bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and construction of the Texas Christian University impedance tube
Authors: Elrod Claire , Hall Hubert S.
Published: July 2024

The two-microphone impedance tube test method is a well-established and widely used technique for determining the acoustic absorption coefficient and impedance ratio of materials. This method uses two closely spaced microphones to simultaneously measure the incident and reflected sound waves. A two-microphone impedance tube measurement system made of 6061-T6 Aluminum with a diameter of 3 inches, a 0.5 inch wall thickness, and microphones spaced 2.7 inches apart has been constructed for undergraduate research at Texas Christian University (TCU). These geometrical values suggest a usable frequency range of 50 Hz to 2637.77 Hz as referenced in ASTM Standard E1050-19. Validation of the system was achieved by taking measurements on Owen Corning Type 705 pressed fiberglass board with a 1-inch thickness and comparing them to absorption data provided by the manufacturer. Additional validation measurements were taken without a test sample in place. All validation tests suggest that the TCU impedance tube is an accurate measurement system.
Building a mathematical model for a simple harmonic oscillator that uses educational methods found in both physics education research and in the language disciplines that make it accessible to undergraduate students in an introductory musical acoustics course
Authors: Linz Jill A.
Published: July 2024

At the basis of any course in acoustics is the fundamental idea of the simple harmonic oscillator. The term alone is confusing to students with little to no background in physics or math. For courses in musical acoustics at the undergraduate level, this topic is often minimized due to the lack of preparation. This, in turn, results in a more superficial approach to the advanced topics. While deriving the mathematical treatment from first principles is out of reach to these students, approaching the math itself as a language where they are building a description of a simple mass and spring system in their new, yet somewhat familiar, language can be accomplished through pictures, graphs and hands on activities. Students begin to build a vocabulary of “words” that can be strung together in “sentences” that tell the story of how the motion of a mass on a spring is produced. Emphasis is placed on the analogous comparison of physical properties by relating variables such as amplitude and frequency to that of volume and pitch. This model can then be used as a building block to the understanding of how sound is produced, propagated and perceived.
Hearing your voice in the crowd: How do bats echolocate in dense swarms?
Authors: Kloepper Laura , Blackstock Stephen P. , Tuninetti Amaro , Vanderelst Dieter , Haberman Michael R.
Published: July 2024

In order to navigate their environment and find food, bats rely on comparing returning echoes to their broadcast signal. Through decades of research, we have a good understanding of how single bats accomplish this task, but we still don’t know how bats in dense groups can echolocate without interference from others. A spectral Jamming Avoidance Response (JAR) has long been proposed as one strategy, in which bats flying together shift frequencies to avoid interference. Recent work, however, questions this strategy, and suggests bats may not use any JAR for sensing in groups. Bats have long served as bioinspiration for active sensing devices, so understanding strategies for collective sensing in bats has implications for applications of synthetic sonar. In this talk, I will review the “hot topic” of bat biosonar in swarms and show new data from our research that suggests spectro-temporal variation may play a role for sensing in even the largest, densest bat swarms.
Improvements to a mobile app for community noise and assessment data collection
Authors: Riegel Kimberly A. , Resko Jody
Published: July 2024

A mobile phone application was developed to collection health history, real time noise levels and participants' perceptions. The goal of this application is to collect data that can directly link community response, noise levels and community health from a large number of participants. This will help identify where noise is causing issues related to physical and mental health on a community scale. In order to identify these effects at a community level large numbers of responses are critical. Ease of use is essential to ensure that participants remain willing to participate in the study and continue to submit samples. This needs to be balanced with the usefulness of the data collected by the public. Previously, a beta version of the app was deployed to evaluate the useability and effectiveness of data collection. Several issues with the data collection were identified and improvements to the app were implemented. Evaluation of the data and data visualization options will be presented using the most recent version of the application.
Revised comprehensive new definition of noise
Authors: Fink Daniel
Published: July 2024

A revised comprehensive new definition of noise is proposed. Noise: a) For living things, noise is unwanted and/orharmfulnd. b) In engineering and electronics, noise is any unwanted disturbance within a useful frequency band, such as undesired lectric waves in a transmission channel or device. c) In scientific measurements, noise is erraic, intermittent, or statistically random oscillation. The revised comphrehensive new definition builds on the Acoustical Society of America/American National Standards institute definition to include technical considerations, and acknowledges the harmful effect of noise on plants. It updates the noise definition presented at the 2019 Acoustical Society of America winter meeting, noise is unwanted and/or harmful sound. Unlike the standard definition, noise is unwanted sound, that new definition emphasized that unwanted sound is harmful, able to cause adverse auditory and non-auditory health effects, and that wanted sound can also caus auditory damage. The Proceedings of Meetings on Acoustics article based on that presentation has been cited 37 times. The prevvious new definition opens the 2021 American Public Health Association policy statement, Noise as a Public Health Hazard, was adopted for use by the International Commission on Biological Effects of Noise (ICBEN) in 2023, and added to the ICBEN Constitution.
Development of a scanning acoustic microscopy-based structural prior for microtexture region characterization
Authors: Homa Laura , Lesthaeghe Tyler , Cherry Matthew , Blasch Erik , Wertz John
Published: July 2024

Nondestructive evaluation (NDE) plays a crucial role in ensuring aircraft availability. The current NDE paradigm often relies on mono-modal testing and signal-over-threshold criteria to provide robust defect or damage detection, not characterization. One example is found in the risk-based management of surface-breaking cracks in metal, where cracks of a given size can be detected by eddy current testing (ECT) with a calculable probability. Yet, there are cases where detection proves insufficient. Consider the case of microtexture regions (MTR) found in certain titanium alloys, which can increase the risk of cold dwell fatigue failure when found above a certain size and in specific orientations relative to the surrounding material. At present, the size and orientation of MTR cannot be characterized using only one NDE modality. In this work, a data fusion-based solution to MTR characterization is developed. First, two inspection methods—scanning acoustic microscopy (SAM) and ECT—are selected, where each method is individually capable of only partial characterization. Then, matching component analysis is used to develop a surrogate forward model relating MTR orientation to ECT output. This data is then inverted using boundaries provided from the SAM data as a structural prior.
A novel ultrasonic technique for the inspection of a plate heat exchanger
Authors: Dubey Pooja , Declercq Nico
Published: July 2024

Biofilm formation in process industries, water treatment devices, and drinking water pipe networks pose a significant risk to public health and cause a variety of operational issues. One of the major challenges is the inspection of biofilms in heat-exchanging devices such as plate heat exchangers. A plate heat exchanger (PHE) is integral to food industries, water treatment plants, and others. Conventional techniques for cleaning biofilm formation in these plates (foulant) include chemical cleaning, steam, and hydro-blasting. However, they are inefficient and labor-intensive because of limitations such as increased handling risk, over-cleaning, and corrosion. Thus, developing novel techniques for real-time monitoring of biofilm growth on these devices is critical for efficient working. Previous studies were restricted to the development of ultrasound-assisted heat exchangers to reduce the deposits in these plates. However, only a few studies have investigated ultrasound as a probable monitoring tool. Thus, this research aims to explore the nonlinear ultrasonic parameters using the second harmonic generation technique as a real-time tool for monitoring biofilms in PHE. The proposed research will help design more effective ultrasonic-assisted plate heat exchangers to achieve maximum heat transfer efficiency.
Quantitative ultrasonic characterization of Ti-6Al-4V components with surface roughness
Authors: Assalita Sydney N. , Cook Olivia J. , Arguelles Andrea P.
Published: July 2024

Ultrasonic immersion testing enables nondestructive characterization of material microstructure through quantitative linkages between wave propagation parameters and features of interest. However, accurate measurements of metrics such as wave speed and attenuation generally require smooth test samples to ensure the reflected wave packets are not distorted. Thus, rough surfaces are mechanically polished before ultrasonic testing, which compromises the nondestructive nature of the measurement, distorting the sample geometry and imparting local damage. This challenge is particularly salient with the advent of manufacturing processes, such as metal additive manufacturing, that result in rough samples that must be characterized for heterogeneities in their as-manufactured state. This work examines the influence of surface roughness on longitudinal wave speed and attenuation in wrought and additively manufactured Ti-6Al-4V specimens. Samples are measured in an ultrasonic immersion setup before and after mechanical polishing using varying transducer frequencies and focal profiles. The resulting data informs the error generated in ultrasonic measurements as a function of roughness parameters, thereby informing the sample preparation needed for desired precision levels. Lastly, new measurement protocols are explored to correct for the presence of surface irregularities in a point-by-point fashion. This work was supported by the Robert W. Young Award for Undergraduate Student Research.
Localizing sounds revolving at very high velocities: An auditory wagon-wheel effect
Authors: Kemp Noa , Lefeuvre Ulysse , Tarlao Cynthia , Guastavino Catherine
Published: July 2024

Localizing sound sources as they move around us is a critical function of the auditory system. Yet most research focuses on static sound sources or sources moving at slow velocities. The present work explores circular trajectories at very high velocities well above the velocity at which we lose the sense of direction (∼2.5 rot/s with white noise). As the number of rotations per second approaches the fundamental frequency of the spinning sound, a sense of direction re-emerges. This creates what has been described informally as the auditory equivalent to the wagon-wheel effect: the sound appears to move in one direction when the velocity is below the fundamental frequency, and it appears to move in the opposite direction when the velocity is above the fundamental frequency. We report on two experiments testing this effect with a 200-Hz complex sound using adaptive VBAP spatialization on a 16-loudspeaker array. Experiment 1 (N = 15) confirmed that participants perceived opposite directions when the velocity was below or above the fundamental frequency. Experiment 2 (N = 7) explores the relationship between this effect at very high velocities and the ability to track sound at slower velocities. Preliminary findings suggest some overlap between localization processes at slow and high velocities.
Characterizing the primary resonator in the cochlea
Authors: Lin Wei-Ching , Macic Anes , Nam Jong-Hoon
Published: July 2024

The cochlear traveling waves are explained by a bank of independent resonators coupled longitudinally by lymphatic fluids. Many cochlear models require at least two resonators to account for observed responses. To investigate the resonators in the cochlea, we used high-resolution optical coherence tomography to measure 2-D vibration patterns of the organ of Corti in acutely excised cochleae from young Mongolian gerbils. The excised tissues were acoustically stimulated. The transverse and radial vibrations of the basilar membrane (BM) and the tectorial membrane (TM) were obtained over their radial span. The BM vibrated from the primary to a higher mode transversely as the stimulating frequency increased. The higher-order mode appeared near the best frequency (BF) of the measured location. Meanwhile, the TM showed no sign of a mode transition up to 1 octave above the BF in radial or transverse vibrating patterns. Within the physiological frequency range, the BM exhibits the characteristic behavior of a resonator. In contrast, the TM does not. Our results suggest that the TM as the second resonator is not the universal mechanism across the entire cochlea.
Acoustic indicators of voice quality in the context of social support
Authors: Hernández Melo Luisa E. , Pell Marc D.
Published: July 2024

Is social support communicated throught the subtle, yet powerful, acoustic variations in speech? This study attempted to answer this question by testing whether acoustic parameters vary when expressing social support. Participants underwent an experiment in which they watched video testimonials of a woman describing either a neutral subject or a sensitive, emotionally-charged experience. After this, participants provided voice messages to the person appearing in the testimony. Employing the openSMILE toolkit, we extracted from these speech responses the Geneva Minimalistic Acoustic Parameter Set (GeMAPS), a set of emotion-related acoustic features. Our investigation reveals an acoustic profile characteristic of supportive speech, distinguished by changes in the Alpha ratio, spectral slope, and the Hammarberg index — parameters representing the high-frequency content and spectral balance. These acoustic differences not only help to differentiate supportive utterances but also characterize its voice quality, thereby enhancing the emotional richness of this affective stance. Our research findings have potential applications in therapeutic and communication settings and open avenues for further exploration in speech science.
Spatial release from masking and pupillometry
Authors: Livingstone Rebecka , Patro Chhayakanta , Srinivasan Nirmal Kumar
Published: July 2024

Speech perception in complex listening environments is driven by both the auditory factors and the cognitive abilities. There are various ways in which cognitive processing while perceiving speech could be measured. In the present study, we applied pupillometry to assess cognitive processing load resulting due to various demands imposed by the presented speech. PupilCore eye glasses were used to capture pupil dilation while doing two tasks: 1. Speech recognition task when the target and the maskers were either colocated or spatially separated, and 2. a localization task where the listeners had to discriminate whether the two sounds originated form the same location or different locations. Initial data analysis revealed different patterns of pupil dilations for the collocated and spatially separated conditions. For the collocated condition, the listeneing effort had a u-shaped pattern as the target-to-masker increased whereas the listening effort linearly increased as the target-to-masker ration increased for the spatially separated condition. Also, the pupil dilation decreased as the localization task became easier. The intricate relationship between listening effort and listening environment will be discussed in detail.
Relationship between attention and spatial processing abilities
Authors: O'Neill Sadie , Barkhouse Morgan , Patro Chhayakanta , Srinivasan Nirmal Kumar
Published: July 2024

Reduction in an individual’s hearing ability and their working memory (WM) capacity are hypothesized to be two of the major contributors to the decline in listener performance seen in complex listening environments. Generally, the improvement in speech intelligibility that may occur when a target is spatially separated from competing talkers is quantified as spatial release from masking (SRM). The goal of this study was to estimate working memory capacity based on a divided attention version of the classic spatial release from masking task (the temporal overlap task) and the classic abbreviated reading span task (aRST). Temporal overlap threshold was estimated by adaptively varying the maximum amount of temporal overlap of the signals where a listener could still correctly identify the speech source presented directly ahead of the listener when the speech material was either colocated or spatially separated. Initial analyses of the data revealed a strong relationship between SRM and temporal overlap thresholds, suggesting that SRM is driven by the listeners’ ability to modulate their attentional mechanisms. The relationship between SRM, temporal overlap thresholds, and reading span measures will also be discussed.
How to model vibration damping in complex materials and structures
Authors: McDaniel James G.
Published: July 2024

Damping is perhaps the most challenging aspect of any model where damping is relevant. For example, an accurate damping model is often important when modeling vibration of metamaterials, vehicles, and machinery. Mass density is easily and accurately calculated from simple measurements of weight and volume. Elastic moduli are easily and accurately calculated from simple measurements of stress and strain. Large databases of mass density and elastic moduli are readily available and accurate for most materials. But damping is elusive. Many models have been proposed in many different research communities. Published numerical values for the parameters are in short supply. But the choice of damping model may dramatically affect the predicted response. The damping model is likely to make the difference between a useful result and a useless result. This presentation seeks to collect and summarize knowledge related to damping to help us model damping more accurately and more efficiently. The three most common models of damping are reviewed. These are material damping, viscous damping, and Coulomb damping. For each, an analysis is presented that begins with the fundamental assumptions and ends with the inclusion of the damping mechanism in finite element models. [Work supported by ONR under Grant N00014-22-1-2785.]
Unflappable? Buckeyes say “whatever” to English flapping rules
Authors: Fulop Sean A. , Ryan Mark P. , Scott Hannah J.
Published: July 2024

American English dialects generally use a 'flap/tap' consonant in some places where /t/ or /d/ is both indicated in the spelling and used in some other dialects. What environments allow a flap to occur instead of /t/ or /d/? This question has inspired considerable debate in the literature, but a consensus has settled on a lack of stress on the syllable following as being the most critical factor in the occurrence of a flap word-internally. This study investigates the occurrence of flaps in the Buckeye Corpus of American English (40 speakers from Columbus, OH), detailing the frequency of flapping in various phonetic environments. One significant finding is that all speakers produced some flaps word-internally before syllables bearing primary or secondary stress (as in “whatever”).
Investigating post-focus compression in code-switching: A comparative study of Twain Mandarin and English
Authors: Kuo Grace
Published: July 2024

On-focus pitch range expansion is a documented phenomenon in both English and Mandarin Chinese. However, the presence of post-focus compression (PFC) contrasts with its absence in Taiwan Mandarin, a regional variant of Mandarin Chinese. This discrepancy becomes particularly intriguing in the context of code-switching, which provides a unique lens to observe the interplay between these two languages. This study probes the manifestation and cognitive processing of PFC in code-switching constructs, employing a bilingual paradigm between English and Taiwan Mandarin. Through a carefully designed production experiment, this research addresses two questions: (a) Is PFC evidence in the code-switching utterances of simultaneous and early bilinguals? (b) Is there an observable correlation between the emergence of PRC in linguistic output and the language proficiency of late bilinguals, potentially indicating a transfer effect from Taiwan Mandarin to English? Anticipated results may substantiate the presence of linguistic transfer in the code-switching sentences of bilingual individuals of diverse English proficiencies. Furthermore, the implications of these findings may extend to pedagogical strategies, offering insights into the deployment of code-switching within multilingual educational settings.
Inversion of partially spanning array data for normal mode parameters using seabed impedance constraint
Authors: Hursky Paul
Published: July 2024

Previous work with fully or nearly spanning vertical line arrays has shown that normal mode shapes can be identified as the eigenvectors of the covariance matrix averaged over lengthy source tracks that served to de-correlate the modes. Recent work with partially spanning arrays has used compressed sensing or super-resolution methods like MUSIC to estimate mode wavenumbers. These methods assume the sound speed profile is available, but not the seabed properties. We will present another alternative for inverting for normal modes under these conditions, including a partially spanning vertical line array, in which sets of candidate modes are restricted to modes that satisfy the same impedance boundary condition at the seabed. Each distinct impedance condition defines a physically consistent set of modes. Thus, our inversion is sparse in impedance conditions. We demonstrate how the normal modes resulting from this process are used to form matched field processing replicas that recover source tracks in range and depth.
Dual-repetitive pilot aided parameter estimation for underwater orthogonal frequency division multiplexing acoustic communications in the presence of strong composite noise
Authors: Liu Zhiqiang
Published: July 2024

In this work, a novel design of signaling parameters and pilot placement is proposed for supporting robust underwater orthogonal frequency division multiplexing acoustic communications in the presence of strong composite noise. The proposed design allows for high-resolution estimation of various channel parameters that are essential to successful symbol recovery. Receiver processing algorithms are developed by exploring special properties of the received signal that hold valid despite complicated channel and noise effects. These algorithms are efficient since they reuse the same set of pilot symbols for multiple tasks of estimation that often require separate sets of pilots. They are also extremely effective because they largely avoid the effects of noise even when the noise is composite. The performance of these algorithms is evaluated via both extensive simulations and an at-sea experiment.
Effects of seabed corrugation and stratification on 3D acoustic propagation along the New England Shelf Break
Authors: DeCourcy Brendan J. , Lin Ying-Tsong , Chaytor Jason
Published: July 2024

Acoustic signals transmitted and recorded during the New England Shelf Break Acoustics Experiment in 2021 (NESBA) display evidence of complex scattering effects which were not captured in in situ modeling efforts. In particular, although the acoustic parabolic equation models used can predict later arrivals of a single transmission, initial arrivals show mismatch between model predictions and observation. In this presentation, estimates of sub-bottom sediment structure are supplemented by a high-resolution model of the bathymetry to simulate 3D sound propagation across a realistic seabed. The influence of the seabed corrugation and stratification on acoustic arrival times is examined in the context of the NESBA environment. [This research is supported by the Office of Naval Research].
Acoustic arrival patterns in the Beaufort duct using normal mode and ray trace acoustic prediction models
Authors: Desrochers Jessica , Van Uffelen Lora , Muniz Alexander
Published: July 2024

The stratification of the Beaufort Sea has experienced significant changes over the last few decades resulting in a subsurface duct between 100- and 300-meters depths, known as the Beaufort Duct. This duct allows for long-range acoustic transmissions due to little interaction with the seafloor or sea surface. Acoustic arrival predictions for broadband acoustic sources centered around 250 Hz, such as those deployed in the Beaufort Sea in 2016–2017 show a peak acoustic arrival prior to the final cutoff centered on the sound speed minimum in the duct. This reverse dispersion feature in the acoustic time front can be connected back to the unique ducting features in the sound-speed profile. This relationship is explored using normal mode modeling and geometric optics. Modal speed predictions and ray path lengths and travel times are used to interpret the acoustic arrival patterns, particularly the dispersion feature present in the acoustic time front.
The effects of bathymetry on estimating the depth of a source in range-dependent environments with a single hydrophone
Authors: Kirsteins Ivars P.
Published: July 2024

The effects of varying or range-dependent bathymetry, e.g., such as a sloping bottom, on the depth resolution characteristics of single hydrophone matched field processing (MFP), e.g., width of depth main-lobe as a function of source and receiver nominal positions, is not well understood. A major challenge is that in the case of range-dependent environments there are generally no analytical representations for the pressure field, thus requiring numerical methods for their evaluation. To provide some theoretical insights into how the shape of the bathymetry and locations of the source and receiver influences the MFP depth ambiguity function, we study the case of an ideal wedge with perfectly reflective pressure-release boundaries using the analytical solutions of Buckingham [1]. We derive a simple approximation for the depth ambiguity function main lobe width and compare it against the theoretical result for an ideal range-independent environment [2] and then numerically for a penetrable wedge and more realistic shelf-like environments. M.K. Buckingham, “Acoustic propagation in a wedge-shaped ocean with perfectly reflecting boundaries,” NRL report 8793, March 1984. M. Cheney and I.P. Kirsteins, “Resolution of matched field processing for a single hydrophone in a rigid waveguide,” J. Acoust Soc. Am. 151, pp. 3186–3197, 2022.
Deconvolution of the waveguide impulse response for source localization at low frequency
Authors: Le Courtois Florent , Kinda Bazile , Lajaunie Myriam
Published: July 2024

Matched-mode processing (MMP) methods have been widely investigated for source localization and geoacoustic inversion. For horizontal line arrays (HLA), it aims at retrieving the horizontal wavenumbers and thus at inferring source range and bearing. In this work, the matched-mode is performed by applying the deconvolution of the waveguide response in a narrowband context in order to improve the localization accuracy. Deconvolution usually refers to a sparse framework when the number of sources is smaller than the number of sensors of the HLA. The Orthogonal Matching Pursuit algorithm is then used in this work. First results from numerical simulations for Pekeris waveguide highlight better localization accuracy than MMP. The deconvolution shows as well stronger robustness to mismatch in the sound speed values of the seabed. Results from measurement campaign, involving large HLA, low to ultra-low frequency and water depth up to 1500 m are investigated as well.
Optimal bi-state acoustic metamaterial for broadband sound absorption and diffusion: A real-estate dilemma
Authors: Ballestero Eric , Meng Yang , Sheng Ping , Tournat Vincent , Romero-Garcia Vicent , Groby Jean-Philippe
Published: July 2024

The advent of metamaterials has given a new breath to acoustic treatment design due to their ability to target much lower frequencies within deep-subwavelength dimensions. However, many practical applications may require a multi-functional structure instead of a static one with a single purpose and, thus, overturn geometry-specific performance. Such hybrid acoustic treatments have been an active field of research for the past decades, in which a trade-off between different acoustical mechanisms has to be struck, the major issue being the inversely decreasing returns for each acoustical mechanism, i.e., the more of one the less of the other. The aim of the present work is to build over previous metamaterial strategies and design a dynamic bi-state passive acoustic metamaterial that can change its acoustic properties within the same structural volume, going from highly absorbent (α ∼ 0.85) to diffusive (δ ∼ 0.65) over more than one octave for each acoustic phenomenon, i.e., 400–1100 and 1000–2500 Hz for absorption and diffusion, respectively, with an overall thickness L = 12 cm two times thinner than traditional acoustic treatments. Such design can help enhance the acoustics of rooms, but it can also be introduced to critical environments with limited space, such as aerospace.
Transparent sound absorption—More than 25 years of applications
Authors: Nocke Christian
Published: July 2024

Optically transparent micro-perforated sound absorbers were introduced more than 25 years ago. One of the first projects carried out was the German Parliament (Bundestag). another project carried out recently is the Canadian Parliament. At first, in the German Parliament, acrylic glas boxes with a sub-millimeter micro-perforations have been developed an applied. Later, on other micro-perforated sheets, such as thin polycarbonate or PVC sheets, have been applied in various projects around the world such as in Ottawa. This contribution concentrates on optically transparent sound absorbers. Fully transparent absorbers can be installed in front of glass facades, under glas roofs and whenever no optical distrubances are wanted. From pandemic times, also transparent screens and other applications are well known. A short review of the applications of various different materials with transparent microperforated sound absorbers is presented. Finally, sound absorption data for different setups are presented.
Some considerations on the simulation of meta-materials acoustic behavior
Authors: Martellotta Francesco , Ayr Ubaldo , Rubino Chiara , Liuzzi Stefania
Published: July 2024

One of the major advantages behind the success of metamaterials is related to the possibility to design them based on theoretical assumptions or when theory gets complicated, thanks to numerical methods. Many efforts have been made in the last years to better support researchers with benchmark tools that allow us to make their calculations more reliable, offering the opportunity to directly model the sound propagating inside the material or allow the determination of the parameters that can be used to feed phenomenological models. However, like any other simulation tool, a proper knowledge of the physics and the ways it is approximated are required to get the best results. The paper presents a selection of issues that may play a relevant role to improve the final results, including geometrical discretization, modelling of boundary conditions, and use of periodical structures. A discussion follows also pointing out the differences pertaining to transmission and absorption problems.
Absorptive performance of layered metasurfaces using microslit panels
Authors: Cunningham Phebe S. , Chen Ziqi , Xiang Ning
Published: July 2024

This work examines the effectiveness of layered metasurface arrangements, prioritizing space efficiency to create a broadband sound absorber. Innovative metasurfaces, including microslit panels with concentrated and coiled cavities, provide frequency-dependent absorptive properties. While these metasurfaces are independently known as efficient sound absorbers, single-layer microslit panel absorbers with a single cavity, in general, lack a wide effective bandwidth. In this work, theoretical models guide the effective creation of metastructures to achieve broadband absorption. These systems are then assembled and measured using an impedance tube to validate their acoustic performance. This paper discusses the formulation of the theoretical model, experimental validation of the model for layered absorbers, and the design specifications that can be met using various metasurface combinations.
Ultrasound-triggered in situ hydrogel formation for spinal disc repair
Authors: Brans Veerle A. , Constantinou Anna P. , Kibble Matthew J. , Newell Nicolas , Bau Luca , Stevens Molly M. , Coussios Constantin , Gray Michael
Published: July 2024

Over 600 million people suffer from lower back pain attributable to spinal disc degeneration. Treatments range from conservative physiotherapy to costly, invasive options like spinal fusion surgery. Injectable engineered materials may allow minimally invasive disc repair, but self-curing lacks process control, and optical in situ curing is depth-limited. We, therefore, propose ultrasound-triggered implant formation, enabling spatiotemporal control at clinically relevant tissue depths. We developed an anionic polysaccharide-based hydrogel, seeded with calcium-loaded thermosensitive liposomes. Focused ultrasound was used to heat this injectable precursor material to just above the lipid phase-transition temperature of 41 °C, inducing calcium release and ionically crosslinked network formation. Controlled heating was achieved by elevating the acoustic attenuation of the precursor solution with purified glass microspheres. The heating and gelation processes were controlled in real-time using thermometry and acoustic cavitation emissions. We optimized the ultrasound frequency and pressure amplitude to provide controlled heating with minimal cavitation. After these parameters were employed for ultrasound-mediated gelation, the rheological properties of the resultant gels were compared to literature values for native spinal disc material. Finally, in situ gel formation was evaluated in ex vivo bovine tail discs, from injection to mechanical assessments, confirming the ability to remotely trigger injectable disc-mimicking materials.
The activation of endothelial nitric oxide synthase, induced by calcium influx plays a crucial role in regulating endothelial hyperpermeability caused by ultrasound-targeted microbubble cavitation
Authors: Paranjape Anurag N. , Chen Xucai , Villanueva Flordeliza S.
Published: July 2024

Ultrasound-targeted microbubble cavitation (UTMC) plays a crucial role in improving drug delivery across the endothelial barrier. For successful application of UTMC in clinic, an understanding of molecular mechanisms involved is essential. Here, we hypothesized that Ca2+ and endothelial nitric oxide synthase (eNOS) pathways regulate UTMC-induced endothelial hyperpermeability. We used human coronary artery endothelial cells seeded on transwell inserts, exposed to microbubbles and ultrasound (frequency 1 MHz; PNP 250 kPa; pulse length 10 μs; pulse interval 10 ms; treatment duration 10 s). UTMC caused cellular influx of Ca2+, which was inhibited by blocking mechanosensitive channels (p < 0.0001) using GsMTx4. Knockdown of Piezo1 using siRNA showed similar effects. UTMC-induced Ca2+ influx activated eNOS and enhanced nitric oxide production, which was necessary for UTMC-induced hyperpermeability. Our data suggest that UTMC induces a Ca2+ influx-dependent increase in S-nitrosylation: An increase in S-nitrosylation was observed on both β-catenin and VE-cadherin after UTMC, potentially contributing to the destabilization of adherens junctions that normally maintain barrier integrity. Our study explains the role of Ca2+ influx, eNOS activation, and enhanced S-nitrosylation of adherens junction proteins in the regulation of endothelial hyperpermeability. Further investigation of these pathways will aid in clinical translation and optimization of UTMC for delivering cell-impermeant drugs.
Designing a benign prostatic hyperplasia dual-mode cavitation cloud and boiling histotripsy therapy transducer
Authors: Nanda Kumar Yashwanth , Contreras Kaizer , Wang Yak-Nam , Kreider Wayne , Totten Stephanie , Schade George R. , Maxwell Adam D.
Published: July 2024

Benign prostatic hyperplasia (BPH) is a condition that causes an enlarged prostate leading to lower urinary tract symptoms (LUTS), affecting quality of life. Histotripsy is a non-invasive focused ultrasound technique that mechanically disintegrates tissue wherein cavitation cloud (CH) and boiling histotripsy (BH) are the two commonly used therapy modes. Recent studies have shown successful ablation of BPH tissue in vitro by transducers that were designed for a transabdominal approach. However, this approach may not be successful in treating tissue in vivo, as evidenced in some of the clinical studies, due to challenges with the anatomical position of prostate within humans. Therefore, a need exists in treating it transrectally with a transducer that can perform both CH and BH for efficient ablation. Initial design studies were performed to determine the appropriate source parameters and materials needed for fabricating the combinational therapy transducer for in vivo use. A 3 MHz multi-element source with a focal length of 40 mm and gain of 64 was chosen. The equivalent aperture is 48.5 mm with a 10 mm central opening for image guidance. Non-linear simulations show sufficient peak positive and negative pressures can be achieved for performing both regimes. Further details on the fabrication and characterization of the transducer with benchtop results will be presented.
Categorization of pickleball paddles as a highly impulsive sound source
Authors: Willis Lance , Leahy Charles E.
Published: July 2024

As the sport of pickleball has grown in popularity and tennis courts close to homes are being converted to this use, noise regulation for pickleball courts has become a topic of discussion among city councils, planners, home owners associations, residents, and, increasingly, attorneys seeking injunctions against poorly sited or mitigated courts. Accurate noise impact assessment of the short duration impulsive sound produced by the impact of the ball on the paddles requires the use of the highly impulsive adjustment in ANSI S12.9 Part 4. Examination of the definitions of impulsive sound in this standard and in ISO 1996 Part 1 identifies characteristics of rapid onset, significant energy in the most sensitive part of the auditory spectrum, and duration as primary differentiators for categorization. The noise impact assessment methodology in ANSI S12.9 Part 4 for highly impulsive sound has proven an effective means of determining the amount of mitigation needed for pickleball facilities, being more repeatable and precise than other commonly used assessment methods while avoiding underestimation of annoyance.
Direct, model-free acoustic evaluation of stresses and strains in loaded nonlinear soft solids
Authors: Destrade Michel , Li Guoyang , Gower Artur L. , Cao Yanping , Yun Seok-Hyun , Zhang Zhaoyi , Yin Ziying
Published: July 2024

We show analytically and experimentally that the states of stress and strain existing in a mechanically loaded elastic material can be accessed directly from elastic wave speed measurements, without having to determine, or even know, its material linear and nonlinear elastic parameters. These techniques are expected to have important applications in the health monitoring of loaded structures. Examples include stressed hydrogels, muscles, and thin membranes, such as a stretched rubber sheet, a piece of cling film (∼10 μm thick), and the animal skin of a bodhrán, a traditional Irish drum. References: Z. Zhang, G.-Y. Li, Y. Jiang, Y. Zheng, A. L. Gower, M. Destrade, and Y. Cao, “Non-invasive measurement of local stress inside soft materials with programmed shear waves,” Sci. Adv. 9, eadd4082 (2023); G.-Y. Li, A.L. Gower, M. Destrade, and S.-H. Yun, “Non-destructive mapping of stress and strain in soft thin films through sound waves,” Commun. Phys. 5, 231 (2022).
Passive structural health monitoring of a vibrating shell using data-based matched field processing
Authors: Rakotonarivo Sandrine T. , Langlet Theo , Sarkar Jit , Kuperman William
Published: July 2024

This study presents experimental results on passive structural health monitoring of a vibrating elastic structure for defect localization. The approach is based on matched field processing (MFP), which requires a model of the pristine structure. An MFP methodology for localizing a defect in a shell equipped with vibration sensors was developed and numerically demonstrated in [JASA EL 2, 025601 (2022)]. This paper further extends this study to experimental implementation of this MFP methodology without requiring full knowledge of the structure parameters and the boundary conditions of the pristine structure. The method is tested on experimental data for localizing a defect on a rectangular steel plate with non-perfectly, fixed boundary conditions.
Optimization of an aircraft fuselage assembly to minimize radiated sound power
Authors: Howes Jordan , McKenzie Adam , Dossett Wesley , Crispo Luke , Kim Il Yong
Published: July 2024

During the structural design of an aircraft fuselage, the acoustic performance is generally not considered. However, vibrations transmitted through the fuselage generate noise leading to passenger discomfort. Currently, the main source of noise reduction comes from the addition of damping material to the fuselage. This work investigates the use of various design optimization techniques to reduce radiated sound power by changing the fuselage structure’s geometry which consists of a skin panel, frames, and stringers. Design optimization tools, such as topology, size, and shape optimization were used to determine an optimal design for each design variable that minimized radiated sound power in the fuselage assembly. The design variables that were studied included skin panel thickness and design, frame and stringer spacing, and frame and stringer cross section. Equivalent radiated power was used as an objective function for numerical optimizations within Altair OptiStruct as an indirect method for minimizing radiated sound power numerically. To understand the source of the sound power improvements, a physics analysis was conducted for each design variable that compared sound power, equivalent radiated power, and radiation efficiency.
Predicting vocal tract shape information from tongue contours and audio using neural networks
Authors: Li Sarah R. , Knapp Alex , Tang Jing , Boyce Suzanne , Mast T. Douglas
Published: July 2024

Midsagittal ultrasound imaging of the tongue is a portable and inexpensive way to provide articulatory information. However, although ultrasound images show a portion of the tongue surface, other vocal tract structures (e.g., palate) are not typically visible. This missing information may be useful for speech therapy and other applications, e.g., by characterizing vocal tract constrictions and informing how morphological variations affect speech patterns. Prediction of the vocal tract shape from information available during ultrasound imaging (e.g., tongue contours and audio recordings) is, thus, potentially valuable. Recent advancements in articulatory prediction from audio recordings (i.e., acoustic inversion) and speech recognition using combined articulatory and acoustic data have used neural network models. Inspired by these models, this study investigates how well fusion of articulatory and acoustic features in speaker-independent models can predict expanded articulatory information. Specifically, recurrent neural network models will be trained to predict the vocal tract shape based on partial tongue contours and acoustic features, during production of vowels and central approximants. Features will be extracted from simultaneously recorded audio and 2D MRI (USC 75-Speaker Database). Different acoustic features and network architectures will be compared, with the goal of refining future models to predict vocal tract shapes during ultrasound imaging.
Influence of airflow and ligament tension on the acoustics of a biomimetic larynx model
Authors: Tur Bogac , Gühring Lucia , Wendler Olaf , Kniesburges Stefan
Published: July 2024

The phonation process is a complex interaction involving the airflow from the lungs, the oscillation of the vocal folds’ tissue, and the resultant acoustics. To understand the underlying physical mechanisms, an experimental model has been designed that allow the control of flowrate and longitudinal tension of the vocal folds. A synthetic biomimetic larynx model was applied that features airflow-driven vocal folds’ oscillations. The longitudinal stiffness of the vocal folds is controlled using embedded ligament fibers. The model enables to measure aerodynamic and acoustic signals as function of airflow rate and the fiber tension. Based on the measured signals, the influence of airflow and fiber tension was statistically analyzed using the parameters F0, Psub, CPP, HNR, Shimmer, and Jitter. The statistical analysis revealed that both flowrate and fiber tension significantly influence acoustic and aerodynamic parameters. In general, the parameters showed different trends for increasing flowrate and fiber tension. Increase in fiber tension produced increasing parameters up to a maximum tension level followed by a saturation of the parameters. In contrast, the flowrate showed varying trends depending on the respective parameter. The results clearly show how flowrate and longitudinal tension control the phonation process and the resulting acoustic quality.
Optimizing parametric acoustic arrays for high-fidelity low-frequency signals
Authors: Uzhansky Ernst , Friedlender Maya , Bucher Izhak
Published: July 2024

Parametric acoustic array (PAA) can leverage the nonlinear behavior of sound travelling through the nonlinear medium (e.g., air, water, human tissues) to generate low-frequency broadband high-directivity sound due to the self-demodulation of finite-amplitude modulated ultrasonic waves. However, while propagating, self-demodulated signals (hereon message) interact one with another, leading to message deformation and increase of the total harmonic distortion (THD). This makes it problematic to use powerful PAA to control complex low-frequency signals. This work explores a method for reducing THD by optimizing the input signal using various digital signal processing algorithms. The sustainability of the required spectral components with distance and the spatial boundaries of the operation of the proposed optimization algorithm are also investigated experimentally with a 520-channel hexagonal PAA and numerically. The simulations were done via k-wave acoustic toolbox considering nonlinearities and power law absorption.