bluuebunny/crossref_metadata_2025 huggingface dataset:
Vertical campus planning impacts on sound isolation and room acoustics design in New Trier High School’s large music rehearsal spaces
Authors: Glosemeyer Petrone Robin S.
Published: November 2019

By 2015, New Trier High School’s student body of 4000 had outgrown its 117-year old campus. With no available land on which to construct new facilities, existing facilities were demolished to allow a vertical campus building to be nestled between the remaining structures. The LEED-Gold certified addition houses the campus' performing arts facilities, a library, cafeteria, applied arts/maker spaces, a culinary lab, interconnected visual arts studios, a technology support bar, STEM laboratories, and flexible classrooms. The performing arts spaces, including five large music rehearsal rooms, are continuously programmed throughout the school day and well into the evening hours, placing high performance requirements on the isolation systems employed in the compact, steel-framed building. The rehearsal rooms employ two distinct sound isolation techniques and room acoustic design approaches as a result of their location within the building and the pre-determined structural spans.
Correlation between acoustic immersion index and other objective parameters in concert halls
Authors: Navvab Mojtaba , Meyer Andy
Published: November 2019

Concert halls’ geometry and volume, impact or shape listeners’ room acoustic experience. The current recommended procedure within ISO3382 in calculation or measurement of the room acoustic parameters or current indexes used by designers do not fully represent the listeners’ audio experiences. In this paper measured and simulated parameters for room acoustic are analyzed in time and frequency domains for a selected number of well-known halls. Computer simulation and room acoustic measurements using beamforming techniques are used to examine the sound quality and acoustic sense of immersion within these uniquely shaped halls. Halls with the audience facing the stage as compared to the audience’s seating surrounding the stage have a noticeable impact on the high-frequency absorption of direct and reflected sounds in each space given the presence of the audience. Correlation between immersion index and other acoustic parameters or indexes such as reverberation time, sound strength, sound texture, listeners’ envelopment, early decay and center time, clarity-definition for speech and music, are explored and used to show contributions of acoustical features or key architectural elements within these selected halls. The practical application of these new indexes associated with space geometry for room acoustic design calculations contributes to the high quality of sound experience in concert halls.
Natural sound (scale) reflecting speaker
Authors: Niu Xiaoyu , Wu Kai , Li Huan , Li Chenguang , Zhao Shang , Yu Gaokun , Fu Shengxue
Published: November 2019

In the natural sound music hall, due to rejection of the electronic facilities, engineers need to design an architectural construct to improve the acoustic effect. Rather, it is widely spread to use horn-like construct to improve acoustic energy distributed on the audience. On the other hand, there has not been a suitable nonelectronic device to act as a reflecting speaker. Thus, we propose the concept of Natural sound (Scale) Reflecting Speaker, aiming to control the energy distribution on the stage, so singers could hear their own voice and perform more excellent. In addition, the reflecting speaker consists of multiple coupled Helmholtz resonators. Theoretically, by combining Helmholtz resonances and Bragg scatterings, acoustic negative reflection is achieved at the Bragg blazing points and non-Bragg blazing points. Meanwhile, owing to couplings among these blazing points, broadband, and wide-angle acoustic negative reflection would also be achieved. Finally, we could illustrate the fundamental feasibility of the device via theoretical derivation, computer simulation, and basic experiments. Therefore, it is significant for natural sound music hall to apply to the reflecting speaker in the future.
Long term PAM to investigate temporal and anthropogenic effects on oyster toadfish, Opsanus tau mating vocalizations
Authors: Putland Rosalyn , Mensinger Allen F. , Van Wert Jacey C. , Mackiewicz Alayna
Published: November 2019

For the oyster toadfish, Opsanus tau, vocal communication and sound detection are critical for reproductive success, however, little is known about how they respond to changes in their acoustic environment. Passive acoustic monitoring was conducted in Eel Pond, MA, USA in the summer months (2017–2019) to investigate vocalization patterns of the resident population and the effect of anthropogenic sound. Male toadfish produce mating vocalizations that are characterized by an initial broadband segment (30–50 ms, 100–1000 Hz) and a longer tonal section (200–650 ms, 100–500 Hz). The pulse repetition rate of the tonal section was significantly related to ambient water temperature during hourly and weekly monitoring. Time difference of arrivals were also used to pinpoint the location of toadfish nests and linked to ambient and anthropogenic sound-maps to understand exposure levels for individual fish. Significantly less vocalizations were detected following exposure to vessel sound (100–12 000 Hz, source level 130 dB re 1 μPa), suggesting individuals changed their vocal behavior in response to anthropogenic activity. Both environmental and the presence of vessel sound influence the acoustic behaviour of toadfish, which could lead to a reduction in communication space, mate attraction and detection.
Sound production of the critically endangered totoaba (Totoaba macdonaldi): Laying the foundation for conservation of this species through passive acoustic monitoring
Authors: Phillips Goldie , D'Spain Gerald L. , López-Sagástegui Catalina , Guevara Daniel , Cisneros-Mata Miguel Angel , Rimington Dennis , Price David , Aburto-Oropeza Octavio
Published: November 2019

Little is known about the sounds produced by totoaba, a critically endangered fish endemic to the Gulf of California. In a multi-national effort to aid management of this population through passive acoustic monitoring (PAM), we collected simultaneous acoustic and video recordings of totoaba housed at the Centro de Reproducción de Especies Marinas del Estado de Sonora in Kino Bay, Mexico. Measurements were made of both sexes and multiple age classes. Furthermore, individuals were placed in isolation tanks to measure individual call rates and call-to-call variability. Video from these isolation tanks permitted determination of source/receiver range for source level estimation, as well as association of acoustic with physical behaviors, resulting in identification of potential alarm calls. Totoaba produce a variety of calls, ranging from short duration (<0.03 s), low-frequency (<1 kHz) narrowband pulses to longer, regularly spaced broadband clicks with significant energy over 15 kHz. Call rates and dominant call type depend on both age and sex. Results are used to develop automated pre-processing/detector algorithms for a future PAM system. Quantitative analysis of the performance of these detector algorithms are presented. [Financial support by the Catena Foundation and experiment support by the Centro de Reproducción de Especies Marinas del Estado de Sonora.]
The effects of tropical storm Debby on soundscapes and marine organisms of the West Florida Shelf (Gulf of Mexico)
Authors: Boyd Anjali D. , Simard Peter , Gowans Shannon , Mann David
Published: November 2019

Tropical cyclones are severe weather systems which can potentially have a large effect on marine ecosystems through direct or indirect effects. In June 2012, Tropical Storm Debby formed in the Gulf of Mexico and had impacted coastal Florida including Tampa Bay. Acoustic recorders were deployed during the storm at a shallow inshore location inside Tampa Bay (Boca 2) and a location offshore in the Gulf of Mexico (Gulf 1). The soundscape before (17–21 June), during (22–26 June) and after (27 June–3 July) Tropical Storm Debby was investigated in two ways: third-octave spectral analysis of root-mean-square sound pressure levels and the identification and quantification of fish sounds in spectrograms. Single-factor ANOVAs indicated a significant increase in ambient noise analyzed in third-octave bands during the storm at both sites (p < 0.001), and an overall decrease in fish sound production during the storm at both sites (p < 0.001). Several species-specific sound production patterns were also found which correlated with the storm’s passage. The changes in ambient noise and biological vocalization was short-lived and returned back to normal within 48 h of the storm. This study is one of three studies to examine the effects of tropical cyclone on marine soundscapes, and the only study to identify sound production to the species level. Furthermore, the results from this study provide important information on the effects of tropical storms on marine communities and the fast rate of recovery after these storms.
Michael J. Buckingham: Leading the way in ocean ambient noise processing and modeling
Authors: Siderius Martin
Published: November 2019

Nearly 40 years ago, Michael Buckingham published a theoretical model for ocean ambient noise in shallow water. His pioneering work of the late 1970s and early 1980s advanced not only the methods for understanding the ambient noise field but also the impact on array signal processing. In the late 1980s, Buckingham made a pivotal shift in thinking about ambient noise. He considered ambient noise not as a nuisance factor but as a usable signal. In the late 1980s Buckingham and Jones had the novel idea to take measured ambient noise from a vertical line array and develop an inversion method to determine the seabed critical angle. A few years later, Buckingham invented a technique known as ambient noise imaging (ANI), or acoustic daylight, which is analogous to conventional photography with daylight as the source of illumination. Buckingham continues to lead the way, and the true significance of his work must include the inspiration his research gives to numerous other scientists, especially those investigating methods to exploit ambient noise as a usable signal. In this presentation, a review of Buckingham’s contributions to understanding ambient noise will be described, particularly as they relate to recent methods for ambient noise processing and modeling.
Estimating low-frequency (<100 Hz) sound speed in fine to very-fine sand sediment from the horizontal coherence of the head wave excited by a light helicopter
Authors: Bevans Dieter A. , Buckingham Michael J.
Published: November 2019

A series of shallow-water acoustic experiments has been conducted off La Jolla, California using a Robinson R44 helicopter as a low-frequency (≈13–2500 Hz) sound source. The sound speed of the sand sediment was recovered from the horizontal coherence of the head wave excited in the water column by the helicopter. Previously, on 14 December 2016, with a horizontal aperture of 3 m, this technique returned the sound speed of the sediment, from 800–2300 Hz, as 1682 ± 16 m/s, consistent with the known sediment type. An additional experiment was conducted on 6 February with larger horizontal apertures of 9, 12, and 15 m. The hydrophones, situated 0.5 m above the seabed, received the head-wave signals, allowing the coherence function to be formed over the bandwidth of the airborne source. The sediment sound speed was recovered by matching the zero crossings of the measured coherence function to those predicted by the theory of head-wave generation in shallow water. The dispersion in the sediment sound speed was estimated over a frequency range extending between 27 Hz, the lowest zero crossing of the coherence function, and 2.5 kHz, the bandwidth of the source. [Research supported by ONR, SMART(DOD), NAVAIR and SIO.]
Moving ship tomography in the Santa Barbara Channel Experiment 2016
Authors: Gemba Kay L. , Vazquez Heriberto J. , Sarkar Jit , Cornuelle Bruce , Hodgkiss William S. , Kuperman William A.
Published: November 2019

Ocean acoustic travel-time-tomography attempts to map heterogeneities such as ocean temperature with mesoscale resolution. The Santa Barbara Channel Experiment in 2016 (SBCEx16) contained both controlled and uncontrolled (i.e., ships of opportunity) sources, in addition to environmental data collected by a variety of sensors. The path to developing a methodology for utilizing noise from ships of opportunity for oceanographic imaging involves benchmarking our processing with a controlled source-tow. This latter moving source tomography, itself, is a procedure that still remains to be quantitatively validated and documented. We present results from the source-tow tomographic component of SBCEx16 with the added objective of understanding the requirements for minimizing the uncertainties associated with uncontrolled, random sources of opportunity.
Personal reminiscences of a career in acoustical oceanography
Authors: Buckingham Michael J.
Published: November 2019

Over recent years, ambient noise in the ocean has come to be recognized as a signal in its own right, containing a wealth of information about the ocean and ocean processes. Ambient noise has thus become a central pillar of acoustical oceanography. Since the attributes of ambient noise are based on straightforward physical principles, the noise field may be inverted to recover, for example, the sound speed in the seabed. Some selective examples of ambient noise oceanography will be reviewed, based on personal experiences gained during a career that includes research in the Arctic, the North Atlantic, the deep ocean trenches, and the shallow, continental shelf waters of the English Channel and the Pacific Ocean, off the coast of California. Much of this work was accomplished with the talented assistance of many students and colleagues; and it was made possible through the consistent support of our sponsors. It is a pleasure to acknowledge that, throughout, the Acoustical Society has provided a cordial environment where acoustical oceanographers could meet and are always made welcome. [Research supported by ONR.]
High frame rate color flow echocardiography: A comparison of different imaging approaches
Authors: Ramalli Alessandro , Rodriguez-Molares Alfonso , Avdal Jorgen , D'hooge Jan , Lovstakken Lasse
Published: November 2019

Quantitative measurements by color flow imaging (CFI) are hindered by both low temporal resolution and a limited field of view. These limitations can be overcome by recent high frame rate (HFR) imaging techniques. However, as these HFR techniques reduce image quality and penetration depth to a different degree, the aim of this study was to compare the impact of HFR techniques on CFI. Hereto, phantom and in-vivo images were recorded using a cardiac phased array (P4-2v) connected to a Vantage 256 system (Verasonics) in order to scan a 90 deg wide, 12 cm deep sector. Different HFR scan sequences were tested, including multi-line transmission with 4 simultaneously transmitted beams (4MLT), diverging waves with 2 different opening angles, 2φ = 20 deg (DW20) and 90 deg (DW90), as well as single-line transmission (SLT) as a benchmark. For a fair comparison and to evaluate a clinical applicability, the acoustic output was equalized for all sequences, for which the heating of the probe was the main restriction. Results show that HFR techniques spread artifacts on larger areas compared to SLT (>+50%), but the velocity estimates are still comparable (relative error < 6%). 4MLT and DW20 achieved similar performance and enable wide-angle CFI at HFRs (78 Hz in continuous acquisition over 90 deg). On the other hand, DW90 boosts the frame rate up to 625 Hz but with a reduction of the penetration depth (up to −5/6 cm).
A convolutional neural network approach to preserve image quality for sparse array data
Authors: Xiao Di , Yiu Billy Y. , Chee Adrian J. , Yu Alfred C.
Published: November 2019

High-frame-rate ultrasound (HiFRUS) has seen recent interest in resolving highly dynamic spatiotemporal events but transferring the large amount of data generated from the probe remains a hurdle for real-time imaging. One method to lessen the data traffic while preserving the field of view is to reduce the channel count, but this can lead to image quality degradation and the appearance of grating lobe artifacts. In this work, we present a convolutional neural network (CNN) based framework that uses a sparse array (half the channel count) and infers the remaining channels to mimic a fully-populated array. On unfocused transmissions, our results show that on a beamformed image of a multiple point target phantom, grating lobe artifacts are reduced from over 8dB (sparse array) to less than 1 dB (CNN interpolated) when compared to an image beamformed using the full array. Additionally, reconstructions from CNN generated data demonstrated improvement (10 dB) in carotid echolucent flow regions in vivo. Our work demonstrates that, using a deep learning approach to channel-domain radiofrequency data interpolation, the required physical channel count on an array and the corresponding data transfer bandwidth can both be reduced without significant image quality trade-off.
Frequency domain beamforming of ultrasound signals from inhomogeneous media using range Doppler method
Authors: Jakovljevic Marko , Michaelides Roger , Biondi Ettore , Zebker Howard , Dahl Jeremy J.
Published: November 2019

Frequency domain beamforming methods, such as Stolt migration, yield efficient and fast processing of ultrasound data. Stolt migration, by migrating the individual element data in a 2-D frequency domain, improves processing speed by up to two orders of magnitude compared to conventional delay-and-sum (DAS) beamforming. However, as commonly implemented, it relies on the assumption that the speed-of-sound is constant, and is unable to be applied with advanced beamforming techniques such as phase aberration correction. Here, we demonstrate another approach to frequency domain beamforming, using the range-Doppler method developed for synthetic aperture radar imaging. The range-Doppler method is similar in speed to Stolt migration, but because it involves only a 1-D Fourier transform in array dimension, it can account for speed-of-sound inhomogeneities. We demonstrate our method with simulated channel signals of point targets and diffuse scatterers, and find similar image quality (e.g., mainlobe width, sidelobe levels, and contrast-to-noise ratio) to DAS beamforming in noise-free conditions. We further analyze signals acquired through a near-field phase-screen and from multi-layered media by modifying Doppler processing to correct for phase aberration and to account for the local sound-speed differences, respectively.
Ultrasound elastography assessment of increased carotid artery wall stiffness in human immunodeficiency virus infected patients
Authors: Cloutier Guy , Roy Cardinal Marie-Hélène , Lefebvre Carl-Chartrand , Soulez Gilles , Tremblay Cécile , Durand Madeleine
Published: November 2019

Prevalence of cardiovascular diseases is higher in HIV subjects when compared to the general population. The chronic immune stimulation and low grade inflammation are possible causes. Carotid artery strain and motion are proposed as markers of premature atherosclerosis. Seventy-four HIV infected and 75 age-matched control subjects were recruited from a prospective, controlled cohort study (mean age 56 years ± 8; 128 men). Elastography applied to longitudinal ultrasound images of common and internal carotid arteries quantified the cumulated axial strain, cumulated shear strain, cumulated axial translation, and cumulated lateral translation. Presence of plaque was also assessed. Association between elastography biomarkers and HIV status were evaluated with Mann–Whitney tests and multivariate linear regression models. A higher occurrence of carotid plaques was found in HIV infected individuals (p = 0.011). Lower cumulated lateral translations were found in HIV infected subjects on both common and internal carotid arteries (p = 0.037 and p = 0.026, respectively). These observations remained significant when considering multivariable models including common cardiovascular risk factors and clinical characteristics (p< 0.05). Lower cumulated axial strains were also observed in internal carotid arteries when considering both multivariate models (p< 0.05). Lower translation and strain of the carotid artery wall in HIV infected individuals, which indicate increased vessel wall stiffness, could be new biomarkers of premature atherosclerosis.
Quantitative liver fat fraction measurement by multi-view sonography using deep learning and attention maps
Authors: Byra Michal , Han Aiguo , Boehringer Andrew S. , Zhang Yingzhen N. , Erdman John W. , Loomba Rohit , Valasek Mark A. , Sirlin Claude B. , O'Brien, W. D. , Andre Michael P.
Published: November 2019

Qualitative sonography is used to assess nonalcoholic fatty liver disease (NAFLD), an important health issue worldwide. We used B-mode image deep-learning to objectively assess NAFLD in 4 views of the liver (hepatic veins at confluence with inferior vena cava, right portal vein, right posterior portal vein and liver/kidney) in 135 patients with known or suspected NAFLD. Transfer learning with a deep convolutional neural network (CNN) was applied for quantifying fat fraction and diagnosing fatty liver (≥ 5%) using contemporaneous MRI-PDFF as ground truth. Single and multi-view learning approaches were compared. Class activation mapping generated attention maps to highlight regions important for deep learning-based recognition. The most accurate single view was hepatic veins, with area under the receiver operating characteristic curve (AUC) of 0.86 and Spearman’s rank correlation coefficient of 0.65. A multi-view ensemble of deep-learning models trained for each view separately improved AUC (0.93) and correlation coefficient (0.76). Attention maps highlighted regions known to be used by radiologists in their qualitative assessment, e.g., hepatic vein-parenchyma interface and liver-kidney interface. Machine learning of four liver views can automatically and objectively assess liver fat. Class activation mapping suggests that the CNN focuses on similar features as radiologists. [No. R01DK106419.]
Development and blinded test of a software tool for ultrasound-based hepatic fat fraction estimation
Authors: Han Aiguo , Boehringer Andrew S. , Montes Vivian , Andre Michael P. , Erdman John W. , Loomba Rohit , Valasek Mark A. , Sirlin Claude B. , O'Brien, W. D.
Published: November 2019

We have developed quantitative ultrasound (QUS) and deep learning algorithms to estimate hepatic fat fraction from radiofrequency (RF) ultrasound data backscattered by the liver. To facilitate the translation of such algorithms for clinical care and research, we developed a standalone software tool that can automatically generate fat fraction estimates using each of four separate algorithms based on ultrasonic attenuation coefficient (AC) (Algorithm 1), backscatter coefficient (BSC) (Algorithm 2), both AC and BSC (Algorithm 3), and deep learning with uncalibrated raw RF data (Algorithm 4). Reference phantom data and sonographer-drawn fields of interest (FOIs) outlining the liver boundary were used for Algorithms 1–3 but not in Algorithm 4. A pre-determined, fixed FOI was used in Algorithm 4. All four algorithms were developed using contemporaneous MRI-PDFF and ultrasound RF liver data acquired from 144 adult participants with and without nonalcoholic fatty liver disease. The software is now being tested on an independent cohort of participants with contemporaneous MRI-PDFF as the reference standard. 26 participants have been enrolled to date. Preliminary results show good agreement among the four algorithms, and good correlation between the ultrasound fat fraction estimates and MRI-PDFF (Person’s r = 0.61, 0.63, 0.66, and 0.76 for Algorithms 1–4, respectively). [No. R01DK106419]
Axial acoustic field barrier for fluidic microparticle separation at high-throughput
Authors: Li Nan , Kale Akshay , Stevenson Adrian C.
Published: November 2019

An acoustic field barrier integrated within a flow tubing system to achieve high-throughput separation of particles in fluid will be reported. We investigate the axial acoustic field of a piezo-tube with an inside diameter of 34 mm, a length of 25 mm, and an operating frequency of 1.15 MHz. Energy concentrates within the tube, and leakage at the ends provides a sharp monotonic acoustic pressure field within a fluidic circuit. This process is not the conventional standing wave mechanism; instead, the geometry produces a spatially stable filtering action without fouling. This powerful filtering action is confirmed theoretically via a COMSOL simulation and demonstrated experimentally by concentrating suspensions of 5 μm proteoglycan tracer particles at a flow rate of 20 ml/min: The corresponding acoustic contrast factor is 0.243, and the trapping force is 11 pN. This tube geometry tackles the limitations of microfluidic standing wave based acoustic concentrators, namely, complex extraction, low-throughput, and distributed focus, by harnessing a stable monotonic field profile.
Nanoacoustofluidics: Unprecedented fluid manipulation via controlled MHz-order vibration at the nanoscale
Authors: Zhang Naiqing , Manor Ofer , Friend James
Published: November 2019

Manipulation of fluids and colloids at the nanoscale is made exceptionally difficult by the dominance of surface and viscous forces. The use of MHz-order vibration has dramatically expanded in microfluidics, enabling fluid manipulation, atomization, and microscale particle/cell separation. We find even more powerful results at the nanoscale, with the key discovery of a new mechanism of acoustic wave-fluid motion interaction. We show that MHz-order surface acoustic waves (SAW) can manipulate fluids and fluid droplets within fully transparent, high-aspect ratio 5–150 nm tall, 10–100 μm wide, 5 mm long nanoslits fabricated via a direct, room temperature bonding method for lithium niobate (LN). The application of SAW causes fluid draining and pumping, developing ∼1 MPa pressure through the nanoslit structure. The mechanism of specific draining pattern is well explained by a detailed theoretical model based on the nonlinear acoustic vibration phenomenon in nanoscale channels. We also show how individual fluid droplets of only 1–10 fl are propelled by incident SAW in the nanoslit structure, entrapping them at locally widened regions along the nanoslit due to the capillary pressure difference. Our results indicate MHz-order SAW as a powerful tool for fluid manipulation in nanoscale.
A uniform rectangular array of isotropic sensors of stochastic gains: The hybrid Cramer-Rao bound for direction finding
Authors: Kitavi Dominic M. , Wong Kainam T.
Published: November 2019

Real-world sensors deviate from their nominal gain; that deviation could be modeled stochastically. Such sensors, populating a rectangular array grid, would affect the consequential direction finding's statistical precision, which is quantified here via the Cramer-Rao lower bound of the direction-of-arrival estimation variance.
Time-reversal techniques for defect detection in pipe system using high frequency acoustic waves
Authors: Nasraoui Saber , Louati Moez , Gozum Mehmet Murat , Grigoropoulos George , Ghidaoui Mohamed S
Published: November 2019

Recent research has shown that transient (acoustic)-based defect detection methods (TBDDM) in water pipelines are a promising new approach that may help achieve more sustainable urban water supply systems (UWSS). These methods are based on the generation of a probing pressure wave in the pipe system, and the use of the measured response to identify defects. This paper develops an analytical solution for sound propagation in inviscid axisymmetric pipe system with sound source at the boundary. The solution is given for rigid and elastic pipe wall. This analytical model is used to apply time reversal and match-field processing to the detection of blockages and leaks in a single pipe system. The wave forms used at the source are Gaussian-modulated sine wave and Chirp with frequency ranging from 5 to 60 kHz. The results show accurate detection with resolution of the order of the probing wave length.
Experimental validation of time-reversal technique for defect detection in air-filled pipes using high frequency acoustic waves
Authors: Gozum Mehmet M. , Louati Moez , Nasraoui Saber , Grigoropoulos George , Ghidaoui Mohamed S
Published: November 2019

Pipeline systems are extensively used for the transportation and distribution of the gas, water and petroleum products. The sustainability of the pipelines can be improved by utilizing the transient (acoustic)-based defect detection methods (TBDDM). In these methods, the probing pressure wave is generated in the pipe system, and the measured response is used to identify the defects. In this paper, experiments are performed on the acrylic pipe to study the acoustic wave propagation. The acrylic pipe is filled with air such that rigid pipe assumption is valid. Theoretical predictions applied with time reversal and match-field processing are validated with the experiments for the leak detection in a pipe system. The waveforms of Gaussian-modulated sine wave and Chirp are utilized as the transmitted signals in the frequency range of 1–15 kHz. The experimental results show that time-reversal technique is capable of accurate detection with a good resolution.
Optimal damping in ducts—The Cremer impedance
Authors: Åbom Mats , Zhang Zhe
Published: November 2019

The Cremer impedance, first proposed by Cremer (1953) and then extended by Tester (1973), is supposed to give the maximum propagation damping in an infinitely long waveguide. Previous works including a uniform grazing flow have shown negative resistance in the low frequency range for both circular and 2-D rectangular waveguides, i.e., implying an active boundary. In order to further analyze the low frequency behavior of the Cremer impedance, especially the negative resistance, two investigations are conducted in the current work. First, the previously used Ingard-Myers boundary condition is replaced by the Brambley boundary condition with the introduction of a thin inviscid boundary layer, and results obtained with the two boundary conditions are compared to see the effect of a sheared flow. Second, discussions regarding the validity of the low frequency result in both the up- and downstream directions from the perspective of mode merging are presented. This analysis is further extended from the fundamental mode to higher order modes in the frequency range where they are “just cut-on.”
Experimental assessment of the sound absorption coefficient of three natural fibers
Authors: Mansur Ana Carolina M. , Zanetti Alisson , Barbieri Nilson , Lima Key F.
Published: November 2019

The acoustic absorptive materials used in noise control stand out for the high efficiency in sound absorption. However, many of these materials are synthetic and hence they have a long or indeterminate decomposition time and does not allow their disposal in nature. In addition, if these materials suffer other destination as incineration in industrial furnaces, they may release toxic gases harmful to health and the environment. Natural fibers are an alternative for the replacement of synthetic materials used in acoustic insulation or in the reverberating surfaces treatment. The main objective of this work is to assess the acoustic efficiency of sisal, coconut husk and sugarcane bagasse fibers in terms of their sound absorption coefficient. The samples were experimentally assessed with the 100 mm diameter impedance tube according to the ASTM C1050-12 standard. The samples evaluated have 30, 40, and 50 mm thick and were tested with and without air gap between the samples and the back rigid of the tube in low and medium frequencies. Moreover, perforated plates were introduced in front of the samples to increase their efficiencies.
Signal Processing: Data analysis, machine learning, and imaging sources
Authors: Anderson Brian E.
Published: November 2019

Whether it is locating an enemy submarine, finding that annoying sound generated inside an airplane, optimizing the focusing of sound to destroy kidney stones, or learning how bats track their food, advanced signal processing is key to the success of these research topics. The Technical Committee on Signal Processing in Acoustics was formed to foster interdisciplinary interaction among the Technical Committees. Techniques used to track a submarine in the ocean, should also work to track a swarm of bees flying through the air or to track the delivery of medicine to a targeted place in the body. For example, at the previous ASA meeting a signal processing session on machine learning brought together researchers using machine learning to identify earthquakes from the global smartphone seismic network, to determine whether noise is further endangering a certain species of birds, and to map out the ocean floor. This presentation will highlight some of the exciting techniques being used in signal processing and in the process give an appreciation for the breadth of the applications of the techniques being developed.
An introduction to research topics in Underwater Acoustics
Authors: Sagers Jason D.
Published: November 2019

The Acoustical Society of America Technical Committee on Underwater Acoustics (UW) investigates sound wave phenomena in marine environments, including oceans, lakes, and rivers. Research interests span a broad spectrum from the measurement and modeling of acoustic propagation and scattering, to the detection and characterization of underwater sound, to signal processing algorithms and statistics. This diverse technical committee also shares interests with Animal Bioacoustics (AB), Acoustical Oceanography (AO), and Signal Processing (SP). This talk will highlight a few past and present research topics in underwater acoustics, emphasizing the important role of sound as a tool in subsea research and exploration.
Military and police small arms firing range noise assessments
Authors: Hale Marlund E.
Published: November 2019

Firing ranges are by their nature sources of very loud noise that can damage the hearing of on-site shooters and observers while also potentially causing a noise disturbance off-site. Small arms firing ranges are typically indoor ranges when located in urban or suburban settings, but when located in rural settings, they are typically outdoor ranges designed with varying types and degrees of noise abatement or no noise abatement at all, depending on the setting. Public firing ranges can be busy and in continuous use under good lighting and favorable weather conditions. Often there are wait times. Military and police (M&P) firing ranges are typically active under scheduled usage times. Both M&P ranges host a variety of small arms, from fully automatic and semi-automatic weapons, to bolt-action sniper rifles and large caliber side arms, all of which are very loud. It is often mandatory for M&P personnel to undergo shooting practice on a regular basis and with some assigned personnel having certification or qualification performance requirements. Several examples of military and police firing ranges, with their issues, similarities and differences, are discussed and personnel and community noise abatement measures are identified for these indoor and outdoor firing ranges.
Active surface sources for the exterior manipulation of acoustic fields
Authors: Onofrei Daniel T. , Egarguin Neil , Platt Eric
Published: November 2019

In this talk, we will describe our recent results about the characterization of continuous boundary data (i.e., pressure or normal velocity) on active single sources or arrays for the approximation of different prescribed scalar wave field patterns in given exterior (near field or far field) regions of space. We will present the theoretical ideas behind our results as well as numerical simulations with applications in decoy characterization, field synthesis of personal audio spots and almost nonradiating sources with controllable near fields.
Metaheuristic algorithm-based optimisation of an elastic metamaterial for robust control of multiple modes of vibration in a structure with parametric uncertainty
Authors: Singleton Lawrence , Cheer Jordan , Daley Stephen
Published: November 2019

Undesirable resonant vibrations in a structure can be suppressed using various techniques. However, parametric uncertainty can reduce modelling accuracy and lead to a reduction in the efficacy of the designed suppression system. The suppression of multiple modes of vibration with robustness to parametric uncertainty is achievable using a large number of tuned-vibration-absorbers (TVAs) with distributed resonance frequencies. However, the performance of TVAs is also dependent on their positions relative to the mode shapes of the structure, which are not always known. Elastic metamaterials (EMMs) consist of distributed resonant substructures, at a scale which is small compared to the wavelength of vibration. This allows the material to be considered homogeneous with one set of defining physical properties, thus reducing the dependence on mode shapes. In this paper, a unit cell of a single-degree-of-freedom resonator-based metamaterial is defined, and the individual resonance frequencies are optimised using different metaheuristic algorithms for a nominal fixed-parameter beam and for the same structure with uncertainty in one or more of its parameters. The performance of the optimised metamaterial unit cell is then assessed when applied to more complex structures.
SignalMaster Update 2019
Authors: Delgado Rafael E. , Davies Patrick
Published: November 2019

SignalMaster is a portable open speech and signal processing system that was developed specifically for researchers interested in developing their own real-time signal processing strategies. The system can be used for a wide range of research applications including development of hearing aid amplification and processing strategies and recording of evoked responses. SignalMaster uses a TMS320C6748 Digital Signal Processor (DSP) and provides two input and two output channels with 32 bit Analog-to-Digital (AD) and Digital-to-Analog (DA) convertors. Lithium-ion batteries provide up to 10 hours of freestanding operation. The system is available in two hardware platforms, the standard SignalMaster and the new SignalMasterLite, more compact and light weight for portable applications. The system may also be used while connected to a personal computer (PC) or Android Table via Bluetooth for additional control of experiments, off-line processing and data storage. A DLL provides functions for user developed applications to communicate with the hardware and be upload C language programs. This allows for different applications to be uploaded in order to reconfigure the processing algorithms being executed for any experiment at any time. DSP, PC-based and Android Table software source code examples provide users with the ability to develop their own user specific applications.
Pipe geometry calibration measurements for the improvement of ultrasonic clamp-on flow meters
Authors: Massaad Jack , van Willigen Douwe M. , van Neer Paul L. , de Jong Nico , Pertijs Michiel A. , Verweij Martin D.
Published: November 2019

Clamp-on flow meters need a-priori knowledge of pipe geometry and material properties for their operation. Estimation of these properties may limit the accuracy of flow measurements. We are currently investigating the use of clamp-on flow meters based on matrix transducer arrays. Besides the benefits for flow measurement, these can be used for a-priori measurement of the required pipe properties. In the axial direction, average longitudinal wave speed and thickness of the pipe can be obtained from the dispersion curves of the Lamb waves in the pipe wall. In the circumferential direction, the arrival time of the fastest Lamb wave mode can be used to measure the pipe diameter. In our presentation, this method is discussed and proof of principle is provided through FEM simulations and measurements. The setup consisted of two pipes (outer diameters 64.5 mm and 93 mm), with two transducers (1 MHz) on top. The arrival time of the fastest Lamb wave mode was measured. For the outer diameter, the error between simulation and measurement was below 1% (small diameter) and below 3% (large diameter). The results suggest that further exploration of the unique possibilities of matrix transducers to accurately measure pipe parameters is opportune.
Inverse acoustical characterization of porous material: A novel approach using diffuse field and transmission loss
Authors: Cavalheiro Thiago , Rizzatti Ricardo S. , Kulakauskas Fabio Luis V. , Kulakauskas Lucas V. , Serafim Luisa P. , Lenzi Arcanjo
Published: November 2019

Porous materials are largely used to improve sound quality in enclosed spaces. Inverse acoustical characterization of porous media is becoming popular due to experimental practicality. Most of the studies have as input data some impedance tube measurements. However, this approach presents several complications, mainly concerning the sample boundary conditions. The purpose of this study is to obtain the macroscopic parameters by inverse characterization, using transmission loss and the absorption coefficient as input data, both measured in reverberant chamber. One-piece and partitioned 2 m2 samples were measured. Several low-density materials were analyzed. The influence of boundary conditions, acoustic diffuse field and impervious screen layering porous material have been investigated. The Transfer Matrix Method is combined with the Johnson-Champoux-Allard equivalent fluid model on an optimization process. Transmission loss and absorption coefficient are simultaneously calculated. The mean square error between calculated and measured values is set as the objective function over the frequency range. Although the mounting condition of the measured transmission loss setup has required appropriate adjustment, good satisfactory repeatability on the optimized parameters was achieved.
Dynamic mechanical characterization of viscoelastic materials using bending wave correlation vibrometry
Authors: Miller Max , Xiang Ning
Published: November 2019

Direct solid-borne sound measurements allow incorporation of phase in characterizing viscoelastic materials. In the absence of excessively large samples, reflections from specimen boundaries obscure this valuable data. Circularly crested bending waves generated in plates provide a means of preserving phase information while maintaining reasonable sample sizes. The coherence of signals measured equidistant from the source and the lack thereof concerning reflections, enables isolation of the direct sound. This talk presents developments in a laser Doppler vibrometer based dynamic mechanical characterization method aimed at broadband classification of viscoelastic materials. The applicability of this technique to in-situ applications is demonstrated. Material properties are shown to correspond with results from existing methods.
Bounds on the imaginary part of complex Poisson’s ratio of viscoelastic materials
Authors: Pritz Tamás
Published: November 2019

Bounds on the imaginary part of complex Poisson’s ratio of viscoelastic materials The Poisson’s ratio of ideally elastic solids is a real number for either static or dynamic loading, and has bounds, namely its magnitude can be between -1 and ½ in case of homogeneous, isotropic, linear materials. In contrast, the Poisson’s ratio of viscoelastic solids subjected to dynamic loading can be considered as a complex number, referred to as complex Poisson’s ratio (CPR), because of the material damping. It is clear that the real part of CPR has the same bounds as the Poisson’s ratio. The question what are the bounds on the imaginary part of CPR is investigated in this paper for homogeneous, isotropic, linear viscoelastic materials with positive Poisson’s ratio. It is shown that the imaginary part of CPR also has bounds, which depend on the Poisson’s ratio itself and the material damping. Equations are developed to determine the bounds in question as functions of the Poisson’s ratio and shear loss factor provided that the latter is lower than 0.3. It is proved that the imaginary part of CPR cannot be larger than approximately one tenth part of the shear loss factor. Experimental data supporting the theoretical findings are presented.
Quantitative evaluation of standard and enhanced feature extraction from individual biological sounds recorded in coral reef environments
Authors: McBride Kelley , D'Spain Gerald L. , Mellinger David K. , Laferriere Alison B. , Nicoletti Mike , Buckingham Michael J.
Published: November 2019

Passive acoustic monitoring of three protected coral reef habitats south of St. John Island in the US Virgin Islands was conducted in April, 2019. Four wideband Autonomous Passive Acoustic Monitoring (APAM) packages, each with 12-element hydrophone arrays, were deployed on the 10-m-deep seafloor and recorded continuously over the 9-day experiment. Previously published methods for robust feature extraction of individual biological sounds [Mellinger and Bradbury, 2007] have been applied to these data and compared with enhanced approaches to feature extraction. This talk presents results of quantitative evaluations of the performance of these methods. Feature extraction is categorized as a parameter estimation problem whose performance is quantified by the statistical distribution of estimates, typically summarized by the bias and variance of these distributions. Results for a simulated case first are presented, and then those from the APAM-recorded data. The enhanced approaches show significant improvement over the standard approaches for several of the extracted features.
Signal and array processing of biological transients
Authors: D'Spain Gerald L. , Phillips Goldie T. , Rimington Dennis
Published: November 2019

Studies of biological transients in the time domain require removing the distorting effects of the data acquisition system (DAQ) system. Unfortunately, amplitude and phase calibration across frequency (equivalently, the DAQ impulse response) rarely is determined for bioacoustic systems. Calibration is not needed for certain types of processing, e.g., detection since signal and noise undergo the same distortion. Under certain assumptions (mainly pertaining to the properties of the noise), the optimal detector for transients is a member of the family of power-law detectors. Therefore, a challenge is determining the pre-processing approach that converts ocean acoustic noise into noise with the assumed properties. A direction-of-arrival estimation approach that is optimal under certain conditions is the minimum variance, distortionless response beamformer. However, transients typically are snapshot-deficient for estimating the data cross spectral matrix. Quantitative performance of sub-optimal but robust approaches with passive acoustic arrays deployed in a variety of ocean environments are investigated. A non-acoustic biological transient is the infrared radiation from the heat of a marine mammal blow. Results from an automated processor based on the power-law detector for infrared video are presented.[Support from the Office of Naval Research, the Joint Industry Programme, and the Walton Foundation].