bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic transmission loss observed on a tomographic array in the Beaufort Gyre during 2016–2017
Authors: Worcester Peter F. , Dzieciuch Matthew A. , Vazquez Heriberto J. , Colosi John A. , Krishfield Richard A.
Published: November 2023

The Arctic Ocean is undergoing dramatic changes. The 2016–2017 Canada Basin Acoustic Propagation Experiment (CANAPE) was conducted to assess the effects of the changes in the sea ice and ocean structure in the Beaufort Gyre on low-frequency underwater acoustic propagation and ambient sound. An ocean acoustic tomography array with a radius of 150 km that consisted of six transceivers and a long vertical receiving array measured the impulse responses of the ocean every four hours using broadband signals with center frequencies that ranged from 172.5 to 275 Hz. Ice-profiling sonar data showed a gradual increase in ice draft over the winter with daily median ice drafts reaching maxima of about 1.5 m, suggesting that the ice was first-year ice. The transmission loss of early, resolved ray arrivals from steep ray paths with lower turning depths below 500 m was lowest when open water was present and increased as the ice draft increased. The transmission loss per surface reflection increased with center frequency and surface grazing angle. The values are greater than observed during the 1988–1989 Greenland Sea Tomography experiment, but the ice conditions likely differed significantly.
Effect of stud dimension and material properties on predicted and tested sound insulation
Authors: Dong Wayland , Shafer Benjamin M. , Girdhar Sunit , LoVerde John
Published: November 2023

A common wall design is gypsum wall board (GWB) cladding on each side of a row of steel studs, which may or may not include insulation. Steel studs are available in a range of metal thicknesses, dimensions, and structural properties. Most published laboratory testing on these walls uses a small subset of the available stud types, and the acoustical effect of changes to stud parameters has not been completely studied or documented. As a result, theoretical models of stud walls have not been evaluated over the full set of stud parameters. This work is a continuation of previous laboratory testing programs to systematically investigate the acoustical effects of stud properties. This paper analyzes the effects of stud depth and structural properties on third-octave transmission loss values and single-number ratings and investigates the capability of existing models for wall transmission loss to predict performance of walls with an expanded set of stud parameters. Our findings indicate that the parameters currently used to describe stud walls in acoustical test report are not sufficient to characterize the assembly.
Acoustic design considerations for vertical education buildings
Authors: Islam MD Nifarul , Chen Kanvin
Published: November 2023

In recent years, the design and construction of vertical (multi-story) education buildings are gaining preference over traditional single storied multi buildings precincts. This change is driven by the need to incorporate modern architectural design features, optimize spatial use, and construct sustainable, energy efficient buildings for education precincts. Vertical education precincts pose multiple acoustic design challenges, including consideration for adequate acoustic separation between noise sensitive adjacencies, noise emissions from rooftop mechanical plant to outdoor learning areas, and the provision of adequate reverberation treatment while aligning with the interior design intent. Also, with the use of cross laminated timber (CLT) gaining in popularity, this presents challenges of its own. This paper discusses typical acoustic design challenges faced while designing vertical education precincts and provides recommendations adopted to resolve each design challenge.
The booming party walls being constructed in the skyscrapers of Toronto
Authors: Mahn Jeffrey , Müller-Trapet Markus , Skoda Sabrina , Cunha Iara
Published: November 2023

With eight new 300 m or higher buildings and another ninety shorter skyscrapers either under construction or proposed for the booming Toronto real estate market, there is no shortage of work for acoustic consultants in Toronto at the moment. Most of the high-rise buildings allocated for residential use include concrete floors and ceilings, glass curtain walls, and lightweight, steel stud gypsum board interior walls. A party wall design that has become popular among architects is a double steel stud wall with one or more layers of gypsum board attached to the studs in the gap between the rows of studs in addition to the gypsum board attached to the exterior of the studs. Typically, the transmission loss values for the wall designs used to demonstrate compliance with the building code are those for single stud walls with equivalent stud gauges and numbers of exterior layers of gypsum board. Due to the lack of available data, the National Research Council of Canada measured the transmission loss of many of these wall designs and found that adding the gypsum board in the cavity between the rows of studs has a significant effect on the transmission loss below 200 Hz.
A case study on flanking noise transmission through curtain wall in an office building
Authors: Sheikh Mahbub A.
Published: November 2023

Curtain walls are a popular architectural element for the design of modern commercial building façade. With the advanced technologies and recent developments in building materials, curtain walls are developed with different lightweight materials, providing a spectacular visual identity of buildings and a number of functional design advantages to building interiors, including acoustic comfort, weather resistance, and thermal comfort. With the availability of high-performing glazed curtain walls these days, external noise in a commercial building adjacent to busy roads and railway lines is easily controlled, and acoustic comfort at internal space be achieved to suit the design intent. However, the lack of building design integration between building envelop, structural, and interior systems would often lead to airborne flanking noise transmission between different occupancies resulting in poor acoustic privacy. Such a post-design issue is often undesirable to the occupants and is an expensive exercise to retrofit. In this paper, a case study is conducted in a building where office workers in a three-story office building raised concerns about noise annoyance and acoustic privacy between two different tenancies on levels one above the other. This paper discusses the acoustic issues causing the compromised acoustic privacy, the method of acoustic investigations, the recommended noise control mechanisms, and finally the outcome of mitigation measures.
Humpback whales increase the length of their songs during nearby airgun operations
Authors: Noad Michael , Dunlop Rebecca
Published: November 2023

There is concern that noise from “airguns” used during oil and gas exploration may cause behavioral changes in marine mammals. One important behavior of some mysticete whales is the production of songs which are likely used as reproductive displays. Humpback whales have conspicuous songs but there are few studies on the impact of noise on their singing behavior. Here, we test the hypothesis that airgun noise causes individual humpback whales to reduce the duration of their songs. In a series of experiments off the east coast of Australia, we exposed migrating humpback whales to airguns. We tracked and recorded singing males when we towed airguns through the study area as well as when there were no vessels or airguns present. We also noted interactions between singers and nearby conspecifics. Humpbacks usually stop singing when they join with others, and so joining is both a predictor of song duration and a biologically relevant outcome. Contrary to expectations, whales that were already singing prior to airgun exposure produced significantly longer songs than unexposed singers. However, the small number of whales that started singing during airgun exposure produced significantly shorter songs.
Does female choice for song complexity drive sexual selection in humpback whales?
Authors: Garland Ellen C. , Allen Jenny A. , Eichenberger Franca , Garrigue Claire , Bonneville Claire , Steel Debbie , Carroll Emma L.
Published: November 2023

Male humpback whales (Megaptera novaeangliae) sing a long, stereotyped, and culturally transmitted song display. While song likely functions in sexual selection, whether it is primarily directed at females and/or males is still debated. Most males within a single population sing the same, slowly evolving song type. However, multiple humpback whale song revolutions (where a song introduced from a neighboring population rapidly and completely replaces the existing song) have spread across the South Pacific region from the east coast of Australia to French Polynesia. How cultural evolution and sexual selection interact in this complex vocal display is not well understood. We investigated song-mediated female mate choice in humpback whales using 20 years of paternity data and song recordings from individually identified males in the small, South Pacific population of New Caledonia. As mating has never been observed in humpback whales, we assessed male reproductive success (calf paternity) and song complexity (unit repertoire and song length) of individual males. We found that males who successfully sired offspring had on average higher song complexity than males who did not sire offspring. This suggests females may select mates at least partially based on song complexity, and thus, song being primarily directed at females.
Air availability and expandable vocal tracts shape the duration of mammal calls
Authors: Rogers Tracey L. , Dunn Jacob , Walker Benjamin J. , Chambers Lucinda E. , Martin Kobe , Ravignani Andrea
Published: November 2023

The longest and shortest duration calls produced by any animal, spanning five orders of magnitude, are produced by whales. This is at odds with our understanding that the duration of an animal’s call is driven by its size. In fact, we intuitively assume that large animals, with large vocal tracts, make long duration sounds, whereas small animals make shorter sounds. We compare the duration of the shortest and longest calls in the repertoire across 174 mammal species and show the relationship between body mass and vocalization length breaks down for mammals. For mammals that call underwater, those with modified vocal tracts (e.g., air sacs, expandable trachea, etc.) that move air between expandable reservoirs produce longer calls than predicted for their size. Those mammals without modified vocal tracts that call underwater produce much shorter calls than expected. We explore here the different evolutionary pressures that shape vocal signaling.
Abandon FLIP! The following being a completely unembellished and sober account of a disastrous field experiment with Doug Cato, with side comments on his subtle influences on bioacoustic animal tracking
Authors: Thode Aaron M.
Published: November 2023

I have only been to sea once with Doug Cato, as a graduate student. It did not end well. In 1996 the R/P FLIP, a manned spar buoy, was deployed off the coast of San Diego to test advanced passive acoustic tracking methods on baleen whales, with Doug along as an invited guest. He had long been interested in acoustic means of localizing whales and was one of the first scientists to suggest using relative differences between received levels on hydrophones (instead of just the relative timing) for fixing an animal call’s location [JASA 104(3), 1667–1678]. This idea is the fundamental basis behind “matched-field processing” (MFP), the technique behind the FLIP test. The trip was supposed to collect three weeks of data; instead, it collected 42 h. This presentation will explain the challenges of abandoning a vessel at sea, and why garbage scows are underappreciated. It will also explain my brief involvement in Mike Noad’s and Doug Cato’s HARC field experiment as part of another MFP demonstration, and why that did not end very well either. Interlaced with these tales of disaster is a review of how Doug’s thoughts on animal tracking have re-emerged under a variety of circumstances, especially in arctic bioacoustics.
Vocalizations of two conspecific damselfish (Pomacentridae) at two Australian World Heritage sites: The Ningaloo Coast and the Great Barrier Reef
Authors: Azofeifa Solano Juan Carlos , Parsons Miles , Brooker Rohan , McCauley Robert , Erbe Christine
Published: November 2023

Novel methods to use Ocean Sound to address ecological questions are increasingly being developed but require optimization and validation to ensure their reliability. Source validation, increasing the number of known soniferous species of marine fauna, and characterizing their acoustic repertoires are important components of this effort. Coral reefs are remarkably complex, diverse, and noisy environments, inhabited by many soniferous species, hindering the association of vocalizations with the emitting species. Damselfish (Pomacentridae) are common and conspicuous reef fishes that have been relatively well-studied due to their abundance, territorial behaviors, and sound production. Most fish sound studies support that fish vocalizations are species-specific, often showing niche acoustic partitioning to avoid competition across frequency and time. It is imperative to record fish vocalizations in the field to avoid distortion in their acoustic attributes, which then can be used for further analyses such as automated detections. Here, we characterize the vocalizations of Dascyllus aruanus and Dascyllus reticulatus using field-experimental settings for in situ recordings from the Ningaloo Coast and the Great Barrier Reef. [Work supported by the BHP-AIMS Australian Coral Reef Resilience Initiative. JCAS was supported by Curtin University and BHP-AIMS in the form of a Curtin Strategic Scholarship and Top-up Scholarship.]
Transient sounds of hydrothermal vents
Authors: Smith Brendan , Barclay David
Published: November 2023

Transient acoustic signals were recently detected at the Main Endeavour Hydrothermal Vent Field which are believed to be generated by both geological and biological sources, including vent chimney collapse, impulsive geological signals, fish grunts, and snapping. These signals provide an opportunity for long-term passive acoustic monitoring of hydrothermal vent activity and ecology. This method offers advantages of longevity and robustness compared with other monitoring techniques, as the sensor can remain a safe distance away from the high-temperature, caustic vent fluid. Utilizing recordings from a bottom-mounted hydrophone on Ocean Networks Canada’s NEPTUNE observatory, a detector was implemented to identify and classify these signals in more than one year of acoustic data after 2016. While only a single hydrophone is available at this site, an array of three seismic accelerometers also on the NEPTUNE observatory was used to localize transient events when sufficient signal-to-noise ratio was available to provide confidence in the location estimate. Correlation of the transient sounds with seismic activity at the vent field was also evaluated, suggesting that passive acoustic monitoring can augment seismic records to provide additional information regarding geological activity at hydrothermal vent sites.
Estimating mixed gas fluxes with geochemically informed broadband acoustic methods: What the flux?
Authors: Ladroit Yoann , Watson Sally , Seabrook Sarah , Weidner Elizabeth , Weber Thomas C. , Nau Amy , Lucieer Vanessa , Lamarche Geoffroy
Published: November 2023

Over the past few years, improvements in broadband split-beam echosounders have made it possible to obtain precise measurements of bubble-size distribution and density of gas seeps. Here, we model acoustic volume backscattering of a group of bubbles with a multi-modal size distribution that we matched to real-time acoustical measurement over a gas seep. The results are profiles of bubble size distribution descriptors (e.g., distribution type and parameters), density and ratio of the various components (i.e., gas composition). To test the ability of this methodology to differentiate gas flux composition and estimate gas flux magnitudes, we applied it in a semi-automated fashion on broadband data (12 to 250 kHz) acquired in the Bay of Plenty (NZ) over mixed gas seeps (e.g., CO2, CH4). Model outputs were compared with real-time dissolved gas measurements to constrain gas composition, magnitude, and ground-truth methodologies. The method can be applied to a variety of marine seeps to produce regional flux estimations, improving oceanic carbon budgets and our understanding of downstream feedbacks, such as localized deoxygenation or ocean acidification.
Toward ultrasound-mediated elasticity modulation and monitoring in the crystalline lens
Authors: Lafond Maxime , Ganeau Alice , Foullounoux Clément , Legrand François , mascarelli Frédéric , Gain Philippe , Thuret Gilles , Catheline Stefan , Lafon Cyril
Published: November 2023

Presbyopia is the age-related stiffening of the crystalline lens, reducing near vision. We propose ultrasonic cavitation to interact with the lens structure and restore flexibility by disrupting the disulfide bonds responsible for lens stiffening. Peak negative pressure of 25MPa for 6-μs pulses at 2 MHz with a 100 Hz pulse repetition frequency allowed cavitation nucleation in the lens nucleus of both 6-months and 3-years old porcine eyes. Disulfide bonds disruption was evaluated in both ovoalbumin gels and ex vivo lens using Raman spectroscopy. We explored the measurement of surface wave dispersion over a 0.1 to 2 kHz frequency range to evaluate viscoelastic properties of the lens samples. We identified two regions in the dispersion curves: a sharp decline at low frequency due to guided waves and a gradual slope at high frequency, attributed to viscoelastic dispersion of a Scholte wave. By fitting the dispersion curves with a Kelvin–Voigt model, we found that while the impact of ultrasound remained uncertain, elastography allowed appreciating the age-dependentshear and viscosity moduli.
Quantitative collagen fiber assessment in myopic guinea pig eye sclera using a cylindrical Gaussian form factor at 80 MHz
Authors: Ito Kazuyo , Hoang Quan V. , Hoerig Cameron , McFadden Sally , Mamou Jonathan
Published: November 2023

Myopia (also called near-sightedness) is an irreversible ocular abnormality that occurs when the eye is excessively elongated, resulting in defocused images and vision. When myopia progresses to pathological myopia, the possibility of permanent vision loss is extremely high. Therefore, it is important to identify early myopic eyes likely to progress to pathologic myopia and vision loss to start treatment and intervene as soon as possible. As myopia progresses, posterior eye elongation is caused by changes in the microstructural properties of the sclera including decreased collagen density and fibril diameters. High-frequency quantitative ultrasound (QUS) allows measuring biomechanical parameters associated with changes in tissue microstructure. This study investigated microstructural changes occurring in the posterior sclera in myopic guinea pig eyes using two independent QUS approaches at 80-MHz: envelope statistics quantification using the Homodyned-K distribution and backscatter coefficient quantification using a cylindrical Gaussian form factor. QUS parameters suggest changes in collagen fiber size occur in myopic sclera and is associated with microstructural changes in the scleral collagen fiber homogeneity and density. In conclusion, high-frequency QUS has the potential to quantitatively characterize microstructural changes that occur in the posterior sclera during myopia development and/or progression.
Loss-based optimizer switching to solve 1-D Helmholtz equation using neural networks
Authors: Dharanalakota Veerababu , J Pavan K. , Ghosh Prasanta K.
Published: November 2023

In this paper, 1-D Helmholtz equation is solved using physics-informed neural networks. In general, either the L-BFGS or ADAM algorithm is used to perform the optimization procedure. Unlike ADAM, L-BFGS is structured to reduce the loss function at each iteration. However, it becomes stagnant and fails to reach the global minimum at higher frequencies due to lack of momentum in the direction of the global minimum. On the other hand, ADAM has the advantage of added momentum. However, it requires a manual tuning of hyperparameters at each frequency to converge to the global minimum. Hence, one optimizer alone is inefficient to predict acoustic field at higher frequencies. This work proposes an algorithm called loss-based optimizer switching (LOS). This approach intelligently switches between L-BFGS and ADAM based on the specific criteria on the loss value to leverage the strengths of both optimizers. The performance of the LOS is evaluated by comparing the relative error between the predicted solution and the exact solution up to 3500 Hz. At 500 Hz, the relative errors with all three algorithms lie below 1.5 × 10−3. However, at 3500 Hz, the relative errors are observed to be 6.6 × 10−3, 0.92, and 0.28 with LOS, ADAM and L-BFGS, respectively.
Impact on quality and diversity from integrating a reconstruction loss into neural audio synthesis
Authors: Liu Yunyi , Jin Craig
Published: November 2023

In digital media or games, sound effects are typically recorded or synthesized. While there are a great many digital synthesis tools, the synthesized audio quality is generally not on par with sound recordings. Nonetheless, sound synthesis techniques provide a popular means to generate new sound variations. In this research, we study sound effects synthesis using generative models that are inspired by the models used for high-quality speech and music synthesis. In particular, we explore the trade-off between synthesis quality and variation. With regard to quality, we integrate a reconstruction loss into the original training objective to penalize imperfect audio reconstruction and compare it with neural vocoders and traditional spectrogram inversion methods. We use a Wasserstein GAN (WGAN) as an example model to explore the synthesis quality of generated sound effects, such as footsteps, birds, guns, rain, and engine sounds. In addition to synthesis quality, we also consider the range of sound variation that is possible with our generative model. We report on the trade-off that we obtain with our model regarding the quality and diversity of synthesized sound effects.
Learning a surrogate Pekeris waveguide model
Authors: Spendlove Jay C. , Transtrum Mark K. , Neilsen Tracianne B.
Published: November 2023

Underwater sound propagation models predict transmission loss (TL) given environmental parameters, such as seafloor sediment parameters. Also of interest is the reverse: Can seafloor parameters, such as sediment density, sound speed, and attenuation, be inferred from ocean acoustic data? This inverse problem can be addressed using information geometry tools for parameter identifiability analysis and model reduction, where we identify parameters that can be removed from a model without sacrificing accuracy. Critical to these methods for model reduction is the ability to evaluate derivatives of the model’s TL predictions with respect to model parameters. Automatic differentiation (AD) allows for rapid evaluation of a model’s derivatives but may face some challenges for implementation with sound propagation models, including models being written in “legacy code” and having non-differentiable points in the function space. Our solution is to train a surrogate machine learning (ML) model which can circumvent these challenges, and which we can apply AD to. We demonstrate this method using the Pekeris waveguide model of the ocean. We compare the surrogate and original model outputs and demonstrate the process of model reduction using a ML surrogate model. [Work supported by Office of Naval Research.]
Challenges for flexible distance learning professional acoustics education
Authors: Burgess Marion
Published: November 2023

A fully flexible, distance learning program comprising a number of modules has been available for those entering the acoustics consulting industry for over a decade. The flexibility requested by the association for the Australasian Acoustical Consultants (AAACs), means each of the modules can be commenced at any time and there are no firm deadlines for completion. The program has been very successful with satisfied students and employers. Clearly there is a great benefit for such flexibility as the industry does not recruit new staff at times that fit the University semester system. Hence, other options such as a microcredential approach are not always suitable. Also the students are able to adjust their progress in accordance with the varying work pressures of consultancies. However, the open approach means that there are challenges for the management of the program. These include always being available for processing new applications, supporting and guiding current students, undertaking the marking as well as updating the content, assignments and tests. This paper will discuss the challenges and the changes that have had to be made and those that will need to be introduced to ensure the long term viability of the program.
What does learning sound like? A STEM outreach experience
Authors: Ottley Matthew , Young Fiona
Published: November 2023

What an acoustic engineer does is generally not well understood by high school students, and this likely applies to the broader architecture and design fields. Acoustic engineers and architects who are engaged in the design of high schools and classrooms also may not have been in a class of students since they left school. This presentation outlines a Problem Based Learning experience run for high school students in Australia which provided insight into the above gaps for both students and practitioners. The student-centred challenge has been run in two formats. The first was run weekly over three 100 minute sessions, while a condensed format was later run as an 80 minute hands-on design challenge. Both formats involved an architect(s) and an acoustician facilitating the challenge. The students considered the use, acoustic requirements and affordances of design in a classroom. Students were given a classroom with poor acoustics and challenged to develop and present a design solution which improved the area for learning, including room acoustics. The challenge involved mathematics (Sabine equation), measurement (including scale and reverberation time), and architecture.
Prediction of psychological impacts of noise from ventilation systems
Authors: Ma Kuen Wai , Mak Cheuk Ming , Chung Fu Lai Korris , Wong Hai Ming
Published: November 2023

Air-conditioning ventilation systems are essential for maintaining good indoor environmental quality. However, the noise generated by these systems can have negative psychological impacts on occupants, such as dissatisfaction, discomfort, disturbance, and unacceptability. This problem cannot be solved simply by reducing the noise level. With the help of a valid, reliable, and applicable psychometric tool called the psychoacoustics perception scale (PPS), the psychological impacts of the noise on human general judgment (Evaluation, E), sensitivity to the magnitude (Potency, P), and sensation of the temporal and spectral compositions (Activity, A) of sounds can be quantified. A holistic sound quality assessment was proposed to cover the objective assessments of traditional indoor criteria and acoustic metrics, as well as subjective assessment using the PPS. The correlations found between the objective characteristics of the noise from ventilation systems, the PPS scores, and the occupants’ cognitive performance can extend traditional noise level prediction to the prediction of psychological impacts of air-conditioned environments. This advanced knowledge of noise prediction will help acoustic professionals in the design of teaching courses in acoustics, noise, and vibration control, as well as in building services engineering, and throughout the built environment.
Design and characterization of a low-speed aeroacoustic wind-tunnel research facility at IIT Kanpur
Authors: Mimani Akhilesh , Kumar Shubham , Kumar Randhir
Published: November 2023

This work presents the design and characterization of a state-of-the-art low-speed aeroacoustic wind-tunnel at Indian Institute of Technology Kanpur (IITK), which is a newly commissioned research facility for the experimental study of flow-induced noise generated from bodies placed in a flow field. This open-circuit, open-jet suction facility which is unique to IITK, is also the first aeroacoustic wind-tunnel in India. The facility is powered by large centrifugal fan of 75 KW rating which is controlled through a variable frequency drive. To achieve a low background noise, carefully designed parallel baffle mufflers (PBMs) are placed at the fan inlet and outlet. The inlet silencer is connected to lined diffuser and a bell-mouth collector which opens in a fully anechoic chamber made from metallic wedges, and its internal dimensions are 3.5 m × 3.5 m × 3 m. The chamber can provide a reflection-free environment beyond 250 Hz. A smooth contraction-nozzle of ratio 10:1 whose profile follows a fourth-order spline, and a settling-chamber with honeycombs and flow-screens is placed on the other side of the anechoic chamber. The test-section of size 600 mm × 600 mm is attached to the exit plane of the nozzle, and can provide flow speeds up to 45 m/s, where the maximum turbulence intensity was less than 1%.
Design and characterisation of a 3-D microphone array for windtunnel measurements
Authors: Wills Angus , Awasthi Manuj , de Silva Charitha , Moreau Danielle , Doolan Con
Published: November 2023

A three-dimensional (3-D) array of GRAS 40PH-10 CCP Free-field Array Microphones has been designed for use in the UNSW anechoic wind tunnel (UAT) for aeroacoustic measurements. The array consists of 192 microphones split into three identical planar arrays of 64 microphones which are placed on both sides and above the potential core of the open-jet that issues into the wind tunnel test section. The planar arrays feature an Underbrink spiral comprised of eight arms of eight microphones each. The spiral configuration was selected to maximize signal-to-noise ratio (SNR) and minimize the beamwidth given the geometrical restrictions of the UAT. A white noise speaker was placed at a range of locations within the testing domain to characterize the source localization abilities of the array as a function of position and frequency. Furthermore, a pair of independent white noise speakers were placed at various separation distances to determine the array’s capability to identify multiple sources within the domain. A 3-D implementation of conventional cross-spectral beamforming and Clean-SC deconvolution algorithms was used, and the performance of each was compared. It was determined that Clean-SC was the preferred method for 3-D beamforming in terms of source localization accuracy, SNR, and beamwidth, despite the higher computational cost.
AeroFeathers: Feathered airfoils inspired by the quiet flight of owls
Authors: Johnston William , Godakawela Janith , Nobles L P. , Lomte Amulya , Carrillo-Munoz Maria , Sharma Bhisham
Published: November 2023

Owls are well-known as the quietest flying birds. Recent studies show that they achieve noise-less flight because of their specialized feather design. Their feathers have three important components: a velvety surface texture, comb-like hooks on their leading edge, and jagged fibrous fringes on their trailing edges. Some researchers have attempted to imitate these design features within airfoil designs to reduce aeroacoustic noise emitted by fixed wing and vertical lift vehicles; however, such features cannot be easily fabricated using traditional manufacturing processes. In this student-led project funded by NASA’s University Student Research Challenge, we leverage our established success at additively manufacturing fibrous structures to introduce a new method to 3-D print velvety textures, fibrous fringes, and flexible edge serration using low-cost material extrusion-based printing methods. By altering the printer’s G-code, we create customized feathered airfoils with individual design parameters, including serration thickness and fringe density. We conduct acoustic tests in an anechoic chamber and aeroacoustic tests in an acoustic wind tunnel to determine the effect of each parameter on the overall acoustic signature of the airfoil. We analyze the data and explain the role of owl feather-like features on the noise reduction performance of propeller blades and scaled fixed-wing airfoils.
Simultaneous measurement of unsteady surface pressure and leading edge noise of a NACA0012 airfoil
Authors: Kisler Roman , Jiang Chaoyang , de Silva Charitha , Doolan Con , Moreau Danielle
Published: November 2023

Airfoil-turbulence interaction noise, which is created whenever turbulent flow encounters an airfoil, is a major source of unwanted noise emitted byaircraft and turbomachinery. Despite being a major research focus overthepast decades, the accurate prediction and understanding of airfoil–turbulence interaction noise remain an open question. This experimental investigation involved simultaneous measurements of unsteady pressure fluctuations at 61 locations across the surface of a NACA0012 airfoil and far field sound pressure at a phased 64-microphone array. Various square-mesh turbulence grids were placed upstream of the airfoil to vary the isotropic free stream turbulence. Additionally, the influence of the airfoil’s angle of attack as well as different mean flow speeds on the unsteady surface pressure and radiated far field noise was investigated. Ultimately, the links between the simultaneously acquired unsteady surface pressure on the airfoil and the microphone array sound pressure were studied. This provided insight into the mechanisms of leading edge noise source generation and their influence on the radiated far field noise.
A vision of the next era of supersonic flight
Authors: Liu Sandy R.
Published: November 2023

Concorde was decommissioned in 2003, ending civil supersonic aircraft operations in the world. However, today there is continued interest by proponents/developers of supersonic aircraft that believe by utilizing advanced technologies, new supersonic aircraft can be economically viable, safe, reliable, and significantly quieter than the Concorde. In 2004, the International Civil Aviation Organization (ICAO)’s formed a Supersonic (noise) Task Group to monitor whether supersonic research and developments could revive lost high-speed capabilities and support commercially viable, environmentally responsible global aviation operations. Since then, the United States has been focused on progressing work related to the need for a landing and takeoff noise standard for supersonic aircraft, and an en-route sonic boom standard. This presentation briefly highlights achievements to date that intend on opening the new era of supersonic flight ahead.
Simulations of X-59 sonic thumps and traditional sonic booms propagated around the world for three atmospheric models
Authors: Doebler William , Sparrow Victor W.
Published: November 2023

Propagation simulations of sonic booms from supersonic aircraft through atmospheric data over time at fixed locations provide the opportunity to assess noise exposure statistics for different climate regions. Knowledge of climate-based differences in sonic boom noise exposure statistics is important to ensure that future civil supersonic aircraft noise certification standards are globally applicable and effective. In this presentation, simulated sonic booms from the NASA X-59 Quesst quiet supersonic aircraft and conventional supersonic aircraft were propagated through atmospheric data at 100 locations across the world using PCBoom. Noise exposure statistics are compared for propagation results from three different atmospheric databases (NOAA Global Forecast System, NOAA Climate Forecast System Version 2, and the ECMWF Reanalysis Version 5). These atmospheric models were chosen due to their global coverage, popularity, and database availability. Preliminary statistical models are fit to assess the impact of several factors including flight direction, season, ground elevation, and climate on noise exposure size and loudness. Areas with prevalence of higher noise due to their climate are identified, which could help inform future supersonic aircraft noise standards.
Analysis of sound emissions and physical properties of bubbles generated by breaking waves
Authors: Nelli Filippo , Zhu Shuang J. , Jacob Chintaka , Ooi Andrew , Manasseh Richard
Published: November 2023

Although the relationship between bubble diameter and the corresponding resonant frequency has been known since 1930s, the link between the amplitude of the sound and the physical properties of the bubble is still unclear. Sound amplitude is a parameter inevitably measured when passive acoustic measuring techniques are employed, and its magnitude as measured is related to not only the size of the bubble but also its position in space relative to the measurement point. Here, we present a study where individual bubbles were first generated through a vertical plunging jet and analyzed to establish a link between their diameters and sound emissions. Subsequently, these data were used to predict bubble properties occurring in breaking waves generated in laboratory experiments. A high frequency camera was used to capture images of the bubbles and visually check the accuracy of the diameter and location predictions. Results show good agreement between plunging jet and breaking waves bubbles within the +− 1.5 dB confidence interval; addressing with residual experimental uncertainties should offer further improvements.
Utility of ocean wave parameters for improving predictions of ambient noise
Authors: Rogers William E. , Fialkowski Laurie T. , Brooker Daniel J.
Published: November 2023

This study is concerned with prediction of the “wind noise” component of ambient noise (AN) in the ocean. It builds on the seminal paper by Felizardo and Melville (1995), in which the authors quantified the correlation between AN and individual wind/wave parameters. We utilize hydrophone observations deployed in the north and northeast Pacific Ocean. Wind/wave parameters are obtained from moored buoys and numerical models. We describe a procedure developed for this study which isolates the correlation of AN with wave parameters, independent of mutual correlation with wind speed (residual correlation). We then describe paired calibration/prediction experiments, whereby multiple wind/wave parameters are used simultaneously to estimate AN. We find that the improvement from inclusion of wave parameters is robust but modest. We interpret the latter outcome as suggesting that wave breaking responds to changes in local winds quickly, relative to, for example, total wave energy, which develops more slowly. This outcome is consistent with prior knowledge of the physics of wave breaking, e.g., Babanin (2011). We discuss this in context of the wave spectrum's time/space response to wind forcing.
Disturbing bubbles in drop-on-demand piezo-acoustic inkjet printing
Authors: Versluis Michel , Reinten Hans , Fraters Arjan , Rump Maaike , Saade Youssef , Diddens Christian , Lohse Detlef , Segers Tim
Published: November 2023

Drop-on-demand piezo-acoustic inkjet printing is the method of choice for high-frequency and high-precision droplet deposition. Microbubbles entrained in a piezo-driven silicon MEMS printhead disturb the acoustics of the microfluidic ink channel and, thereby, the jetting behavior. The strong deformations of the air-liquid interface at the nozzle exit may lead to an inward directed air jet with bubble pinch-off and the subsequent entrainment of an air bubble. Here, we use ultrafast x-ray phase-contrast imaging and direct numerical simulations to study the mechanisms underlying the bubble entrainment, where we demonstrate good agreement between experiments and numerics. The entrained bubbles were also visualized in the ink channel of the silicon printhead in a highly sensitive shortwave infrared (SWIR) imaging setup exploiting the optical window at 1550 nm. The infrared recordings show the rich phenomena of acoustically driven bubble dynamics inside the printhead. We also study the resonance behavior of the ink channel as a function of the microbubble size and number of bubbles through theoretical modeling and experiments. The system is modeled as a set of two coupled harmonic oscillators, one for the compliant ink channel and one for the microbubble and where we find excellent agreement between the predicted and measured eigenfrequencies.
Passive acoustic measurement of bubble size and number from a bubble chain
Authors: Roshid Mohammed M. , Manasseh Richard
Published: November 2023

Experiments and matching simulations are presented on the passive-acoustic emissions of a chain of bubbles, with the aim of deducing both the bubble size and number of bubbles from the emitted sound. It is well known that bubble-acoustic interactions cause shifts in frequency from those predicted for single bubbles, complicating the goal of measuring bubble size by measuring frequency, and also affecting the collective resonances of bubbles driven by ultrasound. A horizontal line of identical bubbles was held fixed in space, eliminating uncertainties in earlier studies due to the variable shape and location of freely rising bubbles. At one end of the line, a first, identical bubble naturally emitted a pulse of sound on formation from an underwater nozzle, exciting the rest of the bubbles into a coupled acoustic emission. It was found that a theoretically predicted relation between frequency and the number of bubbles, which can be derived from the coupled equations of motion, permitted an accurate fit to the data. Measurements of two independent spectral peaks unambiguously determined the two unknowns of bubble size and bubble number. However, experiments diverge from theory and simulations for greater than six bubbles, which are speculated may be explicable by network theory.
Classification of head movements during multi-person conversation
Authors: Higgins Nathan C. , Ozmeral Erol J. , Lertpoompunya Angkana , Eddins David A.
Published: November 2023

Hearing-aid processing strategies could be greatly improved by real-time knowledge of the users’ listening intentions, information that may be encoded by characteristic head movements during conversational turn-takingwith multiple talkers, and measured by accelerometers in the hearing devices. First, however, it must be determined to what degree head movements are stereotypic across listeners, or alternatively, unique to each individual, and whether an automatic classifier can identify specific movements. Three cohorts of three young, normal-hearing individuals participated in a semi-structured conversation for 50 minutes. Participants wore hearing aids with accelerometers and were video-recorded. Video recordings were then used to track head movements using zFace (Jeni et al. 2017) and manually annotate head movement and communication activities. Accelerometer data was segmented into 1-s windows and labeled by the annotated activity identified in that window. Features based on temporal and frequency characteristics were used to train multi-class models with across-subject or within-subject design. Significantly better than chance classification was observed for all activities using both model designs, with higher classification accuracy for the models trained on the individuals’ own-data. In summary, head movement behaviors can be classified with short-scale time resolution, and individual differences are a key factor for accurate classification.
Do individual perceptual abilities affect speech recognition with spatial hearing aid processing?
Authors: Rallapalli Varsha H. , Ozmeral Erol J.
Published: November 2023

Individuals with hearing loss experience persistent communication difficulties in noisy conditions, even with specialized hearing aid (HA) processing. Little is known about how HA processing interacts with auditory perceptual abilities required for speech-in-noise listening, possibly leading to mismatched parameters for certain listeners. We investigated how speech recognition with spatial HA processing—intended to reduce signals from off-axis locations—is affected by individual auditory perceptual abilities. 16 listeners with hearing loss completed a sentence recognition in noise task with wearable HAs in omnidirectional processing or binaural beamforming settings. On- (0°) or off-axis ( + 90°) target sentences were mixed with gender-matched two-talker maskers that were either spatially separated or co-located. The Portable Automated Rapid Testing program was used to obtain individual binaural (Spatial Release from Masking task) and monaural processing (Spectrotemporal Modulation Detection task) measures. Data show positive associations between perceptual abilities and speech recognition with omnidirectional processing across target and noise locations and negative associations with beamforming for off-axis targets in spatially separated noise. Relative associations of binaural and monaural processing abilities varied by test condition. The study has implications for individualizing spatial processing parameters in clinical HA fittings. [Work supported by NIH-K01DC018324.]
Development and perceptual evaluation of hearing aids using interactive virtual environments
Authors: Derleth Ralph Peter , Wuethrich Hannes , Simon Laurent , Klockgether Stefan
Published: November 2023

In hearing research, it has been shown that the realism of the test conditions has an influence on speech intelligibility thresholds, the subject's behavior, learning abilities and listening effort. This talk presents two multimodal experiment setups that aim to bridge the differences between the laboratory and reality, focusing on the development and perceptual evaluation of hearing devices. The first laboratory uses 360° video and higher order ambisonics stimuli, a head-mounted display, and a VR perceptual evaluation interface to asses the effect of hearing devices on noise intrusiveness, speech quality, and naturalness. The second laboratory is a large loudspeaker array inside of which subjects movements and behavior can be tracked and videos can be projected on walls. This talk will introduce several challenges encountered in the audio reproduction in these two laboratories and will also present a broad overview of solutions used and developed to ensure the validity of the experimental conditions.
Association between interaural phase sensitivity and performance on the trail making cognitive test
Authors: Zahorik Pavel , Strelcyk Olaf
Published: November 2023

Sensitivity to interaural differences in time or phase critically supports human abilities to spatially localize sounds in the horizontal plane. The trail making test (TMT) is a non-auditory cognitive test that provides information about visual search speed, visual/spatial attention, and executive function. Surprisingly, we have shown strong positive relationships between interaural phase difference (IPD) sensitivity and TMT performance, both in a sample (n = 20) of older adults (48–85 years) with very similar sensorineural hearing loss profiles [Strelcyk et al., 23, 2331216519864499 (2019)], and in a sample (n = 41) of young to middle-aged adults (21–54 years) with normal audiograms [Shehorn et al., Hear. Res. 392, 107982 (2020)]. The fact that associations between IPD sensitivity and TMT performance were observed in both samples suggests that the associations were not related to audiometric sensitivity. Alternative explanations for the associations will be discussed, including potential higher-order relationships with spatial processing abilities and/or cognitive processing speed.