bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation of vortex-induced cavitation bubble dynamics and acoustic emissions
Authors: Chang Natasha A. , Yakushiji Ryo , Dowling David R. , Ceccio Steven L.
Published: September 2008

The bubble dynamics and corresponding acoustic emission from low-event rate cavitation inception due to the interactions of a pair of parallel counter-rotating vortex was studied experimentally in a water tunnel. The measured bandwidth of the acoustic pulse from the growth/collapse of a small isolated cavitation bubble is more than 200 kHz, and the measured pulse duration is ∼15–20 μs. The underlying vortical flow, static pressure, and nuclei distribution were characterized and are reported. These fluid and flow parameters influenced the acoustic signal, and dynamics of the cavitation bubbles. Details of the acoustic signature of the cavitation bubble were investigated during its inception, growth, splitting, and collapse. In the chosen flow field, it was found that during bubble growth, the acoustic signal is the strongest with the bulk of the signal energy in frequencies between 1 kHz and 6 kHz. Here, the frequency content of the acoustic signal during inception and growth was related to the volumetric change of the bubble measured from images taken with a high-speed video camera with a correlation of 84%. [Work supported by ONR.]
Second mention reduction in Indian, English, and Korean
Authors: Baker Rachel E. , Bradlow Ann R.
Published: September 2008

Phonetic reduction of the second relative to the first mention of a word in a discourse (Second Mention Reduction, or SMR) is a well-documented feature of spoken American English (AE). This phenomenon could be mediated by discourse-level prosodic structure: second mentions are reduced because they are less likely than first mentions to be accented in AE; or it could occur independently of prosodic structure. Impressionistic studies indicate that Indian English (IE) speakers do not deaccent second mentions like AE speakers [J. Gumperz, Discourse Strategies (1982)]. Korean marks information structure through phrasing and word order rather than pitch accents. Therefore, SMR in these languages would support a direct link between lexical probability and duration. Six IE speakers read five paragraphs containing 59 repeated words, and five Korean speakers read a Korean translation of one of these paragraphs. IE speakers were significantly less likely to deaccent second mentions than AE speakers (sign-test, p<.05), and four IE speakers had identical accenting rates for both mentions, providing empirical evidence that IE speakers do not deaccent second mentions. Moreover, significant SMR was found in both Korean (W=43, p<.05) and IE (W=1340, p<.001), suggesting that probabilistic effects on word duration are not mediated by prosodic prominence.
Effects of word length and presentation order in the perception of non-native sequences
Authors: Davidson Lisa
Published: September 2008

Previous research in the perception of non-native phonotactics indicates that listeners have difficulty distinguishing certain sequences like [ebzo]-[ebuzo] (Japanese listeners) or [zgamo]-[z■gamo] (English listeners). Whereas discrimination of phonemes in monosyllables (e.g. [k’a]-[q’a]) is diminished but better than chance [J. Werker and R. Tees J. Acoust. Soc. Am. 75, 1984], discrimination of non-native sequences in longer words is often below chance. In this study, the effect of length and presentation order on the discrimination of non-native phonotactics is investigated. English speakers (n=30) were presented with pairs of the type CCVCV-C■CVCV (e.g., /tkapu-t■kapu/) and CCV-C■CV (/tka-t■ka/) in an AX discrimination task. Half of the ‘‘different’’ pairs were presented with the ■ word first, and half with the cluster word first. Results indicate that English listeners are significantly less accurate on the discrimination of longer words both in ‘‘same’’ and ‘‘different’’ trials. Presentation order was also significant: listeners are more accurate when the cluster word is presented first than when the ■ word is. These results suggest that while adults can discriminate non-native sounds or sequences under optimal contexts, this ability is not necessarily helpful in situations with more realistic input, such as language acquisition. [Research supported by NSF.]
Sensitivity to phonetic detail in perceptual assimilation: The perception of Korean stops by native speakers of Hindi
Authors: Silver Jenna , Wayland Ratree , Harnsberger James
Published: September 2008

The study examines the perceptual assimilation of six Korean stop contrasts (/t/-/th/, /t/-/t*/, /th/-/t*/, /k/-/kh/, /k/-/k*/, /kh/-/k*/) by native speakers of Hindi to explore the question: Does variable assimilation of non-native speech sounds to multiple native perceptual categories reflect 1) an insensitivity to non-native phonetic detail or 2) a residual sensitivity that results in better (although not nativelike) perception? The Korean series was presented in both a categorial AXB discrimination test and an orthographic classification task. The Korean consonants were variably identified by Hindi listeners both in terms of place of articulation (Korean dentialveolar stops were variably assimilated to the dental and retroflex places in Hindi) as well as voicing (Korean tense stops were variably judged as either voiced or voiceless unaspirated; Korean lax stops were judged as either voiceless unaspirated or voiceless aspirated). A comparison with the discrimination scores supports the residual sensitivity hypothesis: The most variably assimilated Korean contrasts also elicited discrimination scores that were significantly above chance. Such residual sensitivity reflects an adult perceptual system in which sensitivity to non-native phonetic detail is not lost, but maintained and available to aid in second language learning.
Word frequency and neighborhood density effects on L2 listeners: English listeners learning Korean
Authors: Kim Sung-A
Published: September 2008

This study investigated the word frequency and neighborhood density effects on native and non-native speakers’ word recognition. There has been a disagreement among previous studies on word frequency and neighborhood density effects on non-native listening (Bradlow and Pisoni, 1999; Imai et al., 2005; Yoneyama, 2006). In the present study, Korean and English test stimuli with varying word frequency and neighborhood density were presented to English speakers learning Korean, who differed in Korean pronunciation proficiency. Two experiments were conducted: In the first experiment, each language was produced by its native speaker, while in the second one, the Korean stimuli were produced by an English-Korean bilingual, in order to color the stimuli with an English accent. The experimental results revealed a strong influence of word frequency and neighborhood density on word recognition in non-native listening of the English speakers. The participants’ pronunciation proficiency turned out to affect word recognition in the non-native listening as well. Yet, English-accented stimuli showed no significant effects on the word recognition of the Korean-learning English speakers across the proficiency levels. These results are discussed in relation to the exemplar model (Bybee, 2000; 2001).
Release direction in clicks correlates with coarticulation patterns
Authors: Miller Amanda
Published: September 2008

Electropalatograhic data from one speaker’s productions of Khoekhoe palatal and alveolar clicks is presented. In alveolar clicks, the anterior part of the posterior constriction lowers first, increasing lingual cavity volume for rarefaction. The apical alveolar anterior constriction is abrupt. These clicks occur more frequently with [ai] than with [i]. Palatal click production exhibits apico-laminal anterior contact from the dental to post-alveolar regions, velar contact, and a small palatal opening. The anterior release starts with dental separation, followed by alveolar separation. Post-alveolar contact is released last, simultaneously with velar contact forming the front edge of the posterior constriction. The palatal click anterior release is simultaneous with the posterior release, involving a larger contact area and a smaller cavity volume than the alveolar click. Anterior constriction contrasts in these clicks are apical alveolar versus laminal post-alveolar. The post-alveolar laminal click occurs freely with front vowels, while the apical alveolar click occurs freely with [ai], and less frequently with [i]. Anterior and posterior click releases follow the direction of airflow: Front to back. Release direction correlates with posterior constriction coarticulation patterns. [Work supported by NSF.]
Are types of filled pause discrete classes?
Authors: Gorman Kyle
Published: September 2008

Clark and Fox Tree hypothesize that filled pauses ‘‘uh’’ and ‘‘um’’ in English serve the discourse function of alerting the interlocutor of production difficulties. They demonstrate that the mean duration of pause immediately after ‘‘um’’ is significantly longer than after ‘‘uh.’’ This account suggests that fillers are categorically differentiated from each other; however, it fails to predict a cross-linguistic generalization. Across languages, fillers tend to have centralized vowels [Vasilescu et al. (2005)]. When there are two realizations of filled pause within a language, one tends to consist of a vowel followed by a nasal, as in ‘‘um’’ [Clark and Fox Tree (2002)]. These observations suggest filled pause is a phonetic process and, therefore, may apply gradiently. English filled pauses are revisited, showing that the discourse effect identified is not categorically distributed, but rather defined acoustically on a gradient scale. Acoustic models of fillers are trained on the identities of ‘‘uh’’ and ‘‘um’’ in a corpus. These models are then applied to predict the duration of pause. This phonetic account of disfluency performs better than the categorical account in predicting the duration of non-null pause, showing that the discourse effects may be caused by a gradient strategy for disfluency realization.
Italian geminates: Interarticulator programming and articulatory dynamics
Authors: Lofqvist Anders
Published: September 2008

This study examined lip and tongue coordination and tongue movement kinematics in Italian long and short consonants with native speakers of Italian as subjects. The linguistic material consisted of Italian word pairs that only differed in the duration of a labial or lingual consonant, which was either long or short. Recordings were made of lip and tongue movements using a magnetometer system. There was a very robust difference in the duration of the oral closure. The duration of the tongue body movement between the two vowels in a sequence of vowel-bilabial nasal-vowel was longer, and its movement path longer, for a long than for a short consonant; the average speed of the movement showed no reliable difference. The onset of the tongue movement relative to the oral closure started earlier for a short than for a long consonant. In lingual stop and fricative consonants, the tongue movement during the closure was longer, and its average speed slower, in the long than in the short consonants. Overall, these results for Italian are comparable to those found in long and short Japanese consonants. In particular, they provide additional evidence for task-specific modulation of tongue movement speed. [Work supported by NIH.]
The role of foreign-accentedness in lexical processing
Authors: Shah Amee , McLennan Conor
Published: September 2008

Previous evidence indicates that foreign-accented speech influences spoken word recognition (accented stimuli are processed with reduced accuracy and slower response times). The present study aims to extend and further explore the relationship between foreign-accentedness and spoken word recognition. Specifically, the present study strives to determine whether word recognition will modulate the ratings of foreign accentedness. Spoken words are easier to recognize in sentences that are in an appropriate context versus an inappropriate context. In order to determine whether listeners attribute the relatively slow and difficult spoken word processing in an inappropriate context to a relatively strong foreign accent, participants were asked to rate the strength of an accent for the final word in a sentence, as spoken by a native or a non-native speaker. Crucially, half of the words were in an appropriate and the other half in an inappropriate sentence context. Ratings of accent and response times were obtained as a function of appropriate and inappropriate sentence context for both the native and non-native speakers. Results provide new information regarding the relationship between foreign-accented speech, indexical variability, and lexical access.
Language contexts in speech categorization: Testing the double phonetic standard in bilinguals
Authors: Garcia-Sierra Adrian , Ramirez-Esparza Nairan , Champlin Craig A. , Rivera-Gaxiola Maritza
Published: September 2008

It is widely known that one’s native language influences where phonetic boundaries are placed. However, it is less understood how bilinguals categorize speech sounds. The goal of this investigation was to test if bilinguals’ phonetic boundary shifts in accordance with the language they use at the moment. In order to accomplish this goal, Spanish-English bilinguals (N=27) and English monolinguals (N=27) were asked to identify the speech sound ‘‘ta’’ from a 10 token speech continuum varying in VOT in two language contexts, while electrophysiological measures were recorded. It was expected that: (a) Bilinguals, but not monolinguals, would show a shift in their phonetic boundary according to the language context, and (b) bilinguals, but not monolinguals, would show different ERP amplitudes (N2/MMN components) in accordance with the language context. The behavioral results showed that bilinguals, but not monolinguals, perceived specific speech sounds—in the ambiguous zone—differently among language contexts. The electrophysiological results showed that bilinguals’, but not monolinguals’, ERP components differed across language contexts. Interestingly, behavioral measures correlated significantly with electrophysiological measures only in bilinguals. The challenges of testing the double phonetic boundary are discussed, along with the limitations of the methodology used in this study.
A speech audiogram of Setswana consonants
Authors: Seoke Sinah Y. , Shrivastav Mini N. , Harnsberger James D.
Published: September 2008

Setswana is a Bantu language used in several regions of Southern Africa, and its phonemic inventory includes a diverse range of consonants. To date, very little information exists about the acoustic correlates of Setswana speech sounds. The present study was aimed at analyzing these speech sounds in order to develop a clinically useful speech audiogram for Setswana. Three native speakers of Setswana produced 45 target phonemes in word initial and medial positions, in three vowel contexts (/a/, /i/, and /u/). The stimuli were then analyzed for peak frequency and intensity. A preliminary analysis revealed an effect of word position and vowel context on peak frequency, and hence, only phonemes in the word medial position and in the /a/ vowel context were used to plot the speech audiogram. The speech audiogram hence developed was then compared to speech audiograms of American English phonemes commonly employed in clinical settings. Consonants common to both Setswana and American English inventories were used to establish the validity of the study’s procedures. The speech audiogram developed can potentially be used to provide partial estimates of the audibility of Setswana phonemes to native speakers with various types of hearing loss. a)Currently at the Dept. of Communication Pathology, Univ. of Pretoria, South Africa
A comparison of speech rate of speakers of Dominican and Puerto Rican Spanish and of New York City English
Authors: Nunez-Agosto Leticia , Bell-Berti Fredericka , Jorge Altagracia , Reynolds Deborah
Published: September 2008

When we hear speakers of other languages or of other dialects of our own language, we perceive them as speaking more rapidly (or, occasionally, more slowly) than do speakers of our own language/dialect. The purpose of this study was to compare speech rates across dialects and languages to begin to understand these perceived differences. To this end, we compared the speech rate across three groups: 25 speakers each of Dominican and of Puerto Rican Spanish and 25 speakers of English from New York City; all were monolingual speakers of their languages. We measured speech rate for a habitual/automatic speech task, reciting the Lord’s Prayer; each speaker repeated the prayer for at least one minute. We measured the durations of the speech and pauses for one repetition of the Lord’s Prayer (usually the second) for each speaker. Results will be presented in terms of syllables per second. Preliminary results suggest that speakers of Puerto Rican Spanish and New York English do not have different habitual/automatic speech rates, and that speakers of Dominican Spanish have slower habitual speech rates. [Supported by St. Johns University.]
The relation between focus effects in production and exemplar locations in perception for stop types in English, Japanese, and Korean
Authors: Oglesbee Eric , de Jong Kenneth
Published: September 2008

This paper examines focus-induced variability in the production of labial stop contrasts in English, Japanese, and Korean, pursuing differences between the languages in how voice onset time (VOT) and fundamental frequency (F0) are used to indicate differences between stop types. Language differences are compared to differences in the perceptual usage of these acoustic cues using AMBEL, an adaptive tracking algorithm that allows subjects to search multi-dimensional stimulus arrays for best exemplars. All three languages exhibit category differences in VOT, though Japanese and Korean exhibit overlap for two of the categories. As found previously, for these categories, both Japanese and Korean exhibit large differences in F0 in the following vowel. Except for the smaller F0 differences in English, all of these VOT and F0 differences are systematically expanded in a focus condition. In particular, VOT increases for the more aspirated stops in all three languages, and substantial rising F0 patterns are observed in lenis Korean and zero-lag Japanese stops. Perceptual data match these focus effects; best exemplars differ in VOT in all three languages, and in Japanese and Korean, where substantial F0 focus effects were observed, F0 differences affect the identification of best exemplars. [Work supported by NSF.]
Effects of native language and training on speaker normalization in lexical tone perception
Authors: Wayland Ratree , Kaan Edith , Bao Mingzhen , Barkley Christopher
Published: September 2008

Tone languages, such as Thai, use pitch differences to distinguish lexical meaning. In this study, we investigated the effects of native language and training on speaker normalization in perception of lexical tones in Thai. Three tokens each of the Thai high, mid, and low tones were generated to simulate three female speakers with three relatively different F0 pitch ranges (high, mid, and low). The stimuli were presented to native Mandarin Chinese (NC), American English (NE), and Thai (NT) for categorization before and after a two-day perceptual training. Results obtained thus far from 32 NC, 30 NE, and 11 NT suggested that, overall: (a) NC outperformed NE both before and after training, (b) NT numerically outperformed NC before training, but not after training, and (c) performance of all three groups of participants improved after training. Interestingly, it was also found that participants’ performance varied from tone to tone, depending on the tonal environment in which it was presented for discrimination. These results suggest that knowledge of a tonal language and perceptual training facilitates the speaker normalization process in lexical tone perception, and that tonal contexts affect discrimination of tones.
Mirroring, not imitation, for the early learning of L1 pronunciation
Authors: Messum Piers
Published: September 2008

To learn to pronounce, a child must learn to produce speech sounds that listeners take to be equivalent to those that they themselves produce. Once this ‘‘correspondence problem’’ is solved, he can learn the pronunciation of any word by imitating the sequence of its constituent sounds. Learning to pronounce has also been assumed to be imitative, but in the different sense of being a mimicry or matching-to-target process applied to the speech signal after some form of normalization for vocal tract size. However, attending to ephemeral words and speech sounds as meaningful unit bars attending to the latter as a signal to be mimicked. Since a child must recognize what is said, basic perceptual psychology provides one reason among several that preclude the possibility of mimicry in the early learning of speech sound qualities. Instead, the normal pattern of mother-infant vocal interaction points to the mother’s reformulation of the child’s output within ‘‘imitative’’ contexts (i.e., vocal mirroring) as enabling the child to establish the correspondences needed. The nature of the representations thus formed resolves, inter alia, the mystery of fast shadowing and the longstanding question of whether speech is fundamentally an acoustic or gestural code.
Incomplete neutralization in Dutch opacity
Authors: Ettlinger Marc
Published: September 2008

In Dutch, syllable-final plosives are devoiced so /bad/ ‘‘bathe’’ is pronounced [bat]. However, despite being resyllabified to syllable-initial position by a clitic in /bad+er/ ‘‘bathe her,’’ the /d/ is still devoiced: [ba.ter]. This is referred to as phonological opacity because a generalization syllable-final devoicing is obscured or rendered opaque by another process—resyllabification. In this experiment, the acoustics and perception of this opaque relationship will be investigated. The voice onset time, release burst, and consonant duration of plosives for native Dutch speakers in phrases such as [ba.ter] will be compared to those in a phrase such as [ba.der] ‘‘bather’’ and /prat+er/ ‘‘speaker’’ [pra.ter]. Also, a perception experiment will be conducted testing whether native Dutch speakers are able to distinguish these phones. Based on a similar study of German [R. Port and M. O’Dell, J. Phonetics 13, 455–471 (1985)], it is expected that the [t] in [ba.ter] is not identical to the [t] in [pra.ter]. If, indeed, this is the case, and the [t] in [ba.ter] instead bears some of the acoustic properties of [d] in [ba.der], this would provide a useful set of perceptual cues enabling speakers to observe the devoicing generalization through the opacity.
Distributed remote surveillance systems: An overview of the Naval Studies Board panel report
Authors: Baggeroer Arthur B.
Published: September 2008

The Chief of Naval Research requested the Naval Studies Board of the Academies to review distiributed remote surveillance (DRS) systems in April 2005. The tasking was to ‘‘conduct an assessment of distributed remote sensing concepts and related technologies’’ for improving Navy capability to conduct undersea warfare missions. The panel reported its findings in November 2006. The technical issues covered included: (i) System concepts, (ii) detection and localization, (iii) classification and automation, (iv) communications, (v) power and processing, (vi) distributed network control, and (vii) survivability. Six findings and recommendations were distributed in an NSB report publicly; however, the USN determined that the detailed technical content should be classified. Since DRS is now thought to be a solution for many Navy missions, an enumeration of the technical issues in any successful DRS was felt to be a useful system. The presentation covers these issues. [Work sponsored by N81, USN.]
Undersea distributed networked systems: A development framework
Authors: Christian Raymond J.
Published: September 2008

Since the early 1990s, the military and commercial undersea communities have experienced dramatic changes in operational, technical, and business climates driven by the confluence of technology advances and increased civilian and military interest for operating in the undersea domain. Undersea distributed networked systems (UDNS) consisting of sensors, unmanned vehicles, platforms, influencers, command/control and, most important, human systems networked to create effects that can be summoned for advantage promise to be a key enabler for military and civilian undersea operations. Presented is a description of the nature and development framework of UDNS, including fundamental functionalities, user paradigm shifts, and operational capabilities tradespace. Traditional system engineering processes are seen to be necessary but not sufficient for engineering UDNS as a complex system; new methods and processes of evolutionary engineering applied to UDNS will be discussed.
Achieving a balance in distributed sensor fields
Authors: Henrick Robert
Published: September 2008

The challenges for DNS processing result in a balance between the laws of Moore, Shannon, probability, and physics, and the key limitation of wireless systems: Energy. Moore’s law supported by the demand for increasingly sophisticated portable electronics indicates that the amount of computations per watt of power continues to decrease. This not only supports increasingly sophisticated sensor processing, but also sophisticated routing such as ad hoc networking and RF components. Shannon’s law provides an invariant set of communication limits, from the amount of power required to send a bit of information to the amount of information in a shared or dedicated RF link. The laws of probabilities imply that to retain a constant field false report rate, false alarm rates per sensor resolution cells (e.g., range, Doppler,...) must decrease with the number of sensors, requiring per sensor OR collaborative behavior exploiting differences in target and clutter correlation statistics. Finally, the laws of physics impose constraints key to the system, such as sensor detection ranges, RF Line of site, and physical sensor size. This talk examines these issues in the context of generic distributed systems and recommends areas of promising research.
The predictability of signal time modulation, induced by nonlinear internal waves for sound transmissions in the South China Sea
Authors: Simon Alban , Colosi John
Published: September 2008

Acoustical remote sensing in the shallow water environment must contend with several confounding factors, one of which is scattering from nonlinear internal waves (NLIWs). An important consequence of sound interaction with NLIWs is the time modulation of the signal as the NLIW propagates across the transmission path. Observations and modeling studies from the shallow water acoustic random medium experiment suggest that this modulation may be more deterministic than random. Using observation from the 2001 South China Sea Experiment in which distinct trans-basin NLIWs were observed propagating across the transmission path, the time modulation of low order mode phase and energy is quantified. The observed time modulation of the modes is compared to a simple analytic model to establish the predictability of ISW-induced modulation. If the scattering by NLIWs is not too strong, the model could be a useful tool in surveillance and ocean-monitoring systems.
Distributed-system detection in correlated clutter
Authors: Abraham Douglas A.
Published: September 2008

Distributed sonar systems decide if a target is present through use of a rule that combines information from each individual sensor. The most basic of these are the ‘‘and’’ and ‘‘or’’ data fusion rules. Analysis of these rules has typically been restricted to cases where the target is detected on some number of sensors, and the false alarms are assumed to arise from processes that are statistically independent from sensor to sensor. In active sonar systems operating in clutter-dominated areas, this assumption may be far from the truth. Active sonar clutter often has its origins in scattering from physical objects (e.g., shipwrecks, fish schools, rock outcroppings, or mud volcanoes). Particularly when the scatterers are small in terms of wavelengths, this leads to false alarms that can be highly correlated from sensor to sensor. In this work, clutter scattering is assumed to arise from a finite number of scatterers with an exponentially-distributed size, which would lead to a K-distributed matched-filter envelope. The performance of the ‘‘and’’ and ‘‘or’’ fusion rules is then evaluated for two sensors with partially overlapping resolution cells. The resulting detection statistics from the two sensors are not independent, necessitating approximation of the joint distribution function.
Effect of Resolution on Synthetic Aperture Sonar Image Statistics
Authors: Johnson Shawn F. , Lyons Anthony P. , Abraham Douglas A.
Published: September 2008

Synthetic Aperture Sonar (SAS) images often exhibit large inter-pixel intensity fluctuations owing to the small resolution scales of such systems, with the reverberation envelope probability density potentially being significantly heavier-tailed than the Rayleigh distribution traditionally assumed for lower-resolution systems. The K-distribution has been shown to well describe sonar reverberation over a wide range of resolutions, with the shape parameter being proportional to the resolution cell size or inversely proportional to the bandwidth. The resolution cell size can be increased by restricting the bandwidth of the data in post processing, which in turn reduces the tails of the reverberation envelope for a higher matched K-distribution shape parameter. Broadband acoustic data suitable for SAS processing collected as part of the SAX04 experiment has been analyzed, and results concerning image resolution and statistics of such data will be presented.
An experiment to investigate aural classification of coherent-source active sonar data
Authors: Young Victor W. , Hines Paul C. , Scrutton Jeff
Published: September 2008

Active sonar performance is degraded by the presence of environmental clutter objects, which lead to false alarm echoes. Earlier research suggests that perceptual signal features similar to those employed in the human auditory system can be used to automatically discriminate between impulsive-source target and clutter echoes, thereby improving sonar performance by reducing the number of false alarms [V.W. Young et al., Can. Acoust. 34(3), 50–51 (2006)]. The present work attempts to extend these findings to the realm of coherent-source active sonar echoes. To this end, an experiment was conducted on the Malta Plateau using a cardioid towed-array and broadband FM sweeps running from 500 Hz up to 3.5 kHz. The data set consists of hundreds of pulse-compressed echoes from several targets, shipwrecks, and clutter objects. It includes both monostatic and bistatic echoes, as well as echoes recorded at different aspect angles and at different propagation ranges between roughly 5 km and 30 km. In this paper the experiment is reviewed and preliminary results are presented for an automatic classifier that employs features based on a simple auditory model.
Statistical analysis and modeling of active sonar echoes from a shipwreck
Authors: Abraham Douglas A.
Published: September 2008

A statistical analysis of active sonar echoes from a shipwreck at 36° 18.804′ north by 14° 41.136′ east (Malta Plateau region in the Mediterranean Sea) is performed as a function of azimuth at both 2 km and 10 km range for broadband transmit waveforms in low- and mid-frequency bands. The data were taken in May 2007 during the NATO Undersea Research Centre (NURC) Clutter 2007 sea trial. The data are compared with standard probability density function models and seen to be extremely heavy-tailed with respect to Rayleigh and even K envelope distributions. Models containing a coherent scattering component (e.g., Rician and generalized K) are seen to provide a better fit to the data. Statistical measures from the two different ranges and two different frequency bands are seen to be correlated as a function of azimuth indicating minimal changes in the statistics of the scattering. [This work was sponsored by the Office of Naval Research under contract number N0001407C0092 and made possible by the CLUTTER Joint Research Project (JRP), including as Participants the NURC, Pennsylvania State University-ARL-PSU (USA), Defence Research and Development Canada-DRDC-A (CAN), and the Naval Research Laboratory-NRL (USA).]
Ocean acoustic effects of explosions on land: Evaluation of Cook Inlet beluga whale habitability
Authors: Tremblay Sara K. , Anderson Thomas S. , Pettit Erin C. , Scheifele Peter M. , Potty Gopu R. , Miller James H.
Published: September 2008

The Eagle River Flats is an impact region for artillery at Fort Richardson, Alaska. Adjacent to the Flats is the Knik Arm of Cook Inlet which is the habitat for a distinct population of beluga whales (Delphinapterus leucas). In order to assess the effects of 155 mm artillery explosions on the habitat of these whales, a series of 6.8 kg C4 plastique charges were detonated on land 500 meters from the waters edge. In addition to land seismic and acoustic arrays, hydrophones were deployed in the Knik Arm at high and low tide. This paper discusses the ocean acoustic measurements. The received signal 30 meters from the shore in water depths of 8 meters was more intense at high tide, with broadband peak levels of approximately 180 dB re 1 microPa. The dominant frequency was about 20 Hz and most of the received acoustic energy was below 500 Hz. The geology and oceanography of the area were used to model the acoustic time series. Modeled and measured time series are compared to validate the geophysical model and provide estimates of peak pressure and energy flux density over the near shore habitat. [Work supported by U.S. Army Corps of Engineers, CRREL.]
Acoustic environments of bottlenose dolphins (Tursiops truncatus) in the Big Bend region of Florida
Authors: Rycyk Athena , Nowacek Douglas
Published: September 2008

The researchers examined the acoustic environments of coastal bottlenose dolphins (Tursiops truncatus) in the Big Bend region of Florida, one of the most pristine coastal environments in the state, by means of remote autonomous acoustic recorders deployed at eight sites. The rates and types of dolphin vocalizations (whistles, echolocation, burst-pulse calls, and pops) differed between the eight sites. Dolphins were not the only source of noise in their marine habitat; other biological and anthropogenic sounds occurred. Each site was found to have a unique soundscape with respect to dolphin, fish, snapping shrimp, and anthropogenic sound. Toadfish (Opsanus beta), silver perch (Bairdiella chrysoura), and sea catfish (Arius felis) were the only identifiable fish species to produce sound and each caused notable increases in sound levels at low frequencies where they vocalized. Locations exhibited different time peaks in fish produced sounds. Overall, anthropogenic noise was uncommon and only found in the form of boat noise. Surprisingly, dolphin vocalizations were not found at all locations only at Alligator Harbor, Dog Island, Carabelle River, and West Pass. The lack of dolphin vocalizations does not imply dolphins were not present in these regions only that no dolphins were vocalizing at the time of recordings.
Sperm whale tracking in the Bahamas: One hydrophone, three dimensions
Authors: Tiemann Christopher O.
Published: September 2008

A passive acoustic localization method for tracking the movement of a clicking sperm whale in three dimensions using data from just one hydrophone is demonstrated, using data made available for the 3rd International Workshop on Detection and Classification of Marine Mammals. One recording contains sperm whale clicks recorded on a bottom-mounted hydrophone on a steep slope of the Navy’s AUTEC test range. When the direct-path acoustic ray arrivals from several clicks are time-aligned, persistent associated multipath arrivals of reflected ray paths can be identified for each click event and used for localization. Although the use of multipath arrival information is a standard procedure for range-depth tracking, a three-dimensional estimate of whale position can be obtained from the same multipath information with knowledge of an azimuthally-dependent environment, relative to the receiver. In this case, azimuthal distinction arises from varied bathymetry. Multipath arrival patterns are matched to unique range-, depth-, and azimuth-dependent modeled arrival patterns to make an estimate of whale location. A three-dimensional whale track in range, depth, and bearing from the fixed hydrophone will be presented.
Tracking baleen whales using the relative relocation method
Authors: Berchok Catherine L. , D’Spain Gerald L. , Hildebrand John A.
Published: September 2008

Passive acoustic tracking of baleen whales is typically accomplished using time-of-arrival difference measurements from widely-separated acoustic sensor arrays. Because these arrays are large, the propagation conditions along the paths from the source to each of the receivers can be quite different, causing the received signal characteristics to vary among arrivals from the same vocalization. These signal variations introduce uncertainty in the time-of-arrival difference measurements, which in turn creates scatter in the localizations, obscuring the tracks of the individual whales. The relative relocation method, developed in the seismic community, provides a means of reducing scatter in the localizations by using the differences in time-of-arrival differences to adjust the locations of signals relative to one another. The method, as used for earthquake localizations, will be described, then applied to a set of fin whale vocalizations recorded on an ocean bottom seismometer array deployed off southern California. The results provide better defined tracks with less scatter than traditional localization techniques.
Whale tracking underwater: High frequency acoustic pingers and the instrumented tag (DTAG)
Authors: Schmidt Val E. , Weber Thomas C. , Ware Colin , Arsenault Roland , Wiley David , Johnson Mark P. , Dawe Erik , Friedlaender Ari S.
Published: September 2008

Since 2004, scientists have been tagging and tracking humpback whales in Stellwagen Bank National Marine Sanctuary to better understand their behavior. Stellwagen Bank is a shoal area east of Boston and north of Cape Cod, MA where many species of baleen whale feed during the summer months. Instrumented tags (DTAGs) are suction-cupped to the whales back from a RHIB. DTAGS, developed at WHOI, record whale pitch, roll, and heading, 3-D acceleration, depth, and sound for up to 20 h. A pseudotrack for the tagged whale can be generated using visual fixes at the surface and dead-reckoning while the whale is underwater. During extended dives, the solution is expected to exhibit substantial drift, placing limits on the ability to understand feeding behavior, mother-calf interactions, etc. In order to develop higher accuracy whale tracks, three GPS-positioned high-frequency (25–32 kHz) acoustic pingers were deployed around tagged animals in July 2007. The pingers produce time-encoded pulses from known positions, which are recorded along with whale vocalizations and ambient noise on the whale tag. Pulse arrival times from each pinger are converted into ranges from the known pinger locations to generate an underwater whale track. Results from this work will be presented.
Acoustic identification of beaked and sperm whales
Authors: Ioup George E. , Ioup Juliette W. , Pflug Lisa A. , Tashmukhambetov Arslan M. , Sidorovskaia Natalia A.
Published: September 2008

Identification of individual marine mammals acoustically was initially motivated in this research by spectrograms of the littoral acoustic demonstration center Northern Gulf of Mexico data containing sperm whale click codas, which showed that clicks in a coda have a spectral pattern that persists across all the clicks in that coda. The hypothesis is that each coda originates from a single whale, and all codas with similar properties come from the same whale. Self-organizing maps (SOMs) are used to compare and classify the time series, Fourier transforms, and wavelet transforms of each coda in order to determine how many whales are present. The results show that SOMs have promise for classifying underwater acoustic coda signals from sperm whales. A similarity measure has been applied to both coda and echolocation clicks and has shown some success in associating both types of clicks with individuals. Other forms of cluster analysis are also considered. Progress in the classification of sperm whale clicks has motivated the application of similar analysis to beaked whale echolocation clicks. Time-frequency plots show interesting details. Preliminary results for beaked whale click analysis are presented. [Research supported by ONR.]
Spawning behavior and spatial distribution of Atlantic herring on Georges Bank revealed by ocean acoustics waveguide remote sensing
Authors: Gong Zheng , Cocuzzo Daniel , Andrews Mark , Ratilal Purnima , Jagannathan Srinivasan , Makris Nicholas , Pena Hector , Patel Ruben , Jech J. Michael
Published: September 2008

An ocean acoustics waveguide remote sensing (OAWRS) system was deployed in the Gulf of Maine, near Georges Bank to image Atlantic herring and other fish population from September–October 2006. OAWRS provides spatially unaliased imaging of herring over wide areas, spannning over 100 km diam. Migration and spawning behavior of Atlantic herring were observed using OAWRS over several diurnal periods, including massive movements on and off the bank to spawn. Measurements made simultaneously with a conventional fish-finding echosounder (CFFS) and a multibeam sonar provide the depth distribution and local 3-D morphology, respectively, of the herring schools in the water column. Concurrent trawl surveys provide identification of the fish species. Measurements made by OAWRS and CFFS systems are highly correlated. Examples will be provided of the co-registration between the two systems over a one-week period. Calibration of the OAWRS system using CFFS estimates of fish population densities, along with a full-field scattering model that takes into account both coherent and incoherent scattering from a fish group, is discussed. Resonance scattering behavior of herring is observed in the OAWRS system with significant changes in scattering amplitude over the 300 Hz to 1.5 kHz frequency range of the OAWRS system.
Measurement of material properties of two gelatinous, coastal zooplankton
Authors: Smith Joy N. , Warren Joseph D.
Published: September 2008

Acoustic scattering models for zooplankton are often used to transform acoustic data (backscattered energy) into biological units (number or size of animals). In order for these models to be used successfully, accurate descriptions of the animals themselves are required including: Species, size, orientation, and their material properties, specifically the density and sound speed of the organism relative to their surroundings. Measurements were made of the density and sound speed of two coastal, gelatinous zooplankton (ctenophore (Mnemiopsis leidyi), lion’s mane jellyfish (Cyanea capillata)) found in the waters around Long Island, New York. Two different methods were used to determine the density of these zooplankton, while an acoustic-travel-time approach was used to measure the sound speed of these animals. Mean animal density was related to animal size for both species and varied between individuals. Values of density and sound speed are reported and their implications with regard to the use of acoustic surveys to assess gelatinous zooplankton are discussed. [Work supported by NSF.]
A feed-back algorithm using ocean acoustic modeling to improve shallow water soliton simulations
Authors: Chin-Bing Stanley A. , Warn-Varnas Alex C. , King David B.
Published: September 2008

Ocean solitons can affect the acoustic signals that travel through them. The effects can range from slight to severe. Computer simulations can be used to predict the large-scale effects on the acoustic signal. The typical sequence of events requires that an ocean model be initialized by tidal velocity and used to estimate the changes in the environmental parameters due to soliton creation and propagation. Changes in the environment are used to calculate the related changes in the ocean sound speed field. The last step is to run an ocean acoustic computer model to predict the changes in the acoustic signal. Often, the tidal velocity is not precisely known and assumptions have to be made. Any variations in the tidal velocity require the time consuming sequence to be repeated. Recently, we have demonstrated a way of estimating the soliton structure that could affect the acoustic signal. This estimation is made before any ocean model simulation is made. This can greatly reduce the number of computer simulations, since only ocean model simulations are made for those conditions that might significantly affect the acoustic signal. Examples will be shown that illustrate this acoustic ‘‘feedback’’ method. [Work supported by the NRL Base program.]
Acoustic cost functions for autonomous adaptive sampling
Authors: Heaney Kevin D.
Published: September 2008

Recent advances in ocean modeling have provided the opportunity to forecast ocean conditions out to 48 h. Accuracy of these models is determined primarily by the input conditions (boundary, as well as internal state). An automated algorithm for adaptively sampling the ocean environment has been developed with the goal of providing sampling paths for regions where input drives the model solutions the most. In this paper, a set of acoustic cost functions is presented, which should indicate regions where acoustic propagation is most sensitive to model uncertainty and/or model-predicted temporal variability. The four cost functions explored will be: Matched mode coherence, mode coupling coefficients, transmission loss variability, and detection range coverage. This technique will be applied to the data-assimilated model results from the Shallow Water 2006 experiment, where oceanographic measurements consisted of a large array of thermistors, six gliders operating continuously, and a ship towed scanfish. Acoustic measurements included fixed source/receivers, AUV mounted sources, as well as sonobuoy receivers. Sampling guidance based upon the acoustic cost functions will be used in an observational systems simulation experiment (OSSE), in collaboration with Pierre Lermusiaux and his group at MIT. For the ocean modeling, data assimilation and sampling suggestions see http://modelseas.mit.edu.
Effects of offshore mesoscale eddies and fronts on inshore shallow water acoustic propagation
Authors: Deferrari Harry
Published: September 2008

Shallow water shelf areas inside of western boundary currents have two distinctly different ocean acoustic environments determined by the type of front that separates deep offshore from shallow inshore. Prograde fronts allow for the ducting of offshore internal waves up onto the shelf as the main source the sound speed fluctuations over the internal wave band. Retrograde fronts block the propagation of offshore internal waves setting up stability conditions that allow for propagation of locally generated, large amplitude non-linear solitary waves as the major source of sound speed variability. Here, acoustic propagation is examined for both environments with data from two similar fixed system propagation experiments, one for the prograde environment off the coast of south Florida near the site off the Acoustic Observatory, and the second for the retrograde front environment of the Mid-Atlantic Bight the SWO6 site. Offshore mesoscale features of fronts and eddies are shown to determine mean sound speed profiles and the energy of the internal wave fields. In turn, intensity fluctuations and temporal coherencies of broadband acoustic signals over several octaves are observed to vary with variations of the sound speed. For some locations, observations of mesoscale features alone can predict sonar performance.