bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of a computational Bayesian approach for active localization of a mobile scatterer in a refractive ocean environment
Authors: Gendron Paul J. , Barros Abner C.
Published: July 2024

Underwater active acoustic systems that employ limited aperture arrays suffer from reduced processing gain and poor angular resolution, thereby hindering inferential objectives such as localization and tracking. Accurate localization is further challenged by the short conventional coherence-time associated with mobile bodies and dynamic environments. A computational Bayesian approach is presented and expanded here, for joint inference of range, depth, and speed of a submerged mobile scatterer in a refractive and multipath environment [Barros and Gendron, JASA-EL, 2019]. The Gibbs-sampling based approach infers the joint posterior probability density (PPD) of the pressure field wave vectors associated with the angle/Doppler spread arrivals and then maps their joint PPD to the target state joint PPD through acoustic ray interpolation. Performance analysis at high frequencies and relevant ranges using simulated acoustic fields are presented. The posterior uncertainty is investigated as a function of aperture and SNR, and we summarize the PPD using posterior credible intervals. A bound on posterior variance due to uncertainty in sound speed is provided and explored using profiles from the HYCOM database.
A new seperation method for rotationg and static sound source localization
Authors: Chu Ning , Djafari Ali
Published: July 2024

Traditional sound source localization methods encounter significant challenges in simultaneously locating rotating and static sources. These challenges arise from the differing motion patterns of these two types of sound sources, and they are typically not situated on the same plane. To address this issue, a method based on Modal Composition Beamforming (MCB) and the equivalent source method is proposed for separating rotating and static sound sources that can fully utilize priori knowledge of the spatiotemporal properties of the sources. The proposed approach involves establishing a Rotating-Static Sources Power Propagation (R-S2P) model, utilizing the relationship between the beamforming output of equivalent sources and the actual beamforming output. Solving this model allows for matching the contributions of rotating and static equivalent sources. Simulations for three cases with different source strengths are presented, and the R-S2P model is solved using the Least Absolute Shrinkage and Selection Operator (LASSO). This method enables accurate separation and localization of rotating and static sources on different planes with varying relative intensities, even if the background noise is strong
The sing-song of old man human ear
Authors: Shera Christopher
Published: July 2024

Otoacoustic emissions evoked from the inner ear are the barely audible, signature by-product of the delicate hydromechanical amplifier that evolved within its bony walls. Compared to the sounds evoked from the ears of common laboratory animals, otoacoustic emissions (OAEs) from human ears have exceptionally long delays, typically exceeding those of cats, guinea pigs, and chinchillas by a factor of two to three. This presentation asks “Why are human OAE delays so long?” and reviews efforts to find answers in the mechanical frequency selectivity of the inner ear. The road to understanding species differences in OAE delay has led to the identification of new invariances and the emergence of new questions.
Poroelastic model of the lungs at low frequencies predicted by Biot's theory
Authors: Uzundurukan Arife , Poncet Sébastien , Boffito Daria C. , Micheau Philippe
Published: July 2024

Biot's theory of poroelastic wave propagation inherently lends itself to elucidate the characteristics of a biphasic medium comprising solid and fluid components, such as biological tissues. One of the intricately complex biological tissues that remains poorly understood is the lungs since their properties diversify significantly through their pore geometries affected by inspiratory positive airway pressure (IPAP) and applied frequency range. One hypothesizes that the vibroacoustic behaviour of the lungs can be predicted by Biot's theory, as the nature of the lungs aligns with the principles of the theory at low frequencies. This study aims to analytically investigate the vibroacoustic behaviour of the lungs, considering 10 and 20-cm H;2O IPAP. Utilizing a fractional derivative formulation, one predicts the complex-valued shear wave speed, as well as the fast and slow compression wave speeds, for frequencies ranging from 5 to 100 Hz. A 3D digital thorax twin study using these predicted wave speeds, particularly at 28 Hz and 20 cm H;2O IPAP, is validated against experimental data from the literature. Consequently, applying Biot's theory provides a valuable framework for understanding the dynamic vibroacoustic behaviour of the lung tissues in response to varying IPAP and low frequencies.
Signal detrending in elastographic wave data with large motion artifacts through a 2D Whittaker smoother
Authors: David Rosen P. , Alizad Azra , Fatemi Mostafa
Published: July 2024

A variety of advanced shear wave elastography techniques require the measurement of frequency-resolved phase velocity to properly characterize wave signals where factors such as tissue viscosity or guided wave effects are present. However, when applying these techniques in a dynamic environment where extrinsic motion cannot be limited, nonlinear and nonstationary trends can be expected in the motion signal used for phase velocity estimation. Because such extrinsic motion signals can contaminate a broad range of frequencies, they can produce significant errors in the phase velocity estimates. In this study, we propose a spatiotemporal detrending approach for elastography wave motion signals built from a 2D Whittaker smoother. This smoother has its origins in nonparametric regression and is well suited for fitting nonlinear curves of arbitrary shape. The resulting detrending filter was applied to Lamb wave signals from clinical ultrasound bladder vibrometry measurements. We found that the proposed detrending filter allowed for phase velocity estimates to be made in acquisitions that are otherwise be too corrupted by large motion. This works was supported by a grant from the NIH (DK131685)
Droplets for acoustic vaporization: Formulations, properties and applications
Authors: Paradossi Gaio , Domenici Fabio
Published: July 2024

The Acoustic Droplet Vaporization (ADV) (1), a phase-change of the droplets core from liquid to vapor phase upon ultrasound irradiation, burst renewed interest in droplet emulsions, a traditional topic of colloidal science, opening up innovative applications in biomedicine. Droplets undergoing ADV share similar liquid cores, typically perfluorocarbons (PFCs), however, the nature of the shells can be polymeric (2) or lipidic (3, 4). Such difference imparts to phase-change droplets diverse acoustic and mechanical behaviors (5). In this contribution we present some results concerning a general strategy for the formulation of polymer or lipid shelled submicron droplets. Other key points for the use of ADV-responsive in biomedical applications will be addressed. Recently we have extended the concepts of ADV to radiation responsive droplets for dosimetry in cancer treatment with hadronic radiation. Results on this activity will be also reported (6). References: (1) J. Acoust. Soc. Am. (2004) 116 (1): 272–281; (2) Chem. Commun., 2013, 49, 5763; (3) JoVE, 169 (2021); (4) Langmuir (2019), 35, 10116–10127; (5) Phys. Chem. Chem. Phys., 2016, 18, 8378; (6) COCIS, 49, 118–132 (2020).
Sound propagation modeling in forests using the transmission line matrix method: Comparison with experimental in situ measurements
Authors: Goestchel Quentin , Guillaume Gwenaël , David Ecotière , Benoit Gauvreau
Published: July 2024

We present efforts to adapt the time-domain Transmission Line Matrix (TLM) method for modeling sound propagation in forests. It is relevant to professionals and researchers in environmental acoustics and to those interested in studying sound propagation in outdoor environments using numerical modeling techniques. The study aims to demonstrate the applicability of the method in complex media where sound waves undergo multiple reflections combined with ground effects during their propagation from a sound source to a receiver point. The TLM method is used to numerically model sound propagation in a 3D forest geometry generated based on a real tree distribution case. Data from an experimental campaign conducted in the rainforest of French Guyana are used as a reference. The results show an encouraging comparison between them and the in situ measurements, even if the hypotheses made to adapt the input data in the model were strong. We find that more measurement points and more specifications (ground impedance measurements, canopy density, etc.) about the experimental site are needed for further simulations, even if obtaining them presents technical difficulties.
The Graduate Program in Acoustics at Penn State
Authors: Barnard Andrew , Russell Daniel A.
Published: July 2024

The Graduate Program in Acoustics at Penn State offers graduate degrees (M.Eng., M.S., Ph.D.) in Acoustics, with courses and research opportunities in a wide variety of subfields. Our 820 alumni are employed around the world in military and government labs, academic institutions, consulting firms, and consumer audio and related industries. Our 40 + faculty from several disciplines conduct research and teach courses in structural acoustics, nonlinear acoustics, architectural acoustics, signal processing, aeroacoustics, biomedical ultrasound, transducers, computational acoustics, noise and vibration control, acoustic metamaterials, psychoacoustics, and underwater acoustics. Course offerings include fundamentals of acoustics and vibration, electroacoustic transducers, signal processing, acoustics in fluid media, sound and structure interaction, digital signal processing, experimental techniques, acoustic measurements and data analysis, ocean acoustics, architectural acoustics, noise control engineering, nonlinear acoustics, outdoor sound propagation, computational acoustics, biomedical ultrasound, flow induced noise, spatial sound and three-dimensional audio, and the acoustics of musical instruments. Distance education students pursuing the M.Eng. degree join resident students in a hybrid classroom environment. This poster highlights faculty research areas, laboratory facilities, student demographics, successful graduates, and recent enrollment and employment trends.
An investigation into the directivity, spectra, and modes of a Tambourine
Authors: Todd Emma , Pavill Hanna , Hales Jacob B. , Coleman Matt , Shepherd Micah
Published: July 2024

As an instrument, the tambourine has been used by various cultures for thousands of years. However, despite this rich history, there remains little literature that investigates the acoustical properties of the tambourine itself and an even greater lack in research that moves beyond discussing the instrument’s membrane alone. As a tambourine’s membrane is only one part of a larger whole, this is problematic; in fact, the membrane is not usually considered the instrument’s main radiator as many tambourines completely lack a membrane and players often actively damp the membrane while playing. Therefore, in order to develop a more in-depth and foundational understanding of the tambourine’s physics, we will discuss the nature of the instrument’s directivity, analyze how its sound spectra varies across diverse playing styles, and present the various modes associated with its wooden frame and metal jingles. The modes have been estimated using finite element techniques.
The development of an automated striking device for repeatable percussion strikes
Authors: Sampson Jacob , Pavill Hanna , Shepherd Micah
Published: July 2024

Many high-quality directivity systems involve a single microphone arc which rotates around a sound source. Since multiple data captures are necessary as the arc rotates around a sound source, the source should emit the sound in a steady and repeatable way at all arc positions. To obtain directivity measurements of a struck percussion instrument, it is crucial to be able to strike the instrument during each microphone arc position as consistently as possible. However, a human player typically cannot strike the instrument in the exact same way for many consecutive measurements. To overcome the shortcomings of human players, an automatic striking device was developed to aid in the study of the directivity of percussion instruments. The device consists of a striking implement holder attached to a stepper motor that is controlled by an Arduino. The striking implement holder allows the user of the striking device to use different-sized mallets/drumsticks depending on the instrument that is being measured. The automatic striking device has been used to obtain directivity measurements on several instruments including a glockenspiel, cymbal, and drum. The details of the automatic striking device will be presented along with a subset of directivity results.
Development of a weather robust microphone configuration for sonic boom measurments
Authors: Blaine Jesse , Anderson Mark C. , Gee Kent L.
Published: July 2024

This paper discusses ongoing development and testing of ground-based, weather-robust microphone measurement systems in conjunction with preparation for community testing of NASA's X-59 low-boom aircraft. Prior efforts [Anderson et al., Proc. Mtgs. Acoust. 42, 040005 (2022)] resulted in the refinement of a ground-plate setup by investigating varied windscreen and plate diameter and thickness. The most recent goal has been to make the setup more compact and easier to manufacture. This paper discusses the results of additional tests performed on updated designs meant to find the balance between compactness and performance. Anechoic chamber testing was performed to show ground plate and windscreen performance and to compared results against prior versions. Outdoor tests included measurements during different wind conditions and over different ground surfaces to examine low-frequency wind noise reduction and ground impedance effects. Results discussed during the presentation suggest the new design strikes an acceptable compromise between compactness, manufacturing ease and robustness, and performance. [Work supported by NASA Langley Research Center through Analytical Mechanics Associates]
A mechanistic investigation of processing costs associated with cross-talker acoustic-phonetic variability
Authors: Luthra Sahil
Published: July 2024

The acoustic realization of speech sounds may differ substantially across talkers, such that (for example) a sound interpreted as “s” in one voice might be considered a “sh” in another. In this talk, I will review select neurobiological and computational data illustrating how listeners cope with this variability. I will also review behavioral data showing how talker variability can hinder processing, with slower and/or less accurate processing when the listening environment contains multiple voices compared to one voice. I argue that at least three mechanisms underlie these multi-talker processing costs. First, multi-talker processing costs may arise because talker changes disrupt a listener’s ability to attend to the target talker. Second, I make the novel claim that talker changes might impose processing penalties by inducing uncertainty about whether the extant acoustic-to-phonetic mapping is appropriate, motivated by recent data that when multi-talker processing costs are attenuated by a preceding carrier phrase, this manifests as slowed responses to single-talker speech rather than improved processing of mixed-talker speech. Finally, talker variability costs may result from making on-the-fly adjustments to the mapping between acoustics and phonetic categories. Overall, this talk highlights the ways in which listeners contend with and are hindered by talker variability.
The contribution of suprasegmental cues to perceived L1 and L2 accent distance
Authors: Henry Malachi , Bent Tessa , Holt Rachael F. , Lind-Combs Holly
Published: July 2024

First (L1) and second language (L2) pronunciations that diverge more segmentally from the local accent are rated as more distant. However, fewer studies have addressed relations between suprasegmental features, such as intonation, and accent distance. We examined the relation between perceived accent distance and four suprasegmental measures: time normalized f0 Euclidean distance, mean F0, pitch range, and speaking rate. Thirty adults completed six ladder tasks in which listeners ranked talkers’ perceived distance from the local accent. For each ladder, listeners heard one sentence produced by 24 talkers: one man and one woman from six L1 and six L2 English varieties. Each suprasegmental measure independently predicted distance rankings with a variety of significant interactions. Talkers with higher accent rankings had narrower pitch ranges, lower mean f0, faster speech, and greater f0 Euclidean distance. Furthermore, suprasegmental measures related to accent distance differentially based on syntactic structure. For example, as f0 Euclidean distance increased, accent rankings increased for interrogative sentences, but not for declarative sentences. These data support the need for future studies examining how suprasegmental features impact perception of L1 and L2 accents. [Work supported by NSF grants 1941691 and 1941662].
Implementation of supervised machine learning classification for detection and severity determination of electrified power train noise and vibration fault diagnosis
Authors: Lee Joohyun , Liu Yangfan , Bolton J. S. , Davies Patricia
Published: July 2024

Vehicles equipped with electrified powertrains produce lower sound and vibration levels compared to those equipped with internal combustion engine powertrains. This makes noise and vibration (N&V) from other non-engine components more perceptible. Gear growl is one of the newly observed N&V that brings concerns by the passengers and manufacturers. The understanding of signal characteristics and the threshold for determining whether gear growl requires attention remains limited. To address this, supervised machine learning classification is employed. Root-mean-square (RMS) and spectral entropy values are sufficient for the classification of vibration data with test accuracy of 0.983. However, the acoustic signal required more features due to background noise, making data linearly inseparable. Features that describe the characteristics of acoustic data are studied, extracted, and selected. Utilizing a support vector machine (SVM) for classification, the study achieves an average test accuracy of 0.918. Further, a multi-class classification model is implemented based on preliminary subjective listening studies, classifying different severities of gear growl. Further listening studies are suggested for improving multi-class classification performance. Methods described in this study mainly focus on the analysis of gear growl, but they can be generalized for N&V signal-based fault diagnosis applications.
On the feasibility of using short-range, high-frequency transmissions to characterize the vertical-spectra of small-scale internal waves and turbulence in a bottom boundary layer
Authors: Colosi John A. , Duda Timothy F. , Alford Matthew , Lin Ying-Tsong , Voet Gunnar
Published: July 2024

Using weak fluctuation theory, we examine the detectability of small-scale internal waves and turbulence via short-range, high-frequency transmissions to a vertical array. For internal waves the theory needs modification since the ranges of interest are shorter than the internal wave correlation lengths. The turbulence spectra are characterized by thermal dissipation, χ, kinetic energy dissipation, ε, and outer scale L;0 (largest turbulent eddies) and regions of this space can be explored with different ranges and acoustic frequencies. Very little is known of the internal-wave structure when wave breaking starts. As an example, we consider an experimental arrangement atop the Atlantis 2 seamount where there is a strong, tidally driven boundary layer approximately 100-m thick.
Robotization of “in situ” acoustic measurements
Authors: Leroux Gabriel , Gagnon Émile , Birglen Lionel , Leveque Nicolas
Published: July 2024

Currently, “in situ” acoustic measurements require a high level of human involvement. Measurements are carried out by technicians or engineers, and most of the time, two people are required. MJM Acoustical Consultants Inc. has explored the possibility of using an autonomous and semi-autonomous robotic solution to assist in the measurement process. Developed in partnership with university Polytechnique Montreal, the research project consists of developing a software platform and hardware for a mobile robot capable of moving around, locating itself and performing measurements using a Type I sound level meter. The prototype generates its own local area network (LAN), making it possible to send commands through high-density partitions such as brick walls or concrete floors remotely from a laptop. Localization system such as a laser remote sensing system allows the robot to navigate around obstacles. Its low noise level when stationary makes it ideally suited to conduct common standard tests such as impact noise isolation, airborne sound attenuation between rooms and background noise level measurements. Through tests carried out on field sites, the solution developed constitutes an effective instrumentation to make acoustic measurements sessions more efficient with a reduced level of human operation.
An overview of green roof acoustic performance
Authors: Juan Shiang-I , Tsaih Lucky S.
Published: July 2024

This comprehensive review provides an in-depth examination of the acoustic performance of green roofs within urban and built environments over the past 15 years. Green roofs, characterized by their vegetative cover and substrate layers, offer a multifaceted solution to address challenges associated with urban noise pollution. The objective of this review is to synthesize existing literature, emphasizing key studies and methodologies employed to assess the noise reduction and sound isolation capabilities of green roofs. Factors influencing green roof acoustic performance, such as plant species selection in the plant layer, soil distribution, moisture content, and compaction level in the vegetation layer, as well as the overall roof design in terms of shapes and building configuration, are discussed in detail. Additionally, the impact of overall roof design, including shapes and building configuration, is explored. The relevant sound absorption coefficient and insertion loss values, drawn from the existing literature, will be reported. By systematically analyzing empirical findings, this overview offers valuable insights into the potential of green roofs as sustainable components for noise mitigation in building construction, contributing to the development of more resilient and harmonious urban landscapes.
Effects of time varying aircraft noise on indoor speech interference
Authors: Collins Adam
Published: July 2024

Aircraft noise can create noticeable speech interference inside buildings adjacent to airports. Outdoor aircraft take off noise measurements were completed and used to study time varying effects on indoor environments. Preliminary results suggest changing levels of speech interference over the duration of aircraft take off events.
Direct emulsification of liquid perfluorobutane: an improved method to formulate superheated perfluorocarbon nanodroplets
Authors: Woodward Adam , Mattrey Robert , de Gracia Lux Caroline
Published: July 2024

This talk will describe a simple and robust method to produce perfluorobutane (PFB) nanodroplets by direct sonication, and will compare the properties of the resultant emulsions with those obtained with the current advocated microbubble condensation method. We found that nearly 100% of particles produced by direct emulsification of PFB liquid at low temperature are liquid PFB-filled, whereas the emulsion produced by microbubble condensation if the microbubbles are not washed, contains 2000 times more non-PFB filled than PFB-filled particles. Consequently, when such suspensions are used to target receptors, the abundance of non-PFB particles will act as competitive inhibitors, and when used to extravasate to reach extravascular targets, the lower count of PFB-filled particles will require larger doses decreasing efficacy and increasing side effects. Adopting this direct formulation could be a game changer for all applications when experimental outcome is dependent on nanodroplet concentration, stability, purity and size. As a result, this method should accelerate the translation of these ultrasound activatable nanodroplets to both image and potentially treat diseased tissues.
Characterization of acoustic droplet vaporization in tissue-mimicking, fibrin-based hydrogels for microrheology applications
Authors: Kaushik Anuj , Abeid Bachir A. , Estrada Jon B. , Fabiilli Mario L. , Aliabouzar Mitra
Published: July 2024

Ultrasound-induced vaporization of phase-shift droplets (PSDs) into microbubbles, termed acoustic droplet vaporization (ADV), has expanded biomedical applications. Here, we explored the potential of ADV as a high-resolution, on-demand microrheometer using theoretical and experimental methodologies. This approach could be used to characterize tissue elasticity at spatial resolutions unrealizable with conventional in situ techniques, thus assisting with identification of underlying pathologies. For theoretical studies, bubble dynamics were combined with appropriate material constitutive models accounting for viscoelasticity of the surrounding tissue. Experiments were conducted on submicron- and micron-sized, perfluoropentane PSDs embedded in fibrin-based hydrogels with varying shear elastic moduli (0.2 kPa–11 kPa) to mimic soft tissues. Experimental studies included optical high-speed imaging and acoustic interrogations to record radial dynamics and acoustic emissions of the ADV-bubbles, respectively. Radial dynamics and the acoustic emissions of microbubbles produced by ADV depended significantly on fibrin elasticity. For example, an increase in fibrin elastic modulus from ∼0.8 kPa to ∼6 kPa reduced the maximum expansion radius of the generated ADV-bubbles by 50%. This increase in elasticity significantly impacted both linear (e.g., fundamental) and nonlinear (e.g., subharmonic) acoustic responses of the ADV-bubbles, by up to 15 dB. These findings open doors to a novel ADV-assisted tissue characterization technique.
Using an instrumented hammer to detect the rupture of the pterygoid bone plate: an animal study
Authors: Bas dit Nugues Manon , Rosi Giuseppe , Flouzat-Lachaniette Charles-Henri , Khonsari Roman H. , Haïat Guillaume
Published: July 2024

Craniofacial osteotomies involving pterygomaxillary disjunction are common procedures in maxillofacial surgery to detach the pterygoid plates from the palatal bones. Surgeons still rely on their proprioception to determine when to stop impacting the osteotome, which is important to avoid complications such as dental damage and bleeding. Our group has developed a technique consisting in using an instrumented hammer that can provide information on the mechanical properties of the tissue located around the osteotome tip. The aim of this study is to determine whether a mallet instrumented with a force sensor can be used to predict the crossing of the osteotome through the pterygomaxillary plate. 31 osteotomies were carried out in 16 lamb skulls. For each impact, the force signal obtained was analyzed using a dedicated signal processing technique. A prediction algorithm based on an SVM classifier was applied to the database. We showed that the device can detect the crossing of the osteotome, sometimes before its occurrence. The prediction accuracy of the device was 94.7%. The method seemed to be sensitive to the thickness of the plate and to crack apparition and propagation. These results pave the way for the development of a per-operative decision support system in maxillofacial surgery.
Elastodynamic property closures of elastic waves in polycrystalline materials
Authors: Kube Christopher M.
Published: July 2024

In polycrystalline materials like many metals, grainy microstructures significantly influence elastodynamics. Bulk waves scattering at grain boundaries cause attenuation and speed variation in waves. This depends on grain characteristics, including local elasticity and spatial properties. These are modeled statistically to homogenize the microstructure or elastodynamic fields, within bounds. For example, the elasticity of a homogenized medium can't exceed that of individual grains. 'Property closure' is the range within which microstructures yield specific properties like Young's modulus. This presentation introduces property closures for modeling elastic wave properties, specifically attenuation and velocity, in metal alloys. The focus is on the modeling framework and integrating microstructure statistics. An excting prospect of this work is in linking measurable wave properties with other physical quantities dependent on microstructure.
The feasibility of building an impedance tube to measure sound absorption coefficients of materials
Authors: Zomparelli Nicholas
Published: July 2024

This presentation focuses on the design and build of an impedance tube to measure sound absorption coefficients of materials. A practical approach was taken to develop an impedance tube from readily available ‘off the shelf’ materials, with the ultimate goal of determining feasibility and accuracy of such a build. The design theory from multiple sources will be discussed, as well as a detailed breakdown of the dimensions and materials used for the apparatus. Measurement methodologies, testing set-up and data processing techniques are also presented to contextualize the results. Finally, comparisons of the tube results are made to existing known sound absorption coefficient data of materials to ultimately assess the accuracy of the low-cost impedance tube and any deficiencies. Methods to improve the design of the tube are also explored, as well as future design improvements.
PCB-based miniature vibro-tactile display for the visually impaired
Authors: Xiang Maijie , White Robert D. , Bernstein Jonathan
Published: July 2024

An estimated 2.2 billion people worldwide are visually impaired (WHO, 2019), yet current Braille readers are limited to one or two rows of text and cannot display images. Thus, a low-cost, electronically refreshable tactile display for accessing graphical and textual information is needed. We are developing such a display using a printed circuit board (PCB) as the substrate and bottom electrode array, and a metalized Kapton film as the vibrating membrane. Punched foam tape is used as a spacer to create a gap between the board and film so the pixels can be actuated electrostatically. The current prototype has 6 pixels at 3.5 mm spacing, Vibration amplitudes of 8 microns peak-to-peak were achieved in a prototype using a drive voltage of 600V at 200 Hz. This is sensible to the human touch. Further optimization requires matching the mechanical impedance of the finger, and maximizing vibration amplitude in the preferred sensible frequency range between 50 and 300 Hz. Finite element analysis (FEA), laser vibrometry, and nano-newton force-displacement measurements have been used to characterize the system. Future versions will increase amplitude, reduce drive voltages, and increase display resolution to larger arrays of more closely spaced pixels through further miniaturization.
Comparative numerical investigation of flow-induced noise characteristics of high-speed trains using high-resolution compressible Large Eddy Simulation
Authors: Lee Kwongi , Cheong Ceholung , Kim Jaehwan
Published: July 2024

The South Korean Ministry of Land, Infrastructure and Transport has developed a “Comprehensive Plan for 400km/h High-Speed Rail” aimed at enhancing the operational speed of the high-speed railways, currently running up to 300km/h. A short-term goal is to elevate the operating speed of high-speed trains to 370 km/h, up from 320 km/h. Because aerodynamic noise proportionally escalates with the 6th powers of the speed, aerodynamic noise becomes more significant at higher speeds. Consequently, there's a pressing need for design solutions that reduce aerodynamic noise in high-speed trains. This study involves an aeroacoustic analysis using real-scale models of the current model and the preliminary design targeting 370 kph operation. Each model's 8-car formation has been simplified to a 5- car setup. A challenge in predicting aerodynamic noise is the generation of detailed sound sources in the near field and precise noise propagation in the acoustic field. For that, a three-dimensional compressible Large Eddy Simulation technique is employed, utilizing high-resolution grids. This allows for concurrent computation of the external flow and acoustic fields for a real-scale, high-speed train in an open environment. The analysis comprehensively examines the aerodynamic and aeroacoustic properties of each train car, including the major contributors to aerodynamic noise in high-speed trains. The radiated noise is predicted using the Ffowcs Williams and Hawkings equation and is further examined in relation to vortex sound sources.
Modular design for optimized acoustic properties of multilayer system
Authors: Yang Tao , Eser Martin , Maeder Marcus , Marburg Steffen
Published: July 2024

It has been demonstrated that multilayer systems have the potential for excellent sound absorption, effectively attenuating sound across a wide range of frequencies and offering a versatile solution for addressing acoustic challenges in various environments. A key consideration is the design of a multi-layer structure and the parameters of each layer to achieve optimal sound absorption performance. Modular design is a crucial aspect of this work, involving the creation of smaller, units that can be customized and combined to achieve specific sound absorption properties. This study applies numerical optimization, inversion, and matrix methods to multilayer sound absorber systems, aiming to provide customized parameters for the modular design of fibrous materials with exceptional sound absorption properties. The effectiveness of the modular design will be validated and improved through impedance tube measurements of the manufactured multilayer systems, ensuring that the resulting sound absorbers meet the desired acoustic performance across diverse real-world scenarios.
Wind shadowing of a sonic anemometer in low Reynolds number flows
Authors: Huckaby Julia , White Robert D. , Neeson Ian , Banfield Don , Colaprete Anthony
Published: July 2024

Computational Fluid Dynamics (CFD) simulations have been carried out to better understand the wind shadowing effects on a sonic anemometer system. The anemometer will measure wind speed on the surface of Mars and the stratosphere of Earth.The wind velocity vector is measured through the difference in acoustic time of flight in 3 directions. However, the structure itself disrupts the flow and creates an internal wake. To understand this and generate correction factors, CFD simulations were run under Mars surface conditions while varying incident angle and flow speed. Spalart-Allmaras turbulence models were employed in both steady and unsteady Reynolds Averaged Navier Stokes (RANS) frameworks and compared to a laminar model. Due to the low Reynold’s number (<150) we observe no shedding at speeds below 10 m/s. At speeds below 10 cm/s the flow diverts around the structure and sensitivity drops. At intermediate speeds near 5 m/s the wind shadow ratio (WSR) varies substantially with incident wind angle. Design changes to the structure allowed us to improve the worst WSR from 38% to 47%. We were also able to quantify correction factors. Validating comparisons to water tunnel and wind tunnel measurements will be presented.
Using musical acoustics to motivate math learning
Authors: Piacsek Andrew A.
Published: July 2024

A course on musical acoustics, at the high school or introductory college level, can be an effective vehicle for improving student math skills. More importantly, it provides an opportunity to develop an appreciation for the utility of mathematics among skeptical students, including those from groups, such as women and minorities, who have historically been steered away from quantitative studies. Having an answer for the rhetorical “What is math good for?” can boost a student's motivation for learning math and open the door to consideration of STEM careers. This presentation gives an overview of how math skills are explicitly addressed throughout a 10-week (one quarter) general education course, “Physics of Musical Sound,” taught at Central Washington University. Examples of specific in-class exercises will be described, as well as how math is incorporated into collaborative term projects. A discussion will be provided of what has worked, and not worked, throughout 25 years of teaching this course.
Sound levels of the UVU pedestrian bridge
Authors: Sampson Jacob , Setter Isaac , Patchett Brian D. , Amin Abolfazl , Goates Joshua , Andersen Bonnie
Published: July 2024

Utah Valley University provides a pedestrian bridge to travel from a train station to the school over Interstate-15. Due to traffic noise, people using the bridge could be exposed to sound levels that damage their hearing. Sound level measurements have been made at several locations on the bridge with two different instruments, the first being an Extech (Knoxville, USA) SL400 noise dosimeter and the other being a Larson Davis (Depew, USA) 831C sound level meter. Sound levels have ranged from 55 to 102 dB, depending on time of day and location on the bridge. In addition to our experimental results a COMSOL model was also developed to simulate the interactions of the freeway noise with the bridge, demonstrating how the geometry of the bridge affects the noise exposure of pedestrians. The Occupational Safety and Health Administration (OSHA) limit for non-occupational noise exposure of 100 dB is 15 minutes, suggesting that pedestrians that linger on the bridge could be exposed to damaging levels of sound. This research seeks to better understand and quantify the noise levels that pedestrians experience on the bridge.
A unified framework for creating soundscape perception indices based on the SSID Protocol
Authors: Mitchell Andrew , Aletta Francesco , Oberman Tin , Kang Jian
Published: July 2024

The soundscape approach provides a basis for considering the holistic perception of sound environments, in context. While steady advancements have been made in methods for assessment and analysis, a gap exists for comparing soundscapes and quantifying improvements in the multi-dimensional perception of a soundscape. To this end, there is a need for the creation of single value indices to compare soundscape quality which incorporate context, aural diversity, and specific design goals. Just as a variety of decibel-based indices have been developed for various purposes (e.g., LAeq, LCeq, L90, Lden, etc.), the soundscape approach requires the ability to create novel indices for different uses, but which share a common language and understanding. We therefore propose a unified framework for creating both bespoke and archetypal single index measures of soundscape perception based on the soundscape circumplex model, allowing for new indices to be defined in the future. The implementation of this framework is demonstrated through the creation of a public space typology-based index using survey data collected under the SSID Protocol. Indices developed under this framework can enable a broader and more efficient application of the soundscape approach in design, planning, and regulation.
Developments in an acoustic resonance test for the detection of manufacturing anomalies in hydroelectric generator stator windings
Authors: Venne Kevin , Kirouac Mathieu , Provencher Hélène , Lévesque Mélanie , Soares Mathieu
Published: July 2024

To meet the ever-increasing demand for electricity, Hydro-Québec (HQ) is seeking to simultaneously increase the power of its generating stations while improving its service quality. Thus, the company has tasked its research institute to investigate innovate methods to meet the aforementioned goals. Of interest in the current study is the development of an acoustic resonance test (ART) to improve the quality control (QC) in the manufacturing of hydroelectric generator stator windings. Since HQ and its suppliers are investigating new fabrication methods for stator windings to meet the required timelines and increased power requirements, QC is required to ensure the service quality of its new hydroelectric generators. Typical manufacturing anomalies found in stator windings are delamination and air pockets between insulation layers. Such anomalies can result in an acceleration in the degradation of the winding insulation, which reduces the service quality of hydroelectric generators. To benchmark the ART method, the results of the suspected locations of the anomalies along the stator windings were compared with an acoustic camera and the locations were dissected and inspected under microscope for validation. Ten different stator windings were tested and two metrics (variations in both force and frequency responses) were found to indicate the location of delamination sites in the stator windings and corroborated with the result of both the acoustic camera and the dissections.
Effect of subsequent context on the real-time interpretation of ambiguous target words in spectrally degraded speech
Authors: Tinnemore Anna R. , Gordon-Salant Sandra , Goupell Matthew J.
Published: July 2024

Subsequent context in a sentence can be used to revise the interpretation of a word that was not clearly heard, a frequent occurrence in degraded speech. One strategy for avoiding the cognitive cost associated with revising an initial interpretation is to delay commitment to an interpretation until the end of the sentence, sometimes called a “wait-and-see” strategy. Listening with a significant hearing loss (i.e., constantly hearing degraded speech), may prompt a listener to use this strategy even in relatively easy listening conditions. This study used an eye-tracker to record gaze patterns during a phoneme classification task of ambiguous target words in two levels of background noise ( + 5 and −5 dB SNR). Participants either used cochlear implants (CIs) or were presented 8-channel noise vocoded speech. The target words were at the beginning of sentences; the subsequent context cued one target word interpretation (based on phoneme classification) or the other. We hypothesized that listeners who use CIs will demonstrate a delaying strategy at both levels of background noise, while listeners who have acoustic hearing will only demonstrate a delaying strategy at the highest level of background noise. These findings have implications for rehabilitative strategies to improve communication outcomes in adults with CIs.
Contributions of auditory processing and cognition to the development of frequency discrimination performance during adolescence
Authors: Benedict Jordin T. , Sereki Serena A. , Mussoi Bruna S. , Huyck Julia J.
Published: July 2024

Performance on auditory perceptual tasks develops throughout adolescence, likely due to the development of auditory and cognitive regions of the brain. We investigated the contributions of auditory processing and cognition to frequency discrimination. Frequency discrimination thresholds were measured in three conditions using a series of 3AFC tasks. For two conditions, each stimulus was two 15-ms tone pips separated by 100 ms. These stimuli were used both with a 3-down, 1-up procedure (threshold = 79.4%) with the method of constant stimuli (threshold = 66.7%). The third condition used a 130-ms stimulus and a 3-down, 1-up procedure. The auditory electrophysiological acoustic change complex was measured passively using an 800-ms tone that changed from 1000 Hz to a lower frequency. Cognitive testing was also administered. Preliminary results suggest thresholds correlate between conditions and performance improves with longer stimuli. Adolescents (10-17 years) performed worse than young adults (18-23) on only the adaptive-tracking conditions. Cognition contributed more to these conditions than the condition using the method of constant stimuli, suggesting that age differences on adaptive conditions are caused by cognitive development. Adolescents had larger acoustic change complex responses to the frequency contrasts. Behavioral data did not correlate with the electrophysiological data. [Funded by NIDCD].
Post-auricular orientation of auditory attention in sound field versus virtual sound space
Authors: Markotjohn Melina , Aiken Steven
Published: July 2024

The post-auricular muscle in many species’ changes orientation of external ears to improve hearing for biologically relevant sounds. The muscle exists in humans but cannot similarly change direction of their ears. Objectives focused on measuring activity of muscle during speech-in-noise task where orientations of speaker and noise were controlled experimentally to determine how signal-to-noise varies as function of presentation mode and azimuth (target speech and noise co-localized, 45°, or spatially separated, 135° and 45°, respectively). It was hypothesized that activity would be elicited in same proportion of subjects when evoked via earphones compared to speakers; there would be no significant differences in magnitude between conditions; maximum engagement would be observed with speech 135°, noise 45°. Activity was recorded with electrodes affixed around ears, outer canthi and neck, while listeners completed a spatialized listening test (locations of speaker/noise controlled experimentally). There was significant main effect of channel; significant interaction between presentation mode and channel; no significant differences between presentation modes for other muscles; no significant effect of azimuth. Engagement in virtual sound-space suggests that muscle activation occurs consequently of spatially directed attention, even when changes in pinna orientation are unlikely to have effect on sound heard.
Finding the ratio of perceived duration between tones with flat and percussive amplitude envelopes
Authors: Wessel Connor , Zhang Cindy , Schutz Michael
Published: July 2024

The extensive literature on duration assessment generally uses tones with clear onsets and offsets. However, simplistic sounds can fail to evoke the same processes used when listening to sounds with time varying amplitude envelopes (Schutz & Gillard, 2020). To facilitate future research on the duration assessment of time varying tones, here we explore the ratio at which constant amplitude ‘flat’ and varying amplitude ‘percussive’ tones are perceived as the same duration. We will use an adaptive staircase procedure, in which flat and percussive tones are presented in pairs and participants state which tone sounded longer in duration. Each response changes the duration difference on subsequent trials and continues until responses converge around a specific point, with convergence defined as four consecutive reversals in response direction. One instance of these trials constitutes a single staircase; we will then calculate the millisecond point of subjective equality between flat and percussive tones by finding the average point of convergence between multiple, interleaved staircases. Beyond providing guidance on stimulus durations for studies comparing amplitude envelope, we aim to shed light on the process of duration assessment in sounds with time-varying amplitude envelopes.