bluuebunny/crossref_metadata_2025 huggingface dataset:
Vector properties of the low-frequency acoustic waves generated by earthquakes on the New England Bight
Authors: Dall'Osto David R. , Dahl Peter H. , Potty Gopu R. , Miller James H.
Published: November 2022

During a recent ONR experiment on the Northwest Atlantic continental shelf (i.e. New England Bight), a series of earthquakes occurred roughly 120 km from the 40 km × 20 km experimental area. A strong signal from these earthquakes was received by near-bottom vector sensors (the intensity vector acoustic recorders, IVARs) and high-bandwidth ocean-bottom seismometers (OBXs) embedded in the thick muddy sediments characteristic of the area. The events are roughly 30 seconds in duration, and are low-frequency (from 3 to 40 Hz). As such, energy is observed well below the acoustic cut-off frequency of the continental shelf. Correlating the arrivals to the USGS epicenter show these arrivals are supersonic in water, with group velocity >5 km/s. These arrivals appear to be leaky waves propagating within the rock below the ocean seafloor, distinct from the well-known T-phase of oceanic earthquakes that propagate at speeds close to the sound speed in seawater. The frequency dependence of the potential and kinetic energy of these arrivals suggest the field is evanescent, in both the water column and upper sediments. Spectral properties of the arrivals are shown to correspond to the water depth and sediment layering.
Methods for accurate acoustic characterization with ultra-low noise and minimal effect from reflection wave
Authors: Lai Junpeng , Karimi Morteza , Miles Ronald
Published: November 2022

It is common to measure the response of devices and structures to sound due to an imposed sound source. Unfortunately, acoustic reflections from walls and/or instruments often contaminate the results. In this presentation, methods of acoustic characterization are described to minimize the influence of acoustic reflections. It is shown that this process results in clean and smooth data. A simple time-domain window is implemented for diminishing the contribution from reflection waves. Moreover, a single frequency curve fitting approach is employed for better parameter identification and noise reduction, compared to traditional fast Fourier Transform analysis. Results obtained from a theoretical acoustic model with a reflection source are compared with measured results. Different cases of data acquisition with time and frequency analysis are experimentally demonstrated and validated. All experimental measurements are performed in an anechoic chamber. Results show that the approach presented here significantly reduces noise and also the influences of reflection waves in experimental data acquisition outcomes.
Holographic signal processing for estimation of sound source direction by a vector receiver in shallow water
Authors: Pereselkov Sergey A. , Kuz'kin Venedikt , Kaznacheev Ilya , Tkachenko Sergey , Rybyanets Pavel
Published: November 2022

A holographic signal processing method for estimation of sound source direction of broadband moving sound source is proposed in the paper. The holographic estimation of sound source direction is based on signal processing of single vector receiver (VR) channels: x-th and y-th components of the oscillatory velocity. The sound field of a moving sound source creates a stable interference pattern of the intensity distribution (interferogram) in the frequency-time domain on VR channels. The two-dimensional Fourier transformation (2D-FT) is applied to analyze the channels interferograms. The result of the 2D-FT are holograms of the x-th and y-th oscillatory velocity components. The angle distributions of channels holograms are calculated. The offered holographic method is based on the ratio of the absolute values of the holograms angle distributions maxima. The expressions for VR channels holograms are derived. The results of the numerical experiment for source direction reconstruction are presented. A significant advantage of the proposed holographic method that there is no need for information about noise signal source, the additive noise obstacle and waveguide transfer function. [This study was supported by Russian Science Foundation grant no. 22-79-10233. Tkachenko’s numerical experiment was supported by grant no. МК-4846.2022.4.]
A noninvasive auditory prosthesis: Evaluation of a safety margin of the transtympanic laser stimulation
Authors: Okamoto Aya , Uenaka Miku , Kobayasi Kohta I. , Tamai Yuta
Published: November 2022

Cochlear implants are widely used for compensating the sensorineural hearing loss. Surgical intervention for implanting electrodes is one of the most significant obstacle for the further widespread of these devices. We proposed a non-invasive auditory prosthesis using infrared laser because the laser can stimulate cochlea nerves from the outer ear. The purpose of this study was to evaluate the safety margin of the transtympanic laser stimulation. Head-fixed classical conditioning was performed on Mongolian gerbils. Subjects were trained using auditory stimulus, a bandpass noise, as a conditioned stimulus for a water reward, and licking behavior was recorded as a conditioned response. After the training, each subject was exposed to continuous pulsed laser irradiation of 1.6, 3.3, 6.6, 26.4, 52.8, or 105.6 W/cm2 for 15 hours. The bandpass noise with various intensities was presented without the reward before and after one-day of the laser exposure. As a result, the licking rate did not change after laser exposure of 6.6 W/cm2 or weaker, but drastically decreased after 26.4 W/cm2or above. The result suggests that the injury threshold in Mongolian gerbils for transtympanic laser stimulation is between 6.6 and 26.4 W/cm2 and the exposure over 6.6 W/cm2 could be out of the safety margin.
Respiratory and articulatory influences on inhalation noise during speech
Authors: Koenig Laura , Fuchs Susanne
Published: November 2022

During speech production, individuals inhale more deeply and rapidly compared to non-speaking inspiration. Such inspirations are also more frequently audible than their non-speech counterparts. To what extent do the acoustic characteristics of inhalation noise reflect respiratory contributions versus other articulatory mechanisms? To gain insight into this question, here we relate acoustics, captured using a head-mounted microphone, with kinematic data collected via respiratory inductance plethysmography (RIP) and optopalatography (OPG). The OPG system permits measurement of lip movements (displacement and velocity), tongue-palate contacts, and midsagittal distance when the tongue has no contact with the palate. Custom-made palates, including both contact sensors as well as optical sensors, were obtained for eight typical female speakers of German. Speech was recorded in normal and loud conditions. In this exploratory analysis, we anticipate that (a) louder speech will be accompanied by deeper, more rapid inhalations; and (b) greater articulatory opening during the inhalation phase; (c) the magnitude of lip aperture will be correlated with inspiration-excited first formant values; and (d) both supralaryngeal and respiratory displacements and velocities will be reflected in the inhalation noise characteristics. That is, speech inspiration, like speech itself, will demonstrate regular correspondences between physiological actions and the acoustic output.
Detecting hydro-acoustic signals using Distributed Acoustics Sensing technology
Authors: Abadi Shima , Wilcock William S. , Lipovsky Brad P.
Published: November 2022

Distributed Acoustic Sensing (DAS) is a relatively new technology that transforms fiber optic cables, typically used for telecommunications, into dense sensor arrays, capable of meter-scale recordings up to ∼100 km. The interest in these technologies for ocean exploration and monitoring has risen in recent years. These systems enable continuous and highly sensitive measurements of both temporal and spatial acoustic data. In this presentation, we use data recorded during a 4-day DAS experiment on the twin cables of the Ocean Observatories Initiative (OOI) Regional Cabled Array (RCA) extending off central Oregon. We demonstrate the capabilities of DAS in recording a wide range of acoustic signals including the 20-Hz call of fin whales, the 15-Hz calls and harmonics of the Northeast Pacific blue whale, and ship noises. We use beamforming and the time difference of arrival (TDOA) algorithm to find the bearing and the location of the signal of interest. We also explain the DAS array response and its sensitivity to paths arriving parallel or perpendicular to the cable and discuss the best practices to overcome the challenges in analyzing this large data set.
Modal-MUSIC extensions
Authors: Akins Franklin H. , Kuperman William
Published: November 2022

Modal-MUSIC [Akins and Kuperman, JASA Express Lett. 2(7), 074802 (2022)] is a variant of the well-known MUSIC plane wave algorithm that extracts direction of arrivals (DOA’s) from data containing multiple sources. Modal-MUSIC, rather than extract the DOA’s of the multiple sources, extracts the acoustic normal modes from incoherently summed data from multiple and/or moving sources received on a short vertical array. The method uses the local sound speed profile but does not require bottom geophysical information. We discuss extensions of the method that include using shorter arrays, geophysical-inversion and the additional application of synthetic source aperture [Akins and Kuperman, J. Acoust. Soc. Am. 150(1), 270–289 (2021)] to enhance source localization.
Assessing cognitive effects of transportation noise on office workers with electroencephalography and performance
Authors: Park Heui Young , Vigeant Michelle C. , Dittberner Andrew
Published: November 2022

Open offices are prone to not only internal noise but also external traffic noise. Noise has been shown to have detrimental effects on cognition and task performance, yet current literature on the effects of noise in open offices lack clarity and the findings are often inconclusive. This study aims to explore the effects of different acoustic conditions in an office: (1) with traffic noise and (2) in quiet, on task performance, brain activity, and subjective ratings. Subjects were given cognitive tasks, such as grammatical reasoning, while wearing an electroencephalography (EEG) headset. Brain activity and performance were recorded after a training session. Recorded traffic noise was auralized in an anechoic chamber with a 32-loudspeaker array to simulate road, rail, and subsonic aircraft noise heard when sitting in an elevated office with open windows. After completion of the tasks in the two acoustic conditions, subjective surveys were conducted for several items including perceived performance and annoyance. A statistical analysis was conducted to study the effects of different acoustic conditions on cognitive task performance, EEG data, and subjective ratings. Study details and results will be presented.
Finding the bubbles in therapeutic ultrasound—For better or for worse
Authors: Fowlkes J. Brian
Published: November 2022

Cavitation has played a variety of roles in therapeutic ultrasound since the field began. Bubble activity has been seen as both a harmful side effect and the means to the therapeutic end. Throughout this range, the monitoring of bubble activity has been an important goal for numerous reasons including safety considerations, progression of treatment, and determining therapeutic efficacy. Methods of cavitation monitoring have been summarized in various contexts including the ASA effort led by Wesley Nyborg, PhD that generated the American National Standards Institute (ANSI) S1.24 TR-2002 (R2007) entitled ANSI Technical Report—Bubble Detection and Cavitation Monitoring. More recently a six-part virtual series, The Detecting, Mapping, and Quantifying Bubble Activity in Therapeutic Ultrasound workshop (https://www.fusfoundation.org/posts/bubble-activity-in-therapeutic-ultrasound-workshop-series/) was held in 2021, sponsored by The Focused Ultrasound Foundation, in partnership with the American Institute of Ultrasound in Medicine’s Future Fund. A summary was released as a white paper. This presentation will provide an introduction to the field of bubble and cavitation detection and monitoring and a summary of this most recent workshop and associated follow-on efforts.
Sub-megahertz cavitation detection and characterization in mouse brains
Authors: Clement Gregory T. , Lopez Asis , Wu Guangying , Ye Meijun
Published: November 2022

A key consideration in ultrasound medical device safety is the potential for cavitation related bioeffects. Device testing should address possible cavitation pathways, such as bubble formation, either in the focal region or at the device-tissue interface along with possible consequences regarding both safety and effectiveness. This has been particularly important in a number of emerging transcranial therapies including ablation, neuromodulation, and targeted opening of the blood-brain barrier (BBB) in conjunction with microbubbles. Subharmonic, and ultraharmonic emissions have been identified as indicators of treatment outcome and are a basis for safety and feedback control in BBB disruption. However, there remains a scarcity of baseline cavitation threshold data in the living mammalian brain, particularly at lower ultrasound frequencies. In our ongoing study, we are measuring and evaluating in vivo cavitation response in mice using a passive cavitation detector (PCD) for ultrasound frequencies as low as 40 kHz. Additional measurements are being carried out using a hydrophone imbedded in the brain tissue of mouse cadavers to characterize absolute pressure values as well as evaluate the sensitivity and reliability of the PCD measurements. Analyzed data will be presented along with detailed methodology and potential implications in future product evaluation will be discussed.
High-frame-rate limited-diffraction beam imaging
Authors: Lu Jian-yu
Published: November 2022

Limited-diffraction beams such as Bessel beam, X wave, and array beam are a class of beams that in theory do not spread as they propagate to infinite distance. When realized with a finite aperture, these beams have a large depth of field. In this paper, limited-diffraction beams and their applications to high-frame rate imaging are reviewed and further studied. Using a limited-diffraction beams (in either transmission or reception, or both, or with spatial Fourier transform of received signals), images can be reconstructed in Fourier domain. This significantly reduces the amount of computation in 3D imaging since FFT can be used. As the bandwidth of the transducer is increased, the image reconstructed can cover a larger field of view since a frequency in limited-diffraction beam corresponds to one angular direction of the beam (similar to the “frequency encoding” in the magnetic resonance imaging or MRI). Using the angular dependence with frequency, focused limited-diffraction beams can be used for high-frame-rate and high-resolution tissue property imaging. When limited-diffraction beams are used in transmissions, no time delay (only amplitude weighting) is needed, which simplifies imaging system hardware. Also, flow vector imaging can be obtained with limited-diffraction beams using sine and cosine (quadrature) aperture weighting.
Distributed aberration correction in diagnostic ultrasound by time-delay computation from sound speed estimates using common midpoint gathers
Authors: Dahl Jeremy J. , Brevett Thurston , Sanabria Sergio
Published: November 2022

We describe a method of distributed aberration correction from local sound speed estimates of tissue. In this case, compensated beamforming delays are computed using the eikonal equation to account for refracted paths of the ultrasound waves based on an estimation of the local sound speed of the tissue. Signals acquired from a multistatic synthetic aperture sequence are used for image reconstruction in order to refocus the ultrasound beam at every image point without re-transmission. We estimate sound speed using the common midpoint gathers (CMGs) of the synthetic aperture signals, which have high signal coherence that can be used for accurate time measurements. These time measurements are used in overlapping ray paths traced onto a discrete grid to solve an inverse ultrasound computed tomography problem. We separately utilize absolute delay measurements at each depth (to capture axial variations) together with differential time-delays between CMG gathers (to capture lateral variations). For generalized sound speed reconstruction, we balance the contributions of both terms with regularization. In simulations, local sound speed was reconstructed with an rmse of 5.3 m/s in four-layered media and 6.0 m/s in focal lesions. In multilayer propanol/agar phantoms, local sound speed was reconstructed with an rmse of 5.0 m/s.
Estimating steelpan note class from attack transients
Authors: Malloy Colin
Published: November 2022

The estimation of fundamental frequency of instruments is an important task in computational audio analysis. The current state of the art methods use neural networks for this task. This process is typically computed periodically over very short segments of a monophonic audio signal so that minute shifts in intonation can be detected. However, the steelpan has discretely tuned notes where the performer has no direct control over pitch once a note has been activated. The activation of a note has great influence over the acoustical properties of the resultant note. Much research has been devoted to the tonality, construction, and acoustical properties of steelpans, but relatively little focuses on the attack transient specifically.This paper evaluates the application of pitch detection methods to the attack transients of steelpan notes. A dataset containing labeled audio samples from multiple tenor steelpans is used for training and evaluation. The accuracy of this approach for pitch detection is compared with established methods applied to both entire notes and only attack transients. Determining a steelpan note’s pitch from the attack transient is an important first step in building a robust low latency automatic transcription system that can be used for both analysis as well as live performance.
Assessing the microarchitecture and microenvironment of cancer in vivo by photoacoustic imaging techniques
Authors: Wang Xueding
Published: November 2022

Majority of current studies on photoacoustic (PA) imaging are focused on the total signal magnitudes as the reflection of the macroscopic optical absorption by specific chemical contents at single or multiple optical wavelengths. Our recent research has demonstrated that the frequency domain power distribution of radio-frequency PA signals contains the microscopic information of the optically absorbing materials in biological samples. In this research, I will present our recent development of quantitative PA methods for in vivo evaluation of histological microarchitectures of biological tissues as well as potential clinical applications of these methods such as the assessment of prostate cancer aggressiveness. In addition, powered by our recently developed polyacrylamide hydrogel nanoparticles containing a variety of functional contrast agents, multi-wavelength PA imaging plus spectral unmixing technique can enable quantitative mapping of the chemical and metabolic properties in cancer microenvironments, such as tissue oxygenation, pH level, and ion concentrations. Imaging of these chemical makeups of an entire tumor in vivo, non-invasively, with high sensitivity and high spatial resolution can shed new light to the understanding of cancer onset, progress, and responses to therapies.
Multispectral photoacoustic fluctuation imaging for full visibility SO2 imaging
Authors: Godefroy Guillaume , Arnal Bastien , Bossy Emmanuel
Published: November 2022

Photoacoustic (PA) imaging (PAI) images blood vessels through the hemoglobin contrast. However, conventional images are affected by visibility artefacts which prevents seeing all the blood vessels morphology. We introduced PA fluctuation imaging (PAFI) exploiting the absorption fluctuations due to blood flow. Here, we demonstrate how PAFI enhances the image quality and elaborate if it can be used for quantitative multispectral (MS) imaging for 3D blood oxygenation (SO2) imaging. A spherical array (256 elements, 8 MHz, Imasonic) connected to a Verasonics Vantage scanner, was coupled to the laser (Innolas Spitlight) through a fiber bundle (Ceramoptek). The PAFI sequence consisted in acquiring 1000 frames at 100 Hz repetition rate while scanning continuously the wavelength from 680 nm to 880 nm. Image processing resulted in PAFI image per wavelength. The compensation of predictable effects of pertubations provided quantitative SO2 images with visibility and contrast enhancement. The technique was validated in glass capillaries and in the chicken embryo model by comparing the SO2 values with the one obtained in the visible structures using conventional imaging (resp. 3.5% and 9% errors). Thus, MS-PAFI can provide quantitative SO2 full-visibility 3D imaging with an intrinsic specificity to blood which simplifies spectral unmixing.
Mechanism of low-frequency spectral scattering by a side-branch electromagnetic device with switching shunt
Authors: Huang Lixi
Published: November 2022

Sound waves are reflected and absorbed by a passive side-branch device in a duct. The performance of such a configuration is limited for low frequencies and if the cavity is compact. In this study, an electro-magnetic mechanism to enhance such low-frequency performance is examined. A common loudspeaker diaphragm is used as a passive interface to the cavity, with its moving-coil immersed in the magnetic field, and a shunt analogue circuit is attached. When the diaphragm is driven by the incident wave, the reactive Lorentz force exerts extra acoustic impedance. A MOSFET switch is added to periodically toggle between the shunt-off state, which is made damping-free in this study, and the shunt-on state which can almost forbid the diaphragm to vibrate if the shunt is close to a short circuit. The repeated transitions scatter a significant portion of the incident sound energy to frequencies other than the incident, with its peak scattering efficiency found when the switching is twice the frequency of the incident. The sudden removal of the Lorentz force by MOSFET switch-off creates a boost in the diaphragm response which is otherwise suppressed by the cavity stiffness, leading to much enhanced sound reflection.
Thin ultrasound non-contact airborne sensor using flexural vibration
Authors: Nakaoka Natsumi , Yamamoto Eimei , Koyama Daisuke
Published: November 2022

A non-contact acoustic sensing system using changes in the radiation impedance was proposed to detect the position of an object in front of an ultrasonic vibrator. The sensor is composed of a rectangular vibrating plate (20 × 100 × 1 mm3) and a PZT transducer (20 × 20 × 2 mm3). The sensor configuration was determined based on the results of a finite element analysis simulation. The flexural vibration modes were excited on the plate at two resonance frequencies, 29.7 and 46.2 kHz. The radiation angle of ultrasound from the sensor and the acoustic field between the object and the plate were compared at the two frequencies to investigate the detection characteristics. When an acoustic standing-wave field was generated in the air, the electrical impedance of the ultrasound transducers dramatically increased, indicating that the radiation impedance of the sensor was dependent on the object position. By measuring the amplitude of the input current to the transducers and the phase difference between the input current and the voltage applied to the sensor, the object position could be determined uniquely within a two-dimensional area.
Sound lateralization ability of elderly individuals in three onset conditions
Authors: Morita Kazumoto , Shiroki Moeko , Toi Takeshi
Published: November 2022

Authors had previously reported that elderly individuals could not sufficiently perceive the onset portion of the sound. To further this research, the current study varied the sound conditions in the onset portion to three—(1) condition in which the onset portion on the delayed ear side was silent, (2) condition in which sound was presented to the onset portion of the delayed ear side as well, (3) condition in which silence was inserted only during onset portion on the delayed ear, with no phase delay in the ongoing portion. Two sound frequencies of 1 kHz and 500 Hz were presented to 23 elderly participants and 22 young adults. Interaural Time Differences (ITDs) of 0.2, 0.4, 0.6, and 0.8 ms were relayed separately to each ear, in addition to the condition of zero ITD to both ears. In the experiments, a test stimulus sound was presented after the reference sound, and participants answered the direction of the sound from among three responses of “‘Right,” “Left,” or “Same” compared with the reference sound. The results of condition (3) revealed that the elderly participants could not perceive the onset portion of sound compared to the younger participants.
Investigating the influence of auditory streaming cues on binaural pitch fusion
Authors: Dean Nicole , Reiss Lina A. , Gallun Frederick J.
Published: November 2022

Binaural pitch fusion occurs when dichotic signals eliciting a different pitch are perceived as one sound. Previously, Oh et al. (ASA 2018) investigated the effects of auditory streaming cues on binaural fusion using a modification of the ABA streaming paradigm. A dichotic stimulus (fixed tone at frequency fref in the reference ear and variable frequency in the contralateral ear) was presented at alternating intervals with a “capture” tone at fref. Binaural fusion frequency range decreased, suggesting competition of the capture with the variable frequency tone for fusion. The present study added more capture tones, allowing for a galloping percept, and varied the inter-stimulus interval (ISI), both hypothesized to decrease binaural fusion by increasing salience of the capture tone. The dichotic stimulus was presented alternating with two or three repetitions of the capture tone at fref for triplet and quadruplet paradigms, respectively. ISIs of 40 or 80ms were used. Participants reported whether they perceived galloping or two streams. Preliminary data from 5 normal-hearing listeners suggest reductions in binaural fusion range with the triplet and quadruplet paradigms, and longer ISI, compared to the original paradigm. These findings indicate that auditory grouping cues may potentially reduce binaural fusion. [Research funded by NIH/NIDCD R01DC013307.]
How do non-native phonemes impact learning words in a second language? Evidence from eyetracking and EEG in a laboratory word learning study
Authors: Joanisse Marc , Desmeules Trudel Félix
Published: November 2022

A classic finding holds that listeners have significant difficulty categorizing and discriminating unfamiliar/nonnative phonemes. In the present study we examined how this influences learning new words in a second language (L2). Adult monolingual English speakers were trained on a pseudo-French vocabulary, by matching images of cartoon “aliens” to auditory CVCV words incorporating French vowels and consonants. Of interest was comparing words incorporating vowels similar to English to those containing highly unfamiliar vowels (here, the French high front rounded vowel [y]). Accuracy, eyetracking and event-related potentials (ERPs, measured with EEG) were then used to assess word recognition post-training. The neurocognitive measures indicated weakened recognition of words containing the novel [y] vowel, compared to words with vowels that more closely resembled those in English. Furthermore, we found that a training regime that emphasized discriminating easily confused vowels (i.e., [u] vs. [y]) during learning yielded somewhat improved recognition, both immediately after training and in a follow-up session. Interestingly, learning words containing the unfamiliar [y] vowel was not accompanied by improved AX discrimination of this vowel. The results have key implications for how we understand the role of phonology in L2 word representations, and for how we approach L2 teaching.
Estimating dispersion relations of ultrasonic guided waves in bone using a modified matrix pencil algorithm
Authors: Tran Tho , Li Boyi , Li Ying , Le Lawrence H. , Ta Dean
Published: November 2022

Guided wave ultrasound technology is well recognized for non-destructive testing. The technology is increasingly applied in bone characterization and imaging to evaluate bone strength and fracture risk. Cortical bone with porous microstructure induces substantial dispersion and attenuation effects on ultrasonic guided waves (UGW). Estimating frequency-dependent propagation characteristics of co-excited wave modes is significant to studying UGW propagation and developing wave-based approaches. This work implements a modified matrix pencil method to simultaneously compute modal wavenumber and attenuation coefficient from dispersive bone UGW signals with improved convergence rate and noise reduction ability. The dispersion estimation is formulated as a matrix pencil or generalized eigenvalue problem with Loewner matrices. The extracted eigenvalues are estimated complex wavevectors, in which the wavenumber and attenuation can be deduced from the real and imaginary components respectively. The performance of the proposed algorithm is demonstrated with low signal-to-noise-ratio synthetic and experimental datasets acquired using axial-transmission measurement settings. The computed dispersive features are validated via comparison with the theoretically calculated dispersion curves by semi-analytical finite-element simulation. The dispersive wave properties are accurately reconstructed in a computationally efficient manner and can be further utilized for bone parametric analyses and subsequently clinical bone health assessment.
Polarization spectrograms: Unraveling the polarization of ocean acoustic normal modes using the Stokes framework
Authors: Bonnel Julien , Dahl Peter H. , Dall'Osto David , Le Bihan Nicolas , Flamant Julien
Published: November 2022

Coastal oceanic environments act as dispersive waveguides for acoustic propagation, which is conveniently described using normal mode theory. Here we propose a framework to describe and estimate the polarization of normal modes, as measured using a single vector sensor in the water column. We introduce the Stokes parameters, four real-valued parameters widely used to describe polarization properties in wave physics, notably optics, but largely ignored in ocean acoustics. Analytic expressions for modal Stokes parameters are derived, and a signal processing framework to estimate them is introduced. The concept of polarization spectrograms, which enables visualization of the Stokes parameters in the time-frequency domain, is notably introduced. The whole framework is illustrated for dispersed impulsive signals using both simulations and experimental marine data collected during the Seabed Characterization Experiment. [Work supported by the Direction Générale de l’Armement and by the Office of Naval Research.]
Lisa Zurk and Matched Field Processing—Her early career at MIT Lincoln Laboratory (1996–2005)
Authors: Baggeroer Arthur B.
Published: November 2022

After completing her doctoral program in electromagnetics in 1995 Lisa decided to go to MIT Lincoln Laboratory to work on Matched Field Processing (MFP) in a nascent group formed for sonar and underwater acousitcs efforts. Then MFP introduced new methods of beamforming which were found to be sensitive to assumptions made for the sonar system, the environment and array processing. The so called adaptive one were especially sensitive. Lisa examined the importance of source motions and array are important for any sonar. In this context she introduced (i) mode based rank reduction, or modal MFP, (ii) array tile corrections, (iii) a “dynamic” snapshot correction method a focused MFP while the source is moving similar to beam steered MVDR, and (iv) “instantaneous” data and model based interference filtering. All these were subsequently discovered by later MFP researchers. Lisa and her coauthors were well ahead of there time.
Focusing on motion and averaging the diagonal: Lisa Zurk’s many contributions to passive sonar array processing
Authors: Buck John R. , Erdim Savas , Liu Yang
Published: November 2022

Lisa Zurk’s numerous contributions to passive sonar signal processing include motion compensation and regularizing sample covariance matrices (SCM) in snapshot deficient environments. While working at MIT Lincoln Labs, Lisa and colleagues compared the performance of several motion compensation methods including mode-based rank reduction and target motion compensation, or focusing, on the Santa Barbara Channel Experiment dataset [Zurk, Lee & Ward, JASA, 2003]. Later at Portland State, Jorge Quijano and Lisa developed methods for regularizing the SCM through Toeplitz averaging, followed by maximum entropy extrapolation of the SCM to additional lags, [Quijano & Zurk, JASA, 2017]. Toeplitz regularization found significant application in developing “augmented covariance matrices” for DOA estimators on sparse arrays. This talk reviews some of Lisa’s contributions to adaptive beamforming and highlights how some of her contributions inspired research in the UMass Dartmouth Signal Processing Group. [Work supported by ONR Code 321US.]
Phase space approximations for dispersive propagation
Authors: Loughlin Patrick
Published: November 2022

Sounds propagating in shallow water can undergo frequency-dependent changes, specifically damping and dispersion. Phase space analysis and approximations have yielded a clear physical picture of these frequency-dependent effects. In particular, in position-wavenumber phase space, each mode propagates, approximately, at constant velocity given by its group velocity. In time-frequency phase space, each mode undergoes a frequency-dependent time shift given, approximately, by its group slowness. The effects of damping (i.e., a complex dispersion relation) are also clearly manifest. We review and extend various phase space approximations for dispersive propagation, and explore their accuracy. We show that one can recover the exact spectral magnitude and group delay of the propagating pulse from the phase space approximations. One reason the approximations are generally very good is that one does not have to assume that the initial spectrum is slowly varying, as is done, for example, in the stationary phase approximation.
A phase-shifting method for computation reduction for high-frame-rate imaging
Authors: Lu Jian-yu
Published: November 2022

High-frame rate (HFR) imaging using steered plane wave (SPW) or limited-diffraction beam has a high-temporal resolution and thus has found many applications. To further study the HFR imaging methods, computer simulations were performed. However, the simulations require a large number of computations, especially for 3D imaging with 2D array transducers for a large imaging volume. In this paper, a phase-shifting method was developed to reduce the number of computations. In the method, the grid points of the transmit and receive beams were calculated at 1-mm interval in the depth direction that is perpendicular to the transducer surface. The interval is much larger than the 1/4 of the 0.58-mm wavelength required for an accurate interpolation for millions of random scatterers in pulse-echo response without aliasing. Since the HFR imaging uses either SPW or LDB, the wave vectors of these beams are fixed at each frequency. Due to the fact that the amplitude of ultrasound beams changes very little over a couple of wavelengths, the interpolation in the depth direction was replaced with a phase shift. Results show that images reconstructed with the phase-shifting method removed the artifacts caused by aliasing when conventional tri-linear interpolations were used for 3D imaging.
The role of histotripsy pulsing rate on clot degradation when combined with thrombolytic drug
Authors: Toledo-Urena Joel , Centner Connor , Bhargava Aarushi , Bader Kenneth B.
Published: November 2022

Histotripsy is a bubble-based focused ultrasound therapy under development for tissue ablation, including the treatment of venous thrombosis. Histotripsy is effective for lysing erythrocytes within the clot, but not its fibrin structures. Our prior work has demonstrated when combined with a standard-of-care thrombolytic drug, histotripsy can degrade both cellular and extracellular clot components. To date, only histotripsy pulsing rates of 20–40 Hz have been tested for this combination approach. Previous studies have shown the pulsing rate influences the bubble dynamics, and therefore treatment outcomes. The goal of this study was to determine the effect of pulsing rate on clot degradation. Human whole blood clots were exposed to thrombolytic drug and histotripsy pulses. The pulsing rate ranged from 5 to 500 Hz. Following treatment, metrics of clot degradation (change in clot mass, and markers of erythrocyte and fibrin degradation) were tabulated. An improvement in treatment outcomes was observed for the combination approach relative to histotripsy alone for the 50 Hz pulsing rate. At 500 Hz, the benefit of combining thrombolytic drug with histotripsy was not well defined. Overall, these results indicate the pulsing rate has a role in the ablative and drug delivery capacity of histotripsy.
An ex vivo experimental demonstration of passive acoustic mapping through the human spinal column
Authors: Farbin Grace , Frizado Andrew , O'Reilly Meaghan
Published: November 2022

The delivery of drugs to the central nervous system is grossly limited by the presence of the blood-brain and blood-spinal cord barriers. These barriers can be transiently permeabilized using low-intensity focused ultrasound combined with circulating microbubbles. The spectral content of acoustic emissions from cavitating microbubbles can be analyzed to control for and mitigate potential bioeffects. However, there is a large degree of uncertainty as to where these cavitation signals are originating. Passive beamforming of microbubble emissions recorded using multi-element arrays can enable spatial mapping of cavitation activity. Passive acoustic mapping (PAM) is challenging to implement in the presence of an intervening bone layer but has been successfully demonstrated through the skull. Here we present the first experimental demonstration of PAM through human vertebral bone. A tube containing flowing microbubbles was placed in the canal of ex vivo human thoracic vertebrae (stack of 3 vertebrae) and excited (250 kHz) through the right laminae. A 64-element large aperture 2D array was used to receive the harmonic emissions through the left laminae. Reconstructed maps successfully localized the cavitation activity to the spinal canal. Future work will examine effects of phase/amplitude correction, receiver number, and location of the cavitation relative to the vertebral anatomy.
Passive and Doppler-based assessment of cavitation activity induced by pulsed focused ultrasound
Authors: Song Minho , Sapozhnikov Oleg A. , Wang Yak-Nam , Hwang Joo Ha , Khokhlova Tatiana D.
Published: November 2022

Pulsed focused ultrasound (pFUS) exposures utilizing short, nonlinearly distorted pulses at low duty cycle have been shown to enhance drug and gene delivery to targeted tissue through inertial cavitation activity. Passive cavitation detection (PCD) and mapping of broadband emissions are current conventional methods to monitor and quantify cavitation but provide limited spatial resolution. Here, plane-wave Doppler imaging was used with PCD to quantify pFUS-induced cavitation in ex vivo bovine tissues and in vivo surgically exposed porcine liver, kidney, and pancreas. A 1.5 MHz FUS transducer (aperture 75 mm, F-number 0.75) was used to deliver 60 pulses (duration 1 ms, 0.1% duty cycle, focal pressure p+ = 70i–110 MPa, p− = 13–20 MPa). A coaxially mounted ATL P7-4 ultrasound imaging probe was used for PCD during the FUS pulse, and Doppler and B-mode sequences. Disrupted tissue areas were collected for histology and compared to Doppler power images. Maximum Doppler power was found to correlate to broadband noise level for each FUS pulse. The Doppler power map integrated over the exposure was observed to correlate spatially with tissue disruption area from histology, which thus represents a promising real-time metric for quantifying cavitation activity induced by pFUS exposures. [Work supported by NIH R01CA154451, R01EB025187, and R01EB23910.]
Infrasound propagation with realistic terrain and atmospheres using a finite-difference time-domain method
Authors: Bishop Jordan W. , Blom Philip S. , Fee David
Published: November 2022

Numerous infrasound observations and complementary numerical simulations have shown that infrasound propagation is strongly influenced by terrain within approximately 10 km from the source. Recent computational efforts using ray theory have shown that terrain influence extends over hundreds of km and is especially strong for waves ducted in the troposphere. Wind and temperature gradients also have a strong influence on propagation at these distances, which suggests that both terrain and atmospheric structure need to be accounted for in waveform modeling at a wide range of distances. Here we show preliminary results from numerical simulations of linear acoustic propagationthrough a moving, inhomogeneous atmosphere using a finite-difference time domain propagation code. We compare our synthetic waveforms in two and three dimensions with existing community infrasound propagation codes and discuss future developments, including open source licensing. Finally, we present preliminary comparisons between modeling and observations from a large-scale explosion at the Utah Testing and Training Range. This scenario highlights the importance of using full-wave modeling compared to ray methods to explain the observed waveforms. [Work funded by the Defense Threat Reduction Agency. Cleared for release.]
RAMP summer bridge: Room acoustics: Connecting research, academics and mentoring
Authors: Remillard Grace , Keefe Aidan , Le Nguyen , Thompson Charles , Chandra Kavitha
Published: November 2022

The Research, Academics and Mentoring Pathways (RAMP) to Success summer bridge program at the University of Massachusetts Lowell prepares new engineering students from all majors for an early transition from high school to college. Over the last five years, RAMP has engaged 107 students, the majority being women and underrepresented minorities, in a six-week research, academics and mentoring experience. During RAMP, students are enrolled in Calculus and Introduction to Engineering courses, earning six credits towards their degree pathway. Groups of 5–6 students take on research projects with engineering faculty while also meeting weekly with professionals from industry. The structuring of a room acoustics research project is presented. A project-based learning model helps build skills in collaborative problem solving while also supporting each student to find authentic interest in the research. The project integrates experiments on measuring room impulse responses and spatial variation of source pressure amplitude in rooms of different sizes with a model-driven analysis of the data collected. Concepts of reverberation time, backward integration and room constants reinforce calculus concepts being studied. Coding experiments on rendering speech and music through measured impulse responses and filters created interest across a range of acoustics topics from concert halls to virtual audio.
Analysis of spark-generated waveforms coalescing in air using schlieren imaging
Authors: Willis William A. , Valdez John A. , Tinney Charles E. , Hamilton Mark F.
Published: November 2022

Mach waves generated by turbulent structures in supersonic jet flows have the potential to intersect and coalesce, a process proposed as a significant contributor to acoustic waveform steepening in the near field of a jet and to the noise referred to as crackle [Baars et al., AIAA (2013); Fiévet et al., AIAA (2016)]. Numerical simulations of intersecting waveforms have demonstrated that coalescence can lead to increased steepening that is dependent on intersection angle, waveform duration, and geometrical spreading [Willis et al., AIAA (2022)]. In this study, two simplified experiments involving a spark source in air are examined. The first involves grazing incidence on a rigid plane to model symmetric intersection between waveforms. The second involves intersecting waveforms emanating from side-by-side openings in a 3D-printed enclosure. Measurements of nonlinear evolution were made for the intersecting waveforms produced with each experimental setup and compared with measurements made for one waveform alone. Schlieren images of the coalescing waves allow for comparison of waveform steepening between the two cases without the limitations imposed by microphones. The measurements permit assessment of the extent to which coalescence enhances waveform steepening. [WAW is supported by the ARL:UT Chester M. McKinney Graduate Fellowship in Acoustics.]
Aeroacoustic and aerodynamic interaction effects between electric vertical takeoff and landing rotors
Authors: Resende Coelho Gustavo , Goldschmidt James D , Tingle Henry J. , Ifju Peter G. , Lawrence Ukeiley , Goldman Ben , Secchi Maicon , Miller Steven A.
Published: November 2022

Electric vertical take-off and landing (eVTOL) aircraft are characterized by their unconventional wing and electric rotor configurations, which involve both side-by-side and tandem rotor configurations. These configurations create unique aerodynamic and acoustic flow-fields. We numerically investigate the interaction effects between rotor pairs as well as their individual and combined acoustic radiation. We examine horizontal and vertical spacing, rotor tilt angles, and forward flight effects. Performance is characterized by thrust coefficient, blade passage frequency (BPF) sound pressure level (SPL), and overall sound pressure level (OASPL). This study is performed with a mid-fidelity aerodynamic solver, Dust, which is used to predict the aerodynamic flow-field. The tonal acoustic pressure at observer positions is predicted via the Farassat F-1A solution of the Ffowcs Williams and Hawkings equation utilizing the aerodynamic flow-field. The configurations studied show strong aerodynamic interaction effects in thrust, as well as out-of-plane acoustic radiation from the aft rotor. Base predictions of thrust and noise are validated via experimental measurement. As rotor separation decreases, we observe that aft rotor thrust decreases and BPF SPL increases. The most forward rotor, however, is marginally impacted by the interactions. [This research is supported by Archer Aviation Inc.]
Low frequency photoacoustic optical absorption measurement of aerosols
Authors: Case John A. , Smith Robert W.
Published: November 2022

Atmospheric optical absorption, including the contribution from aerosols, is important in modeling optical propagation and for climate research. An open-celled photoacoustic aerosol sensing system was developed to operate at 150 Hz for measurement of absorption aerosols up to 3 microns in diameter with the design goal to achieve a sensitivity adequate to measure an absorption corresponding to a 1/e optical absorption length of 1 Mm. The advantage of a photoacoustic system is that it measures optical absorption only and is not sensitive to optical extinction due to scattering at low absorption levels. The system was calibrated against an existing black carbon absorption measurement unit made by Droplet Measurement Technologies, which operates at a shorter optical wavelength and higher acoustic frequency. With previous work focusing on measuring optical absorption by black carbon aerosols [J.A. Case and R.W. Smith,182nd meeting of the Acoustical Society of America in Denver, CO (5aPA)], this work covers measuring absorption by wet salt solutions of similar salt concentration to that oceanic aerosols. Experiments with the current system showed an anomalous photoacoustic signal appearing in the absence of any aerosols. Several solutions to eliminating the unwanted signal from the desired measurement are proposed and tested.