bluuebunny/crossref_metadata_2025 huggingface dataset:
Weighted coherent processing on sparse volumetric vector sensor arrays
Authors: Nichols Brendan , Martin James S. , Verlinden Christopher M. , Sabra Karim G.
Published: November 2017

A network of drifting sensors, such as vector sensors mounted to freely drifting buoys, can be used as an array for locating acoustic sources underwater. Localizing a source using traditional coherent processing methods has been improved through arbitrary selection of element-wise weights of the covariance matrix [Nichols and Sabra, JASA 2015, Vol. 138]. However, the selection of weights offers an opportunity to optimize localization performance measures such as accuracy or precision. Here, the performance of source localization is compared between optimal weightings and traditional weightings for both simulated and at-sea data collected from a freely-drifting vector sensor array deployed in the Long Island Sound.
Tracking aircraft flybys using a microphone array
Authors: Culver R. Lee , Tenney Stephen M. , Noble John
Published: November 2017

Ferguson and Quinn (JASA 96(2), 1994) develop equations to describe the time-frequency characteristics of an acoustic signal radiated by an aircraft and received by a stationary microphone. These equations enable construction of curves in time-frequency space whose shape depends upon several parameters, namely, aircraft speed and height above the microphone. We have utilized Ferguson and Quinn’s equations to track an aircraft fly by under very low signal-to-noise conditions using six microphones which are spaced too far apart to form beams. We make use of signal coherence across the array, and we develop a time-frequency “matched filter” with replicas that are based upon aircraft speed, height above ground, and closest point of approach distance.
Source tracking with linear and circular compact vector sensor arrays
Authors: Gur Berke M. , Akal Tuncay , Uslu Abdurrahman , Yildirim Melih
Published: November 2017

Vector sensors are directional acoustic sensors that can make collocated measurements of both the acoustic pressure and the particle motion (in general velocity or acceleration). Combining the particle acceleration or velocity measurements with pressure, it is possible to estimate the intensity of the acoustic field, which in turn is related to the direction of the net acoustic energy propagation. Recently, several novel beamforming and array processing methods have been proposed that enable the development of compact linear and circular vector sensor arrays with inter-sensor spacing much less than the traditional spacing of one-half the design wavelength. These methods, albeit differing in implementation, both rely on the extraction and processing of the so-called “acoustic modes” of the sound field and have shown to be successful in estimating source direction relative to the array in a 2-D setting. The work described here, builds on previous results and extends the direction-of-arrival estimation methods to source tracking. Several algorithms developed for this purpose and implemented on both array types are introduced. The proposed approaches are experimentally validated using air-borne and underwater sources for compact pressure and 1-D vector sensor arrays.
Detection, localization, and classification of multiple ocean vehicles over continental-shelf regions with passive ocean acoustic waveguide remote sensing
Authors: Zhu Chenyang , Saghir Nada , Li Haoqing , HUANG WEI , Godø Olav Rune , Makris Purnima R.
Published: November 2017

Multiple ocean vehicles, including both surface ships and unknown submerged vehicles, can be simultaneously monitored over instantaneous continental-shelf scale regions via passive ocean acoustic waveguide remote sensing (POAWRS) by employing a large-aperture densely sampled coherent hydrophone array system. Here, the approach is demonstrated for multiple merchant ships present in the Norwegian Sea in 2014. The sounds radiated underwater by ocean vehicles, dominated by narrowband tonals and cyclostationary signals, are detected in the beamformed spectrograms. Coherent beamforming of the receiver array data significantly enhances the signal-to-noise ratio of the ship-radiated signals enabling detection of ocean vehicles roughly two orders of magnitude more distant in range than a single hydrophone. The estimated bearing-time trajectory of a sequence of detections are employed to determine the horizontal location of each vehicle using the moving array triangulation technique. The estimated locations are verified by comparison with historical database of merchant ships present in the region. Several time-frequency characteristics are extracted from the detected signals and used to classify and track the ships.
Echolocation and flight strategies of aerial-feeding bats during natural foraging
Authors: Fujioka Emyo , Hamai Fumiya , Sumiya Miwa , Motoi Kazuya , Fukui Dai , Kobayasi Kohta I. , Hiryu Shizuko
Published: November 2017

Aerial-feeding bats actively emit sonar sounds and capture large amounts of airborne insects a night. Microphone-array system allows us to know not only the positions where the bat emits sonar sounds (i.e., 3-D flight path) but how the bats dynamically control the acoustical field of view during searching and approaching target-prey. Here, we show echolocation strategy of bats during natural foraging revealed by the large-scale microphone-array system which covered the horizontal area of approximately 20 m × 20 m. Pipistrellus abramus was found to expand the width of their sonar beams in both horizontal and vertical planes just before the prey-capture. Since the bats emit echolocation pulses at a high rate (i.e., feeding buzz) just before capturing, the capture positions can additionally be measured. Recently, we have investigated the relationship between flight patterns, capture positions, and foraging efficiency of Myotis macrodactylus during natural foraging above the pond. Further investigation from the viewpoint of the optimal foraging would reveal echolocation and flight strategies of the bats to efficiently search and approach prey items. [This research was supported by a Grant-in-Aid for Young Scientists (B) and Scientific Research on Innovative Areas of JSPS, and the JST PRESTO program.]
Delay-Doppler characteristics of surface interacting underwater sound
Authors: Walstead Sean
Published: November 2017

The interaction of underwater sound with the ocean surface is investigated. Laboratory measurements of the delay-Doppler structure of the surface multipath at a transmission frequency of 300 kHz are compared to physics based analytic predictions. Channel impulse responses and channel scattering functions are measured when the surface is characterized by wind generated roughness, swell-like roughness, and a mix of wind and swell. The distribution of surface scattered energy across delay time and Doppler shift is presented as a function of wind speed ranging from 0.5 m/s to 11.0 m/s. The effect of wave shape and nominal out-of-plane grazing angle on the delay time spread and Doppler spread of the surface multipath are also considered. Proper characterization of surface interacting acoustic energy has direct application to the improved performance of shallow water and near surface underwater acoustic communications systems.
Experiments on the sound transmission at the water-air interface for different source-interface distances
Authors: Wehner Daniel , Landrø Martin
Published: November 2017

The water-air interface is a nearly perfect reflecting boundary for acoustic waves due to the high impedance contrast between the two media. In many marine applications, ranging from geophysical measurements to bioacoustics, the sea surface has an important impact. A rough sea surface topography leads to complex scattering and interference for acoustic frequencies with similar wavelength or higher than the wavelength of the interface. In geophysical applications and infrasound the frequencies of interest often have larger wavelengths. At the same time, the source within these applications is mostly located close to the interface with respect to its wavelength. In this case, an increased transmission could be expected as experiments with acoustic transducers demonstrate [D. C. Calvo et al., J. Acoust. Soc. Am. 134, 3403-3408 (2013)]. We design two experiments with sources close to the interface while changing the distance between the source and the water-air surface. For the first experiment, a water gun, which creates large cavities, is placed in water. Second, a signal gun, as used in athletics, is positioned in air. The acoustic transmission from both sides is measured and investigated. We find an increasing transmission coefficient for lower frequencies and decreasing distance between source and interface.
On target excitation by modulated radiation pressure
Authors: Abawi Ahmad T. , Kirsteins Ivars P. , Marston Philip L. , Daniel Timothy
Published: November 2017

Modulated radiation pressure (MRP), which can be produced by modulating an ultrasound carrier beam with a low-frequency signal provides the capability to interrogate elastic objects in a novel manner: The high-frequency carrier beam enables surgical investigation of target of interest, while the low-frequency modulation signal “shakes” the target to extract useful physical information. By sweeping the modulation frequency, target resonances can be identified, and by physically scanning the target at a modulation frequency that is commensurate with one of its resonant frequencies, the corresponding mode shape can be extracted. Up until now, the application of this technique has been limited to medical ultrasound, where it has been used to look for tumors and kidney stones among other things. The other applications of this technique have been particle trapping and non-contact manipulations. In this presentation, we will show results from experiments conducted at Washington State University involving scaled targets, complemented by finite element modeling results. We will discuss coupling between two targets near each other, while one of them is excited by MRP. We will also discuss how the radiated field from a target excited by MRP scales with its size. [Work supported by ONR.]
Exploration of perceptual differences of virtually enhanced sound fields using timbre toolbox
Authors: Chon Song Hui , Kim Sungyoung
Published: November 2017

In this presentation, we approach the analysis of perceived spatial differences from the perspective of timbre using the Timbre Toolbox [Peeters et al., 2011, J. Acoust. Soc. Am., 130, 2902–2916]. The Timbre Toolbox, using MATLAB, calculates 88 descriptors that have been reported in various timbre perception literature. These include temporal (such as RMS energy), spectral (both in magnitude and power spectra), and harmonic descriptors, as well as those based on the Equivalent Rectangular Bandwidth (ERB) model, which approximates the auditory processing. Analyses were performed on 27 stimuli of nine string quartet groups performing one excerpt in three room conditions, as well as the data from perceptual experiments reported in an earlier study [Chon et al., 2015, Proc. Audio Eng. Soc.]. The three room conditions have different spatial profiles, which consist of one natural room and two virtually enhanced rooms, where many physical parameters were closely controlled (e.g., ST1 and ST2). The experimental data include both the musicians’ ratings of spatial quality for performance (e.g., tonal balance and envelopment) as well as recording engineers’ ratings of recorded spaces (e.g., clarity and room size). The best timbre descriptor for each question will be reported, and an overall merit of this approach discussed.
On the effect of acoustic diffusers in comparison to absorbers on the subjectively perceived quality of speech in ordinary rooms
Authors: Sanavi Ali , Schäffer Beat , Heutschi Kurt , Eggenschwiler Kurt
Published: November 2017

Acoustic diffusers are used to control unwanted reflections responsible for degrading sound quality, or to increase sound diffuseness in spaces such as auditoria. To control unwanted reflections, diffusers are not the only solution. An alternative approach is the use of acoustic absorbers. Whether diffusers or absorbers are chosen as treatment depends on whether the energy conserved by the application of diffusers improves or detracts other aspects of room acoustics including the subjectively perceived qualities. However, not much is known to date about subjectively perceived qualities, e.g., of speech, in ordinary rooms. The aim of this study was twofold. The first aim was to investigate the effect of acoustic diffusers on the subjectively perceived quality of speech in ordinary rooms. The second aim was to determine if and to what extent there are perceptual differences if the diffuser are replaced by acoustic absorbers. Two separate listening tests were performed with stimuli obtained from the convolution of measured binaural impulse responses of a meeting room with excellent speech intelligibility and speech samples recorded in an anechoic chamber. The results of the listening tests confirm that despite the already excellent speech intelligibility and low values of early decay time, speech quality can be further improved by introducing diffusers or acoustic absorbers, with absorbers improving the subjectively perceived speech quality slightly more than the diffusers.
Acoustic design of teachers' cafeteria in Tsinghua University
Authors: Yan Xiang , Li Hui
Published: November 2017

By the end of 2015, Tsinghua University has built a new cafeteria for 600 people. Dining period in university campus is not just eating, but an important conversation opportunity. The university president insists the noisy environment in past campus cafeteria must not happen again. So a comprehensive architectural acoustic design was taken. In order to meet the architect's aesthetic requirements, the restaurant uses a large area of seamless porous sandstone sound-absorbing material. By both ceilings/walls absorption treatments and dining tables layout, three acoustic design goals were reached: (1) mid-frequency reverberation time = 0.7s; (2) at the same table, the speaker's sound level attenuation of not more than 6dB, and passed to the adjacent table sound level attenuation of more than 9dB, this ensures the hearing’s signal to noise ratio; (3) in busy meal peak, the average background noise does not exceed 65dB (A). Teachers are satisfied with the sound environment of the cafeteria.
Investigating the performance of soundscape metrics using known data sources and numerical simulations
Authors: Martin Bruce , Barclay David R. , Cole Aidan
Published: November 2017

Metrics such as the acoustic complexity index, acoustic diversity index, entropy, evenness, and roughness have been correlated with anthropogenic and biologic sound sources in terrestrial soundscapes. The metrics offer the possibility of characterizing the presence of sound sources and the biodiversity of an environment in large datasets without having to perform detailed automated or manual analysis. However, the metrics are less successful at separating soundscape components and measuring biodiversity when applied to marine soundscapes. The reasons provided for the are the spectral overlap between anthropogenic and biologic sources, the wide range of source levels, long propagation ranges, and the difficulty comparing acoustics to observations, especially for species that are soniferous at night and hidden by day. In this analysis, we examine several popular soundscape metrics for marine data containing typical ambient noise, anthropogenic sources, or a single species. We then examine how the metrics change as different magnitudes and repetition rates of simulated marine life vocalizations are added to the data files.
Variation in the soundscapes of Pacific coral reefs over multiple spectral, temporal, and spatial scales
Authors: Lammers Marc , Zang Eden , Kaplan Maxwell B. , Mooney T Aran , Fisher-Pool Pollyanna I. , Brainard Russell
Published: November 2017

Biological sounds occurring on coral reefs are increasingly recognized as important factors influencing reef dynamics and ecological processes. Soundscapes of coral reefs can be broadly divided into a low-frequency band (<1 kHz), dominated by sounds produced by acoustically active fish, and a high-frequency band (2–20 kHz) dominated by snapping shrimp and other invertebrates. Because acoustic activities in both bands are influenced by a variety of ecological (biotic) and environmental (abiotic) factors, coral reef soundscapes are characterized by considerable spatial and temporal variability. The drivers of this variability are not yet well understood, but likely provide important insights into ecosystem processes and condition. We report on an effort to quantify the acoustic activity in both the fish and snapping shrimp frequency bands across twelve coral reef sites in the Pacific Ocean separated by distances ranging from hundreds of meters to thousands of kilometers, including reefs across the Hawaiian Archipelago, the Northern Mariana Islands, and American Samoa. We use data obtained from long-term, bottom-moored acoustic recorders to document the variability observed on multiple temporal scales and examine environmental drivers correlated with this variability at each location and differences among locations.
Soundscape stability in king penguin colonies
Authors: Zitterbart Daniel P. , Toscani Camille , Nesterova Anna , Le Bohec Celine , Bonadonna Francesco
Published: November 2017

King penguin colonies present an acoustically rich environment due to the highly vocal nature of these birds and the large abundance of birds within a colony (100.000 + ). Individual identification in adults and chicks is based on vocal signals. Penguins can recognize the call of their partner or chick even among thousands of calling individuals. However, the range of such identification is limited to a few meters, 8.8 m on average in the colony. In spite of the fact that king penguins are famous for their highly developed acoustic abilities, little is known regarding the overall acoustic colony structure. Using a distributed synchronized microphone array, we collected soundscape information over several months at several locations. We find location specific features in the soundscape that are stable over several weeks, regardless of environmental conditions and only require short integration time. We explore if current acoustic indices are able to capture these features, if soundscape stability information might be useful for navigation and if this information can be associated with current colony structure and spatial use.
The soundscape of bat swarms
Authors: Kloepper Laura , Fu Yanqing , Kinniry Morgan , Stevenson Robert L. , Brighton Caroline , Harding Christian , Domski Paul , Taylor Graham
Published: November 2017

Brazilian free-tailed bats form large maternal colonies numbering in the millions across the American Southwest. Each night, the bats emerge from their roost to travel to foraging locations. During this emergence, individuals fly together in a dense, linear stream and exhibit collective group behavior. Upon morning return to the roost, the flight behavior of bats change and individuals fly in unpredictable paths, with little to no apparent collective group behavior, creating a swarm. To understand the different sensory challenges each of these flight scenarios pose to bats, we recorded the soundscapes of bats in streams and swarms using four different recording platforms: (1) stationary, ground-based directional and omnidirectional microphones, (2) a zip-line microphone that maneuvered through the bat stream and swarm and was monitored by video, (3) a microphone and thermal camera on a quadcopter that recorded bat flight behavior and signals at high altitudes during swarm re-entry, and (4) a trained hawk that flew through the bat stream while carrying a microphone unit and monitored with unique video. We report on the characteristics and variability of soundscapes for bat swarms, including different noise profiles the bats experience during streaming and swarming and the adaptive time-frequency signatures and flight behavior of individuals during group flight.
Investigating bubble transport and fate in the watercolumn with calibrated broadband split-beam echosounder data
Authors: Weidner Elizabeth F. , Weber Thomas C. , Mayer Larry
Published: November 2017

The transport and eventual fate of gas bubbles in the marine environment is a topic of interest to researchers in numerous fields. Acoustic systems are commonly used to study bubble ebullition sites as they provide synoptic measurements of the watercolumn. However, the visualization of individual bubbles has traditionally required the use of point-source equipment, such as vehicle-mounted cameras. Here, we present an acoustic methodology for studying individual bubbles using a calibrated broadband split-beam echosounder. The extended bandwidth (14–24 kHz) provides a vertical resolution on the order of 10 cm, which allows for the discrimination of individual bubbles in the echogram. Split-beam phase differentiation provides phase-angle data which can be used to compensate for beam-pattern effects and precisely locate bubbles within the watercolumn. Bubble target strength is measured and compared to analytical models to estimate bubble radius, and bubbles are tracked through the watercolumn to estimate rise velocity. The resulting range of bubble radii (1–6 mm in radius) is similar to those found in other investigations, and the rise velocities are consistent with published models. Together, the observations of bubble radius and rise velocity offer a measure of gas flux.
Acoustic investigations of natural seeps at GC600
Authors: Razaz Mahdi , Di Iorio Daniela , Kelly James B.
Published: November 2017

We examine the acoustic signature of natural seeps in the Green Canyon block 600 of the Gulf of Mexico. The survey site was 2200'1600 m2 at a depth of 1200 m. Near-bottom multibeam backscatter, side-scan sonar mosaic, and chirp sub-bottom profiles were collected using an AUV cruising at 40 m above the seafloor. The water-column profiles collected by the Kongsberg EM2040 at 200 kHz central frequency were utilized to detect and localize seeps. Geological information from the chirp sonar and side scan images will also augment these data to further our understanding of the geologic structure of natural seeps. Identified seeps from the backscatter intensity were visited with a Comanche ROV for a visual inspection. An oily plume was selected for further investigations and vertical upwelling will be monitored with an Acoustic Scintillation Flow Meter (ASFM), for the first time. Concurrent measurements include nearby Acoustic Doppler profilers, a vertical array of conductivity/temperature instruments and two video cameras (VTLC) for identifying bubble/droplet sizes and distribution and will provide invaluable reference data on temporal variability.
Detection and characterization of hydrocarbon droplets using broadband echosounders
Authors: Loranger Scott , Weber Thomas C.
Published: November 2017

Investigation of the fate and transport of liquid hydrocarbons is limited by the small field of view of current instrumentation. Mass spectrometers, fluorometers, and megahertz sonars—the typical instrumentation for detection and classification of liquid hydrocarbons in the marine environment are limited to detections are ranges of less than a few tens of meters. Lower frequency (80–500 kHz) broadband acoustic backscattering from weakly scattering liquid hydrocarbon targets has been investigated using a novel droplet making device. Results show that such instrumentation should be capable of detections at significantly greater ranges than current instrumentation. The results are compared to a variety of models of acoustic scattering from spherical targets to determine the most accurate model for predicting the frequency response of weakly scattering spheres. The frequency response can be used to characterize the liquid hydrocarbon droplets, as long as the acoustic impedance of the hydrocarbon is well known for the range of temperatures and pressures affecting the droplet.
The acoustic properties of three crude oils at oceanographically relevant temperatures and pressures
Authors: Loranger Scott , Cole Justin P. , Bassett Christopher , Weber Thomas C.
Published: November 2017

The detection and quantification of crude oil in ocean environments is dependent on adequately constrained acoustic properties (e.g., density and sound speed). However, there is a paucity of published acoustic property measurements of crude oil at oceanographically relevant temperatures and pressures. Three medium crude oil samples (Alaska North Slope, Angola Bavuca, and Angola Xikomba) were tested to better constrain these properties for oceanographic applications. A temperature (−10 to 30 °C) and pressure (0.1 to 19.3 MPa) controlled sound speed chamber was developed for highly accurate differential time of flight measurements. Density and viscosity were also measured over the same temperature range. Finally, differential scanning calorimetry measurements (−40 to 50 °C) were conducted to identify phase changes in crude oil constituents that may contribute to nonlinearities in acoustic properties as a function of temperature at a constant pressure. Results are compared to previously available models for sound speed, such as the PC-Shaft model, and density as a function of temperature and pressure. The results can also be used to fully constrain models of the shape of oil droplets in the marine environment as a function of size, an important input for models of acoustic scattering.
A preprocessing method with Hankel matrix-based SVD in strong interference environment
Authors: Yu Ge , Piao Shenchun , Han Xiao , Iqbal Kashif
Published: November 2017

In sonar system, reverberation is an ignored interference as its characteristic is as same as target echo. It is hard to distinguish target in sever environment. Therefore, suppressing reverberation to increase signal-to-noise ratio is very important in underwater signal processing. In this paper, we proposed a pre-processing method which is based on singular value decomposition and Hankel matrix. This method utilized the correlation between target and reverberation is bad to detect target. The proposed method can suppress both the white noise and reverberation as is evident by the simulation results. The proposed method is also verified by processing the experimental data.
Rotor noise control using 3D-printed porous materials
Authors: Doolan Con , Jiang Chaoyang , Moreau Danielle , Yauwenas Yendrew
Published: November 2017

The self-noise created by rotor blades is an important component of the noise generated by aeroengine fans, wind turbines, and propellers. It is created by the passage of boundary layer turbulence over the trailing edge of the blade, where a portion of the unsteady pressure near-field is converted to acoustic waves that subsequently propagate to an observer in the far-field. This paper explores the use of 3D-printed porous materials for controlling rotor self-noise. It is reasoned that the flexibility offered by 3D-printing makes it possible to produce blade trailing edges with tailored, spatially varying porosity that can maximise noise reduction, either by modifying the near-field turbulence or by affecting the production of waves at the trailing edge itself. A number of 3D-printed porous material samples were acoustically characterised using an impedance tube. Using this information as a guide, special rotor blade tips were 3D-printed with varying levels of porosity and evaluated using a rotor-rig and microphone array. Simultaneously, computational modelling of the rotor-rig was performed to understand the flow field and turbulence levels over the blade tip region.
On the character and mechanics of flow-induced wall-mounted finite airfoil noise production
Authors: Moreau Danielle , Doolan Con
Published: November 2017

A major source of noise involves flow interaction with wall-mounted attachments such as fins, guide vanes, aircraft airframe components, and wind turbine blades. In a simplified sense, these objects can be viewed as wall-mounted airfoils of finite length. A wall-mounted finite airfoil has one end immersed in the free stream and the other end fixed to a wall that is subject to a developing boundary layer. The free-end and wall junction introduce three-dimensional flow structures into the wake that affect noise generation in ways that are not yet fully understood. The primary goal of this research is to determine how airfoil end-effects and three-dimensional aerodynamics influence airfoil noise production. To accomplish this goal, anechoic wind tunnel studies have been conducted to determine the characteristics and mechanisms of flow-induced noise production for various wall-mounted finite airfoil configurations. The test models include combinations of airfoil profile shape, aspect ratio, angle of attack and free stream velocity. The motivation for this work is to gain a better understanding of sound generation from wall-mounted finite airfoils to aid future innovation in quiet aerodynamic design and optimisation.
An experimental study on the role and function of the diaphragm in modern acoustic stethoscopes
Authors: Nowak Lukasz
Published: November 2017

Vibrations of a diaphragm of an acoustic stethoscope in contact with the body of an auscultated patient are the source of the sound transmitted to the ears of a physician performing examination. Mechanical properties of a diaphragm are supposed to significantly affect the parameters of the transmitted bioacoustic signals. However, the exact relation remains mostly unclear, as the underlying phenomena involve complex effects of acoustic coupling between the diaphragm and the body of a patient. The present study introduces a detailed methodology for determining vibroacoustic behavior of a diaphragm of a stethoscope during an auscultation examination. A laser Doppler vibrometer is used to measure the velocity of various points on the surface of a diaphragm during heart auscultation. Synchronized recordings of electrocardiography signals are used for segmentation. Representative data sets are selected and analyzed for various kinds of diaphragms. The results show significant differences in vibration velocity levels and their distribution across the surfaces of the considered structures. In this regard, it is also shown that the currently available solutions can be significantly improved by using structures better matched to the acoustic impedance of a body.
Experimental study of nonlinear acoustic effects of orifices in duct systems
Authors: Kawell Samuel T. , Teasley Thomas , Scarborough David
Published: November 2017

Researchers focused on reduced emissions hydrocarbon fuel combustion systems have developed new high-efficiency furnace and gas turbine engine technologies that, unfortunately, regularly suffer from detrimental combustion instabilities. Engineering design tools developed to predict these instabilities in combustion systems frequently neglect nonlinear acoustic effects. However, boundaries and duct junctions, e.g., area changes, valves, and orifices, often exhibit nonlinear effects even at low acoustic pressure amplitudes. Experimental data of these nonlinear effects are required to accurately model engine and duct acoustics and to predict combustion instabilities. This experimental investigation focuses on understanding the nonlinear acoustic response of an orifice with and without steady flow. Various orifices were mounted in a multiple-microphone impedance tube and the acoustic impedance of the combination was used to measure the nonlinear acoustic response and impedance of the orifices at amplitudes from 114 to 190 dB and over frequencies from 100 to 1500 Hz. The preliminary results of the experimental study suggest that the impedance is dependent on the acoustic velocity amplitude. This indicates significant nonlinear effects. These experimental data will assist the development of nonlinear acoustic models of orifices in combustion systems.
A new lumped parameter model for the design of the free-flooded ring transducer
Authors: Been Kyounghun , Nam Seungwon , Lee Haksue , Seo Hee-seon , Moon Wonkyu
Published: November 2017

The free-flooded ring (FFR) transducer is the well-known low-frequency sound sources in underwater because its operating frequency bandwidth is broad and relatively small size. Previous researches were preformed to predict the characteristics of FFR transducers using ECM which is a type of LPM because ECM is widely used to understand its characteristics in transducer design process. However, it is hardly to predict the characteristics of an FFR transducer because the acoustic field is generated from its top and bottom openings, connected by the inner fluid, as well as the cylindrical ring surface. Here, the authors investigated an ECM of an FFR transducer consisting of three parts: the piezoelectric ring, the cylindrical cavity, and the radiation load. In addition, an LPM which can consider mutual radiation loads was proposed to improve the accuracy of the model. The proposed models were verified using commercial finite element method (COMSOL Multiphysics). It was confirmed that LPM could predict characteristics of FFR transducer more accurately than ECM. [Work supported by NRF 2016R1E1A2A02945515).]
Saxophone acoustics and marching bands
Authors: Gibiat Vincent , Selmer Jerome , Cottier Jonathan
Published: November 2017

Historically saxophones appear in bands far after the beginning of Jazz history. Marching bands were mainly built around brass instruments and the saxophone appears alone in these bands. The main question that arises is “how this brass-woodwind succeeded to mix in such brass bands? The power of brass instruments is known to cover most woodwinds but the saxophone survives when flutes, with the exception of piccolo, disappeared. The answer could be in the design of saxophone and mainly in the design of tenor saxophone. The saxophone has been built and designed by A. Sax to be a powerful instrument able to cover or to compete with the sound of brass instruments, and he has been successful. We will show that in addition with the native sound power of its side, the saxophone exhibits a formant in the most sensitive part of our hearing system that gives it such “voicy” sound. Finally, we will show that saxophones are as wild instruments as the other members of marching bands with theses two characteristics power and voice.
Single-reed woodwinds: From physical modeling to sound radiation
Authors: Chatziioannou Vasileios , Hofmann Alex
Published: November 2017

Single-reed woodwind instruments have been traditionally used in marching bands, along with brass and percussion instruments. However their sound is often covered by louder instruments, making them less audible to the audience and the members of the band. Indeed, the saxophone has been designed in order to replace the clarinet in military bands, making the woodwind section of the band more prominent. This study discusses the sound generation mechanism of single-reed woodwind instruments in an attempt to investigate which reed and mouthpiece properties significantly affect the amplitude of the radiated sound. To this end, transfer function measurements and numerical investigations using physical modeling are employed. The former may indicate how the use of different mouthpiece geometries and various types of reeds may have an effect on the sound magnitude. The latter can be used to systematically vary reed and embouchure related parameters while observing how changes in these parameters affect the radiated sound.
Noise sources in a commercial supersonic jet
Authors: Ruscher Christopher J. , Gogineni Sivaram
Published: November 2017

Stringent noise regulations currently limit commercial aviation. These regulations make supersonic commercial flight impractical. The development of an engine that can meet these strict rules is paramount to making supersonic commercial flight a reality. One method of noise reduction is to add additional streams to an engine. As such, the three-stream jet has potential to help reduce exhaust noise. Understanding the noise sources in the jet plume can help to design nozzles that are quieter. To accomplish this, high-fidelity, high-speed data are required. Data for an axisymmetric and offset three-stream nozzle were generated using the LES code JENRE developed by the Naval Research Laboratory. The simulation data has been shown to match well with experimental data. Advanced analyses methods that are based on Proper Orthogonal Decomposition (POD), wavelet decomposition, and Stochastic estimation have been applied to extract noise sources in the jet plume.
From underwater thunder to cavitation from pulsed ultrasound: One graduate student’s perspective of the years leading up to the formation of NCPA
Authors: Atchley Anthony A.
Published: November 2017

The Physical Acoustics Research Group at the University of Mississippi (PARGUM) fostered a vibrant, multidisciplinary research environment in the early 1980s that incubated the concept of the National Center for Physical Acoustics (NCPA). It also provided graduate students, new to physical acoustics, an enticing glimpse into the breadth of the field and an exposure to a range of important contemporary problems. The research programs included terrestrial lightning detection and location, the underwater sound generated by lightning striking the ocean surface, long range sound propagation, propagation through porous materials, sound amplification by selective molecular excitation, acoustic levitation of bubbles and droplets, studies of acoustic cavitation thresholds and sonoluminescence, numerical simulation of bubble dynamics, and others. Beyond the scientific activities, PARGUM introduced a number of new acousticians to the ASA, many of whom have contributed to the leadership of the Society. The purpose of this presentation is to review some of the research results produced by the members of group from the time period as well as their contributions to the ASA.
Vibrometric characterization of a TN-32 dry storage cask for spent nuclear fuel
Authors: Lin Kevin Y. , Prather Wayne E. , Lu Zhiqu , Mobley Joel , Gladden Josh R.
Published: November 2017

The assessment of the internal structural integrity of dry storage casks for used high burnup nuclear fuel assemblies is of critical importance before these are transported to permanent repositories. The size of the casks (5.2 m in height and 2.4 m in diameter), structural complexity, and the inability to access the interior make this a challenging task. This project addresses these difficulties through a multi-modal approach involving nuclear, charged particle, and acoustic methods. In this talk, we report on linear and nonlinear vibrational spectra of intact TN-32 casks. These studies use both impulsive and swept continuous-wave excitations with a variety of sensor placement configurations. From the resulting spectra, resonant frequencies, quality factors, and harmonic responses of various vibrational modes were determined. A detailed finite element model of the TN-32 was constructed and the experimental results are compared to the modal structure determined numerically. [This work was supported by DOE NEUP Award: DENE0008400.]
Acoustic similarities among voices. Part 2: Male speakers
Authors: Kreiman Jody E. , Keating Patricia , Vesselinova Neda
Published: November 2017

Little is known about how to characterize normal variability in voice quality within and across utterances from normal speakers. Our previous study of female voices suggested that only a few acoustic parameters consistently distinguish speakers, with most of the work being done by idiosyncratic subsets of parameters. The present study extends this research to samples of 50 men’s voices. The men read 5 sentences twice on 3 days—30 sentences per speaker. The VoiceSauce analysis program estimated means and standard deviations for many acoustic parameters (including F0, harmonic amplitude differences, harmonic-to-noise ratios, and formant frequencies) for the vowels and approximant consonants in each sentence. Multidimensional scaling and linear discriminant analysis were used to examine the acoustic characteristics of the overall voice space, and to measure how well each speaker’s set of 30 sentences could be acoustically distinguished from all other speakers’ sentences. Additional analyses of small subsets of voices compared the importance of global versus local details in discriminating voices acoustically. Results will be compared to those for female speakers, and implications for recognition by listening will be discussed. [Work supported by NSF and NIH.]
Voice quality variation over the course of the English utterance
Authors: Bird Elizabeth M. , Garellek Marc
Published: November 2017

The presence of atypical voice quality (e.g. breathy and creaky voice) can be used to diagnose voice disorders, but it is also clear that healthy English speakers’ voices vary as a function of phrasing. For example, ends of declarative utterances tend to be produced with creakier voice quality. Yet for speakers who have no diagnosed voice disorder, it is still unclear what factors affect voice variation over an utterance, and how consistent these variations are across speakers. This in turn limits diagnostic utility of perceived non-modal voice. Therefore, the goal of this project is to determine how the voice varies over the course of English utterances. We recorded electroglottographic (EGG) and audio waveforms of 20 male and female speakers of Californian English reading sentences of various lengths that were designed to avoid non-modal voice associated with certain segments. The EGG waveforms were analyzed for contact quotient and f0 at the beginning, middle, and end of the utterance. Discussion will focus on how voice quality differs by position in utterance, and the extent to which it is predictable from f0. We also discuss whether voice quality varies as a function of gender, utterance length, and speakers’ average voice quality.
Direction of arrival estimation using local series expansion evaluated on acoustic data
Authors: Hendeby Gustaf , Lunner Thomas , Gustafsson Fredrik
Published: November 2017

Direction of arrival (DOA) estimation using a local series expansion of the signal is evaluated on acoustic data. It was recently proposed that DOA estimation using a sensor array could be performed using a local temporal/spatial series expansion. That is, to use the local phase of the signal rather than its estimated second order moments or correlation as in classical methods. The approach should provide easier handling of general sensor configurations, ability to deal with very low sampling rates and few samples, and benefits from miniature sensor configurations. Additionally, the signal is not required to be narrow-banded, as sufficient smoothness is enough. Here, the local series expansion method is benchmarked to a standard beam-forming method using experimental data, recorded in an anechoic chamber at the Technical University of Denmark (DTU). The dataset was recorded using 52 high quality microphones distributed on a sphere with radius 50 mm, and contains several recordings from one or two well defined sources from several different directions, with different levels of reverberation. The dataset is used to evaluate important aspects of the new method and its potential to improve on standard DOA methods.
Detection of reflections in different room acoustical conditions using generalized cross correlation phase transform
Authors: Jo HyunIn , Seo Jong Gak , Jeon Jin Yong
Published: November 2017

A framework for localization of the received source emission was implemented in enclosures based on generalized cross correlation (GCC) weighting with phase transform (PHAT) function. It was to achieve the goal of capturing meaningful sounds including speech in actual environments. The effects of room reverberation and ambient noise on the performance of the system were investigated with a linear microphone array. Experiments were performed in different environments with different RT and background noise levels. The sound sources are consisting of pink noise and speech sources were used to observe the relationship between localization accuracy and room acoustical parameters. Results for evaluation indicated that the location of the reflections was noticeable for accurately detection of the sources in reverberant and noisy environments.
Subarray processing with coprime and minimum redundancy arrays
Authors: Jo Guen-Soo , Choi Jung-Woo
Published: November 2017

A coprime sensor array (CSA) refers to a non-uniform linear array consisting of two undersampled uniform linear arrays (ULAs) with coprime numbers of elements, respectively. Its beam pattern can be enhanced by multiplying beampatterns of individual subarrays. This technique, called product processing, provides improved resolution because its sum coarray length is extended from the product of beampatterns. Nevertheless, the extended coarray inevitably includes holes that result in higher peak sidelobes than the full ULA case. In this paper, we propose a technique to reduce peak sidelobes through the combination with minimum redundancy arrays (MRAs) and an additional subarray. Two ULAs comprising the coprime array are thinned by the MRA technique, and the reduced number of sensors is then utilized to construct the third subarray. The third array suppresses peak sidelobes by placing nulls at the peak sidelobe locations. The characteristics of the proposed technique are analyzed in terms of white noise gain (WNG) and maximum sidelobe level (MSL). It is demonstrated that the proposed technique can improve the MSL with similar number of sensors, thereby reducing the estimation error in the presence of multiple sources.
Recording and post-processing speech signals from magnetic resonance imaging experiments
Authors: Kuortti Juha , Malinen Jarmo
Published: November 2017

Speech recordings during an Magnetic Resonance Imaging (MRI) experiment yield valuable but noisy acoustic data for modelling purposes. Despite recent improvements in optical microphones for MRI, using an acoustic sound recording system in dipole configuration, based on shielded electret microphones and waveguides, has some inherent advantages: For example, the bandwidth can be made very wide, and the extremely linear behaviour of all components facilitates the numerical post-processing of signals. Here, the full measurement chain and the critical design decisions are reviewed. In particular, one must take into account the resonant behaviour of the necessarily non-optimally terminated waveguides as well as the environment acoustics within the MRI coils. Two competing approaches for the signal post-processing were developed: (i) Optimal subtraction of the noise and speech signals, and (ii) spectral peak removal by adaptively fitted comb filters. The main objective is the high-quality spectral identification, estimation, and classification of source features, e.g., vowel formants. Approach (i) preserves the phase behaviour of the original signal. Approach (ii) produces excellent speech sound quality when the noise consists of only few harmonic sources; a salient property of MRI acoustic noise. Both of the approaches must compensate the frequency dependent damping of the measurement chain.
Design of an unmanned aerial vehicle based on acoustic navigation algorithm
Authors: Gong Meng Y. , Xu Hu P. , Hu Yu H.
Published: November 2017

Autonomous unmanned aerial vehicles (UAV) navigate using Global Positioning System (GPS). However, in places where GPS signals are interfered, or blocked (e.g., tunnel, downtown with high-rise buildings), auxiliary navigation systems are desirable. In this work, an acoustic based near field (< 1km) UAV guidance system is proposed. This system utilizes acoustic phase array mounted on UAV to provide direction of arrival estimates of narrow band acoustic sources at known locations. As such, the positions of UAV may be easily tracked. Through sensor fusion, this acoustic navigation system may also work together with GPS to provide even more accurate estimates.