bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional load of fundamental frequency in the native language predicts learning and use of these cues in second-language speech segmentation
Authors: Tremblay Annie , Broersma Mirjam , Coughlin Caitlin E. , Wagner Monica
Published: November 2016

This study investigates whether second-language (L2) learners make greater use of prosodic cues to word boundaries if these cues have a higher functional load in the native language (L1). It examines the use of fundamental-frequency (F0) rise in the segmentation of French speech by English- and Dutch-speaking L2 learners of French matched in French proficiency and experience (and native French listeners). In both English and Dutch, an F0 rise tends to signal word-initial boundaries in pitch-accented words with initial stress, but English has more vowel reduction than Dutch, and thus full vowels also signal word-initial boundaries in English. By contrast, in French, an F0 rise tends to signal word-final boundaries. Participants completed an eye-tracking experiment: They heard sentences where the monosyllabic target ended or did not end with an F0 rise (duration being held constant), and saw four orthographic words in the display, including the target (bal “ball“) and a disyllabic competitor (balcon “balcony”). Growth curve analyses on participants’ fixations revealed that Dutch listeners made earlier and greater use of F0 cues than English (and French) listeners. These results suggest that the functional load of F0 in the L1 predicts the learning and use of these cues in the L2.
The examination of acoustic feature of English obstruent coda by Mandarin and Cantonese speakers
Authors: Wanling Lu
Published: November 2016

Mandarin and Cantonese, though are both Chinese, exhibit differences in L2 English pronunciation, especially in obstruent codas. For the reason that only nasals -n, -m and -ng can be found at coda in Mandarin whereas apart from nasals, unreleased consonants -p -t and -k exits as well in Cantonese, it is reasonable to believe that L1 transfer makes influences on modifying codas for L2 learners. This present study aims at comparing the strategies used by Mandarin and Cantonese speakers in coda modification and resyllabification. By embedding the stimuli in a natural conversation, room-cleaning task, data are elicited and analyzed by Praat. Results indicates that up to 93% of codas are released by Mandarin speakers and 41% of those are unreleased by Cantonese speakers. Further, instead of epenthesizing vocalic elements, Mandarin speakers are found to strongly aspirate the codas with 58%, which contradicts most of the previous studies claiming that epenthesis is the main modification used among Mandarin L2 learners.
Perception of the Japanese moraic-nasal (/N/) by Korean native speakers: Concerning /N/ followed by vowels
Authors: Han Heesun
Published: November 2016

This study examines the perception of the Japanese Moraic-Nasals /N/ by Korean native speakers. In the case of the /N/ followed by vowels (/N/ + /a, i, u, e, o/), there is a tendency towards pronunciation as various nasal vowels. The actual sound of each /N/ is, however, prone to change according to the speech style. Korean language has three nasal codas (/m, n, ŋ/). The Korean nasal codas are pronounced [m], [n], [ŋ] respectively, regardless of speech styles. Therefore, if Korean native speakers consider Japanese /N/ from the perspective of the Korean nasal coda, it is possible that they will misjudge Japanese /N/. A perception test was conducted using 6 minimal pairs consisting of “/N/ + vowel (eg. /saNin/)” and “vowel + vowel (eg. /saiin/)”. The test words were recorded in “common,” “emphasized,” and “unclear” speech styles. The results showed that native Japanese speakers recognized /N/ in most cases. On the other hand, Korean speakers with no experience in learning Japanese were unable to recognize the Japanese /N/, and perceived /N/ as vowel. Korean Native speakers with advanced Japanese proficiency had results similar to the native Japanese participants. Interestingly, in some cases they showed more accurate judgement than that of the Japanese. This, therefore, suggests that, as language learning progresses, the Japanese /N/ is acquired. Advanced learners, however, tended to pay greater attention to the /N/ sounds rather than the contextual factors on which Japanese were more likely to rely on.
Bidirectional prosodic effects of code-switching in Spanish-Basque bilinguals
Authors: Aly Ann M.
Published: November 2016

This study investigates the prosody of code-switching in Spanish-Basque bilinguals, which has not been previously documented. Peninsular Spanish and Basque have several prosodic differences, including peak alignment in pitch accents. Spanish has delayed peaks (Estebas Plana & Prieto (2008)), while Basque has early peaks (Elordieta & Hualde (2015)). The current study investigates whether code-switched words are conditioned by prosodic position and whether the peak alignment and f0 maximum of a pitch accent differ between monolingual context (Spanish only) and code-switched contexts. Bilinguals (aged 21-31) from a Basque-dominant region (Lekeitio, n = 3) and a Spanish-dominant region (Bilbao, n = 4) participated in the present study. The data was coded for the following predictor variables: prosodic position, peak alignment, and f0 maximum in pitch accents. Results reveal that code-switches occur almost equally in phrase-medial and final positions. For peak alignment, Lekeitio speakers produced early peaks in both code-switching contexts (Spanish-Basque, Basque-Spanish), which matches monolingual norms for Lekeitio varieties of Spanish and Basque. However, Spanish-dominant speakers also produced early peaks in both code-switching contexts, despite delayed peak norms for Peninsular Spanish. Finally, preliminary results reveal greater f0 during code-switching contexts for Lekeitio speakers only. Further results and implications will be discussed.
Speech rhythm characteristics of L2 English produced by Japanese
Authors: Kawase Saya , Kim Jeesun , Davis Chris
Published: November 2016

This study investigated the durational rhythm characteristics of L2 English produced by L1 Japanese talkers with a particular focus on the interaction between L1 and L2 speech rhythm and the role of L2 experience. More specifically, for English sentences (N = 40) spoken by native Japanese (N = 10) and native Australian English (N = 10) talkers, we examined (1) mean consonant and vowel durations and durational variability and (2) vowel and consonant timing patterns within consonant clusters. Half of the Japanese talkers had more experience in L2 English. L2 productions had longer consonant and vowel duration and less variability compared to native English ones. The degree of L2 experience played a role: inexperienced L2 talkers produced less variable vowel durations than the experienced ones. The analyses of speech timing patterns in consonant cluster productions showed that inexperienced Japanese talkers produced significantly shorter second consonants in consonant clusters compared to native English productions, possibly compensating for the difficulty in producing nonnative consonant clusters. Additional analyses of the pattern of consonant cluster production by experienced L2 talkers will also be reported.
Japanese English learners use a variety of articulation strategies to produce English liquids
Authors: Moore Jeffrey , Shaw Jason , Kawahara Shigeto , Arai Takayuki
Published: November 2016

This study examines the production of English liquids /r/ and /l/ by Japanese speakers. Six speakers of varying levels of proficiency were recorded using an NDI Wave Electromagnetic Articulograph. They produced words containing /r/ and /l/ in initial singletons and initial clusters. Two native speakers of English were also recorded for comparison. The resulting articulatory data are analyzed for spatial targets, gestural timing, and the amount of variation between utterances. Results indicate a variety of strategies employed by speakers to achieve the non-native targets; however, more native-like, though distinctly Japanese-accented production, among advanced speakers was found. Lower-proficiency and intermediate speakers showed relatively large amounts of within-speaker variation, indicating the ongoing development of articulation strategies. These findings suggest that the acquisition of foreign language sounds is not merely a straight path from L1 transfer to target-like pronunciation, but a complex process involving many paths, hypothesis testing, and experimentation to find a suitable articulation.
Articulatory habit versus adaptive flexibility in L2 phone learning
Authors: Faytak Matthew
Published: November 2016

Learning a motor task is thought to be facilitated when it can be achieved within a set of thoroughly-learned motor patterns, here termed articulatory habit. Learners of novel phonological categories in an L2 may first attempt to produce a novel sound by working over the possibility space of acoustic outputs defined by well-known articulatory dimensions. A side effect of this neuromuscular habituation to L1 may be a limit to the adaptive flexibility of articulatory resources to the L2. To evaluate the role of L1 habit in individuals’ L2 category productions, 18 L1 English learners of French repeated French stimuli from a model talker while ultrasound and video of lip movement were recorded. Stimuli include the front rounded vowels /y ø/, which are outside of the subjects’ articulatory habit in inter-articulator coordination and the particulars of tongue position. A second phase of the study captured L1 English articulatory habit by eliciting a range of English words and recording articulator activity in the same way. Principal components analysis was performed on raw image data of both phases in order to gauge L1-L2 articulatory similarity and to highlight any dimensions not exploited in L1 but observed in L2 or vice-versa.
Age and consonantal context effects on second language speech perception of French vowels
Authors: Lee Andrew
Published: November 2016

This study investigated the effects of age of acquisition (AOA) and consonantal contexts on second language (L2) speech perception of French vowel pairs /i/-/y/ and /y/-/u/. A total of 60 Korean learners of French participated in either an Early-AOA group (under 16 years), a Mid-AOA group (16-26 years), or a Late-AOA group (over 26 years). To measure their perceptual accuracy, AX categorical discrimination tasks were employed in which the two target pairs, in addition to a control pair /i/-/u/, were provided with three different consonants (i.e., /p/, /t/, and /k/) in a consonantal-vowel-consonantal structure. Overall, the Korean participants had more difficulty discriminating the pair /i/-/y/ than the pair /y/-/u/. In particular, the Korean participants revealed more difficulty with the former pair in the /p/ context, whereas they showed more difficulty with the latter pair in the /p/ and /t/ contexts. While those in the Early-AOA group significantly outperformed those in the Mid- and Late-AOA groups, those in the former group perceived the two target pairs in a way that was less affected by the consonantal contexts. Accordingly, this paper will conclude by highlighting the importance of AOA and consonantal contexts in L2 speech learning.
The novel Ventriloquist paradigm: Studying L2 phonetic learning in dialogue with experimental control over phonetic detail
Authors: Broersma Mirjam
Published: November 2016

The novel Ventriloquist paradigm enables the study of phonetic accommodation and perceptual learning in dialogue, while allowing full control over the phonetic detail of the input that participants are exposed to. It is being developed to investigate L2 speech learning for production and perception in an ecologically valid yet maximally controlled way. Participants take part in a dialog which they believe to be genuine; in fact, however, their (real-life) interlocutor is a confederate whose speech is not just “scripted” (as in the confederate scripting task), but fully prerecorded. This guarantees control over all characteristics of the speech input, e.g., precluding that a confederate accommodates his/her pronunciation to the participant. The set-up is fully tuned to upholding the illusion that the confederate is actually speaking with the participant. The confederate sits opposite the participant, face briefly hidden when he/she “speaks.” Participants hear the prerecorded speech over closed headphones. In addition to the standard input, to facilitate a smooth flow of the conversation, the confederate can play prerecorded non-verbal interaction markers and stop-gap replies to any unanticipated remarks or questions from the participant. The new paradigm thus reconciles ecological validity with experimental control for the study of (L2) phonetic processing in dialog.
Relationship between learners' attention and perception training effects of a foreign language: Based on questionnaire study to young learners
Authors: Ikuma Yuko
Published: November 2016

Many previous practices studied learners' attitude in the field of the second language (L2) research. They observed the effectiveness of the improvement of learners' motivation or instruction for enhancing learners' self-efficacy. From the author's series of the preceding training research targeting at over one thousand young students who utilized self-study-typed computer-assisted language learning (CALL) system, the author has found that the continuous perceptual training be important in order to maintain the ability. This paper focused on the Japanese-speaking young learner's attitude and its progress towards L2 speech perception training mainly based on the questionnaire response after longitudinal training period using CALL materials. The result showed that the accuracy rates for phoneme and rhythm perception tasks improved; that tendency was observed slightly strong on the students who were interested in “phoneme discrimination” or “conversation” from the questionnaire response. It was also demonstrated that higher proficiency students showed interest in broader perspective like “conversation,” while lower students in rather narrower like “discrimination,” or “sound.” These results suggest that learners who got attention toward phoneme might improve their perception, however, to promote their proficiency, they need some instruction to have attention to wider perspective of speech. [Work supported by JSPS 26780498.]
The effect of training of poetry recitation on English rhythm of Cantonese native speakers
Authors: Chui Angel L.
Published: November 2016

English rhythm, although reported a hurdle to many ESL students, remains one of the least taught aspects of pronunciation. Despite the key role rhythm plays in facilitating comprehension and reducing foreign accentedness, systematic training in the ESL classroom is rare. To promote the teaching of rhythm in the local curriculum, this study explores the effect of poetry recitation training on advanced learners’ acquisition of English rhythm. Two groups of advanced Cantonese-speaking English learners were recorded reading poems of different foot patterns as well as non-poetic materials (BKB sentences and a fable), each on a separate occasion. As reflected from rhythmic metrics, the group trained in recitation manifest nativeness better despite the similar proficiency level of the two. I, therefore, argue that poem recitation is an effective means to help ESL learners acquire native-like rhythm in English.
Generalization in VOT imitation: Feature adaptation or acoustic-phonetic covariation?
Authors: Wilson Colin , Chodroff Eleanor , Nielsen Kuniko
Published: November 2016

After hearing instances of a word initial voiceless stop with lengthened VOT (e.g., long-[ph]), speakers lengthen their VOTs in unheard words beginning with the same stop ([ph]) and, critically, in words beginning with a different stop ([kh]; Nielsen, 2011). This pattern of generalized phonetic imitation has previously been attributed to talker adaptation at the level of distinctive features or gestural organization. Implicit in these accounts is the assumption that talkers implement the same feature or gesture in a uniform way: generalization from long-[ph] to long-[kh] is an effective and rational adaptation strategy only if VOT values for different stops covary across talkers. Building on previous findings (e.g., Theodore, 2009; Chodroff & Wilson, 2015), we establish that covariation is robust in the laboratory speech of Nielsen (2011). In baseline productions, the mean VOTs of [ph] and [kh] were almost perfectly correlated across participants (r = 0.97, p <.001). Following familiarization the correlation remained strong but was somewhat reduced (r = 0.87, p <.001), reflecting clear but imperfect generalization of VOT lengthening. These results are consistent with abstract adaptation accounts targeting features or gestures, but suggest a novel model of VOT adaptation that directly exploits the empirical correlations between stops.
Phonetic convergence in an immersive game-based task
Authors: Biro Tifani M. , Toscano Joseph , Viswanathan Navin
Published: November 2016

Phonetic convergence occurs when talkers change the acoustic-phonetic characteristics of their speech to be more similar to a conversational partner. It is typically studied using laboratory tasks, but the extent to which talkers converge varies considerably across studies. One aspect of these tasks that differs from real-world settings is how engaging they are. Highly contrived tasks may fail to elicit natural speech production, which could influence whether or not talkers converge. We address this issue by comparing the extent to which interlocutors converge in a repetitive, unengaging task versus an immersive video game-based task. Both tasks were designed to elicit production of specific words. Thirty word-initial voicing minimal pairs were used as stimuli, and we measured the degree to which phonetic cues (e.g., voice onset time; VOT) changed over the course of the experiment. For the more engaging task, participants’ VOT values for voiceless tokens trended towards convergence (i.e., they gradually shifted their VOTs to be more similar to their partner’s speech). In contrast, we found no clear evidence for convergence in the less engaging task. These results suggest that engaging, naturalistic tasks may yield results that more accurately reflect real-world conversational speech and phonetic variation than traditional laboratory experiments.
Acoustic correlates of vocal alignment to accented speech
Authors: Lewandowski Eva M. , Nygaard Lynne C.
Published: November 2016

Language users can vocally align to the speech characteristics of other talkers both within and across accent groups. Although perceptual assessments of vocal alignment indicate convergence to accented speech, the acoustic properties of the speech signal that contribute to these perceptual judgments are less clear. The present investigation examined the acoustic correlates of vocal alignment to foreign-accented and native speech and related acoustic to perceptual measures of convergence. Native speakers of American English shadowed utterances produced by four model talkers; male and female native speakers of English and Spanish. Baseline utterances were obtained from visual naming blocks and shadowed utterances were compared to both baseline and model talker utterances. Fundamental frequency (F0), utterance duration, and vowel spectra (F1, F2) served as acoustic indices of vocal alignment. The results showed that different patterns of alignment emerged across the three measures. Utterance duration, but not fundamental frequency or vowel spectra, demonstrated convergence. However, both duration and vowel spectra measures significantly predicted perceptual assessments of vocal alignment. The results suggest that perceptual judgments of alignment behavior depend on multiple acoustic properties and that the dimensions of acoustic change during vocal alignment appear similar across accented and native speech.
An experimental investigation of acoustic task-based carryover effects
Authors: Tatman Rachael
Published: November 2016

Carryover effects, where conditions in one experimental task affect behavior in subsequent tasks, have not received much attention in linguistics. This is worrying, given that linguistic elicitation tasks do affect talkers' production (Labov et al. 1972, Warner et al. 2012). This study used before and after within-subjects design. 16 talkers completed three tasks: a memory task, one of a set of intermediate tasks (passage reading, word reading or an interview), and a second memory task.Pitch, intensity and duration of stressed vowels were measured for productions from each task. Nested mixed linear effects models were constructed for each measure. In all models, acoustic measures were used as the response variable and subject and token as random intercepts. For data from the intermediate tasks, the inclusion of task identity significantly improved model fit for pitch (p < 0.05), intensity (p < 0.001) and duration (p < 0.001). In other words, there were very strong task effects. However, when comparing data from the first and second memory task, including the intermediate task did not improve model fit for pitch (p = 0.71), intensity (p = 0.78) or duration (p = 0.70); these strong task effects did not carry over.
Tomographic sonar imaging of underwater objects and the excitation of structural waves
Authors: Ferguson Brian G. , Wyber Ron J.
Published: November 2016

Tomographic sonar imaging (or image reconstruction from projections) requires insonifying the object to be imaged with a wideband monostatic sonar over a complete set (3600) of look angles (or aspect angles). The tomographic sonar image that is reconstructed from the projection data (variation with aspect angle of the sonar impulse response) represents the projection of the object's three-dimensional acoustic reflectivity function projected on the imaging plane. The tomographic reconstruction of the backscattered sonar signals reveals the geometrical shape of the object, together with any prominent features on the object like lifting lugs. However, the formation of the tomographic image can be adversely affected by the presence of structural waves that can be excited by the insonification of the object at certain aspect angles. It is shown that a variety of these structural waves are readily observed in the projection data space where they are resolved in both time and aspect angle. The mapping of these structural waves to particular featues in the tomographic sonar image is demonstrated. The presence of these structural waves provides another means of classifying the object that complements sonar imagery.
Sonar image reconstruction of objects near a reflective boundary
Authors: Plotnick Daniel , Marston Philip L. , Marston Timothy M.
Published: November 2016

The properties of reconstructed acoustic images, created from data obtained using backscattering synthetic aperture sonar (SAS) systems, have been studied for objects in the free field. The presence of a nearby reflecting boundary, such as the seafloor or surface, greatly increases the number of mechanisms or raypaths by which sound may be backscattered to the sonar system. Some of these raypaths involve one or more interactions with the reflecting boundary (multipaths), and others involve sound scattering multiple times from the same target (multiple scattering). Experiments were conducted using an air-water interface and simple cylindrical targets in order to examine the properties of the reconstructed circular SAS (CSAS) images, including effects due to vertical obliquity of the target [D. Plotnick et al., J. Acoust. Soc. Am. 137, 470-480 (2015)]. The CSAS image is by definition a two-dimensional representation of three-dimensional scattering; the image is thus highly dependent on the object’s 3-D shape, position, and orientation; many of these image properties may be understood. An additional experiment was conducted using a linear SAS system for two closely spaced cylinders in the free field, allowing the effects of multiple scattering to be examined. [Work supported by ONR.]
Quality assessment of acoustic color signatures
Authors: Cook Daniel A. , Park J. D. , Hunter Alan J.
Published: November 2016

Recent years have witnessed increasing research by the minehunting community into the use of wideband, widebeam, low frequency sonar, typically below 50 kHz, whose purpose is to excite and observe an object's structural response. These signatures exhibit uniqueness allowing mines to be more clearly distinguished from clutter objects. Considerable effort has been directed toward studying the scattering physics, but less work has been done to optimize the signal processing used for extracting signatures from data collected at sea under realistic conditions. Specifically, the tradeoff between signals, sources of noise, and signal processing parameters is not well understood. For example, a long observation interval can capture structural acoustic effects occurring later in time than the geometric scattering from an object, at the expense of increasing the interference from sea floor reverberation. Relationships such as this are described, and metrics are suggested for choosing the most appropriate data collection and signal processing strategies.
Scan geometries for three dimensional synthetic aperture sonar tomography
Authors: Marston Timothy , Kennedy Jermaine L.
Published: November 2016

Synthetic aperture sonar (SAS) exploits vehicle motion and coherent multi-ping signal integration to enhance image resolution. SAS is typically used to generate high-resolution 2D sonar imagery; however the generation of high-resolution, voxel-based 3D images of targets has also been demonstrated by synthesizing multi-dimensional apertures from scans conducted at diverse grazing-angles. In the latter case, the geometry of the multi-dimensional synthetic aperture can have significant ramifications for all stages of the beamforming process, ranging from navigation refinement and beamformer design to very practical experimental issues, such as the time necessary to scan a target. In this paper, the effects that different multi-dimensional scans have on three-dimensional SAS are considered. Results of field tests for different scan geometries are shown and interpreted in light of their various benefits and detriments.
Noncontact measurement of body position and vital information using airborne ultrasound
Authors: Hoshiba Kotaro , Nakadai Kazuhiro , Hirata Shinnosuke , Hachiya Hiroyuki
Published: November 2016

Because of a growing need for unconstrained medical monitoring for unobtrusively observing individuals in a living space, we have been studied about non-contact measurement of vital information such as respiration and heartbeat using airborne ultrasound. In previous study, the measurement system of small displacement using the M-sequence-modulated signal and tracking phase difference of reflected signals from the target has been proposed. The measurement of respiration and heartbeat of the target in a standing position using a pair of the loudspeaker and the microphone has also been performed. However, body position cannot be measured using a pair of the loudspeaker and the microphone because the system can measure the distance to the body only. In this paper, we describe a basic study of the measurement of body position, respiration, and heartbeat. In the system, using microphone array, body position was estimated by synthetic aperture processing. In addition, small body-surface velocity by respiration and heartbeat were measured by tracking phase difference of reflected signals.
Two-stage active sonar network track-before-detect processing in a high clutter harbor environment
Authors: Edelson Geoffrey S.
Published: November 2016

Reliable active acoustic detection and tracking of small targets while minimizing the number of false alerts is challenging in a shallow, multipath-inducing, high-clutter harbor environment. These targets often exhibit low target strength and the acoustic clutter fields can be dense and highly dynamic. One approach to detect and track targets in this environment involves a two-stage tracker due to the processing gain required to continually track a weak target in such a significant clutter field. The first stage uses more than a single frame of observations to not only initiate tracks but also to contribute to track maintenance. The second tracking stage is initiated by the tentative target tracks extracted from the first stage. Track segment association algorithms are employed to combat periods or locations track intermittency that inhibit detection and cause tracks to fail and restart. This paper describes the results of this two-stage approach to track-before-detect processing applied to a networked harbor surveillance active acoustic detection and tracking system that consists of a large number of relatively simple nodes, employs a windowed Hough-Transform tracker at the beam level, and a Kalman-based, multi-object tracker at the single- and multi-node levels.
Use of integrated instrumentation to detect and classify targets in shallow water
Authors: Cotter Emma D. , Murphy Paul , Joslin James , Brunton Steven , Stewart Andrew , Polagye Brian L.
Published: November 2016

The detection and classification of targets in shallow water environments (e.g., depth < 20 m) is of increasing interest, both in security applications and more general environmental studies. Here, we report the ability of a cabled integrated instrumentation system to detect and classify targets in a shallow (15 m deep), narrow (150 m wide) channel influenced by moderate tidal currents (peak currents < 2 m/s). The instrumentation system incorporates a passive acoustic array, multibeam sonar, acoustic camera, stereo-optical camera, and acoustic Doppler current profiler. The system effectiveness is benchmarked using autonomous “cooperative” targets (e.g., drifters with known position and acoustic characteristics), divers, and opportunistic observations of fish and marine mammals. By fusing data streams from multiple sensors, detection and classification rates are improved, particularly for smaller targets. Approaches to data management (data rates exceed 80 MB/s), real-time classification, and de-noising of acoustic imagery are also discussed.
Harbor passive acoustic monitoring systems
Authors: Abbot Philip , Premus Vince , Gedney Charles , Helfrick Mark
Published: November 2016

The feasibility of detecting quiet moving targets (e.g., unmanned undersea vehicles) in harsh harbor environments by using passive acoustic bottom-mounted hydrophone arrays, combined with advanced signal processing detection systems tuned to the target’s radiated noise signature characteristics is presented. The harsh shallow water environment is in Narragansett Bay, Rhode Island where UUV operations have been conducted. The sonar equation study considers the use of high resolution, multi-channel hydrophone arrays, measured source levels of representative UUVs (they are quiet), measured noise levels in the harbor (can exhibit high levels), and corresponding array gain. The resulting detection ranges for quiet targets are presented along with estimated false alarm rates. It is shown that passive sonar systems can be a viable component or modality for an underwater harbor defense monitoring system.
Passive and active sonar signal processing methods for port infrastructure protection and harbor security
Authors: Ferguson Brian G. , Lo Kam W.
Published: November 2016

High frequency passive and active sonar signal processing methods can be used in cluttered shallow water complex acoustic harbor environments for the detection, classification, localization and tracking of asymmetric threats including fast inshore attack craft, divers, underwater vehicles, and sea mines. For fast inshore attack craft, the event duration is short (tens of seconds) which necessitates the automation of the functions of a high frequency high resolution active sonar. The sonar also cues effectors that enable a layered defense capability to counter the threat. For wide area passive undersea surveillance, single hydrophones can be used for multipath passive ranging, a pair of hydrophones for direction finding, and an array of hydrophones for estimation of a complete set of target motion parameters. Also, it will be shown that the measurement of the time delays of the direct path and multipath arrivals at a single pair of hydrophones enables estimation of a complete set of target motion parameters for a surface vessel.
Multi-agent acoustic noise field characterization using optimal control
Authors: Bogdan Caitlin , Wixom Andrew , McDaniel J. G.
Published: November 2016

Investigations of acoustic-driven control schemes have stayed away from traditional Optimal Control methods because of the computational load and lack of direct solution methods. The method presented here overcomes these challenges and learns a spatially varying noise field by applying the Pontryagin Maximum Principle (PMP) to solve for optimal trajectories over a changing estimate of the noise field. The resulting control drives the agents to the regions of the estimated field with the most uncertainty. This optimization is conducted with multiple agents interested in the noise field for a single frequency as well as for multiple agents simultaneously optimizing over multiple frequencies of interest. The challenges of finding a solution to the mixed boundary value problems is achieved through an eigenvalue decomposition method. The selected cost function is designed to minimize time and thus bound error introduced by the open loop control derived through the PMP methodology. Simulations and preliminary experimental results are presented to demonstrate the effectiveness of this method. The resulting information from utilizing this method are useful in optimized sensor location problems, which are especially relevant for the large dynamic array system used to do the initial sensing. [Research supported by NAVSEA and Raytheon Company.]
Spatial variation of ocean ambient noise spectrum in offshore China
Authors: Song Guoli , Guo Xinyi , Ma Li , Zhang Qianchu
Published: November 2016

Ocean ambient noise always presents spatial difference because of the diversity of the noise source and the propagation condition. This paper analyzes the noise spectrum level (NL) of two stations measured in offshore China, and finds that the difference of the two NL is more than 10 dB with different variation for per octave. Through analyze the NL and the transmission loss level (TL) from the noise source to the measuring station, a correlation is found between the noise level difference (NLD) and transmission loss difference (TLD), with a correlation coefficient of 0.78 at the band of 50 Hz ~500 Hz. This is a strong proof to connect the spatial variation of NL with the varied propagation channel, and also suggests that at this band the ambient noise is closely related to the ship noise sources. In addition, the difference of the ship noise source level coincides with the number of vessels before and after the fishing moratorium period in China, which further explains the difference between the NL of two experimental stations are highly related to ships.
A multi-year time series of marine mammal distribution in the Alaskan Arctic
Authors: Crance Jessica , Berchok Catherine
Published: November 2016

The Marine Mammal Laboratory has deployed long-term, moored, passive acoustic recorders at numerous locations in the Alaskan Arctic since the BOEM-funded Chukchi Acoustics, Oceanography, and Zooplankton (CHAOZ) study began in 2010. These instruments, often collocated with oceanographic instruments, collect year-round passive acoustic data (16 kHz sampling rate, ~30% duty cycle). All acoustic recordings (100%) were analyzed using an in-house Matlab-based manual analysis program for 12 different Arctic and sub-Arctic cetacean and pinniped species, as well as for vessel, seismic airgun, and ice noise. Bowhead and beluga distributions showed similar patterns, with bimodal temporal distributions representing the fall and spring migrations. Infrequent gray whale detections (isolated on nearshore recorders) followed a similar, albeit less defined, bimodal distribution. Walrus and bearded seal calls were detected almost year-round, with peak bearded seal calling from April through June. Detections of sub-Arctic species (e.g., humpback, fin, killer, and minke whales) were rare north of 70° N. Correlation of marine mammal distribution with concurrent oceanographic parameters revealed strong associations with oceanographic and prey variables, more specifically, ice concentration and thickness, chlorophyll, wind speed, and currents. This study illustrates the importance of collecting concurrent long-term passive acoustic and oceanographic data in a rapidly changing environment.
A preliminary acoustic survey of echolocating marine mammals in the Bering Sea
Authors: Seger Kerri , Miksis-Olds Jennifer , Martin Bruce
Published: November 2016

As the Arctic seas rapidly change with increased ocean temperatures and decreased sea ice extent, traditional Arctic marine mammal distributions will be altered, and non-traditionally Arctic species may shift poleward. Arctic species typically include sperm, bowhead, humpback, right, gray, fin, and blue whales; odontocetes, specifically killer and beluga whales; and several pinnipeds species. Their acoustic presence has been documented because they produce relatively low-frequency sounds that are detectable by many common, remotely-deployed recording platforms. Until recently, however, recording constraints of power and storage limited higher sampling rates and prevented the detection of many high-frequency-producing species in the Arctic seas. Such species likely include Baird’s, Cuvier’s, and Stejneger’s beaked whales, as well as Northern right whale and Pacific white-sided dolphins. Using one of the first long-term data sets to record relatively high frequencies in the Bering Sea, signal types similar to those of Baird’s and Cuvier’s beaked whales, and Pacific white-sided and Northern right whale dolphins have been detected. Their relative acoustic presence from the last several years will be presented, as well as the acoustic presence of other species, like Risso's dolphin, that may be shifting northward into the Arctic seas. [Work supported by ONR.]
How reliable is song as a cue for acoustic surveys of humpback whales (Megaptera novaeangliae) with changing population size and density?
Authors: Noad Michael J. , Dunlop Rebecca A. , Mack Amelia
Published: November 2016

Acoustic surveys of marine mammals have several advantages over traditional visual surveys. For an acoustic survey to be accurate, however, there needs to be a predictable relationship between vocal behavior and density. Humpback whale’s song, produced by males primarily during the breeding season, is potentially a good candidate for such surveys. The function of song, however, remains enigmatic and so its usefulness as a predictor of population density is still not known, particularly when population density changes. We examined aspects of singing behavior during migration off eastern Australia between 1997 and 2015 including the proportion of whales that sang, the spacing between singers, and the use of song by males when joining other whales. Over this period, there was a six-fold increase in the population but this had little effect on the proportion of whales singing, and singers spaced randomly, implying that it could be useful as a survey tool. However, the proportion of singers that continued to sing while joining other whales decreased, showing some density effects on singing behavior. Altogether, while singing behavior can be used as a reasonable proxy of population size at the densities observed, behavioral strategies may start to confound this relationship at higher densities.
Vocalization source level distributions and pulse compression gains of diverse baleen whale species in the Gulf of Maine
Authors: Wang Delin , Huang Wei , Garcia Heriberto , Makris Nicholas C. , Ratilal Purnima
Published: November 2016

The vocalization source level distributions and pulse compression gains are estimated for four distinct baleen whale species in the Gulf of Maine: blue, fin, minke, and sei. The vocalizations were received on a large-aperture densely sampled coherent hydrophone array system deployed to monitor marine mammals over instantaneous wide areas using the passive ocean acoustic waveguide remote sensing technique. For each baleen whale species, between 400 to over 1400 measured vocalizations with significantly high signal-to-noise ratios (SNR>10 dB) after coherent beamforming and localized with high accuracies (<10% localization errors) over ranges spanning roughly 1 km to 38 km are included in the analysis. The whale vocalization received pressure levels are corrected for broadband transmission losses modelled using a calibrated parabolic equation based acoustic propagation model for a random range-dependent ocean waveguide. The broadband vocalization equivalent pulse-compression gains are found to be 2.5±1.1 for fin, 24±10 for blue, and 69±23 for sei. The source level distributions and pulse compression gains are essential for determining signal-to-noise ratios and hence detection regions for baleen whale vocalizations received passively on underwater acoustic sensing systems, as well as for assessing communication ranges and potential for echolocation in baleen whales.
Acoustic wave propagation analysis for detecting a sensor robot in heat transfer pipe
Authors: Nishimura Yoshihiro , Kawagoe Yoshinobu , Harada Yoshihisa
Published: November 2016

Ultrasonic Testings of heat transfer pipes in electric power plant are important. Those pipes, which are over 60 m and whose inner diameters are 25 mm, 50 mm, and 75 mm, have more than 20 curves and are located at directly unaccessible place. We developed a cableless robot for measuring thickness of pipe in a pipe filled with water but it is difficult to know where our robot is in the pipe at real time. We developed a projector to propagate an intensive single-mode wave into the pipes and examined the relations between frequencies-intenseness and wave propagation (3 kHz–50 kHz). Attenuations of acoustic waves in the pipe filled with water were much lager than those in the pie filled with air and examined for metal pipes and plastic pipes. Acoustic wave tunneling through pipe-wall was calculated and compared with experimental results. Acoustic wave tunneling through the pipe-wall was found to be the main reason why acoustic wave could not propagate longer in the pipe filed with water than that with air. We derived useful data to develop a system for measurement of where our robot is.
Sound intensity fluctuations as evidence of mode coupling due to moving nonlinear internal waves in shallow water
Authors: Katsnelson Boris , Ren Yun
Published: November 2016

One of manifestation of mode coupling produced by moving nonlinear internal (NIW) waves is temporal fluctuations of intensity or amplitude. In spectrum of fluctuations measured during a few hours there are maximums at frequencies, corresponding to periodical (in time) interaction of moving NIW with periodical (in range) interference structure of the sound field. If velocity of NIW along acoustic track is v, then peaks are placed at frequencies Fmn~v(km-kn), where km is propagation constant of mode m. Due to a few remaining modes in a long range propagation, spectrum should have peaks at a few predominating frequencies. In given work on the base of experimental data of ASIAEX 01 and the corresponding theoretical analysis, it is shown existence of predominating frequencies in spectrum of the sound intensity fluctuations in the presence of NIW moving along acoustic track of the length ~35 km. Both speed of NIW and scales of interference beating determine mentioned frequencies. Note that acoustic track consists of two parts with different depths: ~250 m (NIW are moving during time interval considered) and 120 m (position of receiving array). So, spectrum of fluctuations depends on modal structure both parts of this acoustic track. [Work was supported by ISF and NSFC.]
Mapping the acoustical properties of the upper sedimentary layer in Lake Kinneret
Authors: Katsnelson Boris , Lunkov Andrey , Katsman Regina , Ostrovsky Ilia
Published: November 2016

A series of field experiments were conducted to estimate the effective acoustical properties of the bottom in Lake Kinneret (Israel). A wideband sound source (300 Hz to 2 kHz) was positioned at different ranges (1 m to 6 km) from a single hydrophone. Both local and long-range measurements of the sound field were carried out. All the acoustic data demonstrated a high reflectivity of the lake bottom at all grazing angles that is specific feature of gas-bearing sediments. Experimental sound pulses were compared with the simulated ones to obtain the values of effective sound speed in the sedimentary layer at different locations in the lake. Using a basic three component sediment’s model (water, rigid particles, and gas bubbles), the gas fraction in the bottom was estimated. A high correlation between the calculated gas fraction and previously measured organic matter concentration was observed. [Work was supported by ISF.]
Simulation of acoustic backscattering from bubbles and droplets under different shape regimes with implications for underwater detection of leakages using active acoustic sensors
Authors: Pedersen Geir
Published: November 2016

Safe subsea production of oil and gas, as well as storage of CO2 in geological formations subsea, require rapid detection of accidental releases, eliminating potential harm to the environment. Monitoring of natural gas seeps are important in a climate and environmental aspect. Previous studies demonstrate the potential of sonars for detection and quantification of oil and gas releases of natural or anthropogenic origin. Simulations of acoustic backscattering from plumes is an important tool for design of leakage detection systems and in situ leakage quantification. Backscattering from subsea leakages are often simulated assuming spherical shapes using, e.g., effective medium theory, however in real world situations bubble and droplets are not spherical. In this study the backscattering from single bubbles (CO2, CH4, and air) and droplets (light and heavy oil) are simulated under different shape regimes (i.e. as a function of Reynolds and Eötvös number). The shapes are extracted from time dependent Computational Fluid Dynamics simulations and the backscattering is modeled using adaptive cross approximation accelerated Boundary Element Method (BEM). The backscattering from single bubbles and droplets are used as input to effective medium theory simulations of plumes. Simulations using BEM and effective medium theory with spherical and non-spherical bubbles and droplets are compared with controlled in situ measurements of backscattering with concurrent shape measurements.