bluuebunny/crossref_metadata_2025 huggingface dataset:
A project-oriented graduate course on ultrasonics
Authors: Haberman Michael R.
Published: November 2016

The study of ultrasonics encompasses a wide range of topics in acoustics. Some topics, like dispersion in elastic waveguides, require mathematical sophistication, while others, like transducer selection and common signal processing techniques, demand detailed technical knowledge. The variety of topics germane to the subject of ultrasonics presents an instructor with a number of challenges that must be addressed through the course design. This talk reports on the current graduate course on ultrasonics in the graduate acoustics program at The University of Texas at Austin. The structure of the course is inspired by the experiential learning model, which emphasizes experimentation and experiences to supplement in-class lectures. This is achieved using numerous in-class demonstrations and an extended team project. Whenever possible, data from in-class demonstrations are used in homework assignments to provide continuity between theory and practice. Specific example course projects will be discussed which illustrate the breadth and depth of course projects resulting from this approach, and perspectives are provided for avenues for improvement using this teaching method for instruction in ultrasonics.
Increasing of work flow on the thermoacoustic system by control of the temperature gradient within the stack
Authors: Fukuda Seiya , Sakamoto Shin-ichi , Watanabe Yosiaki
Published: November 2016

A gas column in a tube with a temperature-gradient spontaneously begins to oscillate when air turbulence occurs. The work flow produced in the stack, ΔI, is important for the thermoacoustic oscillation. The amount of ΔI is determined by the shape of temperature-gradient. Experimental studies on thermoacoustic systems are previously assessed by measurement of temperature ratio, TH/TC, of the stack; however, investigation for distribution of temperature within the stack is less discussed. In order to examine the influence of a temperature-gradient within the stack on the thermoacoustic oscillation, we propose that control method for the temperature-gradient under the same TH/TC. In particular, the control of the temperature distribution is implemented in actively changing the internal temperature by additional nichrome heater in middle of the stack. The sound pressure in the standing-wave thermoacoustic system is measured at several temperature distribution by the proposed method. Furthermore, ΔI was calculated based on the measured sound pressure. As a result, the work flow by the control of a temperature distribution have increased, and it was qualitatively estimated by the slope of heat flux within the stack from temperature distribution.
Numerical study of heat transfer in parallel-plate heat exchangers in thermoacoustic engine
Authors: Kuzuu Kazuto , Hasegawa Shinya
Published: November 2016

For designing thermoacoustic devices, heat transfer problem of heat exchangers is a key point and is not solved completely yet. In the present study, both computational fluid dynamics (CFD) simulations and numerical analysis based on linear thermoacoustic theory are performed, and heat transfer characteristics, heat fluxes, and Nusselt numbers are investigated from both numerical results. Especially, through parametric studies by linear analysis, the effect of displacement amplitude and thermal penetration depth on heat transfer is discussed. In this simulation, a regenerator is located between hot and cold heat exchangers, and the effect of each channel size is also investigated. Furthermore, simulated results are compared with the conventional heat transfer models for oscillatory flow, and the verifications of those models or simulations are executed. On the other hand, by comparing the CFD results with linear analysis, non-linearity of heat transfer included in thermoacoustic phenomena is also discussed. For this discussion, unsteady behavior of temperature field in heat exchangers is observed in the CFD simulation. Finally, by combining the parametric studies of linear analysis and non-linear effect obtained from the CFD simulation, the heat transfer characteristics for heat exchangers in thermoacoustic engine are comprehensively discussed.
A sound absorbing metasurface with coupled resonators
Authors: Li Junfei , Wang Wenqi , Xie Yangbo , Popa Bogdan , Cummer Steven A.
Published: November 2016

An impedance matched surface is able, in principle, to totally absorb the incident sound and yield no reaction, and this is desired in many acoustic applications. Here, we demonstrate a new design of impedance matched sound absorbing surface with a simple construction. By coupling di�erent resonators and generating a hybrid resonance mode, we designed and fabricated a metasurface that is impedance-matched to airborne sound at tunable frequencies with subwavelength scale unit cells. With careful design of the coupled resonators, over 99% energy absorption at central frequency of 511 Hz with a 50% absorption bandwidth of 140 Hz is achieved experimentally. The proposed design can be easily fabricated and is mechanically stable. The proposed metasurface can be used in many sound absorption applications such as loudspeaker design and architectural acoustics.
Emotional voice conversion system for multiple languages based on three-layered model in dimensional space
Authors: Xue Yawen , Hamada Yasuhiro , Akagi Masato
Published: November 2016

This paper proposes a system to convert neutral speech to emotional one with controlled intensity of emotions for multiple languages. Most of previous researches considering synthesis of emotional voices used statistical or concatenative methods that can synthesize emotions in category. While humans sometimes enhance or relieve emotional states and intensity during daily life, synthesized emotional speech in categories is not enough. A dimensional approach which can represent emotion as a point in a dimensional space can express emotions with continuous intensity. Employing the dimensional approach, a three-layered model to estimate displacement of the acoustic features of the target emotional speech from that of source (neutral) speech and a rule-based conversion method to modify acoustic features of source (neutral) speech to synthesize the target emotional speech are proposed. To convert the source speech freely and easily, Fujisaki model for f0 contour and target prediction model for power envelope are introduced to parameterize dynamic features in prosody. Although this system is trained with Japanese database, neutral speech in two different languages, English and Chinese are tried to convert. Evaluation results show that all converted voices can convey the same impression with satisfactory order of emotional intensity and naturalness as Japanese voices. It means that the emotion voice conversion system can work for other languages with controllable emotion category and intensity although it is built in one language.
Example-based spoken chat system which can be customized for each user
Authors: Seto Eichi , Kitaoka Norihide
Published: November 2016

There is a need to develop automated dialog systems, such as chatbots, which are capable of engaging in natural conversations with elderly users. We propose an example-based dialog system featuring an adaptation method which customizes the dialog for each user. After retrieving information about the user from the Web using the user’s profile, morpheme analysis is applied to the retrieval results and only proper nouns are extracted. Words which appear with high frequencies are considered to be related to the user. We then calculate the similarity between words related to the user and words in example phrases in the dialog system. Cosine similarity between distributed representations of words is calculated using Word2vec. We then generate a phrase which has been adapted to include a topic related to the user by substituting user-related words for highly similar words in the original example phrase. We manually evaluated the naturalness of the generated phrases and found that the system did in fact generate natural-sounding phrases. However, Word2vec sometimes mistook words which were grammatically different parts of speech (POS) for similar words, so we added a POS constraint to the substitution process. As a result, the system achieved higher phrase generation precision.
Sound field interpolation in the spatial domain with a rigid spherical microphone array
Authors: Salvador Cesar D. , Sakamoto Shuichi , Trevino Jorge , Suzuki Yôiti
Published: November 2016

Sound field interpolation aims to calculate sound fields at arbitrary points from original measurements at discrete points. Rigid spherical microphone arrays are effective for interpolation because they can capture sound from several directions with uniform resolution. Interpolation from spherical array measurements is typically based on the spherical Fourier transform and assumes no prior knowledge concerning the source positions. The spherical Fourier transform, however, yields results whose accuracy strongly depends on microphone positioning and the inversion method used for its computation. When knowledge of the source positions is available, the pressure generated at any point on the rigid spherical baffle can be estimated with an existing physical model. This model was used in this study to define an analytic transfer function that relates the pressure at two arbitrary points on a rigid sphere. Based on this analytic function, an interpolation method in the spatial domain is presented as an alternative to transformed domain methods. Numerical experiments with a rigid sphere showed that accurate interpolation of magnitude and phase, over the full range of frequencies, is possible on the side of the array ipsilateral to the sound sources. However, on the contralateral side, accuracy systematically decreased as frequency increased.
Acoustic response of an unexploded ordnance in shallow water, layered, environments: Predictions using hybrid and coupled modeling techniques
Authors: Espana Aubrey L. , Abawi Ahmad T. , Kargl Steven G. , Williams Kevin L.
Published: November 2016

Previously, a hybrid, axisymmetric, finite element (FE)—propagation model has shown utility in simulating the response of objects in contact with a flat, undisturbed sand/water interface [Espana et al., J. Acoust. Soc. Am. 136, 190-124, (2014)]. Here, we offer a three-way comparison between data, the hybrid FE/propagation model and a coupled finite element/boundary element model (Coupled FEBE) for the scattering from a replica of a 100-mm unexploded ordnance (UXO) proud, partially buried and fully buried in a sand sediment for geometries where reflection from and refraction into the sand dominate. This comparison offers a more in-depth analysis of the implications of various approximations of the hybrid model, such as the effect of improper fluid loading on the target surface in the partially buried situation. These results will be contrasted to the more complicated mud-over-sand layered environment of the BAYEX14 experiment. Preliminary model results will be compared to data, giving further insight into the dominant physical mechanisms affecting the UXO’s acoustic response in the more complicated layered environment. [Research sponsored by ONR and SERDP.]
Waveguides and whales: A review about using acoustic waveguide theory for localizing whales and inverting for their propagation environment
Authors: Thode Aaron
Published: November 2016

Low-frequency acoustic propagation in shallow-water waveguides is conveniently modeled using sets of normal modes that propagate with different group velocities. Analytical solutions of simple environmental models, such as the Pekeris waveguide, were almost immediately applied to estimate ranges of impulsive sources by measuring the relative arrival times of the modal components, but to the author’s knowledge, it was not until the early 1990s that such techniques were first applied to low-frequency baleen whale calls, in a technical report by Gerald D’Spain. Since then waveguide-based methods have been used to track blue whales off Southern California, right whales in the Bering Sea, sei whales in the Atlantic, and bowhead whales in the Chukchi and Beaufort Seas. Some of these applications have exploited time-separated modal arrivals on a single hydrophone, while others have used vertical arrays to measure modal interference patterns, and subsequently estimate an animal’s range, depth, and local propagation environment. A recent promising development has been the introduction of nonlinear time sampling methods that permit mode isolation without the need for vertical arrays, enabling range estimation of certain whale signals from existing single-hydrophone data, even when the modal arrivals are not cleanly separated in time.
Changes of masseter muscle in a rat unilateral occlusal model assessed by photoacoustic imaging system
Authors: Hatori Kouki , Saijo Yoshifumi , Iikubo Masahiro , Hagiwara Yoshihiro , Izumita Kuniyuki , Naganuma Yukihiro , Sasaki Keiichi
Published: November 2016

Biomedical photoacoustic (PA) imaging system has the unique capability of combining high optical contrast with high ultrasound (US) resolution in a single modality. PA imaging system with 532 nm laser and 50 MHz US transducer has been developed. When the laser with the wavelength of 532 nm is used, PA signals are reflected from blood vessels. Patients with unilateral occlusion due to the extraction of unilateral molars are often seen in dental practice. Although the period of the unilateral occlusion induces the changes of masseter muscle (MM), it is not known that how blood vessels and tissue elasticity of MM are affected by the unilateral occlusion. In this study, we aimed to evaluate the sequential changes of MM due to the unilateral occlusion in rats with PA imaging system. PA signals from the MM of the non-occlusal side were significantly lower than that of the occlusal side, and US signals from the MM of the occlusal side were significantly higher than that of the non-occlusal side depending on the period of the unilateral occlusion. Unilateral occlusion affected both the blood vessels and the tissue elasticity. The PA imaging system could evaluate blood circulation and tissue elasticity simultaneously.
Dependence of inertial cavitation activity on the high intensity focused ultrasound transducer F-number
Authors: Khokhlova Tatiana , Hunter Christopher , Kreider Wayne , Maxwell Adam , Khokhlova Vera , Sapozhnikov Oleg
Published: November 2016

Cavitation induced in tumors by pulsed high intensity focused ultrasound (pHIFU) without ultrasound contrast agents was shown to significantly enhance chemotherapeutic drug uptake. Such de novo cavitation is commonly assumed to require very high rarefactional pressures. However, recent studies have shown that inertial cavitation threshold also correlates with formation of shocks at the focus. The shock amplitude and corresponding peak negative pressure (p-) are primarily determined by the transducer F-number with less focused transducers producing shocks at lower p-. Here, the dependence of inertial cavitation activity on F-number was investigated in gel phantoms and ex vivo tissue samples using passive cavitation detection (PCD). Exposures at 1.5 MHz consisted of 60 pulses delivered at 1 Hz PRF, with each pulse lasting 1 ms and p- from 1 to 15 MPa. Broadband noise emissions recorded by PCD were batch-processed to extract cavitation probability and persistence. At the same p-, both metrics indicate enhanced cavitation activity at higher F-numbers; in agarose phantoms, cavitation probability reached 100% when shocks formed at the focus, with p- values 5, 9, and 14.5 MPa for respective F-numbers 1.5, 1, and 0.75. These results confirm the impact of nonlinear waveform distortion on inertial cavitation. [Work supported by NIH K01EB015745, K01DK104854, and R01EB7643.]
Cavitation-enhanced ultrasonic heating and its monitoring by ultrasound plane wave imaging
Authors: Yoshizawa Shin , Takagi Ryo , Iwasaki Ryosuke , Tomiyasu Kentaro , Suzuki Kai , Umemura Shin-ichiro
Published: November 2016

Cavitation bubbles can accelerate high-intensity focused ultrasound (HIFU) treatments thermally, chemically, and mechanically. Acoustic generation of cavitation bubbles requires extremely high-intensity or long duration time enough to form a standing-wave field. We have proposed and investigated the ultrasound sequence of a high-intensity short pulse, named as trigger pulse, followed by a relatively lower intensity and longer duration burst, named as heating burst, mainly for the cavitation-enhanced ultrasonic heating. Trigger pulses are used to generate cavitation bubbles then form cavitation clouds. The acoustic power of trigger pulses is more than hundreds of W and the duration is less than 100 μs to avoid effects of standing-wave components. Cavitation bubbles induced by trigger pulses continuously oscillate with heating bursts. The sequence was repeated 3—15 s. Cavitation clouds formation by trigger pulses was observed with a high-speed camera. The temperature measured by thermocouple and tissue coagulation region showed the effect of heating enhancement. As the cavitation region localization is an essential factor for the safety and efficacy in this method, a real-time monitoring method of bubbles is necessary to be combined. The high-speed pulse inversion images with plane wave transmissions showed its capability for the objective.
Advanced technical listening training program at Kyushu University
Authors: Kawahara Kazuhiko , Takada Masayuki , Iwamiya Shin-ichiro
Published: November 2016

This presentation introduces the Advanced Technical Listening Training (TLT) program at Kyushu University. TLT is a systematic training program designed to improve auditory sensitivity; it consists of discrimination and identification tasks for a wide variety of acoustic features (e.g., frequency, sound pressure level, and spectrum pattern). The TLT II class (i.e., the advanced TLT program) provides training in identification of reverberation time, quantization bit depth, mixing level balance, and spectral slope of harmonic tones. TLT facilitates improved understanding of acoustic theory and phenomena, and psychoacoustics.
Thin low frequency sound absorbers based on shunted loudspeakers
Authors: Tao Jiancheng , Cong Chaonan , Qiu Xiaojun
Published: November 2016

There are two main reasons for using shunted loudspeakers as sound absorbers. One is that the absorbers can be made very thin for the low frequency sound with electronic energy dissipation mechanism and the other is that their absorption performance can be adjusted with the shunt circuit. A shunted loudspeaker typically has high absorption coefficients around its resonance frequencies which are determined by the loudspeaker unit and the shunt circuit together. To extend the effective frequency range of the shunted loudspeaker, one method is constructing more resonant sub-systems in the absorber to have absorption at more resonance frequencies. In this research, two designs based on shunted loudspeakers will be introduced. One is the composite absorber with a micro-perforated panel in front of a shunted loudspeaker, which combines two resonance subsystems to provide broadband absorption. The other is a shunted loudspeaker with a specifically designed shunt circuit for the absorption of three tonal components. Experimental results in an impedance tube will be reported to demonstrate the feasibility of the designs based on the combination concept of multiple resonances.
Analysis of explosive sources using a distributed network of infrasound arrays
Authors: Blom Philip , Marcillo Omar , Euler Garrett , Dannemann Fransiska , Park Junghyun
Published: November 2016

Analysis of signatures observed on a distributed network requires a model describing the propagation of the energy between network nodes as well as a statistical framework to quantify confidence in analysis conclusions. For the case of infrasound analysis, the propagation model must account for the inhomogeneous, dynamic nature of the atmosphere and the resulting temporal and spatial variations of propagation effects as well as the anisotropic nature of infrasonic propagation due to the dependence on the directionality of the winds. Association and localization methods have been developed utilizing a Bayesian framework to identify explosive sources from distant, infrasonic observations with possible applications to other infrasonic sources. The confidence of the analysis conclusions is dependent on the accuracy and realism of the likelihood definitions utilized in the method, which are therefore an area of ongoing research. An overview of the association and localization methods will be presented along with several possible definitions of the infrasound likelihoods for comparison using explosive infrasonic signatures.
Discrimination of virtual sound fields different in spatial aliasing
Authors: Iwaya Yukio , Otani Makoto , Tsuchiya Takao
Published: November 2016

There are theoretical techniques for sound field reproduction with a loudspeaker array. However, physical precision of synthesized sound field is limited in frequency domain. When the distance among loudspeakers is below a half of wavelength, spatial aliasing will occur. The ideal distance among loudspeakers was less than 8.5 mm@20 kHz, and it is impossible to arrange loudspeakers. Therefore, we carried out experiments to know an upper-limit frequency condition, which can give subjective experience identical to an ideal sound field. We assumed a virtual spherical boundary around a listener. Numerous virtual loudspeakers were set on the boundary to simulate a WFS system. Room impulse responses and head-related impulse responses were calculated by computer simulation. Then, binaural impulse responses were synthesized as combinations of RIRs and HRIRs. We picked up the boundary points so that upper-limit frequency without the spatial aliasing of BRIRs was systematically controlled. Listening test was conducted to investigate discrimination of sound fields different in spatial aliasing. We found that the sound field of upper-limit frequency 4 kHz cannot be discriminated from that of 14 kHz. Therefore, sound field reproduced without spatial aliasing up to 4 kHz could give same sound experience identical to the ideal sound field.
Dynamic response of a beam supported with variable gear to base excitations
Authors: Ham Hyukju , Kim Deokman , Park Junhong
Published: November 2016

The beam supported with gear having nonlinearly varying stiffness characteristics is analyzed to study vibration transfer characteristics. The gear attached at the end of the beam was considered as rotational spring and damper having angular dependent variation. The dynamic characteristics of the gear were determined by the contact point between the gear teeth. The displacement-dependent properties of the gear had an effect on vibration transmissibility of the beam system. The computational simulation based on the spectral element method (SEM) was used with several variables (the dynamic characteristics of the gear, the gear design, and excitation level). The validity was verified by comparison with the measured results. The vibration of the beam was strongly influenced by the gear-pair. These results can be utilized to design the optimal gear-pair system for minimizing undesirable vibration.
Coordination as a simplifying factor in human-machine communicative interaction
Authors: Vatikiotis-Bateson Eric
Published: November 2016

Spoken communication has traditionally been treated as a problem of sending and receiving signals containing elements whose sequential organization specifies meaningful content that is the same for both sender and receiver. Unfortunately, successful communication depends on a host of contextualizing factors that are either not present or impossible to identify in short signal streams (by either humans or machines). This presentation focuses on the crucial role of one such factor, the necessary coordination between perceiver and producer, to suggest that human communicative interaction can be conceived more simply than it has been and thereby improve the likelihood of successful human-machine interaction. For example, humans depend on physiological and cognitive coordination for successful interaction, particularly in signal parsing, alignment, and error correction. However, coordination is loosely constrained under most conditions and can be achieved in human-machine interaction without imbuing machines with human attributes; for example, shared attention. In many other cases, machines outperform humans; for example, in processing multimodal speech signals under adverse acoustic conditions to disambiguate the labial viseme, /p,b,m/. In sum, these and other factors provide texture and coherence, rather than daunting complexity, to our efforts to understand spoken communication.
Phase DEMON algorithm for time delay estimation used in small boat tracking
Authors: Pollara Alexander S. , Sutin Alexander , Chung Kil W. , Salloum Hady
Published: November 2016

The Detection of Envelope Modulation on Noise (DEMON) algorithm is a widely used tool in underwater passive acoustics for the detection and classification of vessel sound. The DEMON algorithm extracts the frequencies that modulate the high frequency cavitation noise created by a vessel’s propeller. We propose an extension of the DEMON method for time delay estimations of acoustic signals received by two or more hydrophones. This method, based on the phase difference between components in the two DEMON spectra received by different hydrophones, allows the extraction of the Time Difference Of Arrival (TDOA) and direction of arrival of the modulated signals. This method was applied to the acoustic signatures of six small boats collected by Stevens in a large glacial lake in NJ and showed agreement with the traditional cross-correlation method of TDOA estimation and boat GPS tracks. This method allows the separation of several boats TDOA. The DEMON algorithm also provides information of potential use for vessel classification. [This work was supported by DHS’s S&T Directorate.]
Measuring low-frequency ocean acoustic coherence with an estimator-correlator
Authors: Dzieciuch Matthew
Published: November 2016

Acoustic signals in the ocean are scattered by a variety of processes, but the end result is a partially coherent signal. The signal processing solution for estimating the travel-time of a partially coherent signal is to use an estimator-correlator (EC). An assumption of the EC is that the coherence time and the coherent bandwidth are known. When used properly, the EC leads to in increase in the SNR of the detected signal as well as reducing the width of the detected peak. An interesting question is “Can the EC be used to estimate the coherence parameters by maximizing the signal SNR and minimizing its width?” This is in contrast to the standard method of estimating the signal coherence from the sample covariance of the matched filter output. A simple model is constructed to test this proposition and is compared to experimental results obtained in the Philippine Sea.
An effective speech compression based on syllable division
Authors: Zhang Yan , Xiao Dong , Ren Qunyan , Guo Shengming , Mo Fuyuan
Published: November 2016

For medium or long distance acoustic speech communication, transmission rate is relatively low due to various disadvantageous factors such as multipath propagation, under such condition, speech compression methods are necessary for effective transmission. A good method needs to retain the characteristics of the speaker and achieve a good compression rate. Considering that the speech signal is usually redundant, a speech pre-compression algorithm based on syllable division is proposed. It can extract the voiced speech and the silence part of the speech signal, and subsequently delete the redundant part that does not affect the semantic comprehension. Through data processing, this pre-compression algorithm is demonstrated can compress the speech signal up to 80% and not affect listener differentiating or semantic comprehension.
Modeling study of underwater acoustic propagation over sand dunes in the South China
Authors: Yang Stephanie , Chen Chi-Fang , Chiu Ching-Sang , Miller Christopher W.
Published: November 2016

There is an extensive field of underwater sand dunes located at depths between 160 m and 600 m in the northeastern South China Sea. The largest amplitude of these sand dunes is about 16 m with horizontal length scales between 200 and 400 m. Underwater acoustic transmission can be affected by these topographic features. Two-dimensional (2-D) and three-dimensional (3-D) underwater acoustic propagation models, RAM and FOR3D, were employed to simulate the acoustic propagation over these sand dunes from a moored source to a vertical-line hydrophone array deployed in an experiment in 2014. Environmental input to the models were the measured bathymetry and sound speed profiles. To prevent model over initializations at steep angles in an ocean with a high-impedance, low-loss bottom, the generalized Gaussian starter was employed and tuned to match the angular beam-pattern of the moored source to give a proper starting field. Simulation results pertaining to the temporal fluctuations, 2-D and 3-D propagation effects in relation to the sand dunes and the water-column variability are presented and discussed. Simulation results are also compared to the measured transmission loss. [This research was supported by both the Ministry of Science and Technology of Taiwan and the Office of Naval Research of the USA.]
Successive explosive sources for geoacoustic inversion: An attempt of particle filtering
Authors: Ren Qunyan , Lu Licheng , Li Jiawei , Liao Tianjun , Guo Shengming , Ma Li
Published: November 2016

This paper presents the results of sequential geoacoustic characterization of ocean bottom in shallow waters from geoacoustic measurement of successive explosive sources. The recording system is a moored vertical line array (VLA) composed of 32 elements, and the bomb sources were successively deployed from a moving ship. The ship straightly sailed at constant speed of 5 knots, and a total number of 15 bombs were deployed with a time interval of 3-min for adjacent bombs. A particle filtering (PF) technique is adapted here to estimate\track the spatial distributions of the geoacoustic parameters by filtering the complex pressure fields recorded on the VLA. As for references, independent batch inversion of conducted by Simulated Annealing (SA) algorithm are applied on bombs at different ranges. The general agreement between PF and SA suggests that, the PF is capable of mapping spatial geoacoustic parameter variability in complex ocean environments.
Sequential source localization in coastal water under the circumstances of time-evolving sound speed profiles
Authors: Su Lin , Guo Shengming , Ren Qunyan , Ma Li
Published: November 2016

The sound speed profile (SSP) in water column is highly variable in time and space and can not be accurately known among measurement periods in coastal water. These factors will lead to the modeling mismatch and influence the performance of source localization of matched filed processor (MFP). The possibility of sequential tracking of source range and depth under the circumstances of time-evolving sound speed profiles is discussed. In this paper, we attempt to describe the time evolution characteristics of SSPs by analyzing the oceanographic dynamics which is the physical reason of the SSP’s change. A sequential approach considering the oceanographic dynamics model into the state-space equation is developed and applied. Synthetic simulations are carried out with experimental SSP data and acoustic pressure data from a vertical line array. Result suggests the sequential approach based on oceanographic dynamics model can improve the tracking capabilities.
Quantifying the spatial variability of low frequency acoustic propagation in the Northern East China Sea
Authors: Cho Sungho , Kang Donhyug , Kim Byoung-Nam , Jung Seom-Kyu , Choi Jee Woong
Published: November 2016

During a period 14-28 May, 2015, the Shallow-water Acoustic Variability EXperiment 2015 (SAVEX15) was made in the northern East China Sea (ECS) to obtain acoustic and oceanographic data for studying the coupling of physical and geophysical parameters, which could affect the variability of acoustic propagation. A strong underwater sound channel (USC) had been existed at depths ranging from 30 to 50 m with channel axis at ~40 m during the SAVEX15 period. Two types of mid-range propagation measurements were conducted in shallow water (nominal water depth of ~100m) using simultaneously both continuous waves superimposed at several fixed frequencies below 1.6 kHz and impulsive broadband signals transmitted by sparker system. A vertical line array composed of temperature and pressure sensors was moored for measuring the acoustic signals and vertical sound speed profiles in time. And a marine geophysical survey using a chirp sonar, sparker system, and sediment cores conducted at the experimental site showed that there was a thin surficial layer of O(1 m) overlaying multiple layers under the water-seabed interface. The measurement results of transmission loss are presented and compared to the model predictions using the measured oceanographic data. [KIOST (Project Code No. PE99331).]
Range estimation of a broadband source using the array/waveguide invariant and a vertical array
Authors: Song Hee-Chun , Cho Chomgun
Published: November 2016

During a recent shallow-water experiment conducted in the northern East China Sea (SAVEX15), a low-frequency (0.5-2 kHz) source (SeaNos) was towed at the mid-depth (~50 m), being close to the channel axis of the underwater sound channel (USC) observed unexpectedly in a shallow water waveguide environment. It provided a variety of distances and propagation directions between the source and two moored vertical line arrays (VLAs). The channel impulse responses from the SeaNos indicate that the earlier reflected and refracted arrivals from the USC are followed by surface/bottom reflected arrivals. The later reflected arrivals are utilized for source-range estimation using the array/waveguide invariant based on the beam-time migration and the VLAs.
Beaked whale species occurrence in the central Pacific and their relation to oceanographic features
Authors: Baumann-Pickering Simone , Simonis Anne E. , Trickey Jennifer S. , Roch Marie A. , Oleson Erin M.
Published: November 2016

Mesoscale oceanographic features are a major force in structuring the marine environment through processes such as eddy-induced upwelling, and as such effect distribution and aggregation patterns of all organisms along the food chain. It has been shown that top pelagic predators such as cetaceans react to these environmental changes in different ways. We present analysis of frequency-modulated (FM) echolocation pulses of Cuvier’s beaked whale (Ziphius cavirostris), Blainville’s beaked whale (Mesoplodon densirostis), and an unknown beaked whale species producing FM pulse type “BWC,” possibly ginkgo-toothed beaked whale (M. ginkgodens), at five locations in the central Pacific. The recordings were collected at Pearl and Hermes Reef (Northwestern Hawaiian Islands), Kona (Main Hawaiian Islands), Wake Atoll, Tinian, and Saipan (Northern Mariana Islands) between 2008 and 2015, ranging from 4 to 8 years per site. All three beaked whale species were present at all sites in different proportions throughout the recording periods, with a strong nocturnal pattern only for the “BWC” pulse type, yet without seasonal pattern. We examine the varying presence in the context of remotely sensed oceanographic data, including sea surface height deviation, temperature, and salinity, as well as chlorophyll a and derived primary productivity.
Echolocation systems of leaf-nosed bats in Taiwan and Iriomote island, Japan
Authors: Riquimaroux Hiroshi
Published: November 2016

The leaf-nosed bats, Hipposideridae, are one of the most common tropical bats found in Asia. Two species of leaf-nosed bats in Iriomote island, Hepposideros turpis, and Taiwan, Hipposideros terasensis, were compared. They emit short echo location pulses (4-7 ms in duration) consisted of constant frequency (CF) component followed by downward frequency modulated (FM) component. The second harmonics are the most intense frequency component. Comparison lists for two species are shown below. Taiwanese leaf-nosed bats, Hipposiderous terasensis CF2: 70 kHz (CF1: 35 kHz) 50-60 g in weight Japanese leaf-nosed bats, Hepposideros turpis CF2: 82 kHz (CF1: 41 kHz) 20-30 g in weight threatened species (Red list). Both Taiwan and Iriomote island are at around the same North latitude 25 degrees. Findings from H. terasensis and H. turpis are introduced and discussed. [Research supported by MEXT, Japan, and Shandong University, China.]
Acoustic response of Indo-Pacific humpback dolphins to the variability of marine soundscape
Authors: Lin Tzu-Hao H. , Yang Chih-Kai , Chou Lien-Siang , Fang Shih-Hau , Tsao Yu
Published: November 2016

Marine mammals can adjust their vocal behaviors when they encounter anthropogenic noise. The acoustic divergence among different populations has also been considered as the effect of ambient noise. The recent studies discover that the marine soundscape is highly dynamic; however, it remains unclear how marine mammals alter their vocal behaviors under various acoustic environments. In this study, autonomous sound recorders were deployed in western Taiwan waters between 2012 and 2015. Soundscape scenes were unsupervised classified according to acoustic features measured in each 5 min interval. Non-negative matrix factorization was used to separate different scenes and to inverse the temporal occurrence of each soundscape scene. Echolocation clicks and whistles of Indo-Pacific humpback dolphins, which represent the only marine mammal species occurred in the study area, were automatically detected and analyzed. The preliminary result indicates the soundscape scenes dominated by biological sounds are correlated with the acoustic detection rate of humpback dolphins. Besides, the dolphin whistles are much complex when the prey associated scene is prominent in the local soundscape. In the future, the soundscape information may be used to predict the occurrence and habitat use of marine mammals.
Navigating the soundscape: The role of acoustic cues in the settlement behavior of larval reef fishes
Authors: Salas Andria K. , Wilson Preston S. , Ballard Megan S. , Altieri Andrew H. , Keitt Timothy H.
Published: November 2016

Nearly all coral reef fishes pass through a pelagic larval stage that concludes when they locate and select appropriate reef habitat. At least some species use the reef soundscape—the collection of sounds produced by reef-dwelling organisms—to achieve this task that is necessary for survival. Since larval fishes in the open ocean are inherently difficult to study, investigating their acoustic environment can allow predictions about their behavior in response to these cues. Further, we can predict the roles of different frequency bands in aiding long-distance navigation or short-distance habitat selection. We recorded the soundscapes at four reefs in Caribbean Panama for six weeks to inform the identity and variability of the most common sounds. We next predict the frequency-dependent transmission loss using an acoustic propagation model calibrated with acoustic transects. Including knowledge of source sound levels allows us to elucidate the sound fields created by low frequency fish and high frequency invertebrate sounds originating at the reef. We find that larval fishes are likely to encounter highly complex acoustic environments as a result of frequency-dependent acoustic structure in the water column coupled with temporal and spatial variation in the sources of the potential cues.
Macro- and micro-scale spatial variation in the acoustic activity of snapping shrimp on coral reefs in the Pacific
Authors: Zang Eden , Lammers Marc , Kaplan Max , Mooney T. A. , Fisher-Pool Pollyanna , Brainard Russell E.
Published: November 2016

Coral reef soundscapes are increasingly becoming recognized as critical factors in the study of reef dynamics, from the role they play in larval recruitment to the assessment of coral reef biodiversity and ecosystem stability. Snapping shrimp produce the predominant source of sound on most coral reefs at frequencies between 2 and 20 kHz. Their activity is influenced by a variety of abiotic factors. As such, coral reef soundscapes are prone to considerable flux and variation. However, this variation is still poorly understood on a variety of spatial and temporal scales, making it difficult to draw meaningful comparisons between the soundscapes of different reefs. We report on an effort to quantify the acoustic activity of snapping shrimp across 12 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 in snapping shrimp activity observed on multiple temporal scales and examine factors correlated with this variability at each location.
A critical review of geoacoustic inversion: What does it really tell us about the ocean bottom?
Authors: Chapman N. Ross
Published: November 2016

Estimation of parameters of geoacoustic models from acoustic field data has been a central theme in acoustical oceanography over the past three decades. Highly efficient numerical techniques based on Bayesian inference have been developed that provide estimates of geoacoustic model parameters and their uncertainties. However, the methods are model-based, requiring accurate knowledge of the acoustic propagation conditions in the ocean to carry out the inversion. More recent research has revealed fundamental limitations of model-based inversion methods in conditions of unknown temporal and spatial variations in the water. In addition, the inversions can generate only effective models of the true structure of the ocean bottom, which are generally highly variable over relatively small spatial scales. There are other questions about the theory for sound propagation in porous sediment media that raise doubt about the validity of inversion results. In most inversions, a visco-elastic theory is used, but is this correct? This paper reviews successes and failures of geoacoustic inversion to understand the limitation of model-based methods. Research directions are suggested in conclusion that show promise for development of new approaches. [Work supported by ONR.]
Reconstruction of the dynamic surface roughness with acoustic imaging technique
Authors: Dolcetti Giulio , Krynkin Anton
Published: November 2016

We present a novel technique which recovers the three dimensional profile of the free surface based on the scattering of the narrow-band ultrasonic waves recorded by a two-dimensional array of receivers. The method is based on the inversion of the discretized Kirchhoff integral. The inverse technique implements the Tikhonov regularisation and the generalised cross validation technique in order to obtain solution to an under-determined system of equations. Using airborne ultrasound, the technique has been validated experimentally to reconstruct a two-dimensional composite static surface and numerically to recover the three-dimensional dynamic surface. The application to the typical three dimensional patterns found on the free surface of shallow turbulent flows is illustrated and discussed. The method has important applications for the remote monitoring of natural rivers, where recent studies confirm the direct link between the fundamental hydraulic properties of the flow and the dynamic behavior of the free surface. The potential significance in the oceanic environment is also discussed.
Detection of long term trends in underwater noise levels
Authors: Powell Claire F. , Merchant Nathan D.
Published: November 2016

The risk of adverse impact to marine ecosystems from underwater noise pollution is increasingly recognised by scientists, policymakers, and wider society. Deep water measurements from the Northeast Pacific indicate that ocean noise has increased substantially over recent decades. Policymakers are now considering establishing noise monitoring programs to determine noise levels and trends in their waters. However, the ability of noise monitoring to detect statistically significant trends is a function of the temporal extent, variance, and autocorrelation of the time series. This has implications for the feasibility of evaluating quantitative policy targets within prescribed time frames and hence should inform the formulation of such targets. The present work demonstrates that methods developed in other environmental science disciplines (e.g., atmospheric temperature measurement) to design long-term monitoring networks and assess their statistical power can be applied to noise monitoring programmes. Example datasets are used to show the application of these methods both to assess the significance of long-term trends in ambient noise, and the required monitoring period to detect a given magnitude of trend (e.g., 3 dB per decade). The implications for the design of noise monitoring networks and target setting for policy purposes are then discussed.
Two-dimensional blood flow vector obtained with high frame rate acquisition of dual-angle Doppler signal
Authors: Saijo Yoshifumi , Akagawa Osamu , Fukazu Kosuke , Tsugita Naoya , Yaegashi Sou , Nagaoka Ryo
Published: November 2016

Quantitative measurement of flow in blood vessels is important to assess cardiovascular dynamics. The objective of the present study is to obtain two-dimensional (2D) blood flow vector in some carotid artery models and to validate the method in comparison with particle image velocimetry (PIV). Plane wave ultrasound with the repetition rate of 14 kHz was transmitted and received by a 7.5 MHz linear array transducer and a programmable ultrasound data acquisition system. Compound B-mode images and dual-angle Doppler data with the transmission angle of -10° and + 10° were obtained. 2D flow vector at arbitrary point was calculated by two velocity components along with each angle. Steady and pulsatile flow in normal and stenosed carotid artery models were simultaneously observed by the proposed method and PIV. 2D velocity vectors were successfully obtained in each flow states and the average error was approximately 5% in comparison with PIV in the carotid artery model. Steady flow in the distal stenosis model showed that the blood flow was influenced by vascular resistance while pulsatile flow seemed to push the blood to the high resistance portion. 2D blood flow obtained with dual-angle Doppler signal may provide important information in understanding cardiovascular dynamics.