bluuebunny/crossref_metadata_2025 huggingface dataset:
Voice onset time and closure duration of word-initial voiceless plosives in Pidgin conversation
Authors: Drager Katie , Grama James , Gonzalez Lorenzo , Copeland Cassidy
Published: November 2016

Hawai‘i is home to many languages, including an English-lexified creole, known locally as Pidgin. Despite much work on the development of Pidgin, little is known about the acoustic properties of Pidgin consonants. This talk presents results from an analysis of word-initial plosives produced by eight speakers of Pidgin across two age groups, investigating what factors influence VOT and closure duration in the plosives. The data were analyzed using linear regression models with by-speaker random intercepts. Results demonstrate that VOT in word-initial plosives tends to be shorter in Pidgin than in English, with mean duration values nearly half those reported for English in Yao (2007). The effects of social and linguistic factors, however, tend to be similar (e.g., shorter VOT for older speakers, VOT for /k/ is longer than for /t/ or /p/). Results also indicate that VOT is significantly shorter both for words of Hawaiian origin (β =-0.01, t(289)=-2.0, and p<0.05) and—in a separate model fit to a subset of the data with only non-Hawaiian words—highly frequent words (β=-0.01, t(216)=-4.2, and p<0.001). In contrast, no factors tested significantly predicted closure duration. Taken together, results demonstrate that a combination of linguistic, social, and probabilistic factors influence VOT in Pidgin.
Modified 2nd-order nonlinear infinite impulse response (IIR) filter for compensating sharpness and nonlinear distortions of electrodynamic loudspeakers
Authors: Iwai Kenta , Kajikawa Yoshinobu
Published: November 2016

Electrodynamic loudspeakers generate the nonlinear distortions and degrade the sound quality. This is because the nonlinearity of electrodynamic loudspeaker is caused by the large displacement of the diaphragm, in particular, around the lowest resonance frequency. One of the compensation methods for the nonlinear distortions is using mirror filter. This filter is derived from the linear and nonlinear differential equations and designed by second-order nonlinear IIR filter or third-order nonlinear IIR filter. The coefficients of these filters are determined by the physical parameters of the loudspeaker. However, it is difficult to compensate the nonlinear distortions when the sharpness of the loudspeaker is high at the lowest resonance frequency because of large displacement of the diaphragm. Although it is required to compensate the sharpness of the loudspeaker, second-order nonlinear IIR filter cannot compensate the sharpness because of the compensation principle, i.e., this filter adds the nonlinear signal into the input signal and does not include the linear filtering. This paper proposes a modified second-order nonlinear IIR filter that can compensate not only the sharpness but also the lowest resonance frequency. The difference between the conventional and proposed filter structures is only coefficients. Experimental results show the effectiveness of the proposed filter.
Study on intelligibility improvement method based on subband waveform processing focusing on dynamic feature of speech
Authors: Kohara Hiroki , Banno Hideki , Asahi Kensaku
Published: November 2016

This paper describes intelligibility improvement method for speech signal based on subband waveform processing. Our approach is based on the observation that clear speech has higher delta-cepstrum value in transient parts between phonemes, and emphasizes delta-cepstrum of input speech by a filter in the cepstral domain which amplifies a particular modulation frequency. However, since this approach generates synthetic sound by using an analysis/synthesis system, quality of the generated sound is sometimes degraded. To prevent this degradation, a subband waveform-based method is introduced. This method divides an input signal into several subband signals by a quadrature mirror filter (QMF) which approximately enables perfect reconstruction of input signal from the subband signals, converts an amplification gain sequence in the cepstral domain into that in the subband-waveform domain, and then multiplies the converted amplification gain sequence to the subband signal on a sample-by-sample basis. Synthetic sounds were generated by the method in the cases where the number of subbands is set to two, four, and eight. We found that the sound that the number of subbands is two includes artificial power fluctuation, and increasing the number of subbands decreases the artificial power fluctuation and makes quality of the generated sound better.
Simultaneous recognition of phone and speaker using three-way restricted Boltzmann machine
Authors: Nakashika Toru , Minami Yasuhiro
Published: November 2016

In this study, we attempt a simultaneous recognition method of phone and speaker using a single energy-based model, a three-way restricted Boltzmann machine (3WRBM). The proposed model is a probabilistic model that includes three variables: acoustic features, latent phonetic features, and speaker-identity features. The model is trained so that it automatically captures the intensity of relationships among the three variables. Once the training is done, we can apply the model to many speech signal processing tasks because it has an ability to separate phoneme and speaker-related information from the observed speech, and generate a speech signal from the phoneme and speaker-related information on the contrary. Simultaneous phone and speaker recognition is achieved by estimating the latent phonetic features and the speaker-identity features given the input signal. In our experiments, we discuss the effectiveness of the mode lin a speaker recognition and a speech (continuous phone) recognition tasks.
AI framework to arrange audio objects according to listener preferences
Authors: Ohtani Kento , Niwa Kenta , Takeda Kazuya
Published: November 2016

We propose a framework for arranging audio objects in recorded music using artificial intelligence (AI) to anticipate the preferences of individual listeners. The signals of audio objects, such as the tracks of guitars and drums in a piece of music, are re-synthesizes in order to provide the preferred spatial arrangements of each listener. Deep learning-based noise suppression ratio estimation is utilized as a technique for enhancing audio objects from mixed signals. Neural networks are tuned for each audio object in advance, and noise suppression ratios are estimated for each frequency band and time frame. After enhancing each audio object, the objects are re-synthesized as stereo sound using the positions of the audio objects and the listener as synthesizing parameters. Each listener supplies simple feedback regarding his/her preferred audio object arrangement using graphical user interface (GUI). Using this listener feedback, the synthesizing parameters are then stochastically optimized in accordance with each listener’s preferences. The system recommends dozens of customized synthesizing parameters, and these parameters can then be adjusted by the listener using a single-dimensional slider bar. Several tests were conducted and the proposed framework scored high marks in subjective evaluations as to whether or not the recommended arrangements were indeed preferable.
Comparing frequency-difference beamforming and delay-and-sum beamforming as an estimator of direction-of-arrival
Authors: Alcantara Eldridge , Atlas Les , Abadi Shima
Published: November 2016

Direction-of-arrival estimation (DOA) is an important and long-studied problem in array signal processing. Existing algorithms such as conventional delay-and-sum beamforming are limited in performance and become inadequate for a high-frequency broadband source and when the receiving linear array is sparse. Abadi, Song, and Dowling (2012), however, showed that DOAS estimation is possible in this case with an algorithm they introduced called frequency-difference beamforming. This was demonstrated empirically in their previous work using a real dataset. In addition, the resemblance between frequency-difference beamforming and delay-and-sum beamforming was briefly discussed. The purpose of this study is to analyze this relationship further and determine how well frequency-difference beamforming compares to delay-and-sum beamforming as an estimator of DOA. The approach taken in this study is to explicitly formulate the estimator equation for frequency-difference beamforming and compare it mathematically to the estimator equation of delay-and-sum beamforming. The equations are compared for the case of one DOA and two DOAs. For both cases, we show the effect of both source frequency and source bandwidth on frequency-difference beamforming. Using these results, we probe the following question: what are the conditions on the source frequency or source bandwidth for which frequency-difference beamforming will outperform delay-and-sum beamforming?
Measurements of mid-frequency bottom interacting signals in Jinhae bay located on the southern coast of Korea
Authors: Choi Jee Woong , Kwon Hyuckjong , Son Su-Uk , Cho Sungho , Park Joung-Soo , Hahn Jooyoung
Published: November 2016

Acoustic bottom interacting measurements were conducted in shallow water (nominal water depth of 60 m) in Jinhae bay, southern coast of Korea, using 4 to 12 kHz CW signals in May 2015 and 2016. The surficial sediment at a site is mainly composed of silty clay with a mean grain size of 8 phi. Since the seafloor is relatively soft, the bottom-bounced path was very weak compared to direct and sea-surface-bounced paths. On the other hand, a strong arrival reflected from the sub-sediment layer was received after the bottom-bounced arrival especially at lower frequencies. The arrival time difference between the arrival reflected from water-sediment interface and that reflected from the second interface is used to estimate the sound speed in the surficial sediment layer. In addition, the bottom loss as a function of grazing angle are estimated using the bottom-bounded path. Finally, the results are compared to the sedimentary structure imaged by chirp sonar survey. [Work supported by Agency for Defense Development, Korea.]
Acoustical characteristics of snapping shrimp noise measured during SAVEX 15 and its use as a natural source to estimate sea surface properties
Authors: Ko Myungkwon , Lee Dae-Hyuk , Choi Jee Woong , Cho Sungho
Published: November 2016

The Shallow-water Acoustic Variability Experiment (SAVEX15) was conducted at a site in the Northern East China Sea (ECS), about 100 km off the southwest of Jeju Island, Korea in May 2015. The purpose of SAVEX15 was to obtain acoustic and environmental data for studying on oceanography, underwater communication, and acoustic propagation characteristics in the ECS. The experiment utilized a vertical line array (VLA) of 16 elements spanning 56.25 m of a 100 m water column. During the experiment, a large number of unintended snapping shrimp noises were recorded by the receiving system. In this talk, the acoustic properties of the snapping shrimp noise are presented. In addition, these noises are used as natural acoustic sources to estimate the sea surface properties from the sea-surface bounced paths. Finally, the results are compared with the sea surface conditions collected by a wave buoy operated during the experimental period. [This work was jointly supported by KRISO, KIOST, MPL, and ONR, and partially supported by ADD, Korea.]
Comparison of underwater communication performances in two shallow-water sites with different sediment types located off the coast of Korea
Authors: Kim Sunhyo , Choi Kanghoon , Choi Jee Woong , Park Joung-Soo , Kim Sea-Moon
Published: November 2016

Shallow water waveguide characterized by multipath channel produces a significant delay spreading of transmitted signals, which is referred to as inter symbol interference (ISI). Since the ISI results in distortion of communication signals, many studies to reduce the effect of ISI have been conducted. For successful underwater communication, it is important to understand the correlation between the spatial and temporal properties of ISI and communication performance. Underwater acoustic communication experiments were conducted in two different seafloor environments with relatively fine-grained and coarse sediments. The experimental geometries were the same; water depths of both sites were about 40 m and source depths were about 32 m. Communication signals were measured by a four-channel receiving array, covering waters 5 to 35 m in depth. Sound speed profiles were measured by CTD casts and the surficial sediment samples were taken by a grab sampler. The received communication signals were demodulated using the time reversal, phase lock loop and decision feedback equalizer techniques. In this talk, the communication performances at two different sites are presented and compared with the channel impulse responses at two sites. [Work supported by ADD(UD140001DD) and KRISO(PMS3310).]
Sound focusing in shallow water using a vertical phased array
Authors: Peng Dayong , Zeng Juan , Liu Haijun , Li Haifeng , Zhao Wenyao
Published: November 2016

Vertical phased array is an efficient and complex equipment in underwater acoustics. Single-mode excitation and time-reversal sound focusing are two typical techniques based on vertical phased array, but both of them have some shortcomings. In order to realize sound focusing at variable distance and depth using vertical phased array, two techniques are proposed in this paper. One of them is the Green's function construction of target sound field based on normal mode eigen-function and attenuation coefficient extraction, and the other is controllable sound focusing based on optimal target sound field determination. Simulation and experiment results are presented. This technique indicates a method for objective depth detecting in shallow water.
Acoustic tracking in shallow coastal areas on spawning migrations of pacific herring (Clupea pallasii) using ultrasonic telemetry
Authors: Tomiyasu Makoto , Shirakawa Hokuto , Iino Yuki , Miyashita Kazushi
Published: November 2016

The behavioral ecology of small pelagic fish has been studied by acoustic method for a long time. In particular, on pacific herring (Clupea pallasii), the behavioral ecology in shallow coastal areas which is observed spawning migration should be understood for the resource management and reproduction protection. In this study, supersonic telemetry was used for behavioral tracking of herring at shallow coastal areas. For the tracking, herring of regional group (n = 23) at Akkeshi bay (Depth ave. 5.78±2.15 m) in east Hokkaido were used. On the horizontal aspect, herring showed two migration patterns (pattern1: staying at the bay, pattern2: migration to Akkeshi lake (ave. 0.84±0.13 m) which is brackish water lake adjacent the bay). The lake is the main spawning grounds for herring, therefore the pattern 2 is indicated to be for spawning, and the pattern1 is before or after spawning. On the vertical aspect, diurnal distribution patterns were shown at the bay (day: ave. 5.41±3.78 m, night: ave. 3.83±2.60 m). Besides, the rapid horizontal migration was mainly observed at night. From these, the distribution patterns may influence on efficient migration at night without predation risk. Migration span at shallow coastal areas is estimated to be comparatively short, during 4-5 days.
Fundamentals of speech privacy in the built-environment
Authors: Good Kenneth W.
Published: November 2016

Since this session intends to bring together experts in speech, architecture, and hearing, this paper will present the fundamentals of Speech Privacy from the architectural perspective. Considering the room as a transfer-function from the talker to the listener, I will cover the importance of various architectural components, measurements, and design considerations for the built-environment. The intent is sharing practices and perspective across disciplines not necessarily new discoveries in the field.
Prediction of speech intelligibility through the use of simulation tools
Authors: Olson Bruce C. , Jaramillo Ana M.
Published: November 2016

In a previous paper, we presented the design of a new sound system for the House of Representatives in the State of Minnesota, with the help of simulations. After the installation was completed, we performed new measurements to compare the predicted speech intelligibility with the resulting one. We will discuss differences between the two sets and how to better use simulation tools for the prediction of speech intelligibility and related metrics in this key project as well as others with similar requirements.
Simulation study of moving ship tomography for mapping the current wakes of Green Island southeast of Taiwan
Authors: Chang Kai-Fu , Huang Chen-Fen
Published: November 2016

This study examines the design of acoustic arrays using moving ship tomography (MST) applied to the horizontal mapping of the Kuroshio-induced current wakes in the lee of Green Island southeast of Taiwan. The acoustic tomographic array consists of six transceivers; each transceiver can be either fixed at one position or towed by a ship. Numerical tomographic experiments using the synthetic ocean currents from the 8 km X 8 km study area are conducted for two configurations: five moored transceivers and one shipboard transceiver or four moored transceivers and two shipboard transceivers. Different spatial configurations of moored and shipboard transceivers are considered. For all configurations the ship moved around the periphery of the study area. Compared with the traditional tomographic arrays with only moored transceivers, the current reconstructions using MST show the reduction in residual error from 21% to 16%. Among all the MST arrays, the smallest residual error variance is obtained for the configuration of the five moored transceivers placed in a pentagon shape and one shipboard transceiver. This study will provide an optimum array design for the coming MST experiment near the Green Island.
Characterization of high-amplitude fields of an annular array using acoustic holograms of its individual elements
Authors: Yuldashev Petr V. , Hoogenboom Martijn , Dumont Erik , den Brok Martijn H. , Rosnitskiy Pavel B. , Sapozhnikov Oleg A. , Fütterer Jurgen J. , Adema Gosse J. , Khokhlova Vera A.
Published: November 2016

High-intensity focused ultrasound system (Image Guided Therapy, Pessac France) with magnetic resonance guidance was developed and used for evaluation of thermal and mechanical ablation methods in mouse tumors. The system comprises a 3 MHz annular array transducer (48 mm diameter and 35 mm radius of curvature) consisting of 16 elements that allow moving the focus electronically along the transducer axis. Experimental characterization of nonlinear acoustic field generated by such high-frequency strongly focused transducer is technically challenging because of the fine spatial structure of the field, small dimensions of the focal lobe, and limited hydrophone bandwidth. Here we evaluated pressure levels and shock-forming conditions for the system using a combination of numerical modeling based on the 3D Westervelt equation with holographic boundary condition obtained from low-power measurements. The holograms were measured separately for each element and combined together to obtain a boundary condition for the array with all operating elements. Then, nonlinear field simulations were performed at increasing power output levels. It was shown that the transducer is capable to produce focal waveforms with 120 MPa shock amplitude at 110 W acoustic power and thus is well suited for shock-based ablation therapies in small animals. [Work supported by Radboudumc Ph.D. grant and RSF-14-12-00974.]
Bubble-seeded histotripsy for cancer treatment
Authors: Kawabata Ken-ichi , Maruoka Takahi , Asami Rei , Yoshikawa Hideki , Ashida Reiko
Published: November 2016

An approach to applying the histotripsy-like mechanical effects of ultrasound for cancer treatments is studied. We investigated the combinational effects of pulsed ultrasound at intensities used for HIFU (high intensity focused ultrasound) therapy and a type of locally injected superheated perfluorocarbon droplet (PCND). The droplets produce microbubbles when exposed to ultrasound. In our approach, chemical agents are also added to obtain combined mechanical and chemical antitumor effects. It was found that, in the presence of locally injected PCND, spatially controlled mechanical effects similar to histotripsy can be achieved with pulsed ultrasound (pHIFU) at several kW/cm2ex vivo. Further, it was suggested that even if the target volume is too vast to distribute PCND with a single injection, one injection is enough because PCND particles migrate inside tissues due to pHIFU. Further, the antitumor effects of pHIFU in combination with the local injection of PCND and an antitumor agent (Adriamycin) were investigated in vivo using murine tumors (Colon 26). Experiments were performed under acoustic conditions and with drug doses not severe enough to induce significant antitumor effects. It was found that PCND and Adriamycin were effective at suppressing tumor growth and tumor regrowth after suppression, respectively. The obtained results are very promising for developing novel cancer treatments.
Comparison of passive cavitation imaging and plane wave B-mode imaging for monitoring histotripsy ablation
Authors: Bader Kenneth B. , Haworth Kevin J. , Maxwell Adam D. , Holland Christy K.
Published: November 2016

Histotripsy utilizes the oscillations of bubbles within a cloud for transcutaneous mechanical ablation of tissue and is currently under development to treat benign prostatic hyperplasia. The bubble clouds are hyperechoic, enabling standard B-mode imaging to be used for image guidance. The volumetric oscillations of the bubbles also generate acoustic emissions that can be imaged. The purpose of this study was to demonstrate the feasibility of monitoring histotripsy-induced ablation with passive cavitation images. Prostate tissue phantoms were exposed to mechanically ablative, 1-MHz histotripsy pulses over a range of pulse durations (5—20 ms) and peak negative pressures (12—23 MPa). Bubble clouds generated by the histotripsy pulses were monitored with a linear array using passive cavitation imaging (PCI) and plane wave B-mode imaging. The utility of PCI and B-mode imaging to predict the phantom ablation zone was assessed using receiver operating characteristic (ROC) curve analysis. The area under the ROC curve, accuracy, and sensitivity were greater for PCI relative to B-mode imaging (p < 0.05). These results will be discussed in the context of the potential advantages of PCI relative to B-mode imaging for the prediction of histotripsy-induced ablation.
Study to fabricate high-quality and portable parametric speakers
Authors: Kuroda Jun , Minami Shota , Oikawa Yasuhiro
Published: November 2016

Parametric speakers provide narrow directional audible sounds using modulated ultrasounds. Parametric speakers are employed to build audio communication with privacy protection, which is expected to be installed into various instruments. To respond to this requirement, slim-sized parametric speakers delivering high-quality sound must be fabricated. Ultrasonic transducers usually consist of piezoelectric elements and metal resonators, which have a number of resonant modes. To demodulate audible sounds by the non-linearity of a finite amplitude sonic wave, a large amplitude carrier wave must be emitted. Therefore a predominant resonant mode of an ultrasonic transducer is used to transmit carrier wave. Moreover, frequency band around the predominant resonance is used to transmit modulated Fourier components of signals. While considering these principals of sonic transmission, two issues must be solved to fabricate a slim-sized and high quality parametric speaker, i.e., 1) widening of available bandwidth and improvement of electroacoustic efficiency and 2) optimization of transmitter circuits and modulation method based on characteristics of ultrasound transducers. It is necessary to study parametric speakers as a total system comprised by ultrasound transducers, transmit circuits, and signal processing of modulation, to solve these issues. This paper denotes outline of these issues and the present status of our studies.
Design improvements of a low cost underwater projector based on clarinet acoustics
Authors: Koh Veronica , Thompson Stephen C.
Published: November 2016

Low frequency (ka<<1) underwater projectors are desired for long range sonar applications and oceanography due to their low absorption losses. However, such low frequency projectors (LFP) tend to be large in size and costly to build. This study aims to assess the feasibility of an underwater clarinet as a low cost LFP. Previous proof-of-concept work on a lab prototype showed stable tone production but with resonance frequencies that were lower than predicted and significant harmonic levels. In this study, a new pressure chamber design for housing the clarinet mouthpiece is built and tested. Improvements in the equivalent circuit model for the underwater clarinet are also made to include the elastic effects of the clarinet wall and the pressure chamber impedance, to better predict its performance. The current measurement results using both PVC and steel resonator for the underwater clarinet will be presented and compared with the improved model. The trade-off considerations between the design parameters of the underwater clarinet and its performance will also be discussed.
Active control of low-frequency underwater echoes using an array of tile projectors
Authors: Chun Wonjong , Noh Eunghwy , Ohm Won-Suk , Kim Jaepil , Ji Youna , Park Youngcheol , Seo Youngsoo
Published: November 2016

With the introduction of low-frequency active sonar in anti-submarine warfare, there is a growing need for a novel underwater invisibility device that could replace the existing passive anechoic tiles. In this talk, we describe an experiment on active reduction of underwater echoes at low frequencies using an array of tile-shaped projectors. Each tile projector was designed with the aid of finite-element computations and tested in an acoustic tank for transmit voltage sensitivity and directivity. An array of tile projectors, covering a scale model submarine in a large acoustic tank, were driven by control signals that were intended to produce the impedance match between water and the object. Depending on the frequency of the incident wave, echo reduction as large as 6 dB was achieved. [This work has been supported by the Low Observable Technology Research Center program of Defense Acquisition Program Administration and Agency for Defense Development.]
Three dimensional noise mapping system with aerial blimp robot
Authors: Saitou Ryouzi , Ikeda Yusuke , Oikawa Yasuhiro
Published: November 2016

Recently, Unmanned Aerial Vehicle (UAV) is used in various situations and research fields, because of low cost and high convenience. For instance, there are many measurement and monitoring systems for taking environmental information by analyzing the image data which is acquired from the air with the UAVs. The UAVs with some propellers, such as quadcopter, always needs to rotate the propellers during flying. The noises of rotating propellers and makes collecting sound information with UAV difficult. In this study, we proposed the environmental sound recording system using a blimp which is filled with helium gas. The system has four propellers in the horizontal direction and two propellers in the vertical direction. This system has also a control board which has a SoC (including both FPGA and CPU) with embedded Linux OS to control six DC motors attaching to the each propeller and to communicate with PC through wireless LAN. The control board can record a sound signal with an A/D converter and an external memory. The experimental results show that it is efficient to make noise maps in horizontal and vertical planes by using the proposed system.
Development of aero-vibro acoustics methods for predicting acoustic environment inside payload fairing at lift-off
Authors: Tsutsumi Seiji , Maruyama Shinichi , Sarae Wataru , Terashima Keita , Hiraiwa Tetsuo , Ishii Tatsuya
Published: November 2016

Prediction of harmful acoustic loading to payloads inside launcher fairing due to intense acoustic wave generated from propulsion systems at lift-off is an important design issue. Aero-vibro acoustics method developed in this study for predicting the acoustic loading consists of four elements. Hydrodynamics of jet flowfield generating aeroacoustic wave is computed by the high-fidelity Large-Eddy simulation. Computational aeroacoustics based on the full Euler equations is conducted to simulate propagating acoustic wave from the jet to the payload fairing. Then, finite element method is applied to simulate the structural vibration that radiates acoustic wave inside the fairing. Finally, acoustic behavior inside the payload fairing is also computed by the finite element method. An overview of the methods and recent work for validation and verification will be presented.
Self-similarity of level-based wavepacket modeling of high-performance military aircraft noise
Authors: Neilsen Tracianne B. , Gee Kent L. , Harker Blaine M. , Wall Alan T. , James Michael M.
Published: November 2016

Construction of the equivalent acoustic source model for high-performance military aircraft noise presented in this paper begins with a decomposition of sound levels, from ground-based microphones 11.7 m from a high-performance military aircraft, into portions matching the similarity spectra associated with large-scale and fine-scale turbulent mixing noise (LSS and FSS). [Tam et al. AIAA Paper 96-1716 (1996)]. A Fourier transform of the spatial distribution of the decomposed levels yields frequency-dependent wavenumber spectra [Morris, Int. J. Aeroacoust. 8, 301-316 (2009)]. Each LSS-educed wavenumber spectrum corresponds to a wavepacket, consisting of a spatially varying amplitude distribution with a constant axial phase relationship. This wavepacket model produces a directional, coherent sound field. However, the asymmetry in the LSS-educed wavenumber spectra may indicate that a nonuniform phase relationship is a more physical choice that could be correlated to the axial variation in convective speed. The FSS component is modeled with a line of incoherent monopoles whose amplitude distribution is related to the FSS-educed wavenumber spectrum. While this level-based model is limited, the addition of the FSS-related source yields a better match to the noise environment of a high-performance military aircraft than is found using a single coherent wavepacket. [Work supported by ONR.]
Near-field array measurements of F-35 aircraft noise
Authors: Wall Alan T. , Gee Kent L. , Neilsen Tracianne B. , Leete Kevin M. , James Michael M. , McKinley Richard L.
Published: November 2016

Noise source measurement and modeling efforts are being conducted for current and future generations of high-performance military aircraft. A near-field microphone array was used in a noise measurement of F-35A and F-35B aircraft at Edwards Air Force Base in 2013 in order to extract source models. The two aircraft measured were tethered to the ground on a concrete run-up pad. The array consisted of 76 sensors, spanned 32 m, and was placed on the ground approximately 7 m from the jet plume. The engines operated over a full range of power settings from idle through full afterburner. In preparation for the execution of source modeling efforts, these near-field data are explored and compared to far-field data published previously [James et al., AIAA Paper 2015-2375]. [Work supported by USAFRL through F-35 JPO.]
Nonlinear characteristics of F-35 flyover waveforms
Authors: Reichman Brent O. , Gee Kent L. , Neilsen Tracianne B. , McInerny Sally A.
Published: November 2016

Metrics indicating the presence of acoustic shocks are calculated from noise measurements of F-35 aircraft during flyover operations. The sound pressure level, average steepening factor, and skewness of the first time derivative of the pressure waveform are calculated for the A and B variants of the aircraft. Other metrics more specific to flyover measurements are also shown. Comparisons of nonlinear indicators are made between engine thrust conditions, aircraft type, microphone height, microphone size, and sampling rate. Nonlinear indicators are also compared against other full-scale military aircraft. Comparisons are made with similar conditions during ground run-up operations.
Coherence influences sound-field localization dominance in a precedence paradigm
Authors: Grosse Julian , van de Par Steven , Trahiotis Constantine
Published: November 2016

The ability to localize sound sources in reverberant environments is dependent upon first-arriving information, an outcome commonly termed “the precedence effect.” For example, a combination of a leading (direct) sound followed by a lagging (reflected) sound is localized in the direction of the leading sound. We measured how the compactness/diffuseness (i.e., the interaural coherence) of leading and lagging sounds, respectively, influences performance. The compactness/diffuseness of leading or lagging sounds was varied by either presenting a sound from a single loudspeaker or by presenting mutually uncorrelated versions of similar sounds from nine adjacent loudspeakers. The listener pointed to the perceived location of leading and lagging sources of sounds which were 10-ms long, low-pass filtered white noises or 2-second long tokens of speech. The sounds were presented either from speakers located directly in front of the listener or from speakers located 45° to the right or left. Leading compact/coherent sounds, be they Gaussian noises or tokens of speech, influenced perceived location more so than did leading diffuse/incoherent sounds. The results strongly support the hypothesis that stimulus coherence, often modeled by “straightness” within a cross-correlogram, plays an important role in precedence.
Spatial and temporal competitors bias auditory localization of impulse events
Authors: Gaston Jeremy R. , Dickerson Kelly , Foots Ashley , Mermagen Timothy , Ericson Mark , Perelman Brandon
Published: November 2016

Sound events in the real-world rarely occur in isolation and when competing sounds are present, the effect on perception can be significant (e.g., various forms of masking). The present study examines auditory localization for impulse sounds modeled after the real-world sound event of small-arms fire. Small-arms fire consists of two distinct sounds, the muzzle blast and ballistic crack. Across different shooter-observer positions, there can be substantial offsets in spatial and temporal stimulus relationships between the sounds. To examine these relationships, impulse targets were presented across a loudspeaker array in the context of impulse competitors varying across timing and spatial relationships. Results showed that there was a significant increase in absolute localization error as a function of the magnitude of these relationships, and signed error indicated significant bias toward the direction of the competing impulse. These results suggest that listeners integrated information from the competing stimulus into their localization decision.
Effect of non-uniform mean flow to the scattering pattern of acoustic cloak
Authors: Jeon Wonju
Published: November 2016

During the last decade, most of acoustic cloak researches have been done within a theoretical framework in which the medium is at rest. However, such acoustic cloaks cannot preserve its unique properties or functions in the presence of flow. In this study, we propose a theoretical framework to consider the effect of non-uniform mean flow to acoustic cloak for the purpose of understanding the physics of acoustic cloak within flow and designing a new concept of metamaterial so called aeroacoustic cloak. We formulate a convective wave equation in which the differential operator contains the non-uniform velocity vector coupled with gradient operator and the equivalent source terms due to the mean flow are divided into two terms with their own physical meanings. The performance of existing convective cloak is investigated by using the present formulation in the presence of non-uniform flow. By comparing the existing and present formulations, the polarity and magnitude of equivalent source are compared: the present source shows hexapole pattern whereas the existing source shows quadrupole pattern. The non-uniformity effect was dominant in hexapole pattern. Finally, we found that although the compressibility effect is much smaller than non-uniformity effect in low Mach number range, it is not negligible in high Mach number flow, especially for small Helmholtz number. Understanding the nature of equivalent source is expected to provide a physical insight to design a new acoustic cloak within fluid convection.
Acoustic detection, localization, and tracking of tactical autonomous aerial and underwater vehicles
Authors: Ferguson Brian G. , Lo Kam W.
Published: November 2016

By applying single sensor narrowband and multisensor broadband passive acoustic signal processing methods to real microphone data, it is shown that low observable tactical autonomous aerial vehicles can be detected, classified, localized, and tracked by unattended land-based acoustic surveillance systems that exploit a target's acoustic signature. Similarly, the application of passive sonar signal processing methods to real hydrophone data reveals the presence, position and track of an autonomous underwater vehicle by exploiting its radiated noise and its underwater acoustic communication transmissions. A suite of these narrowband and broadband acoustic signal processing methods will be identified and their functional performances quantified.
Something just clicked: Whitlow Au and the sonar of dolphins
Authors: Gisiner Robert C.
Published: November 2016

I suspect that no one, especially not Whit, imagined in 1970 that he would become the world's authority on dolphin biosonar, also known as active echolocation. Since that time Whit has amassed an astonishing list of hundreds of publications on the subject, including the seminal text on marine mammal echolocation, The Sonar of Dolphins, published in 1993. It may surprise many of the younger members of ASA to know that there was a Cold War “arms race” for knowledge about dolphin sonar and that Whit and his U.S. colleagues carried on a lively and mutually enriching correspondence with Soviet colleagues against a background of government intrigues and limitations on travel and conference attendance out of concerns about a “biosonar gap” every bit as worrisome to military leaders as the nuclear arms race (well, maybe not quite as worrisome). Since then Whit has branched out to many other fields of bioacoustics and mentored a diverse array of students at the University of Hawaii, but I will focus on the years at the Navy's marine mammal facility in Kaneohe, Hawaii, where I had the good fortune to work alongside Whit for several years.
Biosonar detection range of mesopelagic patches by spinner dolphins in Hawaii
Authors: Au Whitlow , Lammers Marc O. , Jung Jakob
Published: November 2016

Spinner dolphins (Stenella longirostris) in the near-shore waters of the Hawaiian islands forage on the mesopelagic boundary community (mbc) of organisms consisting of myctophids, mid-water shrimp, and small squids. They forage at night in a coordinated fashion swimming parallel to shore hunting for patches of prey that they can encircle and herd into a tight three-dimensional patch. A profiler housing a broadband echo-ranger that projected dolphin-like biosonar signals was used to measure the target strength of the mbc. Echoes consisted of a number of highlights bunched together with target strength between -45 and -55 dB based on a dolphin’s integration window of 264 ms. Noise values collected by an autonomous acoustic recorder at midnight in the location where the profiler data were obtained were used to estimate the biosonar detection range of spinner dolphins for mesopelagic patches. The receiving directivity index and the width of the auditory filter for Tursiops trun catus were used to estimate the biosonar detection ranges of Stenella longirostris searching for mbc patches. Using the sonar equation, the biosonar threshold detection range of spinner dolphins was estimated to be approximately 100 plus m, more than sufficient range for the animals to formulate their prey herding behavior.
Echolocation parameters of toothed whales measured at sea
Authors: Koblitz Jens C. , Stilz Peter , Steiner Lisa , Rassmussen Marianne H.
Published: November 2016

Historically, data on toothed whale echolocation parameters and abilities were collected from captive animals. Acoustic parameters under investigation were inter-click-interval, spectral content, source level, directionality, emission direction, including correlation and variation of those parameters. Technological advances over the past decade have allowed collecting data on those parameters from animals at sea using acoustic recording tags or hydrophone arrays. Using a vertical, linear array of 16 hydrophones, echolocation clicks from harbor porpoises, white-beaked dolphins, common dolphins, and bottlenose dolphins were recorded around Iceland and the Azores. The animal’s position at click production was computed for each click based on the time of arrival differences. Intensity and spectral differences at the array allowed measuring source levels, beam width, and spectral variation at different angles relative to on-axis. Advancing knowledge on the use and variation of echolocation signals of toothed whales in their natural habitat will allow widespread and effective use of acoustic monitoring.
Recent progress in coastal acoustic tomography in China: Experiments and data assimilation
Authors: Zhu Xiao-Hua , Zhu Ze-Nan , Fan Xiaopeng , Liu Wen-Hu , Zhang Chuanzheng , Dong Menghong , Long Yu , Ma Yun-Long
Published: November 2016

We will review three recent coastal acoustic tomography (CAT) experiments carried out in China: (1) A 15-day tomography experiment that was carried out for the first time in the Qiongzhou Strait to measure the major tidal current constituents, residual currents, and volume transport; (2) A high precision CAT experiment with 11 CAT systems performed in the winter of 2015 in the Dalian bay, China. The number of successful reciprocal transmission lines reached 51, which may be the highest number in ocean acoustic tomography history. The CAT results showed a very high accuracy of velocity measurements with a root-mean-square difference of 4 cm/s compared with moored ADCP measurements; (3) Rapid sampling CAT measurements were used to map the structure of nonlinear tidal (M4 and M6) currents. The results indicate that M4 is predominantly generated by the advection terms, while friction mechanisms are predominant for generating M6. Finally, we will introduce the CAT data assimilated into an unstructured triangular grid ocean model (FVCOM) using the ensemble Kalman filter scheme. The assimilated velocities agreed better with independent ADCP data than those obtained by inversion and simulation, indicating that data assimilation of the CAT data is the optimal method for reconstructing the current field.
Deducing environmental mismatch from matched-mode processing ambiguity surface sidelobes
Authors: Thode Aaron , Bonnel Julien , Verlinden Chris , Thieury Margaux , Fagan Aileen
Published: November 2016

The application of non-linear time sampling to broadband acoustic signals propagating in shallow water has made modal filtering possible using a single hydrophone. As a result, incoherent matched-mode processing (MMP) techniques are now practical using only single-hydrophone data. When MMP ambiguity surfaces are constructed from pairs of modes and plotted as a function of range and frequency, both the mainlobe and sidelobes form striations that embed information about the type and amount of environmental mismatch present between the modeled and true environment. Thus the degree of symmetry that a two-mode frequency-averaged ambiguity surface displays around the mainlobe provides a metric for identifying environmental mismatch. Acoustic invariant theory, combined with simulations, demonstrate how mismatched waveguide replicas can be used to (1) estimate the true bottom interface sound speed, (2) determine whether a downward-refracting waterborne profile is present in data, and (3) estimate waterborne sound speed profile slopes. The theory also explains why certain mismatched environments can generate very high MMP correlations, even with broadband signals. In a shallow water environment with a downward-refracting sound speed profile, taking full advantage of this approach requires reformulation of non-linear time-sampling methods to extract refractive modes. [Work sponsored by the North Pacific Research Board.]
Acoustic mode travel time variability in the Philippine Sea
Authors: Chandrayadula Tarun K. , Colosi John A. , Worcester Peter F. , Dzieciuch Matthew A.
Published: November 2016

During the 2009 NPAL (North Pacific Acoustic Laboratory) PhilSea deep water acoustic propagation experiment, a low frequency source transmitted broadband chirps to a mid-water spanning hydrophone array at a distance of 185 km every three hours for approximately one month. In addition, transmissions took place every five minutes during some time periods. The source and the receiver array contained conductivity and temperature sensors. The motions of the source and receiver moorings were measured using long-baseline acoustic navigation systems. The experiment site was oceanographically dynamic and contained significant internal tide activity. This work builds a model to compare the acoustic and oceanographic variabilities. The acoustic observations are used to estimate the mode travel times, and then related to the internal tide displacements at the source and the receiver arrays. This paper presents the work in three parts. The first part uses matched subspace detectors to estimate the mode travel times. The second uses the environmental observations to build an internal tide model. The third constructs a linear perturbation model to relate the internal tides to the adiabatic mode travel times. The discrepancies between the model and the observations are attributed to factors such as limitations of the perturbation model for the travel times, range variability not accounted for in the adiabatic mode propagation, and signal processing issues.
Compressing and shearing the transplanted kidney
Authors: Urban Matthew W. , Amador Carolina , Aristizabal Sara
Published: November 2016

Kidney transplantation is one treatment for end-stage renal disease. Transplant rejection is typically evaluated with an invasive biopsy. Noninvasive methods for evaluating renal transplants would be beneficial for frequent evaluation. We propose the use of shear wave elastography (SWE) to evaluate viscoelastic properties in renal transplants. Further, we also use acoustoelasticity to measure the nonlinear modulus of the renal transplants. Acoustoelasticity is the phenomenon where the shear wave velocity (SWV) in a material varies with applied stress and is quantified by a nonlinear modulus, A. By applying pressure with the ultrasound transducer, stress is applied to the kidney under investigation and B-mode imaging was used to measure induced strain and SWE was used to make measurements of SWV. Using relationships involving the measured strain and shear moduli at different compression levels, we can obtain estimates of A. In our ongoing study, we use a General Electric Logiq E9 to perform SWE measurements in renal transplant patients coming for protocol biopsies. We have studied 63 patients with SWE to quantify viscoelastic properties of the transplanted kidney. We have obtained data from 19 patients for estimation of the nonlinear modulus, A. We compared the measured viscoelastic and nonlinear shear parameters with clinical variables such as the serum creatinine, Banff biopsy scores, and resistive index. We continue to evaluate these methods and their efficacy as indicators for transplant rejection.