bluuebunny/crossref_metadata_2025 huggingface dataset:
Azimuthal, range, and depth tracking of marine mammal sounds using a drifting acoustic vector sensor and hydrophone array platform
Authors: Laferriere Alison B. , Thode Aaron M. , Bevans Dieter A. , Berkenpas Eric J. , Shepard Charles M. , Freeman Lauren A.
Published: November 2023

Deep-water acoustic tracking of marine mammals typically requires correlating hydrophone signals across both short and large-aperture hydrophone arrays. Here, we demonstrate how a single drifting, depth-controlled platform can obtain two and three-dimensional positional fixes of marine mammal sounds using an acoustic vector sensor and short-aperture arrays, both mounted on an autonomous drifting platform. In February and June 2023 two autonomous opto-acoustic drifters were deployed 50km off San Diego, CA at 250 m depth in 1030 m deep water. Both drifters were equipped with a CTD and acoustic recording system comprised of a 1.75 m aperture vertical hydrophone array, a tetrahedral hydrophone array, and either a 2-D Geospectrum M-35 or 3-D Wilcoxon VS-209 acoustic vector sensor. Throughout the two to three-day deployments, all acoustic sensors detected numerous marine mammal calls, including humpback whales and a pod of common dolphins. Estimates of azimuth and elevation were obtained from the simultaneously sampled acoustic vector sensor and hydrophone arrays, while multi-path and cross-platform processing were employed to extract range information. The results suggest that sparse deployments of drifting vector sensor platforms may be able to map biological distributions over spatial scales that would otherwise require larger numbers of hydrophone-only platforms. [Work supported by ONR TFO.]
Multibeam sonar water column data simulation for improved and automated detection of gas seeps
Authors: Nau Amy , Lucieer Vanessa , Ladroit Yoann , Kunnath Haris , Martin Tara
Published: November 2023

Water column data (WCD) collected by multibeam echosounders (MBES) provide valuable datasets for the detection of gas bubbles. However, the presence of noise patterns, primarily caused by sidelobe interference from seafloor reverberation, limits the usability of WCD. We present a method for simulating characteristic noise patterns in WCD, particularly in Mills Cross configurations, by simulating predicted seafloor reverberation and transducer artefacts. The simulation is based on a reference pattern created from a subset of data and then applied as a correction based on the depth and seafloor backscatter of each ping within the dataset. Noise patterns can be removed by subtracting the simulated data from the original data, allowing for improved analysis of near-benthic water column features such as gas seeps. This method requires no prior knowledge of specific transducer characteristics, making it applicable to a wide range of MBES systems and acoustic targets. This method was applied to two MBES datasets collected simultaneously over a seep field in the Bay of Plenty, New Zealand, as part of the Quantitative Ocean-Column Imaging (QUOI) voyage in July 2018. We demonstrate the utility of applying a reference pattern for detecting the spatial extent of gas seep bases mapped using two different frequencies.
Physics-informed neural network for predicting unmeasured ocean acoustic pressure field
Authors: Yoon Seunghyun , Park Yongsung , Gerstoft Peter , Seong Woojae
Published: November 2023

This study employs a physics-informed neural network in an ocean waveguide to predict the unmeasured acoustic pressure field, leveraging partially measured data. The method addresses a scenario where an acoustic source transmits signals across different ranges and is measured by multiple receivers. The acoustic pressure field in ocean waveguides exhibits rapid spatial variations over kilometer-range scales. The fully connected neural networks encounter challenges when approximating high-frequency functions, known as spectral bias. To mitigate this problem, the measured pressure field is transformed into a low-frequency function for training the neural network. We propose two methods sharing the same neural network architecture but utilizing different information. The first method uses a complex value of the pressure field (i.e., both magnitude and phase), while the second method uses only magnitude. We validate the proposed methods using simulations and experimental data from the SWellEx-96 environment. Results demonstrate that the first method exhibits superior performance with sparse data, while the second method works better in real-world scenarios.
Advancing sound field analysis with physics-informed neural networks
Authors: Karakonstantis Xenofon , Fernandez-Grande Efren
Published: November 2023

This work introduces a method that employs physics-informed neural networks to reconstruct sound fields in diverse rooms, including both typical acoustically damped meeting rooms and more spaces of cultural significance, such as concert halls or theatres. The neural network is trained using a limited set of room impulse responses, integrating the expressive capacity of neural networks with the fundamental physics of sound propagation governed by the wave equation. Consequently, the network accurately represents sound fields within an aperture without requiring extensive measurements, regardless of the complexity of the sound field. Notably, our approach extends beyond sound pressure estimation and includes valuable vectorial quantities, such as particle velocity and intensity, resembling classical holography methods. Experimental results confirm the efficacy of the proposed approach, underscoring its reconstruction accuracy and computational efficiency. Moreover, by enabling the acquisition of sound field quantities in the time domain, which were previously challenging to obtain from measurements, our method opens up new frontiers for the analysis and comprehension of sound propagation phenomena in rooms.
Physics-informed neural networks for characterization of structural dynamic boundary conditions
Authors: Schmid Johannes D. , Bauerschmidt Philipp , Gurbuz Caglar , Marburg Steffen
Published: November 2023

Structural dynamics simulations are often faced with challenges arising from unknown boundary conditions, leading to considerable prediction uncertainties. Direct measurement of these boundary conditions can be impractical for certain mounting scenarios, such as joints or screw connections. In addition, conventional inverse methods face limitations in integrating measured data and solving inverse problems when the forward model is computationally expensive. In this study, we explore the potential of physics-informed neural networks that incorporate the residual of a partial differential equation into the loss function of a neural network to ensure physically consistent predictions. We train the neural network using noisy boundary displacement data of a structure from a finite element reference solution. The network learns to predict the displacement field within the structure while satisfying the Navier–Lamé equations in the frequency domain. Our results show that physics-informed neural networks accurately predict the displacement field within a three-dimensional structure using only boundary training data. Additionally, differentiating the trained network allows precise characterization of previously unknown boundary conditions and facilitates the assessment of non-measurable quantities, such as the stress tensor.
Teaching acoustics across multi-disciplines
Authors: Brown David A.
Published: November 2023

Vibration, sound, and acoustics fundamentals appear in many disciplines and at all stages of life. This presentation covers acoustic concepts and foundations applicable in many professional disciplines that may be suitable for short professional courses, undergraduate, and graduate courses with a particular focus in engineering and underwater acoustics although the lessons may apply to music, noise, bioacoustics, audio, and electromagnetics. Topics include frequency, resonance, quality factor, damping, sensors, transducers, sensitivities, beam patterns, decibels, intensity, power, traveling and standing waves, speed, waveguides, dispersion and more.
Demonstration of colored noise on brainwave activity during reading tasks: An electroencephalogram study
Authors: Tamariska Stirena R. , Tsaih Lucky , Manullang Martin Clinton T.
Published: November 2023

This study investigates the effects of different types of colored noise on brainwave activity during reading task, with a unique intent to use this research as a practical demonstration for the participant to learn about acoustics. Electroencephalogram (EEG) data from 29 participants were obtained and analyzed to assess brainwave activity across all channels when exposed to these colored noises. After brainwave recording process, participants were invited to view their recorded individual brainwave activities and topo mapping, so that they could learn the different colored noises might affecting their brainwave responses. The study found that most of the participants are interested to learn more about how the colored noise affects their daily activity. Besides demonstration to get participants interested in learning noise effects on brainwave activity, our brainwave study revealed that pink noise significantly influenced theta, low alpha, high alpha, low beta, and high beta frequencies during the reading tasks. In comparison, white noise had a notable impact on low and high alpha frequencies, while brown noise yielded significant changes in theta brainwave activity. This research points out that colored noise, could alter brainwave activity. It is potentially affecting cognitive engagement such as alertness and focus. By involving different major students as participants, we demonstrated the tangible effects of acoustics on cognitive functions, fostering a more profound understanding of the subject matter.
When less is more: Reducing environmental noise from open cycle gas turbines with acoustically transparent stacks
Authors: Cazzolato Benjamin , Leav Orddom , Howard Carl
Published: November 2023

Sound radiation from large open cycle gas turbine power stations is strongly refracted by high temperature and velocity gradients in the near field of the exhaust stack outlet. Recent research by the authors has shown that in the presence of a cross-flow, the exhaust plume bends downwind and in doing so leads to significant increases in far-field sound pressure levels of up to 10dB compared to levels predicted from spherical spreading. This paper is the second in a series that explores a unique “acoustically transparent silencer,” which limits sound refraction consequently reducing downwind SPLs by separating the sound from the bulk exhaust flow. The efficacy of the approach is demonstrated two ways; initial characterization studies conducted in the reverberation chambers at the newly renovated Acoustic and Vibration Laboratory, University of Adelaide, and subsequent trials undertaken on a laboratory scale of 250 kW gas turbine in the field. Numerous designs are explored to quantify the effective insertion loss, where it will be shown as the transmission loss of the stack walls is reduced, the effective insertion loss increases, thus demonstrating that less is more. Reductions in ground-plane SPLs of up to 10 dB are achieved with less material and weight compared to traditional hard-walled stacks.
An aeroengine fault diagnosis method using high-frequency acoustic coupling with rotating blade flow field
Authors: Liang Sicong , Huang Xun
Published: November 2023

Utilizing high-frequency sound waves for aeroengine structure diagnosis has been established in previous works. However, exploring its potential in analyzing rotating blade flow fields remains an open area of research. In this study, we propose a non-invasive fault diagnosis method that couples high-frequency sound waves with rotating blade flow fields, performing mode detection of the coupled frequency. As a widely used noise detection technique, acoustic mode detection enables the extraction of spatial information from noise, providing essential insights for noise reduction design. Essentially, the flow-sound coupling arises from nonlinear interactions, wherein the characteristic low-frequency periodic flow is excited by the high-frequencyexternal sound source, generating new coupled acoustic sources that radiate and propagate inside the duct. Mode detection aids in understanding the location and spatial phase information of the coupled acoustic sources. Furthermore, through both simulations and experiments, we have established the connection between fault information and mode spectrum. Finally, we endeavor to employ a machine learning approach to build a fault diagnosis model. In summary, this method ingeniously superimposes low-frequency periodic flow field information onto high-frequency sound waves, achieving high-precision diagnosis of the rotating blade flow field.
Aeroacoustics of finite wall-mounted square cylinders in pressure gradient flows
Authors: Jiang Chaoyang , Doolan Con , de Silva Charitha , Moreau Danielle
Published: November 2023

Flow-induced noise produced by finite wall-mounted cylinders (FWMCs) is a major noise source for aircraft landing gear, rail pantographs and submarine appendages. These applications often encounter flows with various pressure gradients, however, there is little information in the literature on the effects of pressure gradients. Our recent work has demonstrated that the presence of a pressure gradient can significantly affect the near-wake flow structures of a square FWMC with a low aspect ratio of 2.4, thereby suppressing/enhancing the vortex-shedding tones. The current study extends this work to square FWMCs with varying aspect ratios, focusing on the role that aspect ratio plays in the noise generation of square FWMCs in pressure gradient flows. Experiments were undertaken using the open-jet pressure-gradient test rig in the UNSW anechoic wind tunnel, where the square FWMC model was immersed in flows with favourable-, near-zero-, and adverse-pressure gradients at a width-based Reynolds number of 28800. The square FWMC model was installed on a traversing system to realize the change in cylinder aspect ratio. Inside the test model, a series of channels and surface pressure taps were created to measure the unsteady surface pressure using a remote microphone technique. Far-field noise and unsteady surface pressure signals were simultaneously acquired to characterize the combined effects of aspect ratio and pressure gradient on the far-field noise production and reveal the noise generation mechanisms.
Theoretical prediction of unsteady wall pressure during turbulence-airfoil-interaction
Authors: Doolan Con , Kisler Roman , Jiang Chaoyang , de Silva Charitha , Moreau Danielle
Published: November 2023

The turbulence-airfoil-interaction generates unsteady surface pressure, which is an unwanted source of noise in many aerospace and marine applications. Consequently, an accurate methodology is desired to calculate the wall-pressure-spectrum along the chord to create new technology such as quiet wind turbine and drone propeller blades. Theoretical approaches are ideal as they not only provide an efficient means of predicting wall pressure spectra, but also give improved insights into the physical mechanisms controlling noise generation. This paper will explore the accuracy of current theoretical approaches to unsteady wall pressure prediction. It will do this by comparing experimental measurements of wall pressure spectra in a variety of turbulent flow fields with theory. The results show the limitations of common theoretical approaches and the importance of including the effects of turbulence distortion in the theoretical model.
Variability of speech spectra in offices by room types and communication methods
Authors: Toubar Rewan , Mackenzie Roderick , Lee Joonhee
Published: November 2023

The acoustic characteristics of room environments can significantly influence speech levels and spectra, an aspect often overlooked in the current method for predicting speech privacy. This paper presents an investigation into the variability of speech spectra in various office contexts, with a specific focus on the influence of room type, communication medium, and language. The study involved over 70 workers in different office room types in Quebec, Canada, who participated in measuring speech spectra within those spaces. Two communication methods, in-person and video-conferencing scenarios, were utilized with participants using either English or French languages. The real-world scenarios shed light on the significant impact of various parameters on speech characteristics within office settings. Comparing the results with standardized speech levels and spectra from ASTM and ISO standards, derived from controlled environments like anechoic chambers, the study reveals significant differences when applying the standard speech spectra to actual office environments. Based on these findings, the study proposes potential modifications to the existing standards, aiming to enhance the accuracy of speech privacy and intelligibility predictions.
Effects of vowel coloration on perceived directional offsets between single-syllable speech sounds
Authors: Martens William , Sakamoto Shuichi
Published: November 2023

The ability of normal hearing listeners to spatially localize single-syllable speech sounds was examined via a two-interval, two alternative forced choice (2AFC) spatial offset discrimination task. To examine directional biases in horizontal sound localization, this task required listeners to observe the direction of an unseen second talker’s voice immediately after hearing a first talker’s voice in an alternative direction. Listeners reported only the relative frontward versus rearward spatial offset between the two voices heard during each trial. Headphone-based virtual acoustic simulation enabled blind listening tests that were completed without feedback to the listener, revealing the ease with which listeners judged the relative spatial offset of the second speech sound, although those judgments were strongly biased by differences in the source spectra. The single-syllable speech-sound stimuli were processed using individually measured head-related transfer functions (HRTFs) of 15 listeners for whom individually measured earphone transfer functions (ETFs) were also employed. While analysis of the 2AFC response data via receiver operating characteristic (ROC) curves showed a generally high level of directional sensitivity, systematic biases were observed that could be explained via the differences in vowel coloration between the first and second source presented during each trial.
Using simple virtual environments to study the differentiation and integration of sensory cues in complex scenes
Authors: Stecker G. Christopher
Published: November 2023

The promise of virtual environments for studying sensory perception and cognition cannot be overstated. Because such environments can approximate aspects of the real world while affording a high degree of experimental and stimulus control, they promise to “bring the real world into the lab” and vice-versa [Stecker 2019, Hear J. 72(6):20-23], helping to make research and clinical testing more valid and relevant to real-world situations. Such benefits accrue to all sorts of investigations, and in this presentation we focus on relatively low-level aspects of auditory cognition—specifically the ability of listeners to differentiate sensory cues belonging to different objects in a complex scene (e.g., talkers) and to integrate information across disparate partially informative cues. Across multiple studies, we investigate the potential for virtual environments to enhance this work. A particular focus on simplified environments aims to elucidate a minimum feature set supporting different aspects of reality-like performance. [Work supported by US NIH R01-DC016643.]
Acoustic cloaking via a hybrid passive–active technique
Authors: Parnell William J. , Lin Cikai , Kessissoglou Nicole
Published: November 2023

Both passive and active methods have been employed extensively in recent times to create the effect of acoustic cloaking, with obstacles being made near-invisible over specific frequency ranges. Passive methods typically rely on metamaterials with complex microstructures, whereas active methods require an external power supply. Furthermore, a large number of active sources and sensors are typically required for active control. In this work, a hybrid method that combines passive and active approaches is developed. The passive acoustic cloak is designed theoretically via layered shells with alternating, functionally graded properties. The layer properties are informed by coupling transformation acoustics with homogenization theory and require unphysical values on the inner cloak wall. As such, some scattering occurs from the obstacle to be cloaked as well as due to the discontinuity in material properties across the shell boundaries. Using distributed monopole control sources, active control is then employed to nullify the non-zero scattered field outside the passive cloak domain. Effective cloaking is achieved using the hybrid passive–active control system.
Design of acoustic coatings with symmetric and asymmetric resonant inclusions
Authors: McIntosh Alexander , Sharma Gyani S. , Skvortsov Alex , MacGillivray Ian , Kessissoglou Nicole
Published: November 2023

An acoustic coating for underwater applications, designed using periodically distributed cavities and hard spherical particles embedded in a soft matrix, is herein modelled as monopolar and dipolar scatterers positioned along the centre of a sound hard duct. Modified equations of motion for the scatterers account for resonance phenomena as well as multiple scattering of waves by a lattice. Combinations of monopolar and dipolar scatterers in the direction of the incident sound field are considered. The acoustic performance of the various coating designs composed of symmetric and asymmetric resonant inclusions are compared. The influence of asymmetry in coating designs, arising from variation in scatterer size and material distribution, on effective material properties and Willing coupling are reported.
Homogenization and analysis of planar piezoelectric metamaterials: A comprehensive study
Authors: JI Guosheng , Huber John
Published: November 2023

This article presents a comprehensive investigation into the homogenization and analysis of planar piezoelectric metamaterials. The classical transfer matrix method is extended by using homogenization methods to evaluate the sound transmission of piezoelectric metamaterials in both normal and oblique incidences. This has been validated numerically using the finite element method and experimentally in the solid medium propagation in normal incidence. Several vibro-acoustic analytical models are compared in oblique incidence, including the Kirchhoff thin plate theory, the Reissner-Mindlin thick plate theory, and the theory of wave propagation in elastic solids. These theories are used to determine the dispersion relation, coincidence, and transition frequency of thin and thick plate theories in analyzing piezoelectric metamaterials. Additionally, acoustic properties of piezoelectric layers connected to external circuits are parametrically studied, exploring both dimensional and dimensionless variables. Results indicate that significant control over the resonance frequency and sound transmission can be enabled by adjusting the external electrical impedance, flat-layer structures, and piezoelectric materials. This demonstrates excellent tunability and compactness of planar piezoelectric metamaterials for space-sensitive applications. The study indicates a straightforward and powerful analytical approach for the optimization of acoustic insulation using planar piezoelectric metamaterials.
Non-reciprocal selective frequency transmission with nonlinear bi-layer cylinder chains
Authors: Oh Beomseok , Jang Yeongtae , Rho Junsuk
Published: November 2023

Recent advancements in wave physics have led to the development of systems that break the principle of wave transmission reciprocity. In this study, we present selective frequency transmission with asymmetry in bi-layer phononic crystals, which are composed of two layers of cylinder contact chains. We demonstrate significant non-reciprocal harmonic transmission effects, as well as self-demodulated displacement amplification under excitation from different sides. These effects are achieved through a combination of contact nonlinearity and cascaded bandgaps formed by adjusting the chain lengths in both layers. We find that the evanescent waves generated through nonlinear frequency conversion in the stopband are converted into propagating waves at the interface, subsequently leading to the transmission. Our findings have implications for programmable asymmetric acoustic devices, providing a novel framework for energy mitigation, conversion, and harvesting.
Voice quality and its effects on university students' listening effort in a virtual seminar room
Authors: Schiller Isabel S. , Aspöck Lukas , Breuer Carolin , Ehret Jonathan , Bönsch Andrea , Fels Janina , Kuhlen Torsten W , Schlittmeier Sabine J
Published: November 2023

A teacher’s poor voice quality may increase listening effort in pupils, but it is unclear whether this effect persists in adult listeners. Thus, the goal of this study is to examine the impact of vocal hoarseness on university students' listening effort in a virtual seminar room. An audio-visual immersive virtual reality environment is utilized to simulate a typical seminar room with common background sounds and fellow students represented as wooden mannequins. Participants wear a head-mounted display and are equipped with two controllers to engage in a dual-task paradigm. The primary task is to listen to a virtual professor reading short texts and retain relevant content information to be recalled later. The texts are presented either in a normal or an imitated hoarse voice. In parallel, participants perform a secondary task which is responding to tactile vibration patterns via the controllers. It is hypothesized that listening to the hoarse voice induces listening effort, resulting in more cognitive resources needed for primary task performance while secondary task performance is hindered. Results are presented and discussed in light of students’ cognitive performance and listening challenges in higher education learning environments.
Shear speed in Arctic ice and underwater acoustic reflection
Authors: Chotiros Nicholas P. , Bayrakci Gaye , Sanford Oliver , Clarke Timothy , Best Angus
Published: November 2023

The underwater reflected sound wave under a sheet of Arctic ice contains information about the ice including thickness and mechanical properties. The ideal case of a perfectly flat ice floe floating above the water may be modeled using the OASES wavenumber integration code. A spectrogram of the acoustic response contains features related to the compressional and shear waves. The resonance associated with the shear wave speed in the ice is particularly distinctive. In the real world, the ice-water interface is not perfectly smooth. The finite element code SPECFEM2D is used to simulate the response of ice with a rough ice–water interface. It is particularly well suited to this problem since it accounts for all orders of multiple reflections. It shows the effects of fine-scale roughness on the acoustic response. Depending on the severity of the roughness, it may enhance or diminish the acoustic features related to the properties of the ice. [Work supported by the U. S. Office of Naval Research, Code 32 Grant N00014-20-1-2041 (N. Chotiros). G. Bayrakci and A. Best were funded by the UK Defence and Security Accelerator, Grant ACC2016927. The Texas Advanced Computing Center provided the high-performance computing resources.]
On the evaluation of the target strength for comparison between monostatic simulations and measurements
Authors: Fillinger Laurent
Published: November 2023

The target strength (TS) quantifies the acoustic return on an active sonar from a submerged object. It is a far-field quantity that varies with frequency and orientation of the object with respect to the sonar source and receiver. Numerical modelling allows to perform simulations in the far-field at an arbitrary frequency. Experimentally, a sonar pulse covers a finite bandwidth, the presence of the water surface and other aspects of the environments complicate the propagation, and the presence of noise and reverberation limit the ability to measure the weakest components of the acoustic return. A numerical investigation is conducted to support the comparison and understanding of the differences between measurements and simulations in monostatic scenario (source and receiver in the same direction). Elastic spheres (for which an analytic solution is available) and an elongated object (simulated with Kirchhoff diffraction approximation) are considered. These objects are simulated in the far-field and in the near-field, at single frequencies and with pulses of several duration and bandwidth. Various TS metrics, including peak TS and integrated TS are evaluated. The comparison of these metrics with the single frequency TS is discussed, as well as the impact of measurement noise and reverberation on these metrics.
A study on the evaluation of impact sound reduction performance of floor mats for reducing floor impact sound in apartment buildings
Authors: Yeon Junoh , Goo Himo , Moon Soonseong
Published: November 2023

This is a study on the performance evaluation of floor mats used to reduce floor impact sound in apartment houses in South of Korea. A total of 8 types of floor mats and 5 or more test rooms with different floor structures were used to measure and evaluate impact sound reduction performance. The impact source is a Bang machine (heavy-weight impact sound 1), a rubber ball (drop of height 100 cmHeavy-weight impact sound 2) tapping machine (light-weight impact sound), and a rubber ball drop height of 40cm that simulates the actual impact force. As a result of the test, the impact sound reduction performance for the light-weight impact sound was evaluated as excellent. It was evaluated at the level of ambient background noise. Also, the reduction performance of the bang machine was somewhat different depending on the floor structure. In addition, there are cases where it is rather amplified in the low frequency band (63 Hz). In the case of rubber ball (drop of height 100 cm), the reduction performance was different depending on the floor structure. However, the impact sound reduction performance was evaluated to be sufficiently reduced. The impact noise reduction performance at the rubber ball drop height of 40 cm was found to be slightly higher than that at the drop height of 100 cm.
Dr Doug Cato’s contributions to the understanding, measurement, and characterization of Australia’s ambient acoustic sea noise environment
Authors: Ferguson Brian G.
Published: November 2023

In 1966, Dr Douglas H. Cato began his investigation of ambient noise in Australian waters as part of the Royal Australian Navy Research Laboratory’s Project BARRABOOL. His research involved identifying and understanding the various ambient noise mechanisms that limit the performance of operational sonar systems in Australian waters. He is responsible for the “Cato Curves” of ocean noise, which have been used extensively for predicting sonar performance. Similarly, his understanding of the ocean environment and the spatial and temporal variability of ambient undersea noise is exploited by the Royal Australian Navy to ensure effective sonar and submarine performance. Dr Cato is a Fellow of the Acoustical Society of America and his research achievements are published in international peer-reviewed journals including the Journal of the Acoustical Society of America and as book chapters in reference texts in underwater acoustics. In 2012, he was the recipient of the Minister’s Achievement Award in Defence Science for his outstanding contributions in underwater acoustics and the effect of sound on marine mammals. This presentation provides examples of Doug’s achievements in defence science and their significance to the Commonwealth of Australia, Department of Defence.
Passive ocean acoustic waveguide remote sensing of vocalization behavior and spatial distribution of diverse marine mammal species in the Norwegian and Barents Sea
Authors: Mohebbi-Kalkhoran Hamed , Pednekar Shourav , Zhu Chenyang , Ahonen Heidi , Rune Godø Olav , Ratilal Purnima , Makris Nicholas C.
Published: November 2023

Leveraging data acquired using a 160-element coherent hydrophone array deployed in the Norwegian and Barents Seas during spring 2014, and the passive ocean acoustic waveguide remote sensing (POAWRS) technique is employed to enable instantaneous wide-area monitoring of marine mammal vocalizations over expanses exceeding 100 km in diameter. The vocalization behavior of diverse marine mammal species including Fin, Humpback, Minke, Sperm, and Beluga whales are analyzed, quantifying time-frequency characteristics and call patterns from their vocalization signals present in high-resolution beamformed power spectrograms. Previously developed automatic detection and machine learning algorithms are employed for clustering and classification of underwater acoustic events, facilitating the subsequent manual audio-visual inspection of whale calls. Bearing-time trajectories of repetitive species-specific vocalizations signals are utilized to estimate locations of the whale calls and hence their temporo-spatial distributions. Through comparative studies, we assess the presence and abundance of marine mammal species-specific vocalization signals in three distinct coastal regions off Norway, namely, Alesund, Lofoten, and Northern Finmark. In addition, we investigate correspondences of marine mammal distributions with concurrently imaged instantaneous wide-area fish distributions from distinct fish species to elucidate potential predator-prey interactions and habitat preferences.
Wind noise source level and Bio-Goose: Perspectives on Doug Cato’s contributions in ocean ambient noise
Authors: Chapman Ross
Published: November 2023

Doug Cato’s research has provided insights that form the basis of our understanding of ambient noise in the ocean. This paper focuses on only two aspects of ambient noise that are strongly linked to Doug’s work. One is source level of ambient sound due to local wind at the sea surface. Estimates of wind sound source level derived from noise measurements with vertical line hydrophone arrays are shown to be consistent with the levels for noise due to wind reported in the Cato curves—up to date relationships for levels of components of ambient noise over a wide frequency band. The second aspect revisits a curious sound that was recorded in waters around Australia and New Zealand some years ago. The sounds were believed to be generated by marine animals, but the type of creature was not identified at sea or in subsequent analysis. Owing to the limited bandwidth of the recordings, the sound was accordingly dubbed as Bio-Duck in New Zealand and Bio-Goose in Australia. Further characteristics of the sound are presented, along with evidence of a probable conversation between two speakers and an example of the Lombard effect in the communications.
A study on the prediction model of water column sound absorption coefficients considering the characteristics of the East Sea of South Korea
Authors: IM Seung Uk , Lee Cheong Ah , Kim Changsoo , Paeng Dong-guk
Published: November 2023

East Sea of Korea has the deepest water depth among Korean seas, and the water column changes are distinct in space and time, resulting in a wide range of water column sound absorption coefficients. In this study, we calculate and analysis the spatiotemporal variation of water column sound absorption coefficient in the East Sea of Korea, which has unique oceanographic characteristics. Using extensive CTD data from the Korea Oceanographic Data Centre (KODC) from 1991 to 2021, we calculate the sound absorption coefficient using the widely applied Francois–Garrison model and reveal the unique absorption characteristics of the East Sea. The derived coefficients are then used to calibrate and improve past multibeam echosounder system (MBES) data, which suffered from incomplete water column information and arbitrary mean values. To facilitate the calculation and development of sound absorption coefficient, a MATLAB-based graphical user interface (GUI) was developed. The results of this study contribute to the calculation and inference of sound absorption coefficients along spatial and temporal dimensions of the water column in the East Sea and to the extraction of more accurate seafloor information from MBES data. This study developed the way for future research focusing on algorithmic advances and new methodologies for the calculation of sound absorption coefficients in the West and South Seas of Korea.
Frequency dependent effects of environmental parameters on the broadband acoustic wave propagation in shallow water waveguides
Authors: Badiey Mohsen , Wan Lin , Escobar-Amado Christian D.
Published: November 2023

Acoustic wave intensity plays a crucial role in underwater acoustics, particularly in shallow water regions in which the signal suffers substantial energy fluctuations. The physical properties of the environment significantly impact the intensity of broadband acoustic waves in shallow water waveguides. The accuracy of the intensity is vital for the reliability of any inverse algorithm used to obtain the physical properties of the waveguide boundaries. In this paper, we explore the effects of sound speed fluctuations in the water column on broadband acoustic propagation across different frequencies. Our observations reveal that at higher frequencies the sound intensity is more sensitive to oceanographic variability. This poses challenges for geo-acoustic inversions when parameters in the water column are not well-known, particularly at higher frequencies. To validate our findings, we present simulations using normal modes and parabolic equation with examples from recent experimental observations conducted on the New England Mud Patch Area and the continental shelf region of the United States during 2017, 2021, and 2022. These experiments provide valuable insight into the intricate behavior of acoustic waves in shallow water environments at different frequency bands. [Work supported by ONR (Grant No. N00014-21-1-2760).]
Fundamental study for vehicle abnormal sound detection and the direction estimation methods using machine learning with noise reduction
Authors: Takagi Masanori
Published: November 2023

Detecting abnormal sounds during vehicle running condition is important to find out the vehicle’s problems at the early stage. In the mass production process, the detection test is generally carried out by the inspector. However, continuous inspection by a human for long time is hard and miss false inspection may occur. In addition, normal running noise, such as road noise, deteriorates the inspection accuracy. Therefore, an automatic accurate abnormal sound detection method under the normal noise is necessary to improve the detection accuracy with small man-hour. Furthermore, if the method has an ability to localize the abnormal sound direction, the countermeasure also becomes easy. In this study, we considered the noise detection method using machine learning with a noise reduction method and attempted the noise direction using two microphones. As a fundamental study, we applied these methods in an open room and the result showed that the method could detect the abnormal sound under normal noise condition and indicate the direction well in the simple verification test.
Application of one-dimensional convolutional neural network in guitar factory quality inspection
Authors: Chen I-Hsin , Tsai Yu-Ting , Zheng Zi-Wei
Published: November 2023

After the completion of guitar manufacturing, it is necessary to conduct quality testing and final adjustments to ensure that the guitar meets the factory standards. This stage often requires the involvement of professional musicians. In this project, a supervised learning approach is employed, where guitar vibration signals are inputted and correspond to the output sound quality. Multiple test subjects perform guitar strumming, and the guitars are adjusted to simulate various abnormal conditions for experimental comparison. By classifying the differences in energy and frequency, different guitar factory standards are identified, and the stability of guitar quality is explored. For data analysis, a one-dimensional convolutional neural network (1D CNN) is used as the base model, analyzing the Mel-frequency cepstral coefficients to identify elements of stable guitar quality and tonal characteristics. The research results show that the model can predict variations due to factors, such as environmental temperature, humidity, and worn-out strings, ensuring objective and consistent analysis of each guitar's factory quality. This innovative technology eliminates the need for traditional labor-intensive inspection procedures, enabling the traditional luthier industry to utilize automated methods for rapid factory testing.
Numerical investigation on the rotor-turbulence interaction noise
Authors: Qin Denghui , Huang Xun
Published: November 2023

Noise from a turbomachinery component, such as compressors and turbines, is an important issue to be resolved in aerospace and ocean engineering applications. The rotor of a turbomachinery assembly usually could operate downstream to other flow structures (fuselages, stators, control surfaces, etc.) that produce either large-scale or small-scale turbulence structures, which are highly complex and are being distorted while they are ingested into the rotor, which generate the rotor-turbulence interaction noise. The presented work conducted numerical simulation research on a ten-bladed rotor ingesting different turbulence structures. The large eddy simulation (LES) and Ffowcs-Williams and Hawkings (FW-H) methods were used to predict the flow-induced noise from the rotor. The results show that the time-space evolution of the upstream turbulent structure when it passes towards the rotor. In addition, the differences in the turbulence ingestion noise at different inflow speeds and rotational speeds were studied. Furthermore, the sound generation mechanism of turbulent ingestion noise was explored using a newly proposed near-field sound source analysis method. In summary, this study can help to improve the understanding of the physical mechanisms of unsteady forces and noise generated by a rotor when it interacts with ingesting turbulent flows.
A new model of Crossflow fluid-structure instabilities for helicopter blades
Authors: Howell Richard , Lucey Tony , Ng Thomas , Tsigklifis Konstantinos , Dylejko Paul
Published: November 2023

Crossflows that induce fluid-structure instabilities arise in many engineering applications, such as flow over a road bridge or an aircraft wing. At a certain flow speed, an aeroelastic flutter instability is induced arising from the coupled translational and rotational movement of the structure. This instability is modified in a subgroup of these applications that include the additional effect of rotation, e.g., propellers. The structure now experiences a linearly varying effective mean flow (faster near the tip than at the root) and an induced stiffness (via tension) due to the centrifugal force that is also spatially varying. The flutter instability can create vibration fatigue issues and can also create a significant acoustic signature. This paper reports a newlinearised numerical model of the problem that fully couples a finite-difference Euler–Bernoulli beam model to a Theodorsen unsteady lift model that includes these effects of rotation. Comparisons with theoretical predictions in non-rotating flow demonstrate the effect on the trends for the onset of linear instability. The model is then applied to the problem of helicopter blade flutter, and the effects of various strategies for delaying the onset of linear instability are modelled.
An investigation of drone propeller noise generation in a turbulent wake
Authors: Bian Zhengpang , Yauwenas Yendrew , Moreau Danielle , Doolan Con
Published: November 2023

Unmanned aerial vehicles (UAVs) are becoming popular as they can be used in a range of applications including surveillance, delivery, agriculture, aerial photography, and search and rescue. This paper presents an experimental study to characterise the effect of turbulent inflow disturbance on the noise generated by a drone propeller using a low-noise, open-jet anechoic wind tunnel facility at UNSW. Advanced precision composites (APC) two-bladed, 12-inch rotors were tested at rotational speeds between 4000 and 8000 RPM at a freestream velocity of 15 m/s. The inflow disturbance upstream of the propeller is the wake of a NACA0012 profile wing to which the propeller is mounted. Hot-wire anemometry has been used to characterise the wake of the strut. The turbulence intensity, mean velocity, and turbulence length scale is calculated to characterise the turbulence ingested by the propeller. Acoustic measurements have been taken with multiple microphones to study the sound directivity and noise radiation of the propeller. A load cell is used to measure the torque and thrust produced by the propeller. This experimental program aims to characterise the wake profile ingested by the propeller and examine the associated noise generation.
Leveraging machine learning and similarity judgements to identify perceptually relevant acoustic features of small, unmanned aircraft system signal similarity
Authors: Reeves Mason A. , Mobley Frank S. , Campbell Steven C. , Wall Alan T. , Rasband Reese , Bowers Gregory
Published: November 2023

Auditory signals can be described quantitatively by a set of measurable acoustic features (i.e., zero crossing rate, attack slope, etc.) or qualitatively with adjectives, such as whooping, thunderous, melodic, or in comparative terms such as different, louder, etc. Listeners can rate the similarity of signals and assign qualitative descriptions relatively easily; however, most lack the ability to articulate the quantitative basis of these judgments. Because the qualitative differences in signals typically correlate to a measurable difference in the acoustic features, signal similarity ratings can be used to recover the acoustic features that define signal similarity. In the present study, subjects were given combinations of small, unmanned aircraft systems (SUAS) signals consisting of either two different SUASs or SUAS and non-SUAS and asked to rate similarity on a scale from non-similar to highly similar. Using these similarity ratings along with acoustic difference features, machine learning algorithms were trained to predict human responses. These algorithms predict the position of a withheld UAS signal within the similarity feature-space. Crucial prediction acoustic difference features are extracted from the algorithms via feature importance and sensitivity analysis techniques. The extracted acoustic difference features may be inferred as prominent information impacting the human perception of signal similarity.