to synthesize metals, ceramics, and composites. Some cold sintered parts do not reach the mechanical properties of conventionally sintered parts even at high relative densities. These diminished mechanical properties are presumed to be in part a result of either in inhomogeneous removal of transient liquid phases or inability to reach the proper cold sintering temperature/pressure everywhere in the part. In this presentation, we evaluate the spatial variability in the properties of cold sintered ZnO parts with decreasing relative densities through ultrasonic testing. The presence of homogeneously distributed porosity is assessed by ultrasonic wave speed, while macro-flaws larger than the average pore size are assessed through ultrasonic attenuation. The results are compared to the response of conventionally sintered ZnO samples with densities ranging from 86% to 89%. Conventionally sintered and cold sintered parts exhibited different slopes in the decrease of wave speed with density. This difference suggests microstructural discrepancies beyond porosity in cold versus conventionally sintered ZnO components. Attenuation results suggested the presence of macro-flaws even in the samples with highest relative density. These results underscore the importance of nondestructive characterization of the cold sintered components.
Audio-frequency characterization of cranial sutures via non-contact vibration experiments
Authors: Kohtanen Eetu , Mazzotti Matteo , Ruzzene Massimo , Erturk Alper
Published: November 2021

There are many factors that affect the structural dynamics of the human skull, including but not limited to skull-specific geometry, the composite nature of cranial bone including the cortical tables and the diploë, and the presence of sutures, with the latter being the focus of this study. Sutures are joints between the cranial bones that tend to decrease the overall bone strength in three-point flexural tests, but their effects on the dynamic properties of the bone including mode shapes and natural frequencies remain largely unexplored. Knowledge of the suture dynamics in human skulls is relevant to various research domains spanning from hearing by bone conduction to cranial wave propagation, and an accurate representation of the cranial sutures can be important to establish high-fidelity skull models to use in such applications. To this end, non-contact vibration experiments are carried out to extract the mode shapes, natural frequencies, and damping ratios of several skull segments containing sutures (specifically the coronal, sagittal, lambdoid, and lateral sutures). Furthermore, high-fidelity finite element models of the bone segments are constructed from fine resolution (50 μm) computed tomographic scans. These numerical models are employed to identify the appropriate suture elastic properties that most closely replicate the experimental results.
Flexural wave parameter measurements of viscoelastic panels using a laser doppler correlation vibrometry
Authors: Xiang Ning , Miller Max
Published: November 2021

Characterizing broadband dynamic properties of viscoelastic panel materials represents a challenging task, particularly when the frequency band of interest needs to be extended toward low frequency range. This work applies a laser Doppler vibrometer in measuring flexural wave properties of the viscoelastic panel materials. The measurement relies on a time-domain broadband correlation technique which experimentally measures impulse responses at two points radially away from a flexural wave exciter. Using reasonable sized panel samples, boundary conditions of the measurements present insignificant obstacles towards high frequency range, since a time-domain windowing facilitates extraction of direct wave components. While boundary reflections will still obscure measurement results towards low frequencies. This work examines a possible mitigation approach by rotating the sample panel, the coherence of direct wave pulses measured equidistant from the exciter and the lack thereof disturbing boundary reflections enables largely removing the undesirable reflections. In this way angular averaging significantly reduces boundary reflections. This paper discusses experimental investigations on the characterization method of flexural wave parameters including wave speed, flexural modules and loss factor.
Visco-elastic material characterization by means of full field Lamb waves
Authors: Orta Adil H. , Segers Joost , Roozen Nicolaas B. , Van Paepegem Wim , Kersemans Mathias , Van Den Abeele Koen
Published: November 2021

In structural design and structural health monitoring (SHM), the identification of the visco-elastic stiffness tensor of composite materials is considered fundamental, however, the reconstruction of the stiffness coefficients is not straightforward due to the inherent presence of anisotropy and heterogeneity. In the current study, an inverse procedure is proposed based on full field wave dispersion curves to characterize the (18) visco-elastic stiffness parameters of an orthotropic composite plate. The procedure is illustrated by means of finite element method simulations conducted with broadband signals. First, the FEM simulation data, consisting of the in-plane and out-of-plane velocities on the 2D top surface of a composite plate, were converted into the frequency-complex wavenumber domain, including information on elasticity and viscosity, by using the matrix pencil method. The converted data set was then considered as input to a surrogate optimization inversion algorithm, using the semi analytical finite element method (SAFE) as the forward model owing to its accuracy, efficiency and robustness. The full tensorial visco-elastic stiffness parameters were calculated and updated by minimizing the error between the simulated and the calculated complex wavenumbers. The final reconstructed stiffness properties in case of an aluminum plate and of a unidirectional composite laminate show good agreement with the exact input stiffness values, with average errors below 5% for all 18 visco-elastic stiffness parameters.
An ultrasound study of rest position and pre-acoustic articulation in adults and children
Authors: Palo Pertti , Lulich Steven M.
Published: November 2021

The position of the tongue during rest and its relationship to subsequent pre-acoustic speech movements have shed light on speech motor planning. They may find applications in technologies such as silent speech interfaces. Palo [“Measuring pre-speech articulation,” Ph.D. thesis (Queen Margaret University, Edinburgh, 2019)] found that the duration of pre-acoustic speech movements are strongly correlated with acoustic utterance duration, but it remains an open question whether this correlation is modulated by different rest positions. This study investigates variability in rest position among children and adults, and examines whether rest position affects pre-acoustic speech movements and their correlation with acoustic utterance durations. [This work has been supported by a personal grant from The Emil Aaltonen Foundation (Palo) and by NSF Grant No. 1551131 (Lulich).]
Modeling speaker-specific vocal tract kinematics from gestural scores
Authors: Lu Yijing , Ly Justin , Narayanan Shrikanth , Goldstein Louis , Toutios Asterios
Published: November 2021

The theory of Task Dynamics provides a method of predicting articulatory kinematics from a discrete phonologically-relevant representation (“gestural score”). However, because the implementations of that model (e.g., Nam et al., 2004) have generally used a simplified articulatory geometry (Mermelstein et al., 1981) whose forward model (from articulator to constriction coordinates) can be analytically derived, quantitative predictions of the model for individual human vocal tracts have not been possible. Recently, methods of deriving individual speaker forward models from real-time MRI data have been developed (Sorensen et al., 2019). This has further allowed development of task dynamic models for individual speakers, which make quantitative predictions. Thus far, however, these models (Alexander et al., 2019) could only synthesize limited types of utterances due to their inability to model temporally overlapping gestures. An updated implementation is presented, which can accommodate overlapping gestures and incorporates an optimization loop to improve the fit of modeled articulatory trajectories to the observed ones. Using an analysis-by-synthesis approach, the updated implementation can be utilized: (1) to refine the hypothesized speaker-general gestural parameters (target, stiffness) for individual speakers; (2) to test different degrees of temporal overlapping among multiple gestures such as a CCVC syllable. [Work supported by NSF, Grant 1908865.]
Human beatboxing: Physiological aspects of drum imitation
Authors: Dehais-Underdown Alexis , Vignes Paul , Crevier-Buchman Lise , Demolin Didier
Published: November 2021

Human Beatboxing (HBB) is a musical technique produced with vocal tract movements. In this study we investigate HBB production mechanisms of 3 drums imitations, that is the labial kick drum, the lingual closed hi-hat and the velar ingressive snare drum, produced in isolation by 5 beatboxers. Based on aerodynamic (intraoral pressure and oral airflow), acoustic and laryngoscopic data, we were able to identify gestures. The kick was produced as a labial stop and the hi-hat as an coronal affricate; both were initiated by a glottalic egressive airstream. Differences in intraoral pressure, oral airflow and laryngeal configuration were observed across beatboxers. The snare was produced as a velar pulmonic ingressive affricate [↓k⌢L̥]; however 1 beatboxer produced a velar glottalic ingressive stop + a velar pulmonic ingressive fricative [k↓L̥]. The combination of glottalic and pulmonic airstreams raises questions concerning the coordination of initiatory mechanisms and its planification. HBB differs from speech production because it is a musical system and thus do not rely on linguistic constraints such as phonotactic; it implies that articulatory patterns are not as restricted as in speech. Thus, it is a rich paradigm to investigate vocal tract physiology and mental representations of non-linguistic sounds.
Segmental effects on the transmission of variability between articulation and acoustics
Authors: Harper Sarah
Published: November 2021

Previous research on articulatory-acoustic relations has generated conflicting results regarding the extent to which variability in articulation can be recovered from the acoustic signal (e.g., Guenther et al., 1999; Whalen etal., 2018). This study extends previous research probing the relationship between articulatory and acoustic variability by examining the extent to which individual differences in articulatory variability are recoverable from acoustics, and vice versa, for a set of American English consonants. A series of linear mixed effects regression models were fit to articulatory and acoustic data from tokens of /s/, /ʃ/, /l/, and /ɹ/ produced by 40 speakers in the Wisconsin X-Ray Microbeam Corpus (Westbury, 1994) to evaluate the extent to which the variability exhibited in one of these physical dimensions was recoverable from the signal in the other domain. The output of these statistical models was then compared to measurements of individual speakers’ variability along specific articulatory and acoustic dimensions to evaluate whether individual differences in variability were conveyed between articulation and acoustics. The results of the analyses suggest that the variability exhibited in one physical domain is to some extent recoverable from the other, although this capacity varies across segments and articulatory/acoustic dimensions. [Work supported by NIH.]
Sponge-layer damping techniques for enhancing the resolution and localization accuracy of acoustic time-reversal simulation
Authors: Mimani Akhilesh
Published: November 2021

This work reviews the development of a set of sponge-layer damping techniques aimed at enhancing the focal-resolution of acoustic source(s) using Time-Reversal (TR) simulations. The method, termed as the Point-Time-Reversal-Sponge-layer (PTRSL) is based on damping the radial components of fluxes propagating towards and away from the assumed location resulting in local focusing of acoustic power. First, the test-case of an idealized monopole source was considered whereby it is demonstrated that a repeated application of PTRSL produced a point-like resolution while using a sensitivity analysis, it can resolve two or more sources in-proximity. Next, the method was demonstrated for canonical experimental aeroacoustic problems, namely, the rod-airfoil interaction and airfoil trailing-edge self-noise. When self-scattering due to airfoil was modeled, focal spots resembling a cardioid were obtained, however, large side-lobes posed difficulty in readily identifying the true source location. To overcome the problem, a (Line) LTRSL technique was developed which assumes that dipole sources of varying strength are distributed along the chord, and computes the root-mean-square (RMS) average of the PTRSL maps for each location. An iterative implementation of LTRSL was shown to suppress the side-lobes, and deliver the true scattered location of dipole source(s) along the chord whilst simultaneously producing a highly enhanced resolution.
Subsurface target illumination in elastic hosts: a comparison of time-reversal and inverse-source approaches
Authors: Goh Heedong , Koo Seungbum , Karve Pranav , Kallivokas Loukas
Published: November 2021

The need for focusing wave energy to selected targets embedded within a host is commonly shared among various engineering fields, whether for stimulation and imaging in exploration geophysics, for contaminant removal in geo-environmental engineering, or for diagnostic/therapeutic purposes in medicine. In this presentation, we discuss the problem of focusing wave energy to multiple subsurface targets embedded within a semi-infinite heterogeneous elastic host. We review the advantages and disadvantages of two distinct approaches: first, using the apparatus of PDE-constrained optimization, we describe an inverse source (IS) approach, where we seek to design optimal excitations (both in space and time) in order to maximize target illumination. The second approach is rooted on the time-reversibility (TR) of the lossless wave equation; however the unboundness of the host, and equipment limitations that necessitate that recorded Dirichlet data be time reversed as Neumann data, create particularly adverse conditions for time-reversal. To overcome, we discuss a switching time-reversing mirror, and report on numerical experiments that show illumination resolution improvement. We define target illumination metrics to assess the relative performance of the IS and TR methods, and, using numerical experiments, we show that both approaches have similar efficiency.
Quantifying nonlinear characteristics in time reversal focusing of airborne sound
Authors: Patchett Brian D. , Anderson Brian E.
Published: November 2021

Time reversal can be used to focus sound to a chosen location within a reverberant environment. Virtual sources in the reverberant environment increase the amplitude of the focusing. Recent investigations into the focusing of high-amplitude sound waves, up to peak levels of 200 dB, has led to the observation of nonlinear characteristics in the focus event. This study investigates these nonlinear characteristics, including distortion of the focus wave, shift in harmonic content, and nonlinear increase in the peak pressure compressions. This study also attempts to quantify a threshold where the focus events begin to transition from a linear to the nonlinear regime. Additionally, a comparison of the microphones and transducers used to record these focus events is made in order to both verify the levels of pressure attained, and to ensure that microphone distortion is not the cause of the nonlinear features in the focusing.
Self-portrait of an ultrasonic wave propagating in a random scattering medium
Authors: Giraudat Elsa , Lambert William , Bureau Flavien , Fink Mathias , Aubry Alexandre
Published: November 2021

Synthetic beamforming for ultrasound imaging relies on a double focusing operation of back-scattered waves at transmission and reception on each point of the medium. Matrix imaging consists in decoupling the location of these transmitted and received focal spots .The response between those virtual transducers forms the focused reflection matrix that contains much more information than raw ultrasound images. Here, we aim to investigate the focused reflection matrix beyond the focusing time to fully leverage the available temporal information. In this time-dependent frame, each virtual source is associated with a focused incident wave while each virtual sensor enables to probe the propagation of this wave through the medium in thetime domain. . This approach is the matrix equivalent of iterative time-reversal methods developed in speckle noise(Montaldo, PRL 2011). However, the matrix formalism enables to perform this whole process in post-processing and provides a much greater flexibility and efficiency. It constitutes a promising tool for an optimized local spatio-temporal focusing of ultrasonic waves, even in presence of reverberation and multiple scattering phenomena. It also paves the way towards a quantitative characterization of random scattering media, by providing, for instance, a high resolution map of integrated speed-of-sounds in soft tissues.
Identifying the optimal k-mean clustering for ship noise spectrograms
Authors: Wu Bethany , Neilsen Tracianne B.
Published: November 2021

Unsupervised learning techniques have the potential to be useful for ocean acoustic data. For example, the k-means clustering algorithm has been trained on synthetic spectrograms from surface ships and then applied to measured data to try to identify probabilities of seabed type and details such as the speed and location of the ships. Although the algorithm is effective in grouping data into clusters, the variability of these clusters is heavily dependent on the number of clusters, “k.” This paper aims to investigate the range of variability in clusters when different values of k are chosen for a given ocean acoustics dataset. To assess the variability of the results, different methods will be used to measure distances from the centroid of each cluster. These methods include measuring the average, maximum, and sum of squared distances from each data sample to its assigned centroid. The results when using the optimal number of clusters are shown and a discussion is provided about how to interpret the results.
Evaluating applicability of an azimuthally symmetric model in a laboratory tank with absorptive panels
Authors: Hollingsworth Scott P. , Vongsawad Cameron T. , Neilsen Tracianne B.
Published: November 2021

In our lab at Brigham Young University, a tank of water will be used to help validate machine learning algorithms that could be applied to ocean acoustics. A model for sound propagation in the tank is required, and we are exploring the possibility of using ORCA, a range-independent normal mode model [Westwood et al., JASA (1996)]. Because ORCA assumes azimuthal symmetry in cylindrical coordinates, reflections from the tank walls must be significantly attenuated for ORCA to be a good model. To compare our measurements to ORCA, two approaches have been tried: (1) timegating and (2) absorptive panels on the walls. The layering used in ORCA is air on top, water with a maximum depth of 0.91 m, 3 cm thick acrylic bottom, a lower air layer, and then concrete on bottom. A simpler model excluding the air between the acrylic and the concrete was also tested. Both models were compared to measured data; both relative and absolute transmission loss were compared across a large frequency band and as a function of source/receiver distances at set depths. If ORCA is a good model for the tank, then we could easily generate training data for machine learning applications.
Mode coupling in a coastal wedge due to quasi crossing of range-dependent modal eigenvalues and spatial sound field variability
Authors: Katsnelson Boris , Jiang Yanyu , Zhang Qianchu
Published: November 2021

In the paper sound waves propagation in a coastal wedge with sound speed profile (the presence of thermocline) is studied. In down- and up-slope propagation each adiabatic waveguide mode is transformed from the “bottom—surface reflected” shape to the “bottom-bottom refracted” one at some distance from the edge, depending on mode number. Analysis of mode composition and the corresponding spatial variability of the sound field is carried out using Parabolic Equation with the following decomposition of the field over adiabatic modes. It is shown, that there is significant change of amplitudes of adiabatic modes which is interpreted as manifestation of mode coupling. It is shown that mode coupling has local character, at the definite distance from the source, where two range dependent eigenvalues convergent to each other. This phenomenon is analog to the so called quasi crossing of states in atomic physics (Landau–Zener theory of nonadiabatic transitions in two-level system). This leads to sequential excitation of more and more higher modes in down-slope propagation and even creation of higher modes which did not exist at the position of the source. Results of modeling are presented, possible experimental observations are discussed. [Work was supported by RFBR, Grant 20-55-S52005.]
Acoustic propagation in heterogeneous environments and its implications on the active space of rock ptarmigan
Authors: Guibard Arthur , Dragna Didier , Ollivier Sebastien , Sèbe Frédéric
Published: November 2021

Acoustic communication networks among birds are widely studied in homogeneous environment like tropical forest or open field. There is no study in heterogeneous environment to our knowledge. However, the propagation of an acoustic signal is strongly influenced by topography, meteorological and ground effects, especially at long distance. For bird species living in high mountains, these effects can have a prominent impact on how their vocalization spreads. Here we try to redefine the active space notion, using the rock ptarmigan as a model. We develop a sound propagation code dedicated to bioacoustic studies based on the parabolic equation method and taking into account the above mentioned effects. Propagation measurements were carried out at a mountain site to provide information on typical conditions encountered and to test the validity of our model in this context. Using this model, we describe how the mountainous conditions affect active spaces of communication compared to typical homogeneous situations. We further test how singing during display flights can be a good strategy for a transmitter to expand its active space in such a context. A fine modeling of the propagation of acoustic signals is likely to provide important cues for understanding communication networks of mountainous species.
Understanding marine life through long-term passive acoustic time series
Authors: Sirovic Ana
Published: November 2021

Sound allows us to study the ocean on a much finer time scales than other methods of study as it is feasible to collect continuous underwater recordings over months or years at a time. My work has been focused on using such long recordings to improve our understanding of the ecology of large whales and marine fishes. However, ecological insights can only be gained from data that are truly comparable across time and space. The initial steps to achieving comparable time series from long-term recordings collected at vastly different locations include: effective detection of signals of interest, full knowledge of the characteristics of those signals and interfering noise, and normalization of those detections by appropriate recording effort across time and space. I will highlight a few things we have learned about baleen whale and fish species through long-term passive acoustic monitoring effort, such as an improved understanding of call function for some baleen whales or a better sense of animal occurrence. This, in turn, will allow us to start coupling the occurrence of these animals into the larger patterns of ecosystem dynamics, ultimately leading to a fuller understanding of their roles in the ocean.
Novel 3D ultrasound imaging and automated deep learning analysis in ophthalmology
Authors: Bayat Mahdi , Minhaz Ahmed T. , Wilson David L. , Orge Faruk
Published: November 2021

We present novel 3D ultrasound technologies for imaging of the eye. We computationally align and improve imaging volumes acquired by mechanical scanning of conventional ophthalmic ultrasound systems. We also present results of using emerging ultrahigh frequency array systems that increase volumetric image reconstruction speed by several orders of magnitude and allowing Doppler processing of blood flow. The easily interpretable 3D visualizations can greatly assist in automated analysis and reducing operator dependency. We present deep learning methods for volumetric segmentation and quantification. The 3D ophthalmic ultrasound combined with automated deep learning analysis allows non-expert users to easily use this technology for diagnosis, monitoring response to therapy and improving overall ocular disease management at low cost, versatility, and safety for repeated and timely scanning.
The lowest frequency modes of the mandolin modeled as a coupled oscillator system
Authors: Robertson Connor , Schowalter Gretchen , Tufte Steve
Published: November 2021

The mandolin is an acoustically unique musical instrument with elements similar to the guitar and violin. Inspired by a classic guitar study by Christensen and Vistisen, we tested if the mandolin’s low-frequency response could be modeled as a simple 3-mass coupled oscillator system. We measured the response of the front plate, back plate, and air within thecavity from sinusoidal forcing of the front plate using microphones, accelerometers, and a force probe. We calculated the mobility (i.e., 1/impedance = v/F) and compared this to a theoretical model. To determine how the collective resonances are affected by the individual oscillators in the system, we added small masses to the front and back plates, and “collared” the f-holes to add mass to the moving air, thus lowering the resonances of the corresponding oscillator. We found clear evidence of coupling: by changing any one element, the resulting three resonant frequencies of the coupled system were affected. We also found the expected phase relations between the individual oscillators for each of the three resonances of the coupled system. From a detailed analysis, we found that a 3-mass coupled oscillator model can reasonably approximate the low-frequency behavior of the mandolin.
Hybrid lattice-Boltzmann digital-waveguide simulation of wind instruments
Authors: Wang Song , Scavone Gary
Published: November 2021

A hybrid lattice-Boltzmann digital-waveguide model is proposed to improve the efficiency of the computational aeroacoustics modeling of wind instruments. The nonlinear sound generator and the assumed linear resonator of a wind instrument are modeled separately using the lattice Boltzmann (LB) method and digital waveguide (DWG) method, correspondingly. Their coupling is achieved through the characteristic boundary condition, which breaks down the lattice Boltzmann solutions at the junction into separated traveling waves along different characteristic lines. The lattice Boltzmann solver then sends the outgoing acoustic wave to the digital waveguide, and receives the incoming acoustic wave to complete the boundary condition. Two examples are tested to demonstrate the validity of the proposed method, including a hybrid cylindrical pipe composed of two coupled cylindrical segments, one represented by LB and the other by DWG, and a hybrid single-reed instrument that comprises an LB mouthpiece-reed system and a DWG pipe.
Spatiospectral lobe characteristics for F404 engine noise
Authors: Olaveson Tyce , Ward Jacob A. , Gee Kent L. , Johnson Jon P. , Wall Alan T.
Published: November 2021

Spatiospectral lobes are a currently unexplained phenomenon seen in noise radiation from tactical aircraft. These lobes can be seen as either multiple peaks in the noise spectra at a given field location or multiple local maxima in the directivity when observing the radiated noise field at a particular frequency. Using hybrid beamforming of a 120-microphone near-field array, the characteristics of these lobes are studied for a GE F404 engine installed on a T-7A aircraft and at different engine conditions. Both the measured field and field reconstructions show multiple spatiospectral lobes. While the overall directivity of the noise shifts forward with increase in frequency, individual lobes appear, shift aft, and then disappear as frequency is increased. Individual lobes were also raytraced back to the jet centerline to determine an apparent acoustic source location. For frequencies where multiple lobes are present, they generally radiate from an overlapping maximum source region that moves upstream with frequency. This corroborates the characteristics of spatiospectral lobes observed in other aircraft. [Work supported by ONR.]
Optimized metal foam liners with spatially gradient properties for aircraft engine noise reduction
Authors: Lomte Amulya , Mahajan Manish , Sharma Bhisham
Published: November 2021

Recent studies conducted by NASA have identified over the rotor liners as one of the most promising avenues for aircraft noise reduction. However, conventional noise absorption technologies cannot withstand the harsh pressure and temperature conditions near the engine core. While open celled metal foams are an alternative material choice, their open porous structure results in comparatively lower absorption characteristics. In this talk, we summarize the results from our recent efforts on improving the acoustical properties of metal foams for aircraft noise reduction applications. We show that compressing the foams substantially improves their absorption coefficient because of the reduction in the effective pore size. Unfortunately, this improvement comes with an undesirable weight penalty. To overcome this, we propose an optimized layered configuration to create a step-wise relative density gradient that provides comparable absorption characteristics while being over 20% lighter than the benchmark compressed foam. Our results show that metal foam liners with spatially gradient property configurations can provide broadband engine noise reduction while minimizing the resulting weight penalty.
Have I learned anything? Sharing my perspectives from a career in acoustics
Authors: Sommerfeldt Scott D.
Published: November 2021

After graduation, a career of 30–40 years can seem like a long time to many of us, with so many questions to resolve. Where do I want to work – both in terms of company and geography? How do I get ahead—in my career and in life? How do I best contribute to advancing and balancing my personal ambitions, the mission of my company, professional opportunities, and so forth? And what about non-work activities? How do I best balance those? I cannot answer these questions for anyone, but in this presentation, I will share some of my perspectives on some of these questions, and what I have personally learned over many years of striving to contribute in my discipline, while also striving to live a fulfilled life.
Toward adaptive auralization of dynamic immersive virtual environments in room-centered virtual reality systems
Authors: Huang Mincong , Braasch Jonas
Published: November 2021

Existing auralization frameworks for interactive virtual environments have found applications in simulating acoustic conditions for binaural listening and real-time audiovisual navigation. This work, situated at the Collaborative-Research Augmented Immersive Virtual Environment Laboratory (CRAIVE-Lab), extends elements of these frameworks for human-scale interactive audiovisual display with movement of virtual sound sources and non-static virtual representation of the facility’s footprint. The work involves the development of an adaptive acoustic ray-tracing prototype that is capable of generating impulse responses for individual virtual loudspeaker representation based upon changes of room orientation in virtual space at runtime. Through the integrated use of game engines (i.e., Unity and Unreal Engine), the prototype is presented in the context of dynamic audiovisual display, and actively analyzes the virtual scene geometries using a multi-detailed rendering approach. With both reconstructed high-resolution 3D models of existing spaces, and automatically generated virtual landscapes from geo-spatial data, the developed system is evaluated both in terms of computational efficiency, and in terms of conventional room acoustics parameters using model-based acoustic energy decay analysis across listening region. [Work supported by the Cognitive Immersive Systems Laboratory (CISL) and NSF IIS-1909229.]
A sound absorber made of copper to reduce virus spread in architectural applications
Authors: Arenas Jorge P.
Published: November 2021

For many years, copper and copper alloys materials have been recognized as an efficient antimicrobial. Experimental studies have reported that solid copper surfaces can kill 99.9% of microorganisms within two hours of contact, mainly attributed to the release of ions. However, copper materials in acoustical applications have not been usual, mainly because of their costs. The COVID-19 outbreak has boosted the use of copper in the most frequently touched surfaces to help reduce the spread of the virus. In addition to being malleable, ductile, and an extremely good conductor of electricity, copper exhibits other interesting material properties. The characteristic impedance of copper is 80% of the characteristic impedance of stainless steel and it is slightly twice the characteristic impedance of aluminum. Meanwhile, the critical frequency by unit thickness (Hz-m) of a copper panel is about 50% greater than that of an aluminum or steel plate. In this communication, a sound-absorbing device completely made of copper is presented, which makes use of a copper perforated panel and a copper fibrous infill material. The device would be useful to provide sound absorption in those environments where the protection of people's health is important.
Sound and movement data from two overlapping populations of killer whales reveal noise effects on foraging behavior
Authors: Tennessen Jennifer B. , Holt Marla M. , Wright Brianna , Hanson M. Bradley M. , Emmons Candice , Giles Deborah , Hogan Jeffrey , Thornton Sheila J. , Deecke Volker
Published: November 2021

Understanding ambient noise effects on foraging ecology of endangered killer whales is a necessary step toward predicting population-level consequences of acoustic disturbance. However, this has been limited by the difficulty of identifying prey capture which typically occurs out of sight, and by the challenge of obtaining a sufficient range of noise conditions. We addressed these problems using sound and movement data from suction cup-attached archival tags deployed on 52 Northern resident and endangered Southern resident killer whales sampled during overlapping field efforts. We measured broadband ambient noise levels above low-frequency cut-offs that minimized flow noise, and quantified foraging behavior using established acoustic and movement signatures to detect prey capture events. Statistical models revealed significant effects of noise level on searching, pursuit and capture outcomes, including the likelihood that a prey pursuit dive was aborted. We discuss the utility of broadening the range of noise level conditions available by sampling from multiple populations within overlapping geographic regions, and highlight the implications of noise-induced foraging interference on two killer whale populations with different population trajectories. Finally, we suggest future applications of this comparative approach to foster a greater understanding of the population consequences of acoustic disturbance in killer whales.
Southern Resident killer whale acoustic monitoring and noise measurements to inform noise mitigation and potential management strategies
Authors: Wood Jason , Palmer Kaitlin , Trounce Krista , Yack Tina M. , Robertson Frances , Yurk Harald
Published: November 2021

SMRU Consulting, in collaboration with the ECHO Program, the San Juan County MRC and DFO, has been monitoring Salish Sea underwater soundscapes for the presence of Southern Resident killer whales (SRKW), to measure ambient noise levels, evaluate the efficacy of noise mitigation measures and inform potential management strategies. This talk will highlight results from four projects across the years 2019–2021. This includes measurements from a cabled observatory at Lime Kiln Point State Park in support of the ECHO Program’s Haro Strait commercial vessel slowdowns; measurements from autonomous recorders at five locations in Burrard Inlet for the ECHO Program and the Tsleil-Waututh Nation to monitor trends in ambient noise and marine mammal presence; measurements from Coastal Acoustic Buoys at eight locations south of San Juan Island in support of San Juan County’s management efforts, and a Coastal Acoustic Buoy for Offshore Wind deployment near Point Roberts to allow DFO to evaluate acoustic technology. This talk will discuss the pros and cons of these four different acoustic systems and highlight trends in the data that may help inform mitigation and management strategies.
Uncrewed surface vehicle survey of walleye pollock, Gadus chalcogrammus, in response to the cancellation of ship-based surveys
Authors: De Robertis Alex , Levine Mike , Lauffenburger Nathan , Ianelli James , Monnahan Cole , Stienessen Sarah , McKelvey Denise
Published: November 2021

In 2020, the developing COVID-19 pandemic disrupted fisheries surveys to an unprecedented extent. Many surveys were cancelled, including those for walleye pollock (Gadus chalcogrammus) in the eastern Bering Sea (EBS), the largest fishery in the United States. To partially mitigate the loss of survey information, we deployed three uncrewed surface vehicles (USVs) equipped with echosounders to extend the ship-based acoustic-trawl time series of pollock abundance. Trawling was not possible from USVs, so an empirical relationship between pollock backscatter and biomass established from previous surveys was developed to convert USV backscatter observations to pollock abundance. The EBS is well-suited for this approach since pollock dominate midwater fishes in the survey area. Acoustic data from the USVs were combined with historical surveys to provide a consistent fishery-independent index in 2020. This application demonstrates the unique capabilities of USVs and how they could be rapidly deployed to collect information on pollock abundance and distribution when a ship-based survey was not feasible. We note the limitations of this approach (e.g., higher uncertainty relative to previous ship-based surveys), but found the USV survey to be useful in informing the stock assessment in a situation where ship-based surveys were not possible.