bluuebunny/crossref_metadata_2025 huggingface dataset:
Thirty years of Australian marine bioacoustics and the Cummings connection
Authors: Cato Douglas H. , McCauley Robert D. , Noad Michael J. , Rogers Tracey
Published: July 2012

Marine bioacoustics research in Australian waters has developed for more than 30 years, and has revealed a wide diversity of sounds and acoustic environments. The number of researchers and the complexity of the experiments has increased over the years. In the early days we had little knowledge or experience, and so relied on advice and help from American researchers. Of those, Dr. William C. Cummings remains one of our greatest supporters. This paper reviews some of the main features of the Australian work and the Cummings influence. Some of the earliest work, on fish sounds, echoes his work of the 1960s. This has since developed substantially, and we are planning to apply methods developed by Cummings of combined video and acoustic observation to source identification. Humpback whale sounds have been studied continually for more than 20 years and have revealed the complex songs of similar overall structure to those of the northern hemisphere, but with some surprises. Recordings have been made of southern right whales and Antarctic seals, and this year we recorded a large set of diverse sounds from blue whales. This data set and visual / acoustic observations of humpback whales are being used in censusing.
Foraging behavior of the Hawaiian spinner dolphin observed with active acoustics
Authors: Benoit Bird Kelly , Au Whitlow
Published: July 2012

The mesopelagic boundary community (MBC) in the Hawaiian Islands is an important food resource for many organisms, including spinner dolphins (Stenella longirostris). To understand the role of this community in the feeding ecology of spinner dolphins, spatial and temporal patterns in the density of the MBC and relative abundance of dolphins were characterized using acoustic sampling. A 200 kHz echosounder modified to sample directly into a computer was used to survey the leeward coast of Hawaii from 2100 until 0400. Acoustic data were mapped in ArcView to show the distribution of both the predator and its prey. Individual echoes were color-coded by target strength to allow the separation of spinner dolphins and mesopelagic organisms. Dolphin species identification from active acoustics was confirmed using a combination of passive acoustics and visual observations. The MBC migrated horizontally, raising questions about the accepted (Norris) model of spinner dolphin foraging in Hawaii. Observations of spinner dolphins suggest a more complex foraging pattern, compatible with patterns observed in their food resource. Spinner dolphin foraging patterns closely matched the spatial patterns of their prey both horizontally and vertically. Patches exploited by dolphins were also significantly different than other patches measured under similar conditions.
Coherent Doppler profiler measurements of near-bed suspended sediment fluxes for different bed states
Authors: Smyth Carolyn E. , Hay Alex E. , Zedel Len
Published: July 2012

Vertical profiles of vertical turbulence intensity and vertical sediment fluxes were collected by an acoustic coherent Doppler profiler at two locations: Queensland Beach (Nova Scotia), and Duck (North Carolina). Observations of the turbulence intensity over different bed states (irregular ripples, cross ripples, linear-transition ripples, and flat bed) reveal that the near-bed turbulence levels are strongly affected by bed forms. This study examines the mechanisms of distributing suspended sediments and generating near-bed turbulence for the four bed states based on the characteristics of two previously observed mechanisms: diffusion and vortex shedding. Wave-phase averages of turbulence intensity, suspended sediment concentration, and suspended sediment fluxes are compared to vortex shedding and diffusion signatures. Evidence of vortex shedding is found for the low-energy ripples, but no signatures of diffusion are observed. Two diffusion models including a bed stress model, and an eddy diffusion model are found to predict near-bed turbulence levels reasonably well, but predictions are inconsistent with the trend of the data. A vortex-shedding model [J. F. A. Sleath, J. Fluid Mech. 182, 369–409 (1987)] predicts the vertical structure of the turbulence for rippled beds when the ripple wavelength is used as a ripple roughness.
Analysis of acoustic measurements of suspended sediments collected in a large-scale wave flume facility
Authors: Thorne Peter D.
Published: July 2012

Our capability to accurately predict suspended sediment concentration in the marine environment is relatively limited; generally, measuring techniques to obtain suspended concentration have been somewhat primitive. In recent years acoustics has been applied to the measurement of suspended sediments, and through a series of theoretical and experimental studies, a comprehensive description of the interaction of sound with suspensions of marine sediments has been developed. In the present work these developments have been applied to obtain detailed acoustic profiles of suspended sediment concentration under waves in a large-scale flume facility. Utilizing the acoustic concentration profiles, an assessment of suspended sediment models for predicting sediment concentration has been conducted, and the underlying intrawave mechanisms of sediment entrainment investigated.
Effects of the top transition layer in marine sediments on seabed roughness and volume scattering
Authors: Ivakin Anatoliy N.
Published: July 2012

Most models of high-frequency seabed scattering normally assume that the sediment is a statistically homogeneous half space and there is a discontinuity of acoustical parameters at the water–sediment interface. It is known, however, that in many cases properties of the very top layer of real marine sediments actually represent almost continuous transition within a few centimeters from those in water to those essentially constant in sediments at greater depths. At the Key West site, e.g., a definite transition layer in silty sand was found to be of 6-cm thickness. The discontinuity at the water–sediment interface, if it exists, is actually much smaller than assumed in conventional models of high-frequency scattering, where roughness scatter component is usually predicted to be strong and dominating for most types of sediments except very fine ones, such as mud and fine silt. In this paper, effects of the transition layer on both roughness and volume-scattering components are considered. These effects are shown to reduce substantially the role of roughness scattering at high frequencies. In particular, the roughness contribution is shown to be strongly dependent on real discontinuity of acoustical parameters at the water–sediment interface, which can be significantly reduced even for some sands due to existence of the transition layer. The possibly dominating role of volume scattering caused by continuous and discrete heterogeneity of the sediment is discussed. The necessity of more detailed study of physical properties of the transition sediment layer is emphasized. Related issues of interpretation of recent results on seabed scattering obtained in the Key West and SAX99 experiments are discussed as well. [Work supported by ONR-US and CNRS-France.]
An acoustical comparison of the serpent and the ophicleide
Authors: Campbell D. Murray
Published: July 2012

The serpent is a lip-excited wind instrument with an air column length of around 2 m and an approximately conical bore. In the form in which it emerged in France in the sixteenth century, it is a wooden tube with six finger holes and a chromatic compass of three octaves. The serpent suffers from some problems related to the fact that all the holes are covered directly by the fingers. The holes are grouped in two clusters, and the hole diameter is too small to provide adequate venting. The ophicleide, invented in the early nineteenth century, has a similar bore profile to the serpent. Eleven or more side holes in the thin-walled metal tube are covered by lever-operated padded keys; these allow most notes to be obtained without cross fingering, and the size and placing of the holes are not limited by the anatomy of the human hand. Several acoustical investigation techniques, including input impedance analysis, pulse reflectometry and excitation by an artificial mouth, have been used to investigate the extent to which the ophicleide is a successful solution to the acoustical problems posed by the serpent.
New ISO standards for hearing protectors
Authors: Poulsen Torben
Published: July 2012

Working Group 17 under ISO/TC43/SC1 deals with measurement of hearing protector attenuation. WG17 is presently involved in revision of the present 4869-1 standard (especially sound field requirements and reproducibility estimations) and formulation of a new standard where inexperienced hearing protector users are mandatory as test subjects. The latter procedure has recently been introduced in the USA, Australia, and New Zealand. Both the present and the new standard use the Real Ear At Threshold (REAT) method. Results from investigations of the sound field in different test environments will be presented and the status of coming standards for impulse noise and for devices with active noise control will be mentioned.
Effect of active noise reduction (ANR) and passive hearing protectors on detectability of a vehicle backup alarm in noise
Authors: Casali John G. , Dabney Erika , Robinson Gary S. , Gauger Dan
Published: July 2012

In a within-subject laboratory experiment, ten subjects of normal-hearing abilities listened for a standard vehicle backup (reverse) alarm that was presented against either an 85 or 100 dBA background noise having either a pink or red spectrum. Subjects’ masked thresholds to the alarms were determined under four listening conditions: ANR earmuff, passive earmuff, foam earplug, and unprotected (at 85 dBA only). To become immersed in a workload situation, subjects continuously attended to a computer-generated visual monitoring task while performing the auditory detection experiment. Analysis of variance and post-hoc tests were applied to the mean masked threshold results. In 85 dBA noise, masked thresholds were significantly lower when any protector was worn, as compared to the unoccluded condition, lending support for the use of hearing protection with normal hearers when backup alarm signals need to be heard in noise. The ANR earmuff provided a significant advantage over the passive earmuff in both levels of the red noise, and for both noise spectra at 100 dBA. However, the foam earplug yielded lower masked thresholds than either other protector in 100 dBA noise. Subjects’ perceptions about efficacy of warning signal detection and about comfort revealed no differences among the three protectors.
Vibration analysis by digital shearography
Authors: Steinchen W. , Kupfer G. , Mäckel P.
Published: July 2012

Digital shearography, a laser interferometric technique in conjunction with the digital image processing, has the potential for vibration analysis due to its simple optical system and sensitivity against small rigid body motions. This paper will focus on its recent developments for vibration analysis and for nondestructive testing (NDT) by dynamic (harmonic) excitation. With the introduction of real-time observation using an automatically and permanently refreshing reference frame, both small and large rigid body motions are greatly suppressed. The development of a smaller and more mobile measuring device in conjunction with a user-guided comfortable program shearwin enables the digital shearography to be applied easily as an industrial on-line testing tool.
The modes and loss mechanisms of a high Q mechanical oscillator
Authors: Liu Xiao , Vignola J. F. , Morse S. F. , Photiadis D. M. , Sarkissian A. , Marcus M. H. , Houston B. H.
Published: July 2012

In order to understand the unusually high Q nature of the double paddle oscillator employed in a number of recent experiments, laser Doppler vibrometry (LDV) measurements of the normal modes of the oscillator were carried out. The observed resonance frequencies and mode shapes are in excellent agreement with three-dimensional finite element simulations. The second antisymmetric torsional mode was found to have exceptionally good vibration isolation because of its mode shape. This explains its extremely small low temperature (T<10 K) internal friction (2×10−8). A design criterion is established to minimize the damping of similar oscillators by correlating features of the measured and predicted mode shapes.
Determination of design trends in the structural acoustic optimization of a multi-ply laminated composite cylindrical shell
Authors: Johnson W. M. , Cunefare K. A.
Published: July 2012

Structural acoustic optimization (SAO) is a multidisciplinary design technique used to determine the optimal acoustic properties of a structural design. Previous works have applied structural acoustic optimization to stiffened and unstiffened aluminum cylindrical shells subject to acoustic and structural vibration excitation. Most recently, SAO has also been applied to multiply laminated composite cylinders. In this case the ply angles served as the design variables but were not allowed to vary over the cylinder length. In this work we perform a structural acoustic optimization on a laminated composite cylinder with variable ply angles along the cylinder length. This is accomplished with a computational design tool incorporating finite- and boundary-element methods. It is anticipated that these results will help to clarify what design trends control the interior acoustic environment. [This work was supported by the Structural Acoustics Branch of NASA Langley Research Center and Graduate Student Research Program Grant (NGT-1-52167).]
Transmission loss of heterogeneous porous materials
Authors: Atalla Noureddine , Sgard Franck
Published: July 2012

Recently, the authors have investigated the acoustic absorption performance of heterogeneous materials made up from a combination of thin porous patches, with different acoustic properties. It has been shown that absorption could be significantly increased in the case of properly designed macroperforated wools in a large frequency band. This paper investigates the transmission loss of similar macroheterogeneous materials. The studied materials are made up of porous elastic materials containing solid inclusions. They are placed into an infinite rectangular waveguide. The numerical model used combines a finite-element formulation for the heterogeneous porous material and a modal description of the acoustic field in the waveguide. The coupling between the solid and the porous patches is accounted for naturally through the use of a modified Biot’s formulation. Numerical results are presented to show the effect of several geometric and physical parameters on the transmission loss performance of heterogeneous porous materials.
Effects of tube shape on nonlinear resonant oscillations of interior gas
Authors: Chun Young-Doo , Kim Yang-Hann
Published: July 2012

An investigation is conducted to get an outline of designing the tube shape for a sonic compressor with high efficiency. When a closed tube oscillates with its resonant frequency, the interior acoustic properties such as density, velocity, and pressure undergo very large perturbation with nonlinear patterns. In order to analyze the nonlinear acoustic phenomena such as harmonic generation, shock formation, and resonant frequency shift, two-dimensional axisymmetric governing equations are derived and solved numerically. Numerical simulations are performed to investigate the effect of the tube shape that gives us maximum possible pressure. Results show that the resonant frequency and patterns of pressure waves strongly depend on not only the tube shape but also the amplitude of driving acceleration. The degree of nonlinearity of pressure signals is measured by the newly defined nonlinear energy ratio of the signals. The nonlinear energy ratio well describes not only the energy transfer to higher harmonics but also the compression efficiency, so that it can be a good measure for designing tube shape.
A model of speech motor control and supporting data: Influences of quantal effects
Authors: Perkell Joseph S. , Guenther Frank H.
Published: July 2012

A model of speech motor control is presented, along with examples of supporting data. In the model, segmental speech movements result from a process which plans a trajectory that passes through a sequence of phoneme-specific auditory goals. Some auditory goals are constrained by quantal relations between the vocal-tract area function and the resulting acoustics, as Stevens has proposed, and some are defined by quantal relations between motor commands and the area function, called biomechanical saturation effects. Both types of quantal relations make it possible to produce sounds that have relatively stable acoustic properties using somewhat imprecise motor commands. Therefore, quantal effects influence motor control strategies of individual speakers. They also influence sound patterns of languages, in that they help to define sounds such as the vowels /i/ and /a/ that occur frequently among languages of the world. Although there are other influences on speech motor control mechanisms and sound patterns, quantal effects are considered to be one of the defining characteristics of spoken language. [Work supported by NIDCD, NIH.]
Overview of blind signal separation, part I: Criteria and algorithms
Authors: Douglas Scott
Published: July 2012

In blind signal separation, multiple independent source signals are separated from multiple linear mixtures of these signals without specific knowledge of either the source signal characteristics or the mixing conditions. This talk provides an introduction to the blind signal separation task. Three different problem formulations—signal separation of instantaneous mixtures, signal separation of convolutive mixtures, and multichannel blind deconvolution—are described, and their similarities and differences are highlighted. An overview of both information-theoretic and contrast-based separation criteria is then given. Natural gradient optimization procedures, when combined with such criteria, yield simple and useful blind signal separation algorithms. An example of speech separation of real room recordings illustrates the capabilities and limitations of one such approach.
Deriving optimal codes for speech and natural sounds using generalized independent component analysis
Authors: Lewicki Michael S.
Published: July 2012

A Bayesian method for inferring an optimal basis is applied to the problem of finding efficient codes for natural sounds. The key to the algorithm is multivariate non-Gaussian density estimation, which is an equivalent independent component analysis when the form of the marginal density is fixed. An important advantage of the probabilistic framework is that it provides a method for comparing the coding efficiency of different bases objectively, and the derived codes can be shown to have better coding efficiency compared to traditional Fourier and wavelet bases. It also provides a method for Bayesian signal denoising and filling in of missing samples using a basis that is optimized to the structures in the data. When this framework is applied to deriving efficient codes of speech and natural sounds, the codes share many of the coding properties of the cochlear nerve. Time–frequency analysis shows that it is possible to derive both Fourier-like and wavelet-like representations by deriving efficient codes for different classes of natural sounds.
Blind source separation of mixtures of speech signals with unknown propagation delays
Authors: De Leon Phillip , Ma Yunsheng
Published: July 2012

Blind source separation of mixtures of speech signals has received considerable attention in the research community over the last 2 years. One computationally efficient method employs a gradient search algorithm to maximize the kurtosis of the outputs thereby achieving separation of the source signals. While this method has reported excellent separation results (30–50-dB SIR), it assumes a simple linear mixing model. In the general case, convolutional mixing models are used, however, this is a rather difficult problem due to causality and stability restrictions on the inverse not to mention length requirements in the FIR approximation. Research results with the general problem are modest at best. In this paper, we extend the kurtosis maximization ideas for source separation to include delays in the mixing model to at least account for propagation delays from speakers to microphones. The algorithm is designed to first estimate the relative delays of the sources within each mixture using a standard autocorrelation technique. These delay estimates are then used in the kurtosis maximization algorithm where the separation matrix is now modified to include these delays. Simulation results (using the TIMIT speech corpus) generally indicate good separation quality (10–20 dB) with little additional computational overhead.
Short duration sounds recorded from blue whales (Balaenoptera musculus) off Peru
Authors: Norris Tom , Barlow Jay
Published: July 2012

Recordings of low-frequency sounds were made in the presence of blue whales (Balaenoptera musculus) in 1998 and 1999 in waters off northern Peru during a marine mammal research cruise. Recordings were made on DAT from sonobuoys deployed near vocalizing whales. Photographic identifications and biopsy samples were collected from several animals that were recorded. Over 20 signals were extracted and analyzed from DAT segments that contained the best signal quality. All signals from the 1998 encounter consisted of rapid, frequency modulated (FM) downsweeps (begin frequency x̄=94, S.D.=13.6 Hz; end frequency x̄=59, S.D.=7.8 Hz; frequency range x̄=41.7, S.D.=14.9) of relatively short duration (x̄=1.2, S.D.=0.3 s). Approximately half of the signals exhibited a characteristic s-shape pattern when examined spectrographically. Long duration sweeps and pulses, typical of blue whales sounds from the eastern North and Central Pacific, were not detected. The vocalizations recorded in this study are compared to recordings of short duration blue whale sounds made elsewhere, including off California, Baja California, and southwestern Australia. In general, short duration blue whale sounds from these other areas are more variable and/or have different frequency characteristics. The function of short duration, FM blue whale sounds is unknown.
Sterotyped and other vocalizations of fin whales (Balaenoptera physalus) off Chile
Authors: Thompson Paul O. , Cummings William C.
Published: July 2012

Underwater vocalizations from a small group of fin whales were recorded from the U.S. National Science Foundation’s (NSF) research vessel ‘‘Hero’’ in Golfo de Penas, Chile, May, 1970. The most outstanding and frequent vocalizations were patterned utterances of about 1.5-s duration that swept upward from about 35 to 65 Hz. Endings typically were emphasized with an outstanding increase in sound level. The second most frequent type of vocalization was 1-s downward sweeps in a range of about 100–30 Hz. Both types occurred in small groupings with evenly spaced intersound intervals of about 8.5 s (upsweeps) and about 4 s (downsweeps). These sterotyped vocalizations had acoustical characteristics that were very similar to those of sounds that we had recorded from fin whales in the Gulf of California (Mexico) during 1969. [Work supported by NSF.]
Echolocation in the Risso’s dolphin, Grampus griseus
Authors: Philips Jennifer D. , Nachtigall Paul E. , Au Whitlow W. L. , Pawloski Jeffrey L. , Roitblat Herbert L.
Published: July 2012

This study investigated whether the Rissos dolphin, Grampus griseus, echolocates. The Rissos dolphin is a gregarious, near-shore pelagic delphinid that consumes nearly exclusively cephalopods and has a distinctive groove along its forehead. In this study, an individual female Rissos dolphin was trained to discriminate an aluminum cylinder from a nylon sphere (Experiment 1) or an aluminum sphere (Experiment 2). The animal wore eyecups and was required to swim to and touch the standard cylinder. The animals choice accuracy was 98.3% in Experiment 1 and 99.6% in Experiment 2, indicating that she was able to perform the target discriminations with little difficulty despite being blindfolded. Clicks were acquired at amplitudes up to 202 dB (M=199 dB), peak frequencies up to 105 kHz (M=51 kHz), center frequencies up to 70–75 kHz (M=57 kHz), bandwidths of 31 to 92 kHz, and durations of 40–70 ms. The data establish that the Rissos dolphin echolocates and that its clicks are very similar to the clicks of other echolocating dolphins. Implications of the unique behavioral and physical characteristics of this species on its sonar system are discussed.
Horizontal angular discrimination by an echolocating bottlenose dolphin (Tursiops truncatus)
Authors: Branstetter Brian K. , Herman Louis M. , Pack Adam A. , Mevissen Sonja J. , Moore Amanda M. , Granum Jamie , Carsrud Lea , Butler Carol , Lecaroz Sarah B. , Roberts Scotty
Published: July 2012

A bottlenose dolphin was tested on its ability to echoically discriminate horizontal angular differences between two arrays of vertical, air-filled PVC rods. The blindfolded dolphin was required to station in a submerged vertically oriented hoop 2 radial meters from the stimuli and indicate if an array with four rods (S+) was to the left or the right of an array with two rods (S−) by pressing a corresponding paddle. The rods within each array were separated by 2 deg and the two arrays were separated by eight different angles between 2.25 and 6 degrees. A modified method of constant stimuli was used to test for angular discrimination ability. The results yielded a high-pass psychometric function with an arbitrary 75% correct threshold of 1.5 deg. These data agree well with passive listening minimum audible angle thresholds of 0.9 deg for click signals and 2.1 deg for a pure tone signal (Renaud and Popper, 1975). Analyses of response times, number of clicks and inter-click intervals suggested no significant adaptive behavior was used as the task became more difficult. These results help define angular resolution capabilities of dolphin sonar that may play an important role in representing spatial information in the dolphin’s environment.
Design of actively tuned flexural piezoceramic bar/disk transducers
Authors: Bernard Julien , Lesieutre George A.
Published: July 2012

Underwater transducers with variable and controllable resonance frequency can efficiently transmit stepped or linear chirp signals of greater bandwidth by continuously matching their resonance frequency to the dominant frequency of the transmitted signal. This paper presents a technique to vary the first resonance frequency of some widely used underwater transducers: flexural piezoceramic bars and disks. Positive-bias electric fields are added to the driving ac field to generate either a tensile in-plane load in k31 coupling, or a compressive in-plane load in k33 coupling. This load modifies the flexural rigidity of the transducer, which in turn affects its resonance frequencies. Ideally, supported transducers are first analyzed, from the point of view of the electrochemical coupling coefficient at the first resonance, and the frequency shift per applied bias field. Transducers using elastic hinges to approximate simply supported boundary conditions are then examined. The response of the transducers to the combined dynamic bias field and driving ac field is simulated to look for possible dynamic effects, such as the excitation of high-frequency extension and bending modes. Finally, experimental measurements of the coupling coefficient and frequency shift per bias field of prototype transducers are presented. [Work supported by ONR.]
Nonlinear propagation of multitone one-dimensional waves. Application to sound systems modeling and analysis
Authors: Voishvillo Alexander
Published: July 2012

Multitone stimulus is used in identification of weakly nonlinear systems and for assessment of nonlinearity in sound and broadcasting equipment. Multitones’ spectral and statistical characteristics resemble those of the musical signals; the nonlinear response to multitone stimulus yields more versatile information about nonlinearity than conventional measurements of harmonic and two-tone intermodulation distortion. Earlier work has demonstrated that strong harmonic and intermodulation distortions accompany the propagation of waves radiated by large horn arrays. In this current work, the models of propagation of multitone waves are developed. The modeling considers propagation of multitone one-dimensional waves. The modeling is based on numerical solution of implicit equations describing distorted one-dimensional waveforms. A nonlinear model of multitone waves propagating within a horn is developed. The model considers linear propagation of the fundamental tones with reflections from the mouth and the nonlinear, reflection-free propagation of distortion products. Further research may include radiation of multitone waves by a complex source and substitution of multitone stimulus by a musical signal to provide listening tests and auralization of propagation nonlinearity. The data obtained from modeling may be used to build Volterra models of nonlinear propagation. These models might lead to signal processing solutions to minimize distortion in propagating waves.
Localization of acoustic waves in 1-D random liquid media
Authors: Luan Pi-Gang , Ye Zhen
Published: July 2012

We study acoustic propagation in one-dimensional water ducts containing many air-filled blocks. The acoustic band structures for the periodic arrangements of the blocks are calculated, whereas the transmission for various random configurations of the blocks is computed by the transfer matrix method. It is shown that waves at all frequencies become localized even with a small amount of randomness. The spatial distribution of the localized energy is investigated, and is shown not to be trapped near the source, contrary to higher dimensional cases. The results also reveal a distinct collective behavior for localized waves, a feature useful for distinguishing the localization from the residual absorption effect.
Acoustic scattering by arrays of air bubbles in water
Authors: Ye Zhen
Published: July 2012

Wave localization is a ubiquitous phenomenon. It refers to situations that transmitted waves in scattering media are trapped in space and remain confined in the vicinity of the initial site until dissipated. Here we report a phase transition from acoustically extended to localized states in arrays of identical air-filled bubbles in water. It is shown that the acoustic localization in such media is coincident with the complete band gap of a lattice arrangement of the air bubbles. When the localization or the band gap occurs, a peculiar collective behavior of the bubbles appears. The acoustic transmission through a planar array of air bubbles is also studied.
Acoustic stop bands for two-dimensional periodic arrays of metallic rods: Honeycomb geometry
Authors: Kushwaha M. S. , Djafari-Rouhani B.
Published: July 2012

Extensive band structures have been computed for periodic arrays of rigid metallic rods in air for honeycomb structure. Multiple complete acoustic stop bands have been obtained within which sound and vibrations are forbidden. These gaps start opening up for a filling fraction f≥8% and tend to increase with the filling fraction, exhibiting a maximum at the close-packing. A tandem structure has also been proposed that allows an ultrawideband filter for environmental or industrial noise to be achieved in the desired frequency range. This work is motivated by the recent experimental observation of sound attenuation on the sculpture by Eusebio Sempere, exhibited at the Juan March Foundation in Madrid [Nature 378, 241 (1995)] and complements the corresponding theoretical work (see the preceding abstract). [Work partially supported by CONACyT Grant No. 28110E.]
Sound control by two-dimensional periodic structures
Authors: Sánchez-Dehesa J. , Caballero D. , Martínez-Sala R. , Rubio C. , Sánchez-Pérez J. V. , Sanchis L. , Meseguer F.
Published: July 2012

Sound transmission properties of two-dimensional triangular arrays of rigid cylinders in which we created a lattice of vacancies with rectangular symmetry will be presented. At low frequencies, the attenuation spectra measured along the high-symmetry directions show an attenuation band corresponding to the lattice of vacancies. On the other hand, at high frequencies, the attenuation bands associated with the full triangular lattice still remain. This result indicates that the vacancies act as a true lattice of scatterers embedded in a triangular lattice. Acoustic band structures have been calculated by a variational method and compared with attenuation spectra. The features of the spectra are well described by the band calculation. An intuitive approach that explains the experimental results will be given. [Work supported by CICyT of Spain.]
Magnetic brain responses to second formant transitions in dependency of transition time, signal voicing, and attention
Authors: Hertrich Ingo , Mathiak Klaus , Ackermann Hermann , Lutzenberger Werner
Published: July 2012

Using an oddball paradigm, magnetoencephalographic (MEG) recordings were performed during perception of synthetic /i/-like signals (frequent stimuli) and interspersed /bi/ or /yi/-like deviants with an initial second formant (F2) transition of 20, 40, 60, or 80 ms. The experiment was run under two different signal conditions: formant-synthesized voiced stimuli or spectrally and loudness-matched unvoiced cognates generated by filtered white noise. Listeners’ attention was directed either to the infrequent stimuli or to a moving geometric pattern (visual distraction task). Left- and right-hemispheric M50, M100, and MMNm dipole strengths were derived from the MEG measurements. The results show a strong bilateral effect of signal voicing on the M50 and M100 responses, irrespective of F2 transition time, being enhanced with attention directed to the acoustic signal. The deviant stimuli evoked a significant mismatch reaction which under directed attention was lateralized to the left hemisphere. The strength of the MMNm increased across transition time, but exhibited a nonlinearity at 40 ms in terms of an interaction with signal voicing. In conclusion, these results suggest signal-related bilateral preprocessing during the M50 and M100 responses and attention-dependent lateralization of mismatch reactions to speech-relevant acoustic features.
The relation between backward masking and measures of reading, language, and other cognitive abilities in fourth-grade children
Authors: Watson Charles S. , Kidd Gary R. , Eddins David A.
Published: July 2012

A backward masking test was administered to 247 fourth-grade children participating in the Benton-IU Project, an epidemiological, longitudinal study of the factors that lead to success or failure in grade school. It has been hypothesized that children with language disorders, including reading disabilities, demonstrate high levels of backward masking. Low correlations between masked thresholds, speech recognition abilities, and reading achievement in the overall population provided only weak support for this hypothesis. Within the subgroup of poor readers, there was a substantially larger correlation between masking and speech processing abilities, but neither of these abilities was strongly associated with reading achievement. Reading achievement was much more strongly associated with other cognitive, intellectual, and linguistic measures; the correlation between predicted and obtained teacher-assigned reading grades was 0.73. This study illustrates that research with selected samples of normal and impaired subjects can lead to different conclusions from those based on the entire population. [Work supported by NIH/NIDCD and Indiana University.]
Subsystems in human auditory cortex revealed by functional imaging
Authors: Scott Sophie , Rosen Stuart , Blank Catrin , Wise Richard
Published: July 2012

This study investigated the neural systems involved in speech perception, controlling for the complexity of the speech signal. Using speech stimuli of varying intelligibility but equivalent structural complexity, functional neuroimaging (PET) was used to investigate the brain activation involved in processing intelligible speech in eight right-handed native English speaking volunteers. A stream of processing in the left temporal lobe was demonstrated, associated with the intelligibility of speech. The left superior temporal sulcus responded to the presence of phonetic information, but the anterior region only responded if the stimulus was also intelligible. This novel observation demonstrates a left-lateralized anterior temporal pathway for speech comprehension. Work in visual neuroscience has identified at least two possible functional subsystems in visual processing, a ventral ‘‘what’’ pathway passing from visual cortex to the ventral temporal lobes and a dorsal ‘‘where/how’’ pathway passing from visual cortex to the parietal lobes. Work in nonhuman primates has revealed analogous pathways in the auditory system. The left lateralized stream of processing shown in this study may form a verbal ‘‘what’’ pathway in human auditory perception. The right temporal lobe, in contrast, showed selective activation for stimuli that contained dynamic pitch variation, regardless of intelligibility.
Robust adaptive nulling in matched field processing
Authors: Kim J. S. , Kuperman W. A. , Song H. C. , Hodgkiss W. S.
Published: July 2012

Nulling out sources of interference is a major goal of adaptive array processing. For moving interferers, null-broadening is a useful technique to reduce the interference. A null-broadening approach has been recently developed for planewave beamforming [R. J. Mailloux, Electron. Lett. 31, 771–772 (1995)] [M. Zatman, ibid. 31, 2141–2142 (1995)] to cover the angular extent of the motion. One way to achieve this is to introduce the effects of dispersion into a covariance matrix, which is equivalent to averaging the covariance matrix over a finite bandwidth in frequency. In this study, the null-broadening approach is extended to the matched field processing (MFP) in an ocean waveguide, based on an MV processor with a white noise constraint. In particular, the null-broadening in range is accomplished through using waveguide invariant properties. Simulations as well as the SWELLEX-96 experimental data clearly demonstrate the null-broadening effect.
Source localization in a shallow water random environment
Authors: Stamoulis Catherine , Orr Marshall , Dyer Ira
Published: July 2012

Source localization in a random ocean environment has been investigated through analysis of data from the SWARM 95 experiment. Both broadband matched-field processing and matched-mode processing have been used for localization. In particular, acoustic data collected with a vertical line array and a moving upsweep source have been analyzed, in the frequency range 275–350 Hz. The source distance varied between 2.5 and 27 km. Due to the dynamic nature of the shallow water column and in particular the presence of soliton packets, the available environmental data used in matched-field processing was not sufficiently accurate for correctly localizing the source via this method. The mismatch between data and replica fields, particularly their phase differences, was significant. Source range errors were of the order of the source distance from the array, 2 to 20 km. In contrast, matched-mode processing yielded much better results. The modal time series were first estimated from the data, mode filtering was then used to eliminate noisy or nonparticipating modes and localization was finally performed. The source range errors varied between 200 m to 5 km.
Rank-N stochastic matched field processing
Authors: Daly Peter M. , Baggeroer Arthur B.
Published: July 2012

Underwater acoustic source localization can be performed using matched field processing (MFP). Successful localization depends on accurate signal and environmental input parameters to a propagation model. Some parameters, notably the sound velocity profile (SVP), vary both spatially and temporally, and are thus difficult to treat as deterministic quantities. Instead, one can model the SVP and the resultant pressure field as random vectors. This allows one to detect targets using second order statistics of the received and modeled pressure fields. Baggeroer et al. [J. Acoust. Soc. Am. 106, 2126] demonstrated successful target localization using individual singular vectors of a modeled covariance matrix. A new method of MFP is proposed which combines energy from orthogonal singular vectors of the modeled covariance matrix. Each correlation is weighted and summed to yield a detection statistic. A maximum-likelihood nonrandom parameter estimation method is then applied to determine the source location. Through inclusion of signal energy which would normally be lost to environmental mismatch, this method significantly reduces estimation bias in a simulated 200-m shallow water waveguide. Localization results are shown using both simulated and experimental data from the 1998 Santa Barbara Channel Experiment. [Work supported by SAIC, DARPA and ONR.]
Acoustical scattering amplitudes of waveletlike atmospheric temperature distributions
Authors: Auvermann Harry J.
Published: July 2012

As an alternative to Fourier space representation of turbulence, wavelet decomposition has certain advantages associated with the ability to calculate effects localized in space, such as turbulent intermittency. Wavelet-based turbulence simulation is particularly useful when calculating the acoustic field scattered into a detector by a turbulent region of the atmosphere. Wavelet decomposition theory utilizes the orthonormal properties of these functions to make a chosen distribution easier to simulate. In this paper, the first step in the process, that is determination of the scattering amplitude, is reported for a number of candidate waveletlike functions. Since a wavelet is defined to have a zero volume integral, some candidates are not wavelets, but may have useful properties. The candidates are: Gaussian, exponential, ‘‘Mexican hat,’’ Morlet, cosine, and concentric spheres. While the method of generating three-dimensional velocity distributions is indicated briefly, the results are confined to temperature turbulence. The scattering amplitudes are calculated using the Born approximation in the far field. The concentric sphere candidate allows an exact solution in the form of an infinite series. The result of this calculation is presented also.
On the perception and production of Japanese stops by native speakers of Korean
Authors: Nozawa Takeshi , Katayama Mari , Sasaki Midori , Ishihara Yoshihito
Published: July 2012

In a series of experiments, native Korean (NK) speakers’ production and perception of Japanese stops was examined. It was predicted that Koreans would not produce Japanese voiced stops authentically given the fact that Korean does not contain these phonetic tokens and that this may also be due in part to their perception of these tokens [i.e., they perceive them differently than do native Japanese (NJ) speakers]. First, a production study revealed that NK produced /g/ VOT values that were significantly different than NJ subjects. Second, perceptual experiments where NK and NJ heard Japanese stops produced by NK and NJ speakers revealed that in general, the two groups were in agreement when deciding whether the tokens were voiced or voiceless. However, there was a disparity between the two in that some of the NK tokens of /g/ were perceived as /k/ by NJ but were perceived as intended /g/ tokens by NK subjects. Results of an additional perceptual experiment also demonstrated that NK subjects treat Japanese voiceless stops as equivalent to Korean aspirated stops and Japanese voiced stops as Korean plain unaspirated stops (even though the VOT values for the Japanese voiceless and Korean unaspirated plain stop are more similar).
Predictive Self-Assembly of Polyhedra into Complex Structures
Authors: Damasceno Pablo F. , Engel Michael , Glotzer Sharon C.
Published: July 2012

Getting Packed

If one neglects the role of specific interactions, the packing of similar-shaped objects will depend only on the particular shape of the object.

Damasceno
et al.

(p.
453
; see the Perspective by

de Graaf and Manna

) present computer simulations of the behavior of different types of polyhedra with simple and complex shapes that are packed under thermal equilibrium into various structures, from crystals to amorphous materials through liquid crystals. Despite the wide variety of starting shapes, the packing behavior could be quantitatively described using just two criteria; one for the particle shape as a function of its volume and surface area, and one for the number of nearest neighbors.
Isotropic Events Observed with a Borehole Array in the Chelungpu Fault Zone, Taiwan
Authors: Ma Kuo-Fong , Lin Yen-Yu , Lee Shiann-Jong , Mori Jim , Brodsky Emily E.
Published: July 2012

Cracking Up

Hydraulic fracturing by fluids at high pressure results in damage or breakage along cracks in deep rocks, a process that in some cases causes earthquakes. This process can occur naturally when the hydrologic setting is just right, or can be induced by human activity when fluids are pumped at high pressure into deep aquifers. By studying the fault along which the 1999 magnitude 7.6 Chi-Chi earthquake occurred in Taiwan, where there are currently low tectonic stresses following the large earthquake,

Ma
et al.

(p.
459
) observed an unusual type of earthquake-like event that they attribute to natural hydraulic fracturing.
Excitation of Orbital Angular Momentum Resonances in Helically Twisted Photonic Crystal Fiber
Authors: Wong G. K. L. , Kang M. S. , Lee H. W. , Biancalana F. , Conti C. , Weiss T. , Russell P. St. J.
Published: July 2012

Fiber with a Twist

Optic fibers provide the backbone of communication networks. Controlling light propagation through the fiber is key to maximizing the capacity of information flow. By introducing a literal twist on the photonic crystal fiber,

Wong
et al.

(p.
446
) show that adding chirality to the cladding surrounding the core may provide another route to manipulating the transmission of light. Coupling between the twisted cladding and the core results in dips in the transmission spectrum, which are dependent on the degree of twist introduced into the fiber. Such twisted microstructure fibers may offer opportunities for coupling, filtering and manipulating light.
Use and Abuse of RNAi to Study Mammalian Gene Function
Authors: Kaelin William G.
Published: July 2012

Realizing the full potential of si/shRNA technology requires more sophisticated approaches to address the pitfalls.
Phillip V. Tobias (1925–2012)
Authors: White Tim D.
Published: July 2012

The preeminent paleoanthropologist's courage, humanity, and research led the way in African academia and paleoanthropology.
Needed Antarctic Upgrades Would Trim Science Budget
Authors: Gramling Carolyn
Published: July 2012

The aging scientific facilities in Antarctica are in dire need of repair and upgrades—and paying for that will require cuts to Antarctic research activities in the short term, according to a new report.
Data Dispute Revives Exoplanet Claim
Authors: Bhattacharjee Yudhijit
Published: July 2012

Last week, the team that discovered Gliese 581g, the first potentially habitable planet outside the solar system, concluded that their own analysis of their critics' data shows that Gliese 581g does indeed exist.
Panel Votes to End Prevention Fund, Cut Economics Studies, Freeze NIH
Authors: Kaiser Jocelyn
Published: July 2012

Last week, a House of Representatives panel passed a 2013 spending bill that would freeze the budget of the National Institutes of Health and trim the Department of Health and Human Services.
Using Radiocarbon to Go Beyond Good Faith in Measuring CO
2
Emissions
Authors: Balter Michael
Published: July 2012

Researchers have found a better way to estimate CO
2
emissions: by measuring the proportion of CO
2
in the atmosphere that contains the radioactive isotope carbon-14.