bluuebunny/crossref_metadata_2025 huggingface dataset:
Propagation of radially polarized shear wave beams with cubic and quadratic nonlinearities.
Authors: Spratt Kyle S. , Wochner Mark S. , Ilinskii Yurii A. , Zabolotskaya Evgenia A. , Hamilton Mark F.
Published: July 2011

This presentation describes an extension of the work by Wochner et al. [J. Acoust. Soc. Am. 123, 2488–2495 (2008)], wherein a coupled pair of nonlinear parabolic equations was derived for the two components of the particle motion perpendicular to the axis of a shear wave beam in an isotropic hyperelastic medium. Although the equations derived in that work contain both cubic and quadratic nonlinearities, the latter were discarded based on the fact that they are not present in plane shear waves, and hence assumed negligible within the quasiplane paraxial region of linearly polarized shear wave beams. However, the experimental observation of prominent second harmonic generation by nonplanar shear waves in soft solids [Jacob et al., J. Acoust. Soc. Am. 122, 1917–1926 (2007)] has motivated a more thorough understanding of these quadratic nonlinear terms. In the present work, the quadratic nonlinearity is explored, and, in particular, it is found that the form of this nonlinearity simplifies for axisymmetric radially polarized beams. Numerical results are presented comparing the effects of the cubic and quadratic nonlinearities on the generation of harmonics along the beam axis and the directivity patterns of those harmonics. [Work supported by the ARL:UT McKinney Fellowship in Acoustics.]
Optical freezing of Faraday waves for precise pore distributions in tissue scaffolds.
Authors: Sampathkumar A. , Klapperich C. M. , Saylor J. R. , Holt R. G.
Published: July 2011

Collagen-glycosaminoglycan (GAG) tissue scaffolds have been widely employed to function as the structural support and nutrient-supply for in vitro and in vivo cell growths. The traditional scaffold fabrication process may take up to 3 days to complete, with the pattern formation step requiring nearly 24 h. We describe a bench-top optical curing system that implements a novel fluid-acoustic technique that uses Faraday waves for rapid fabrication/prototyping of tissue scaffolds on the time-scale of minutes. The scaffold patterns and spacings are easily variable by varying the frequency and the amplitude of the Faraday waves. The experimental setup incorporates a 450 mJ/pulse Nd:YAG laser operating at 532 nm to photopolymerize the Faraday wave patterns generated using 30 kHz vibrations on the GAG emulsions. Preliminary results on freezing Faraday patterns on photoresists and a study of the acoustic driving and the optical curing parameter spaces will be presented.
Characterization of the acoustic field of a clinical electromagnetic shockwave therapy device.
Authors: Perez Camilo , Chen Hong , Matula Thomas J.
Published: July 2011

Extracorporeal shockwave therapy devices are used in clinical settings for different medical applications such as orthopedics and urology. Having several clinical devices out in the field creates a challenge when comparing treatments and energy deposition mechanisms between different devices. In this work, the field of an electromagnetic shockwave device (Duolith SD1 T-Top, Storz) was characterized using a fiber optic hydrophone (FOPH2000, RP Acoustics). The acoustic field from two hand-held probes was measured: one probe was focused (with different length coupling cones) and the second one was a ballistic (radial therapy) probe. With the focused probe, measured pressures ranged from 45 MPa peak-positive to 12 MPa peak-negative. Axial and transverse beam profiles were acquired while analyzing the peak-positive and peak-negative pressures at each machine energy level and pulse repetition frequency. The focused source showed an extended −6 dB peak-positive focal region along the axis of propagation and shorter in the orthogonal planes to the propagation (30 × 3 × 3 mm3). Linear scans along the axis of propagation showed quadratic decay distal to the focus. Measured peak-negative pressures were higher pre-focal than post-focal. The results compared qualitatively, but not quantitatively with manufacturer specifications. [Work supported by NIH AR053652.]
Effect of language, speaking style and talker on a spectral rhythm measure.
Authors: Rao Gayatri , Smiljanic Rajka
Published: July 2011

Recently, two spectro-temporal approaches have been proposed for characterizing cross-language and disordered speech rhythm: power spectrum [Tilsen and Johnson (2008)] and speech envelope modulation spectrum (EMS) [Liss et al. (2010)]. These measures quantify the rhythmicity of speech within specified frequency bands. In the present study, the EMS measure was employed to assess the effect of language, speaking style, and talker on rhythm. In order to examine the rhythmic characteristics of conversational and speaking styles in English and Croatian, utterances produced by two female speakers of each language in clear and conversational speaking styles were analyzed [Smiljanic and Bradlow (2005)]. The spectral centroid, a weighted mean of a spectrum, was used to measure the center of mass of the EMS extracted for each utterance. Results from nested factorial analyzes revealed that the spectro-temporal characteristics differed for English and Croatian, for the conversational and clear speaking sentences, and for individual talkers. These results suggest that the low rate amplitude modulations of a signal can be used to distinguish rhythmic properties across languages, speaking styles, and talkers. Furthermore, these automated spectral measures provide a new means for characterizing rhythm that bypasses laborious manual measurements and phonologically dependent segmentation criteria.
Stable production rhythms across languages for bilingual speakers.
Authors: Carbonell Kathy M. , Lansford Kaitlin L. , Utianski Rene L. , Liss Julie M. , Sullivan Sarah C. , Lotto Andrew J.
Published: July 2011

There has been a great deal of work on classifying spoken languages according to their perceived or acoustically-measured rhythmic structures. The current study examined the speech of 12 Spanish-English bilinguals producing sentences in both languages using rhythmic measures based on the amplitude envelopes extracted from different frequency regions—the envelope modulation spectrum (EMS). Using discriminant factor analysis, EMS variables demonstrated a moderate ability to classify the language being spoken suggesting that rhythmic differences between languages survive even when speaker is controlled. More interesting is the fact that EMS variables could reliably classify which speaker produced each sentence even across languages. This result suggests that there are stable rhythmic structures in an individual talker’s speech that are apparent above and beyond the structural constraints of the language spoken. The EMS appears capable of describing systematic characteristics of both the talker and the language spoken. [Work supported by NIH-NIDCD].
Rhythmic speech perception predicts novice musical composition in English and French.
Authors: Neuhoff John G. , Lidji Pascale
Published: July 2011

Music and speech have long been thought to have common cognitive underpinnings, and recent work demonstrates that the music of expert composers reflects the speech rhythm of their native language [H. Ollen (2003), P. Daniele (2003)]. In the current study, monolingual English speaking music novices composed simple “English” and “French” tunes on a piano keyboard. The rhythms produced reflected speech rhythms perceived in English and French, respectively. Yet, the pattern was opposite that produced by expert English and French composers and opposite that predicted by the acoustic determinants of speech rhythm that specify English speech as more rhythmically varied than French. Surprise recognition tests 2 weeks later confirmed that the music-speech relationship remained over time. Participants then rated the rhythmic variability of French and English speech samples. We found that native English speakers perceived French as more variable than English despite the measured greater variability of English. Finally, we repeated these procedures with a sample of monolingual French speakers and found similar, but opposite effects. The results suggest that common cognitive underpinnings of music and speech rhythm are more widespread than previously thought, and that novice rhythm production in music is concordant with perceived speech rhythms.
The role of lexical processing in the discrimination of English vowel contrasts by Spanish learners.
Authors: Lopez-Soto Teresa , Calvo-Carmona Daniel
Published: July 2011

In our study we present the results of measuring the discrimination of English vowel contrasts that prove to be particularly complex for Spanish learners of English in a lexical versus non-lexical context. We have developed a series of discrimination tasks in which we have used both lexical and non-lexical (non-words) stimuli for three minimal pairs: cat-cut, seat-sit, and sit-set. A group of 30 Spanish speakers trained on the discrimination of monosyllabic CVC English words and non-words in a perception task that included vowel discrimination. Lexical and non-lexical minimal pairs were randomly presented and participants received feedback after their response. Results showed the following. (1) For all three vowel contrasts, perception accuracy as being measured in a discrimination task proved to be higher for lexical words (mean 79.2%) than for non-words (mean 57.6%) in the pre-test. (2) After four 1-h perception training sessions, all participants improved in every vowel contrast, but the results were comparatively higher for non-lexical (mean 80.1%) than for lexical words (85%). A post-training questionnaire was used to make sure that participants could correctly identify both lexical and non-lexical words. We believe that this study lays ground for further investigation on the limits of phonological processing and lexical access.
Lexical effects on nasal coda neutralization in Taiwan Mandarin.
Authors: Li Yingshing
Published: July 2011

Recent disputes concerning lexical effects on speech variability in speech production are whether these effects are due to lexically selective encoding processes or post-access phonological processes. This study investigates how lexical variables (inherent frequency and contextual predictability) affect nasal coda neutralization (alveolar /n/ versus velar /ŋ/) in Taiwan Mandarin, as measured in degree of vocalic nasalization (A1-P0 and A1-P1), formant transition (F1, F2, and F3), and nasal consonant duration and intensity. Participants read a random list of 527 monosyllabic Chinese morphemes in a speeded naming task. The results of linear regression reveal that (1) while sociolinguistic (genders and home languages), phonological (adjacent segmental features), orthographic (familiarity of characters and accuracy of transcription), and processing variables (response times and speaking rates) are factored out, lexical variables are found to enhance nasal coda neutralization; (2) however, a larger proportion of the variance is predicted by the correlation of both lexical and processing variables, suggesting that phonological planning and articulatory velocity are the means of achieving lexically-driven nasal coda neutralization.
Individual differences in spoken word recognition: Regional dialect variation.
Authors: Tamati Terrin N. , Gilbert Jaimie L. , Pisoni David B.
Published: July 2011

Regional dialect is an important source of variation in the speech signal. However, little is known about individual differences in the ability to perceive and accommodate for this type of variability. In the current study, individual listeners’ performance on a speech recognition task with different American English (AE) dialects was explored. Ninety-eight listeners completed a novel high-variability sentence recognition task (PRESTO), which contains sentences produced by talkers from seven AE dialect regions. Correlational analyzes were carried out on performance on the task and scores from a self-report questionnaire on executive function. Results revealed significant correlations between measures of behavioral regulation (executive function) and performance accuracy for several of the standard and non-standard talker dialects. This was especially the case for non-mobile listeners, who had lived in only one dialect region before the age of 18, as opposed to mobile listeners, who had lived in more than one dialect region before the age of 18. These findings indicate possible group differences based on both residential history and basic underlying cognitive abilities in adapting to differences in regional dialect variation. The results will be discussed with respect to individual differences in the perception of indexical properties of speech under adverse listening conditions.
The effect of semantic context on speech intelligibility in reverberant rooms.
Authors: Srinivasan Nirmal Kumar , Zahorik Pavel
Published: July 2011

Although it is well known that semantic context affects speech intelligibility and that different reverberant rooms affect speech intelligibility differentially, these effects have seldom been studied together. Revised SPIN sentences in a background of Gaussian noise in simulated rooms with reverberation time (T60) of 1 and 0.25 s were used. The carrier phrase and the target word of the speech stimuli were manipulated to be either in the same room or in different rooms. As expected, intelligibility of predictable sentences was higher compared to unpredictable sentences—the context effect. The context effect was higher in the low-reverberant room as compared to the high-reverberant room. When the carrier phrase and target words were in different rooms, the context effect was higher when the carrier phrase was in the low-reverberant room and target word in the high-reverberant room. For predictable sentences, changing the target word from high-reverberation to low reverberation with a high reverberant carrier increased intelligibility. However, with a low-reverberant carrier and different rooms for the target word, there was no change in intelligibility. Overall, it could be concluded that there is an interaction between semantic context and room acoustics for speech intelligibility.
Dyadic postural coordination and discourse structure.
Authors: Oberg Martin A. , Barbosa Adriano , Vatikiotis-Bateson Eric
Published: July 2011

This study reports on the relationship between coordinated behavior in dyadic conversation and discourse boundaries in audio-visual and audio only conditions over various conversation tasks. Instantaneous inter- and intraspeaker correlations of time varying head motion and body posture are analyzed for cues marking turn-taking behavior and are compared against human-labeled discourse boundaries. Transitions in two-dimensional (time and delay lag) instantaneous correlation are compared across conditions. Implications for the structure of interaction and development of entrainment in dyadic conversation are discussed. Preliminary analyzes of correlations from mismatched conversations suggest the existence of rhythmic behaviors characteristic of conversation in general. Differences between AV v A only conditions suggest the importance of visual feedback in postural entrainment.
Effects of morpheme boundaries on the timing of fundamental frequency (F0) peaks.
Authors: Chang Seung-Eun
Published: July 2011

This research examines the effects of morpheme boundaries on the timing of fundamental frequency (f0) peaks and demonstrates that phonetic realization is influenced by morphological structure. It reports the timing of f0 peak and peak plateau in monomorphemic HH (high, high tone) and HL (high, low tone) as well as bimorphemic H+H and H+L in South Kyungsang Korean, spoken in the southeastern part of Korea. The results show that f0 peak came significantly later in bimorphemic H+H than in monomorphemic HH and peak plateau was significantly longer for monomorphemic HH than for bimorphemic H+H. It suggests that f0 peak plateau is implemented more stably within a single lexical item than across a boundary between lexical items. However, a significant morpheme effect was not found in monomorphemic HL and bimorphemic H+L. In accounting for these asymmetrical results, several hypotheses were discussed including speakers hyperspeech effort [H&H theory, Lindblom (1990)], intrinsic vowel height on f0 [Hombert et al. (1979)], and f0 peak delay effect on phonologically suggested H tone spreading [de Jong and McDonough (1993)]. It is proposed that the bimorphemic H+H in this language is the phonetic image of the f0 peak delay effect of high tone.
Acoustic correlates of stress and their use in diagnosing syllable fusion in Tongan.
Authors: White James , Garellek Marc
Published: July 2011

The first goal of this study is to determine which acoustic cues correlate with stress in Tongan. Preliminary data indicate that pitch (F0), duration, and vowel height (F1) are the best cues to stress. Differences are also found for vowel frontness (F2), intensity, and voice quality. The second goal is to use these acoustic stress correlates to test for syllable fusion, an alleged phonological process in Tongan by which sequences of vowels in separate syllables fuse into a single syllable (e.g., Poser 1985). Lower-to-higher sequences (e.g., /ai/) are said to undergo fusion while higher-to-lower sequences (e.g., /ia/) are not. However, no empirical studies have been conducted testing these claims. Using the acoustic stress cues identified for Tongan, these two types of sequences are compared, where the first vowel of each sequence falls in a stressed position. For higher-to-lower sequences (e.g., /ia/), the first vowel should show acoustic cues of stress whereas the second vowel should appear unstressed. For lower-to-higher sequences (e.g., /ai/), if syllable fusion occurs, acoustic stress cues should be present over the entire sequence; otherwise, stress cues should be seen only on the first vowel as in nonfusing higher-to-lower sequences. Preliminary data indicate that syllable fusion does occur.
Low frequency scattering from elastic objects embedded in a waveguide by the finite element technique.
Authors: Abawi Ahmad T.
Published: July 2011

Computation of scattering from an object in a waveguide is a challenging task because of the enormous size of the computational domain. It requires the solution of the wave equation by simultaneously satisfying the boundary conditions on the surface of the object and the boundaries of the waveguide. While the finite element solution of scattering from an object in free space can be managed by limiting the size of the computational domain by the use of infinite elements or perfectly matched layers for an object in a waveguide, the waveguide itself is part of the computational domain. Since an accurate solution requires that the computational domain be discretized at least at one-tenth of the acoustic wavelength for a computational domain tens or hundreds of wavelength large, this results in very large systems of equations, whose solution is a daunting numerical task. To cope with the numerical complexity, in this paper we use the principles of fluid-structure interaction to compute scattering from the object using the finite element technique and couple it to the waveguide using the Helmholtz–Kirchhoff integral, where acoustic propagation models are used to compute the environment Green’s functions. The technique is applied to buried and proud objects.
Acoustic scattering from underwater munitions near a water-sediment interface.
Authors: Kargl Steven G. , Williams Kevin L. , España Aubrey L. , Kennedy Jermaine L. , Marston Timothy T. , Lopes Joseph L. , Lim Raymond
Published: July 2011

Monostatic and bistatic scattering measurements were conducted on a set of targets near a fresh water-sand sediment interface. The measurements were performed during March 2010 and are referred to as the Pond Experiment 2010 (PondEx10). Monostatic synthetic aperture sonar (SAS) data were collected on a rail system with a mobile tower, while a stationary sonar tower simultaneously collected bistatic SAS data. Each tower is instrumented with receivers while the sources are located only on the mobile tower. For PondEx10, 11 targets, including 6 underwater munitions, were deployed at 2 ranges from the mobile tower system. Initially, the data were processed using standard SAS techniques, and then, the data were further processed to generate acoustic templates for the target strength as a function of frequency and aspect angle. Results of the data processing from proud targets are presented. Finite element model (FEM) predictions of the scattering from an ordnance in the free field and proud on the interface are also discussed. A processing technique that separates an individual target’s response from nearby targets is also briefly discussed. [Research supported by the SERDP and the ONR.]
Multistatic scattering by scaled metallic targets: Experimental results and modeling.
Authors: La Follett Jon R. , Lim Raymond
Published: July 2011

Multistatic scattering measurements provide multiaspect target information that can potentially be used for classification. In the present work, bistatic and monostatic scattering measurements are conducted on multiple solid metal scaled targets using a previously described small scale test bed facility [Malvoso et al., J. Acoust. Soc. Am. 127, 1748 (2010)], and comparisons are made. Line-scan configurations with fixed and moving sources are used to construct monostatic and bistatic synthetic aperture sonar images for targets in the free field and proud on scaled sediment. One bistatic configuration uses a fixed source and two receivers that are scanned along parallel lines. The alternate bistatic configuration uses a translating source-receiver and a fixed receiver to obtain scattering information in quasi-forward directions while simultaneously acquiring monostatic measurements. Comparing monostatic and bistatic results demonstrate that, for certain cylinder orientations, bistatic scattering is dominated by specular reflection while monostatic scattering collected along the same receiver scan line is mostly due to elastic target responses. Several elastic scattering responses can be interpreted using ray models involving leaky-Rayleigh waves. Data-model comparisons are also made with T-matrix calculations for solid aluminum cylinders and stainless steel spheres. [Research supported by ONR.]
Mode properties and coupling conditions for scattering by circular cylinders: Comparison of liquid-filled shells and solid cylinders.
Authors: Marston Philip L.
Published: July 2011

Simple circular cylinders are sometimes used as proud test objects when developing and testing sonar systems in realistic environments [Williams et al., J. Acoust. Soc. Am. 127, 3356–3371 (2010)]. In endeavors of this type it remains important to have a good physical understanding of the coupling of sound to the modes of infinite and finite tilted and broadside circular cylinders. The present talk reviews some experimental and theoretical investigations of the free field scattering properties including some results of quantitative ray theory for scattering amplitudes. Plotting the frequency response as a function of the tilt angle of a cylinder reveals coupling loci normally associated with axial modes of the cylinder. In certain limiting cases the coupling loci for helical modes of solid metallic cylinders resemble the coupling loci for liquid-filled shells having appropriate boundary conditions. It is also possible for internal modal properties of long liquid-filled metallic shells to modulate the backscattering amplitude of meridional ray features. [Work supported by the ONR.]
Scattering by square and rectangular metallic cylinders: Circular synthetic aperture sonar images and spectral coupling loci.
Authors: Smith Anthony R. , Plotnick Daniel S. , Marston Timothy M. , Marston Philip L.
Published: July 2011

Reversible circular synthetic aperture sonar (CSAS) is one approach to displaying and studying the evolution of monostatic sonar data with changes in the orientation of the viewed object. The present investigation concerns the evolution of backscattering by a solid slender square brass cylinder and a rectangular brass cylinder, both objects being examples of a horizontal rectangular parallelepiped elastic waveguide. In both cases, substantial elastic glints are visible in CSAS images for orientations suitable for generating surface guided elastic waves. The square cylinder is also useful for examining the effect of changing the azimuthal orientation relative to the cylinder’s axis and the direction of the horizontal illumination. While rotating the azimuthal angle by 45 deg greatly modifies the magnitude of the backscattering, some of the frequency domain coupling loci (functions of rotation of the cylinder’s axis about a vertical axis) are in common for both orientations. After azimuthal rotation, an apex line of the cylinder is viewed by the transducer instead of the cylinder’s long flat side. This kind of spectral investigation is relevant to characterizing the coupling loci for elastic waveguides lacking the rotational symmetry of a circular cylinder. Additional insight is obtained from the CSAS images. [Work supported by ONR.]
A model for under-ice-target acoustic scattering.
Authors: Bishop Garner C.
Published: July 2011

A model is described that has been developed to calculate the scatter of a high-frequency acoustic pulse that originates from a stationary source and is incident on and is scattered from the under-ice surface characteristic of the Arctic and from a stationary target. The under-ice surface is modeled by an ensemble of ice keels and ice keels are modeled by an ensemble of ice blocks with rectangular facets. The Helmholtz–Kirchhoff integral in the Kirchhoff approximation is used to calculate the scatter from an ice facet. The scatter from an ice keel is given by a coherent sum of the scatter from all the ice facets. A T-matrix is used to calculate the scatter from the stationary target. The first order terms in the multiple scattering process between the target and the ice surface are also calculated, i.e., the scattering from the target of the free field scatter from ice facets and the scatter from ice facets of the free field scatter of the target. Numerical results show the extent to which the scatter from the target in the under-ice environment differs from its free field scatter.
Characterization of non-Gaussian, bistatic, echoes from a shipwreck.
Authors: Preston John R.
Published: July 2011

Sonar clutter is one of the primary limitations to active ASW. This work focuses on statistical analysis of clutterlike echoes from some bistatic measurements. Non-Gaussian characterizations of bistatic echoes from a shipwreck are presented. The received data are taken from the five octave research array (FORA) that has been used to collect extensive monostatic and bistatic data in two recent sea trials on the Malta Plateau off Sicily called Clutter 07 and BASE 07. This work uses data from the above mentioned sea trials to characterize non-Gaussian behavior of bistatic echoes from a shipwreck using pulsed sources in the 800–3500 Hz band. The page test is used to isolate the shipwreck echoes before processing. K-distributions with their shape and scale parameters are used to describe non-Gaussian behavior together with the models of Abraham and Lyons to infer physical descriptors from the echoes. The ability to georeference key statistical measures of clutter allows CFAR processors to adaptively set thresholds and reduce false alarms. Examples are shown to demonstrate this. Also included are presentations of the shape parameter versus bistatic aspect angle. [Work supported by ONR Code No. 321US].
Acoustic-derived indicators for marine reserve zoning, assessments, and monitoring in coral reef ecosystems.
Authors: Taylor J. Christopher , Burke John , Viehman Shay , Ebert Erik
Published: July 2011

The Tortugas Ecological Reserve was established in 2001 as a no-take research reserve extending the area of the Florida Keys National Marine Sanctuary. The Sanctuary is evaluating the effects of management areas, including the TER. In 2008 we initiated a fisheries hydroacoustic survey to compliment the visual census for reef fishes and coral communities that was initiated in 2000. The hydroacoustic survey was specifically designed to map the distribution and abundance of reef fishes in relation to the reserve boundary, and over a broader spatial extent that is possible using scuba divers. Biomass of large, exploited species observed by divers was significantly higher within the reserve, and biomass increased with proximity to the boundary. Fish densities assessed using hydroacoustics showed a similar pattern. We developed an indicator from the acoustic data analogous to the biomass size spectrum and found that biomass of larger size classes was higher within the reserve. Indicators produced from fisheries hydroacoustic surveys cannot only inform marine reserve design and monitoring, but can also enhance the interpretation of smaller-scale visual surveys by providing landscape-scale maps of fish densities at high spatial resolution.
Multiple frequency acoustic backscatter discrimination of zooplankton and fish scatterers in Cape Cod Bay in Spring 2010.
Authors: Warren Joseph D. , Patrician Melissa
Published: July 2011

During the late winter and early spring, Cape Cod Bay has large numbers of marine mammal and seabird predators that feed on aggregations of zooplankton (copepods) and fish (sand lance and herring). As part of a study investigating the foraging behavior of these top predators, we sampled the waters of Cape Cod Bay using multiple frequency (38, 120, 200, and 710 kHz) echosounders and a 600 kHz acoustic Doppler current profiler. To ground truth our data net tows and video plankton recorder casts were used to sample zooplankton, primarily small copepods, while a drop camera system was used to identify aggregations of fish. Combining the backscatter data with target strength estimates for the different scatterer types allowed us to estimate the identity, distribution, and abundance (numerical density) of zooplankton and fish in this area at spatial and temporal scales relevant to the foraging behavior of baleen whales. This method worked best when scattering aggregations were monospecific and target scattering spectra were distinct.
Introduction of multi-frequency acoustics and mid-water trawl sampling to the CALCOFI program.
Authors: Lara Lopez Ana , Davison Peter , Koslow J. Anthony
Published: July 2011

The CALCOFI program has evolved over time, continually expanding its interdisciplinary study of the southern California Current ecosystem. Historically, CALCOFI comprised studies of physical and chemical oceanography, phytoplankton, zooplankton, ichthyoplankton, marine mammals, and seabirds. However, there was little focus on the mid-trophic level and the mesopelagic micronekton. In 2010, multi-frequency acoustics, combined with mid-water trawl sampling, was introduced. Data were collected with an EK-60 equipped with five frequencies (18, 38, 70, 120, and 200 kHz) and a Matsuda–Oozeki–-Hu Trawl (MOHT). Frequency spectrums were generated for all organisms caught in the net using target strength models and categorized into different acoustic groups. Inverse techniques and dB differencing were subsequently used to estimate their abundance and distribution across the CALCOFI grid. [Work supported by NOAA and The Moore Foundation.]
Evaluating freshwater habitat restoration with active acoustics.
Authors: Madden Laura E. , Miksis-Olds Jennifer L.
Published: July 2011

The effectiveness of adding a submerged physical structure in order to increase fishery production is uncertain. Measuring fishery response to these alterations with conventional techniques is difficult. Electrofishing is a typical assessment method in freshwater fishery management and is often limited in sample size and sampling frequency. This study used active acoustic technology to evaluate the distribution and behavior of fish assemblages associated with added submerged rock structures in a reservoir currently undergoing habitat improvement. An acoustic water column profiler was deployed for three 1-week intervals at each of three replicate sites consisting of adjacent treatment areas with added rock structures and control areas without added structures. Electrofishing was conducted during each sampling interval. Fish abundance and behavior at each site were assessed from the volume backscatter time series and electrofishing data. Differences between areas with and without structures were compared. Combining acoustic technology with conventional assessment methods has enabled a more thorough evaluation of habitat restoration projects and helps guide the development of future conservation efforts.
Acoustic sea bed classification of Pacific Sand Lance habitat.
Authors: Biffard Ben R. , Chapman N. Ross , Bloomer Stephen , Robinson Cliff
Published: July 2011

This paper describes the results of preliminary acoustic sea bed classification surveys in three areas in the southern Gulf Islands of British Columbia to develop methods for mapping habitat of Pacific Sand Lance (PSL). Little is known about this important species, and much less is known about their use of subtidal burying habitat for overwintering. Grid surveys were run using a dual-frequency (24 and 200 kHz) single beam echosounder, and the data were classified using conventional statistical segmentation procedures using QTC IMPACT. This type of seabed classification separates the seabed into self-consistent regions called seabed classes based on acoustic diversity—primarily on the basis of echo shape. Sediment grab samples and video were also obtained to provide ground-truth and labels for the acoustic seabed classes. The acoustic seabed classification surveys were successful in identifying subtidal sands with low fractions of fines (silts) and sand wave fields among a variety of seabed types identified. Grab samples captured PSL buried in the medium to coarse subtidal sands, mostly in sand wave fields, and mostly in winter. Future work will be to observe diel migrations and develop methods to estimate biomass of buried PSL based on seabed classification.
Acoustic observations of the deep scattering layer during the Deepwater Horizon oil spill.
Authors: De Robertis Alex , Weber Thomas C. , Mayer Larry , Wilson Christopher D.
Published: July 2011

The explosion of the Deepwater Horizon drilling rig on April 20, 2010 resulted in the release of large quantities of oil and gas from the damaged wellhead into the deep waters of the Gulf of Mexico. During the monitoring effort that ensued, a large body of acoustic measurements with scientific echosounders was collected from May to October with the goal of mapping subsurface oil and gas and monitoring the integrity of the well head. These measurements will be used to observe the deep scattering layer (DSL), a ubiquitous community of sound-scattering mesopelagic organisms in the vicinity of the spill site. Preliminary observations of reduced backscatter in the near-field of the rising oil indicate that the DSL is perturbed by the rising oil close to the well head. It is unclear whether this is a highly localized effect occurring only near the well, or whether the DSL was also perturbed by a deep oil plume that spreads from the well site. The acoustic measurements of the DSL will be related to fluorometric indices of hydrocarbons from CTD profiles to gauge if there was a larger-scale perturbation on the abundance, behavior, and distribution of the midwater community.
Influence of biophysical coupling on age-0 pollock survey results.
Authors: Parker-Stetter Sandra , Horne John , Farley Edward , Eisner Lisa
Published: July 2011

Age-0 walleye pollock relative abundance and distribution in the eastern Bering Sea has been characterized with data from a surface trawl survey [Bering Aleutian Salmon International Survey (BASIS)]. Based on surface trawl catches since 2003, age-0 pollock abundances appeared to be highest during climatic warm years and lowest in cold years, with predictable distributions based on water column stratification. In 2008–2010, all cold years, acoustics, and midwater trawling were added to the BASIS survey. Acoustics confirmed that low numbers of age-0 pollock were found in the surface waters, but revealed the presence of previously unsampled, large (over 50 m high, several km long) aggregations in deep (greater than 100-m bottom depth) water. Acoustic and midwater trawling results suggest that the deep biomass may exceed that found in surface waters. Relationships are now being evaluated between oceanographic characteristics (water column stability, extent of the bottom cold pool) and biomass of age-0 pollock in surface and deep aggregations. Clarifying these biophysical linkages is important for evaluating potential gear-specific biases in survey data and for informing survey design decisions under changing climate conditions.
Estimating total uncertainty for abundance at age estimates from acoustic-trawl surveys.
Authors: Walline Paul D. , Woillez Mathieu
Published: July 2011

A comprehensive quantitative treatment of acoustic-trawl survey uncertainty that includes all major components of measurement and sampling error is needed to help specify the level of risk in stock assessment models. Acoustic and trawl sampling errors can be addressed by geostatistical simulations, which account for autocorrelation, non-independence, and non-random sampling, while additional sources of uncertainty, such as ship motion and instrument errors, can be incorporated into uncertainty estimates by bootstrapping. A conceptual model is presented in the form of a flow diagram, which identifies sources of uncertainty and recommends analytical methods to quantitatively assess the uncertainty associated with abundance at size estimates. Sequential geostatistical simulations of the spatial distribution of backscatter attributed to walleye pollock from Eastern Bering Sea acoustic-trawl surveys show that the acoustic sampling error is one of the two largest sources of uncertainty in estimates of total abundance. Sampling error associated with the spatial distribution of fish size is the next largest uncertainty source, and was simulated using co-Kriging for spatial functional data, which extends the simulation method to allow estimation of uncertainty by age-class.
Uncertainty in hydroacoustic-derived fisheries data: An analysis of simultaneous hydroacoustic-trawl surveys.
Authors: Simonin Paul W. , Tideman Samuel A. , Pientka Bernard , Rudstam Lars G. , Sullivan Patrick J. , Parrish Donna L.
Published: July 2011

Fish biomass estimates from hydroacoustic surveys contain uncertainty that must be quantified before such estimates are of use. To better understand uncertainty associated with down-looking hydroacoustics, analyzes were conducted on simultaneously collected trawl and hydroacoustic data from over 200 sampling events in Lake Champlain, a mesotrophic freshwater lake located between New York, Vermont, and Quebec (Canada). A model set, which used a number of factors to explore sources of variance, was analyzed. Factors explored were acoustic density estimation method, sampling time, sampling season, water temperature, light, invertebrate presence, fish size, fish species, and collection depth. Trawl avoidance was higher during the day, and varied with trawl type. Sources of variance in hydroacoustic estimates were the size and depth of analysis regions, presence of invertebrates, and fish shoaling behavior. All fish species could not be differentiated using acoustic target strength, thus necessitating trawl collections to estimate species-specific abundance. Trawl collection showed vertical separation of adult pelagic species in Lake Champlain, and suggested that side- or up-looking hydroacoustic and surface gillnet surveys may be necessary to reduce uncertainty in abundance estimates. Surveys using multiple sampling methods likely result in abundance estimates closest to reality.
Estimation of the take of fish in a riverine environment by sound generated by confined explosions.
Authors: Carlson Thomas J. , Johnson Gary E. , Woodley Christa M.
Published: July 2011

The Columbia River Navigation Channel Improvement Project required removal of a large shelf of basalt rock from the Columbia River near Portland, OR. Blasting was conducted over a 2 month period to fracture the rock for removal. Nearly 100 blast events, each consisting of up to 130 individual charges, were detonated. Monitoring was conducted to estimate the take of adult and juvenile salmonids and sturgeon. The number and distribution of fish exposed to blast pressure were estimated by applying active acoustic methods to observe the flux of fish into a region surrounding blast events. Blast pressures were measured and a propagation model used to estimate the level of blast pressure through the region monitored for take. A likelihood model was fitted to data for the response of adult fish to impulsive sound exposure and used to estimate the take of fish given the estimated distribution and exposure of fish through the river volume impacted by blast events. The explosive charges, which were located at depth in the massive rock formation and further confined by stemming in addition to time delayed detonation of individual charges, resulted in low peak pressures in the water column and negligible take of fish.
Using acoustic data from fishing vessels to estimate walleye pollock abundance in the eastern Bering Sea.
Authors: Honkalehto Taina , Ressler Patrick H. , Towler Richard H. , Wilson Christopher D.
Published: July 2011

Eastern Bering Sea walleye pollock (Theragra chalcogramma) supports one of the world’s largest fisheries. Due to pollock’s high recruitment variability and relatively short life span, timely and accurate abundance indices are needed for fisheries management. Annual bottom trawl (BT) surveys track the demersal portion of the pollock population using chartered commercial fishing vessels, while biennial acoustic-trawl (AT) surveys use NOAA research vessels to track the younger, midwater portion of the population. More frequent, annual indices of walleye pollock stock size may be obtained using acoustic backscatter data collected from the commercial fishing vessels conducting the BT survey at relatively low cost. A retrospective analysis of 38 kHz, AT survey data (1999–2004) identified a suitable index area to track midwater pollock abundance. The BT survey acoustic data (2006–2009) collected in that area tracked both the AT survey pollock abundance and the large-scale pollock distribution patterns. This study is unique because commercial vessel acoustic data were used to estimate a new annual abundance index whose performance can be evaluated by a biennial research vessel survey. The new index will benefit managers by providing more accurate information on near-term abundance trends when dedicated research ship time is not available.
Bioacoustic absorption/scintillation spectroscopy based classification of fish by size and depth.
Authors: Diachok Orest
Published: July 2011

Bioacoustic absorption/scintillation spectroscopy (BASS), which exploits frequency selective attenuation and scintillation due to swim bladder resonances, promises classification of fish by size (and with ancillary information and species) and depth and unbiased (by avoidance and proximity of fish to boundaries) estimates of number densities versus fish length. A BASS experiment in the Santa Barbara Channel, which employed a fixed ultrabroadband (0.3–10 kHz) source and a fixed vertical array separated by 4 km, demonstrated the power of this method. The source, which was employed during this experiment, had an environmentally friendly source level of 170 dB. Absorption lines in frequency/depth space, which were associated with year classes of physostomes, sardines, and anchovies, were evident at night when the fish were dispersed. BASS results were consistent with trawl and echo sounder data. Interpretation of absorption lines during daytime was complicated by “bubble cloud” resonances associated with fish schools. Displays of the scintillation index in frequency-depth space facilitated classification of absorption lines associated with species/year classes. Future experiments will focus on hake, a physoclist. [This work was supported by the Office of Naval Research.]
Marine Ecosystem Acoustics, a conceptual approach to enhanced process understanding and system evaluation.
Authors: Godoe Olav Rune
Published: July 2011

Institute of Marine Research has participated in developing marine acoustics for fisheries and ecosystem quantification since the mid 1930s. This development has motivated the recent focus on the concept, Marine Ecosystem Acoustics. This concept defines acoustics as the principal tools in ecosystem-based studies of marine organisms and their environment. Only acoustics can provide-information with appropriate resolution at spatial and temporal scales across the range of the fundamental biophysical processes as well as at the scales needed to resolve trophic interactions from individuals to populations. Exploiting acoustic band and beam widths as well as advanced platform technologies ecosystem processes can be observed on scales at which they occur, an essential requirement for quantitative ecosystem understanding and modeling. Further, the approach also supports the knowledge and information needed to establish a better fundament for an ecosystem-based fisheries management. Acoustics is presently underutilized in ecosystem research and still needs substantial development. The concept and its potential are exemplified with results from field experiment.
A new wide-band sonar for zooplankton studies.
Authors: Jaffe Jules , Roberts Paul , Briseno-Avena Christian , Genin Amatzia
Published: July 2011

A wide-band (1.5–2.5 MHz) multi-transducer sonar system has been developed for zooplankton studies. The system consists of multiple transmit/receivers that can be configured in either a multiple mono-static or multi-static mode. In the latter case, one transmitter and multiple receivers permit multi-angle backscatter measurements. The wide bandwidth permits resolving individual echoes separated by less than 2 mm. With an optical imager that records high resolution (25 μm), high contrast, images of animals over short exposures; 10–40 μm, the system records both acoustic reflections and optical images at 1 Hz. In multi-monostatic mode, the volume of interrogation for the sonar is 4 li, while that of the optical imaging system is 150 ml. Initial tests consisted of towing the system in multi-angle mode. During a recent cruise in September 2010, vertical profiles to 500 m revealed dense aggregates of Calanus pacificus californicus in the Santa Barbara Basin as recorded by the sonar and verified via the imaging system. A set of such multi-transducer systems, deployed in a coral reef environment, are being used to quantify in situ rates of zooplankton predation by fish and invertebrates, from the level of single predators to the whole community.
Standard-target calibration of sonars for marine ecosystem assessment.
Authors: Foote Kenneth G.
Published: July 2011

Remote acoustic observation and sampling of multiple trophic levels in the marine ecosystem generally require s ubstantial bandwidth, if not the coordinated use of two or more sonars. Calibration is essential. The standard-target method has a history of application, spanning the total frequency range 1–2500 kHz, with precision solid elastic spheres used as standard targets. The theory of measurement of volume backscattering and form functions of arbitrary targets is elaborated, also revealing the basis for the standard-target method. [Work supported by ONR Award No. N000140910482.]