bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluid-structure effects of cloaking a submerged spherical shell
Authors: Scandrett C. L. , Vieira A. M.
Published: August 2013

Backscattering from a cloaked submerged spherical shell is analyzed in the low, mid, and high frequency regimes. Complex poles of the scattered pressure amplitudes using Cauchy residue theory are evaluated in an effort to explain dominant features of the scattered pressure and how they are affected by the introduction of a cloak. The methodology used is similar to that performed by Sammelmann and Hackman [J. Acoust. Soc. Am. 85, 114–124 (1989); J. Acoust. Soc. Am. 89, 2096–2103 (1991); J. Acoust. Soc. Am. 90, 2705–2717 (1991)] in a series of papers written on scattering from an uncloaked spherical shell. In general, it is found that cloaking has the effect of diminishing the amplitude and shifting tonal backscatter responses. Extreme changes of normal and tangential fluid phase velocities at the fluid–solid interface when cloaking is employed leads to elimination of the “mid-frequency enhancement” near the coincidence frequency for even modestly effective cloaks, while reduction of the “high-frequency enhancement” resulting from the “thickness quasi-resonance” near the cut-off frequency of the symmetric (S2B) mode requires more effective cloaking, but can be practically eliminated by employing a cloak that creates tangential acoustic velocities in excess of the S2B mode phase speed near cutoff.
The clarinet: How blowing pressure, lip force, lip position and reed “hardness” affect pitch, sound level, and spectrum
Authors: Almeida Andre , George David , Smith John , Wolfe Joe
Published: August 2013

Using an automated clarinet playing system, the frequency f, sound level L, and spectral characteristics are measured as functions of blowing pressure P and the force F applied by the mechanical lip at different places on the reed. The playing regime on the (P,F) plane lies below an extinction line F(P) with a negative slope of a few square centimeters and above a pressure threshold with a more negative slope. Lower values of F and P can produce squeaks. Over much of the playing regime, lines of equal frequency have negative slope. This is qualitatively consistent with passive reed behavior: Increasing F or P gradually closes the reed, reducing its equivalent acoustic compliance, which increases the frequency of the peaks of the parallel impedance of bore and reed. High P and low F produce the highest sound levels and stronger higher harmonics. At low P, sound level can be increased at constant frequency by increasing P while simultaneously decreasing F. At high P, where lines of equal f and of equal L are nearly parallel, this compensation is less effective. Applying F further from the mouthpiece tip moves the playing regime to higher F and P, as does a stiffer reed.
Effect of long-term training on sound localization performance with spectrally warped and band-limited head-related transfer functions
Authors: Majdak Piotr , Walder Thomas , Laback Bernhard
Published: August 2013

Sound localization in the sagittal planes, including the ability to distinguish front from back, relies on spectral features caused by the filtering effects of the head, pinna, and torso. It is assumed that important spatial cues are encoded in the frequency range between 4 and 16 kHz. In this study, in a double-blind design and using audio-visual training covering the full 3-D space, normal-hearing listeners were trained 2 h per day over three weeks to localize sounds which were either band limited up to 8.5 kHz or spectrally warped from the range between 2.8 and 16 kHz to the range between 2.8 and 8.5 kHz. The training effect for the warped condition exceeded that for procedural task learning, suggesting a stable auditory recalibration due to the training. After the training, performance with band-limited sounds was better than that with warped ones. The results show that training can improve sound localization in cases where spectral cues have been reduced by band-limiting or remapped by warping. This suggests that hearing-impaired listeners, who have limited access to high frequencies, might also improve their localization ability when provided with spectrally warped or band-limited sounds and adequately trained on sound localization.
Accounting for the listener: Comparing the production of contrastive intonation in typically-developing speakers and speakers with autism
Authors: Kaland Constantijn , Swerts Marc , Krahmer Emiel
Published: August 2013

The present research investigates what drives the prosodic marking of contrastive information. For example, a typically developing speaker of a Germanic language like Dutch generally refers to a pink car as a “PINK car” (accented words in capitals) when a previously mentioned car was red. The main question addressed in this paper is whether contrastive intonation is produced with respect to the speaker's or (also) the listener's perspective on the preceding discourse. Furthermore, this research investigates the production of contrastive intonation by typically developing speakers and speakers with autism. The latter group is investigated because people with autism are argued to have difficulties accounting for another person's mental state and exhibit difficulties in the production and perception of accentuation and pitch range. To this end, utterances with contrastive intonation are elicited from both groups and analyzed in terms of function and form of prosody using production and perception measures. Contrary to expectations, typically developing speakers and speakers with autism produce functionally similar contrastive intonation as both groups account for both their own and their listener's perspective. However, typically developing speakers use a larger pitch range and are perceived as speaking more dynamically than speakers with autism, suggesting differences in their use of prosodic form.
Methods for tracking multiple marine mammals with wide-baseline passive acoustic arrays
Authors: Nosal Eva-Marie
Published: August 2013

Most methods used to track marine mammals with passive acoustics require that time differences of arrivals (TDOAs) are established and are associated between hydrophone pairs. Consequently, multiple animal trackers commonly apply single-animal TDOA localization methods after performing a call separation and/or TDOA association step. When a wide-baseline array is used with multiple animals that make similar calls with short inter-call-intervals, the separation/association step can be challenging and potentially rejects valid TDOAs. This paper extends a model-based TDOA method to deal with multiple-animal datasets in a way that does not require a TDOA association step; animals are separated based on position. Advantageously, false TDOAs (e.g., a direct path associated with a multipath arrival) do not need to be removed. An analogous development is also presented for a model-based time of arrival tracking method. Results from simulations and application to a multiple sperm whale dataset are used to illustrate the multiple-animal methods. Although computationally more demanding than most track-after-association methods because separation is performed in a higher-dimensional space, the methods are computationally tractable and represent a useful new tool in the suite of options available for tracking multiple animals with passive acoustics.
Effect of towed array stability on instantaneous localization of marine mammals
Authors: von Benda-Beckmann A. M. , Beerens S. P. , van IJsselmuide S. P.
Published: August 2013

Reliable localization of marine mammals using towed arrays is often required for mitigation, population density estimates, and bioacoustics research. The accuracy of the range estimates using towed arrays is often not well quantified. Triangulation methods using multiple hydrophones allow for fast range estimates but are sensitive to the species type, location of the animal with respect to the array, sound propagation conditions, and array stability. A simple model is presented that is used to estimate the range accuracy of towed arrays for different vocalizations and is compared to measured range accuracies of sperm whale clicks recorded with a 15 m baseline towed array. The ranging performance is particularly sensitive to hydrophone position errors which are found to dominate. Hydrophone position errors could be estimated using heading sensors placed in the array and are taken into account in the model. A good agreement is found between the empirical range errors and theoretically predicted ones. Extrapolation of the model to other species suggests that species emitting high frequency clicks and calls can be localized from distances out to a few kilometers with a baseline of 15 m, but baleen whales transmitting low frequency calls require longer baselines to obtain range estimates.
Acoustically derived growth rates of sperm whales (Physeter macrocephalus) in Kaikoura, New Zealand
Authors: Miller Brian S. , Growcott Abraham , Slooten Elisabeth , Dawson Stephen M.
Published: August 2013

A non-invasive acoustic method for measuring the growth of sperm whales was developed based on estimating the length of individuals by measuring the inter-pulse interval (IPI) of their clicks. Most prior knowledge of growth in male sperm whales has come from from fitting growth curves to length data gained from whaling. Recordings made at Kaikoura, New Zealand, were used to estimate the length and growth of 32 photographically identified, resident whales that have been recorded repeatedly between 1991 and 2009. All whales recorded more than six months apart (n = 30) showed an increase in IPI. Using established relationships between IPI and total length, it was found that the average growth rate in the Kaikoura population is lower, especially for smaller whales (13–14.5 m), than that derived from historical whaling data from other populations. This difference may be due to ecological differences among populations but might also reflect upward bias in measurements gained in whaling. The ability to track growth of individuals through time is only possible via non-lethal means and offers a fundamentally different kind of data because differences among individuals can be measured.
Acoustic tracking of sperm whales in the Gulf of Alaska using a two-element vertical array and tags
Authors: Mathias Delphine , Thode Aaron M. , Straley Jan , Andrews Russel D.
Published: August 2013

Between 15 and 17 August 2010, a simple two-element vertical array was deployed off the continental slope of Southeast Alaska in 1200 m water depth. The array was attached to a vertical buoy line used to mark each end of a longline fishing set, at 300 m depth, close to the sound-speed minimum of the deep-water profile. The buoy line also served as a depredation decoy, attracting seven sperm whales to the area. One animal was tagged with both a LIMPET dive depth-transmitting satellite and bioacoustic “B-probe” tag. Both tag datasets were used as an independent check of various passive acoustic schemes for tracking the whale in depth and range, which exploited the elevation angles and relative arrival times of multiple ray paths recorded on the array. Analytical tracking formulas were viable up to 2 km range, but only numerical propagation models yielded accurate locations up to at least 35 km range at Beaufort sea state 3. Neither localization approach required knowledge of the local bottom bathymetry. The tracking system was successfully used to estimate the source level of an individual sperm whale's “clicks” and “creaks” and predict the maximum detection range of the signals as a function of sea state.
The effects of acoustic misclassification on cetacean species abundance estimation
Authors: Caillat Marjolaine , Thomas Len , Gillespie Douglas
Published: August 2013

To estimate the density or abundance of a cetacean species using acoustic detection data, it is necessary to correctly identify the species that are detected. Developing an automated species classifier with 100% correct classification rate for any species is likely to stay out of reach. It is therefore necessary to consider the effect of misidentified detections on the number of observed data and consequently on abundance or density estimation, and develop methods to cope with these misidentifications. If misclassification rates are known, it is possible to estimate the true numbers of detected calls without bias. However, misclassification and uncertainties in the level of misclassification increase the variance of the estimates. If the true numbers of calls from different species are similar, then a small amount of misclassification between species and a small amount of uncertainty around the classification probabilities does not have an overly detrimental effect on the overall variance. However, if there is a difference in the encounter rate between species calls and/or a large amount of uncertainty in misclassification rates, then the variance of the estimates becomes very large and this dramatically increases the variance of the final abundance estimate.
Trackline and point detection probabilities for acoustic surveys of Cuvier's and Blainville's beaked whales
Authors: Barlow Jay , Tyack Peter L. , Johnson Mark P. , Baird Robin W. , Schorr Gregory S. , Andrews Russel D. , Aguilar de Soto Natacha
Published: August 2013

Acoustic survey methods can be used to estimate density and abundance using sounds produced by cetaceans and detected using hydrophones if the probability of detection can be estimated. For passive acoustic surveys, probability of detection at zero horizontal distance from a sensor, commonly called g(0), depends on the temporal patterns of vocalizations. Methods to estimate g(0) are developed based on the assumption that a beaked whale will be detected if it is producing regular echolocation clicks directly under or above a hydrophone. Data from acoustic recording tags placed on two species of beaked whales (Cuvier's beaked whale—Ziphius cavirostris and Blainville's beaked whale—Mesoplodon densirostris) are used to directly estimate the percentage of time they produce echolocation clicks. A model of vocal behavior for these species as a function of their diving behavior is applied to other types of dive data (from time-depth recorders and time-depth-transmitting satellite tags) to indirectly determine g(0) in other locations for low ambient noise conditions. Estimates of g(0) for a single instant in time are 0.28 [standard deviation (s.d.) = 0.05] for Cuvier's beaked whale and 0.19 (s.d. = 0.01) for Blainville's beaked whale.
Acoustic detection and long-term monitoring of pygmy blue whales over the continental slope in southwest Australia
Authors: Gavrilov Alexander N. , McCauley Robert D.
Published: August 2013

A 9-yr dataset of continuous sea noise recording made at the Cape Leeuwin station of the Comprehensive Nuclear-Test-Ban Treaty hydroacoustic network in 2002–2010 was processed to detect calls from pygmy blue whales and to analyze diel, seasonal, and interannual variations in their vocal activity. Because the conventional spectrogram correlation method for recognizing whale calls in sea noise resulted in a too high false detection rate, alternative algorithms were tested and the most robust one applied to the multi-year dataset. The detection method was based on multivariate classification using two spectrogram features of transients in sea noise and Fisher's linear discriminant, which provided a misclassification rate of approximately 1% for missed and false detections at moderate sensitivity settings. An analysis of the detection results revealed a consistent seasonal pattern in the whale presence and considerable interannual changes with a steady increase in the number of calls detected in 2002–2006. An apparent diel pattern of whales' vocal activity was also observed. The acoustic detection range for pygmy blue whales was estimated to vary from about 50 km to nearly 200 km from the Cape Leeuwin station, depending on the ambient noise level, source level, and azimuth to a vocalizing whale.
Methodology and results of calibration of tonal click detectors for small odontocetes (C-PODs)
Authors: Dähne Michael , Katharina Verfuß Ursula , Brandecker Anja , Siebert Ursula , Benke Harald
Published: August 2013

Static acoustic monitoring (SAM) is one major technology for observing small cetacean species. Automatic click loggers deployed for long time periods (>2 months) with a single hydrophone are a standard solution. Acoustic properties, like detection thresholds of these instruments, are essential for interpretation of results, but have nevertheless received little attention. A methodology for calibrating tonal click detectors in small tanks consisting of the determination of the horizontal directivity pattern and detection thresholds including a transfer function is presented. Two approaches were tested to determine detection thresholds by (a) determining the 50% detection threshold and (b) fitting a linear regression model to the recorded relative amplitudes. The tests were carried out on C-PODs (Cetacean PODs, tonal click detectors), the most commonly used instrument for SAM in Europe. Directivity and threshold were tested between 60 and 150 kHz. Directivity showed a maximum variation of 8.5 dB in the horizontal plane. Sensitivity is highest between 80 and 130 kHz and linear (±3 dB) in this frequency range for most of the instruments tested. C-PODs have a detection threshold (calculated with the linear model) of 114.5 ± 1.2 (standard deviation) dB re 1 μPa peak–peak at 130 kHz.
Underwater passive acoustic localization of Pacific walruses in the northeastern Chukchi Sea
Authors: Rideout Brendan P. , Dosso Stan E. , Hannay David E.
Published: August 2013

This paper develops and applies a linearized Bayesian localization algorithm based on acoustic arrival times of marine mammal vocalizations at spatially-separated receivers which provides three-dimensional (3D) location estimates with rigorous uncertainty analysis. To properly account for uncertainty in receiver parameters (3D hydrophone locations and synchronization times) and environmental parameters (water depth and sound-speed correction), these quantities are treated as unknowns constrained by prior estimates and prior uncertainties. Unknown scaling factors on both the prior and arrival-time uncertainties are estimated by minimizing Akaike's Bayesian information criterion (a maximum entropy condition). Maximum a posteriori estimates for sound source locations and times, receiver parameters, and environmental parameters are calculated simultaneously using measurements of arrival times for direct and interface-reflected acoustic paths. Posterior uncertainties for all unknowns incorporate both arrival time and prior uncertainties. Monte Carlo simulation results demonstrate that, for the cases considered here, linearization errors are small and the lack of an accurate sound-speed profile does not cause significant biases in the estimated locations. A sequence of Pacific walrus vocalizations, recorded in the Chukchi Sea northwest of Alaska, is localized using this technique, yielding a track estimate and uncertainties with an estimated speed comparable to normal walrus swim speeds.
Calling depths of baleen whales from single sensor data: Development of an autocorrelation method using multipath localization
Authors: Valtierra Robert D. , Glynn Holt R. , Cholewiak Danielle , Van Parijs Sofie M.
Published: August 2013

Multipath localization techniques have not previously been applied to baleen whale vocalizations due to difficulties in application to tonal vocalizations. Here it is shown that an autocorrelation method coupled with the direct reflected time difference of arrival localization technique can successfully resolve location information. A derivation was made to model the autocorrelation of a direct signal and its overlapping reflections to illustrate that an autocorrelation may be used to extract reflection information from longer duration signals containing a frequency sweep, such as some calls produced by baleen whales. An analysis was performed to characterize the difference in behavior of the autocorrelation when applied to call types with varying parameters (sweep rate, call duration). The method's feasibility was tested using data from playback transmissions to localize an acoustic transducer at a known depth and location. The method was then used to estimate the depth and range of a single North Atlantic right whale (Eubalaena glacialis) and humpback whale (Megaptera novaeangliae) from two separate experiments.
Passive acoustic monitoring using a towed hydrophone array results in identification of a previously unknown beaked whale habitat
Authors: Yack Tina M. , Barlow Jay , Calambokidis John , Southall Brandon , Coates Shannon
Published: August 2013

Beaked whales are diverse and species rich taxa. They spend the vast majority of their time submerged, regularly diving to depths of hundreds to thousands of meters, typically occur in small groups, and behave inconspicuously at the surface. These factors make them extremely difficult to detect using standard visual survey methods. However, recent advancements in acoustic detection capabilities have made passive acoustic monitoring (PAM) a viable alternative. Beaked whales can be discriminated from other odontocetes by the unique characteristics of their echolocation clicks. In 2009 and 2010, PAM methods using towed hydrophone arrays were tested. These methods proved highly effective for real-time detection of beaked whales in the Southern California Bight (SCB) and were subsequently implemented in 2011 to successfully detect and track beaked whales during the ongoing Southern California Behavioral Response Study. The three year field effort has resulted in (1) the successful classification and tracking of Cuvier's (Ziphius cavirostris), Baird's (Berardius bairdii), and unidentified Mesoplodon beaked whale species and (2) the identification of areas of previously unknown beaked whale habitat use. Identification of habitat use areas will contribute to a better understanding of the complex relationship between beaked whale distribution, occurrence, and preferred habitat characteristics on a relatively small spatial scale. These findings will also provide information that can be used to promote more effective management and conservation of beaked whales in the SCB, a heavily used Naval operation and training region.
Narrow band noise response of a Belleville spring resonator
Authors: Lyon Richard H.
Published: August 2013

This study of nonlinear dynamics includes (i) an identification of quasi-steady states of response using equivalent linearization, (ii) the temporal simulation of the system using Heun's time step procedure on time domain analytic signals, and (iii) a laboratory experiment. An attempt has been made to select material and measurement parameters so that nearly the same systems are used and analyzed for all three parts of the study. This study illustrates important features of nonlinear response to narrow band excitation: (a) states of response that the system can acquire with transitions of the system between those states, (b) the interaction between the noise source and the vibrating load in which the source transmits energy to or draws energy from the load as transitions occur; (c) the lag or lead of the system response relative to the source as transitions occur that causes the average frequencies of source and response to differ; and (d) the determination of the state of response (mass or stiffness controlled) by observation of the instantaneous phase of the influence function. These analyses take advantage of the use of time domain analytic signals that have a complementary role to functions that are analytic in the frequency domain.
Irrelevant speech effect under stationary and adaptive masking conditions
Authors: Park Munhum , Kohlrausch Armin , van Leest Arno
Published: August 2013

The irrelevant speech effect was investigated in this study where the serial-recall task was performed under six different conditions: Silence, speech-only, noise-only, speech masked by a stationary noise at two different signal-to-noise ratios (SNRs), and speech masked by an adaptive noise. Measured in five test blocks distributed throughout the four test days, the error rate of the serial-recall task under the silence condition sharply decreased in the first few test blocks, halved after completing about seven blocks. When the adaptive masking scheme was used, the error rate of the serial-recall test was reduced compared to the speech-only condition (by 9%) and to the lower-SNR stationary noise (by 4.4%). However, the serial-recall performance was not significantly different between the stationary and the adaptive maskers when the average sound level was carefully matched. Speech Transmission Index (STI) and the correlation coefficient of power spectra were used as the estimators of the temporal and spectral distinctiveness between sound tokens, respectively. The comparison to the test results implied that the frequency-domain estimator may be a better predictor of the relative ISE especially for a non-stationary masker, although it was also suggested that such estimators may have to be combined possibly with an appropriate weighting.
Short-latency transient-evoked otoacoustic emissions as predictors of hearing status and thresholds
Authors: Mertes Ian B. , Goodman Shawn S.
Published: August 2013

Estimating audiometric thresholds using objective measures can be clinically useful when reliable behavioral information cannot be obtained. Transient-evoked otoacoustic emissions (TEOAEs) are effective for determining hearing status (normal hearing vs hearing loss), but previous studies have found them less useful for predicting audiometric thresholds. Recent work has demonstrated the presence of short-latency TEOAE components in normal-hearing ears, which have typically been eliminated from the analyses used in previous studies. The current study investigated the ability of short-latency components to predict hearing status and thresholds from 1–4 kHz. TEOAEs were measured in 77 adult ears with thresholds ranging from normal hearing to moderate sensorineural hearing loss. Emissions were bandpass filtered at center frequencies from 1 to 4 kHz. TEOAE waveforms were analyzed within two time windows that contained either short- or long-latency components. Waveforms were quantified by root-mean-square amplitude. Long-latency components were better overall predictors of hearing status and thresholds, relative to short-latency components. There were no significant improvements in predictions when short-latency components were included with long-latency components in multivariate analyses. The results showed that short-latency TEOAE components, as analyzed in the current study, were less predictive of both hearing status and thresholds from 1–4 kHz than long-latency components.
Species-specific beaked whale echolocation signals
Authors: Baumann-Pickering Simone , McDonald Mark A. , Simonis Anne E. , Solsona Berga Alba , Merkens Karlina P. B. , Oleson Erin M. , Roch Marie A. , Wiggins Sean M. , Rankin Shannon , Yack Tina M. , Hildebrand John A.
Published: August 2013

Beaked whale echolocation signals are mostly frequency-modulated (FM) upsweep pulses and appear to be species specific. Evolutionary processes of niche separation may have driven differentiation of beaked whale signals used for spatial orientation and foraging. FM pulses of eight species of beaked whales were identified, as well as five distinct pulse types of unknown species, but presumed to be from beaked whales. Current evidence suggests these five distinct but unidentified FM pulse types are also species-specific and are each produced by a separate species. There may be a relationship between adult body length and center frequency with smaller whales producing higher frequency signals. This could be due to anatomical and physiological restraints or it could be an evolutionary adaption for detection of smaller prey for smaller whales with higher resolution using higher frequencies. The disadvantage of higher frequencies is a shorter detection range. Whales echolocating with the highest frequencies, or broadband, likely lower source level signals also use a higher repetition rate, which might compensate for the shorter detection range. Habitat modeling with acoustic detections should give further insights into how niches and prey may have shaped species-specific FM pulse types.
Acoustic mapping of ocean currents using networked distributed sensors
Authors: Huang Chen-Fen , Yang T. C. , Liu Jin-Yuan , Schindall Jeff
Published: August 2013

Distributed underwater sensors are expected to provide oceanographic monitoring over large areas. As fabrication technology advances, low cost sensors will be available for many uses. The sensors communicate to each other and are networked using acoustic communications. This paper first studies the performance of such systems for current measurements using tomographic inversion approaches to compare with that of a conventional system which distributes the sensors on the periphery of the area of interest. It then proposes two simple signal processing methods for ocean current mapping (using distributed networked sensors) aimed at real-time in-buoy processing. Tomographic inversion generally requires solving a challenging high dimensional inverse problem, involving substantial computations. Given distributed sensors, currents can be constructed locally based on data from neighboring sensors. It is shown using simulated data that similar results are obtained using distributed processing as using conventional tomographic approaches. The advantage for distributed systems is that by increasing the number of nodes, one gains a much more improved performance. Furthermore, distributed systems use much less energy than a conventional tomographic system for the same area coverage. Experimental data from an acoustic communication and networking experiment are used to demonstrate the feasibility of acoustic current mapping.
Finite-size effects on the quasistatic displacement pulse in a solid specimen with quadratic nonlinearity
Authors: Nagy Peter B. , Qu Jianmin , Jacobs Laurence J.
Published: August 2013

There is an unresolved debate in the scientific community about the shape of the quasistatic displacement pulse produced by nonlinear acoustic wave propagation in an elastic solid with quadratic nonlinearity. Early analytical and experimental studies suggested that the quasistatic pulse exhibits a right-triangular shape with the peak displacement of the leading edge being proportional to the length of the tone burst. In contrast, more recent theoretical, analytical, numerical, and experimental studies suggested that the quasistatic displacement pulse has a flat-top shape where the peak displacement is proportional to the propagation distance. This study presents rigorous mathematical analyses and numerical simulations of the quasistatic displacement pulse. In the case of semi-infinite solids, it is confirmed that the time-domain shape of the quasistatic pulse generated by a longitudinal plane wave is not a right-angle triangle. In the case of finite-size solids, the finite axial dimension of the specimen cannot simply be modeled with a linear reflection coefficient that neglects the nonlinear interaction between the combined incident and reflected fields. More profoundly, the quasistatic pulse generated by a transducer of finite aperture suffers more severe divergence than both the fundamental and second order harmonic pulses generated by the same transducer.
Mechanisms of microbubble–vessel interactions and induced stresses: A numerical study
Authors: Hosseinkhah N. , Chen H. , Matula T. J. , Burns P. N. , Hynynen K.
Published: August 2013

Oscillating microbubbles within microvessels could induce stresses that lead to bioeffects or vascular damage. Previous work has attributed vascular damage to the vessel expansion or bubble jet. However, ultra-high speed images of recent studies suggest that it could happen due to the vascular invagination. Numerical simulations of confined bubbles could provide insight into understanding the mechanism behind bubble–vessel interactions. In this study, a finite element model of a coupled bubble/fluid/vessel system was developed and validated with experimental data. Also, for a more realistic study viscoelastic properties of microvessels were assessed and incorporated into this comprehensive numerical model. The wall shear stress (WSS) and circumferential stress (CS), metrics of vascular damage, were calculated from these simulations. Resultant amplitudes of oscillation were within 15% of those measured in experiments (four cases). Among the experimental cases, it was numerically found that maximum WSS values were between 1.1–18.3 kPa during bubble expansion and 1.5–74 kPa during bubble collapse. CS was between 0.43–2.2 MPa during expansion and 0.44–6 MPa while invaginated. This finding confirmed that vascular damage could occur during vascular invaginations. Predicted thresholds in which these stresses are higher during vessel invagination were calculated from simulations.
Auditory enhancement and second language experience in Spanish and English weighting of secondary voicing cues
Authors: Llanos Fernando , Dmitrieva Olga , Shultz Amanda , Francis Alexander L.
Published: August 2013

The role of secondary cues in voicing categorization was investigated in three listener groups: Monolingual English (n = 20) and Spanish speakers (n = 20), and Spanish speakers with significant English experience (n = 16). Results showed that, in all three groups, participants used onset f0 in making voicing decisions only in the positive voice onset time (VOT) range (short lag and long lag tokens), while there was no effect of onset f0 on voicing categorization within the negative VOT range (voicing lead tokens) for any of the participant groups. These results support an auditory enhancement view of perceptual cue weighting: Onset f0 serves as a secondary cue to voicing only in the positive VOT range where it is not overshadowed by the presence of pre-voicing. Moreover, results showed that Spanish learners of English gave a significantly greater weight to onset f0 in their voicing decisions than did listeners in either of the other two groups. This result supports the view that learners may overweight secondary cues to distinguish between non-native categories that are assimilated to the same native category on the basis of a primary cue.
The information-divergence hypothesis of informational masking
Authors: Lutfi Robert A. , Gilbertson Lynn , Heo Inseok , Chang An-Chieh , Stamas Jacob
Published: August 2013

In recent years there has been growing interest in masking that cannot be attributed to interactions in the cochlea—so-called informational masking (IM). Similarity in the acoustic properties of target and masker and uncertainty regarding the masker are the two major factors identified with IM. These factors involve quite different manipulations of signals and are believed to entail fundamentally different processes resulting in IM. Here, however, evidence is presented that these factors affect IM through their mutual influence on a single factor—the information divergence of target and masker given by Simpson–Fitter's da [Lutfi et al. (2012). J. Acoust. Soc. Am. 132, EL109–113]. Four experiments are described involving multitone pattern discrimination, multi-talker word recognition, sound-source identification, and sound localization. In each case standard manipulations of masker uncertainty and target-masker similarity (including the covariation of target-masker frequencies) are found to have the same effect on performance provided they produce the same change in da. The function relating d′ performance to da, moreover, appears to be linear with constant slope across listeners. The overriding dependence of IM on da is taken to reflect a general principle of perception that exploits differences in the statistical structure of signals to separate figure from ground.
Optimizing stepwise rotation of dodecahedron sound source to improve the accuracy of room acoustic measures
Authors: Martellotta Francesco
Published: August 2013

Dodecahedron sound sources are widely used for acoustical measurement purposes as they produce a good approximation of omnidirectional radiation. Evidence shows that such an assumption is acceptable only in the low-frequency range (namely below 1 kHz), while at higher frequencies sound radiation is far from being uniform. In order to improve the accuracy of acoustical measurements obtained from dodecahedron sources, international standard ISO 3382 suggests an averaging of results after a source rotation. This paper investigates the effects of such rotations, both in terms of variations in acoustical parameters and spatial distribution of sound reflections. Taking advantage of a spherical microphone array, the different reflection patterns were mapped as a function of source rotation, showing that some reflections may be considerably attenuated for different aiming directions. This paper investigates the concept of averaging results while changing rotation angles and the minimum number of rotations required to improve the accuracy of the average value. Results show that averages of three measurements carried out at 30° angular steps are closer to actual values and show much less fluctuation. In addition, an averaging of the directional intensity components of the selected responses stabilizes the spatial distribution of the reflections.
Modeling, analysis, and validation of an active T-shaped noise barrier
Authors: Fan Rongping , Su Zhongqing , Cheng Li
Published: August 2013

With ever-increasing land traffic, abatement of traffic noise using noise barriers remains significant, yet it is a challenging task due to spatial competition with other infrastructure. In this study, a deep insight into the diffraction characteristics of acoustic fields near noise barriers of various geometries and surface conditions was achieved using numerical simulations. A T-shaped passive noise barrier with acoustically soft upper surfaces was demonstrated to outperform other candidates in a middle- or high-frequency range. Based on attributes of the acoustic field diffracted by T-shaped barriers, an active control strategy was developed to revamp the T-shaped barrier, in which a filtered minimax algorithm was established to drive the secondary sound sources. This algorithm resulted in more uniformly distributed residual sound fields than a filtered-X least mean square algorithm. Performance of the actively controlled barrier was evaluated at different positions and spacings of secondary sound sources and error sensors, leading to a series of optimal criteria for the design of active noise barriers. A prototype was fabricated and validated experimentally, manifesting particular effectiveness in insulating low-frequency noise, supplementing well the capacity of a passive T-shaped barrier which is effective in the middle- or high-frequency range.
Scattering of a fluid-structure coupled wave at a flanged junction between two flexible waveguides
Authors: Nawaz Rab , Lawrie Jane B.
Published: August 2013

The scattering of a fluid-structure coupled wave at a flanged junction between two flexible waveguides is investigated. The flange is assumed to be rigid on one side and soft on the other; this enables a solution to be formulated using mode-matching. It is shown that both the choice of the edge conditions imposed on the plates at the junction and the choice of incident forcing significantly affect the transmission of energy along the duct. In particular, the edge conditions crucially affect the transmission of structure-borne vibration but have little effect on fluid-borne noise. Given the singular nature of the velocity field at the flange tip, particular attention is paid to the validity of the mode-matching method. It is demonstrated that the velocity field can be accurately reconstructed by incorporating the Lanczos filter into the truncated modal expansions. The mode-matching method is thus confirmed as an viable tool for this class of problem.
Local resonance bandgaps in periodic media: Theory and experiment
Authors: Raghavan L. , Phani A. Srikantha
Published: August 2013

Periodic composites such as acoustic metamaterials use local resonance phenomenon in designing low frequency sub-Bragg bandgaps. These bandgaps emerge from a resonant scattering interaction between a propagating wave and periodically arranged resonators. This paper develops a receptance coupling technique to combine the dynamics of the resonator with the unit cell dynamics of the background medium to analyze flexural wave transmission in a periodic structure, involving a single degree of freedom coupling between the medium and the resonator. Receptance techniques allow for a straightforward extension to higher dimensional systems with multiple degrees of freedom coupling and for easier experimental measurements. Closed-form expressions for the location and width of sub-Bragg bandgaps are obtained. Rigid body modes of the unit cell of the background medium are shown to set the bounding frequencies for local resonance bandgaps. Results from the receptance analysis compare well with Bloch wave analysis and experiments performed on a finite structural beam with periodic masses and resonators. Stronger coupling and inertia of the resonator increase the local resonance bandgap width. Two-fold periodicity widens the Bragg bandgap, narrowed by local resonators, thus expanding the design space and highlighting the advantages of hierarchical periodicity.
Control of the stop band of an acoustic double fishnet
Authors: Murray Alasdair R. J. , Hendry Euan , Summers Ian R. , Sambles J. Roy , Hibbins Alastair P.
Published: August 2013

The acoustic transmittance of two closely spaced solid plates, each perforated with a square array of cylindrical holes, exhibits a band of near-perfect acoustic attenuation originating from hybridization between a resonance in the gap separating the plates and pipe resonances in the holes. Displacement of one plate relative to the other, such that the holes are no longer aligned, or an increase in the plate separation leads to an increased center frequency of the stop band. This ability to easily tune the frequency of the stop band may prove advantageous.
The effects of working memory capacity and semantic cues on the intelligibility of speech in noise
Authors: Zekveld Adriana A. , Rudner Mary , Johnsrude Ingrid S. , Rönnberg Jerker
Published: August 2013

This study examined how semantically related information facilitates the intelligibility of spoken sentences in the presence of masking sound, and how this facilitation is influenced by masker type and by individual differences in cognitive functioning. Dutch sentences were masked by stationary noise, fluctuating noise, or an interfering talker. Each sentence was preceded by a text cue; cues were either three words that were semantically related to the sentence or three unpronounceable nonwords. Speech reception thresholds were adaptively measured. Additional measures included working memory capacity (reading span and size comparison span), linguistic closure ability (text reception threshold), and delayed sentence recognition. Word cues facilitated speech perception in noise similarly for all masker types. Cue benefit was related to reading span performance when the masker was interfering speech, but not when other maskers were used, and it did not correlate with text reception threshold or size comparison span. Better reading span performance was furthermore associated with enhanced delayed recognition of sentences preceded by word relative to nonword cues, across masker types. The results suggest that working memory capacity is associated with release from informational masking by semantically related information, and additionally with the encoding, storage, or retrieval of speech content in memory.
Malignant transformation of superficial peritoneal endometriosis lesion
Authors: Marchand Eva , Hequet Delphine , Thoury Anne , Barranger Emmanuel
Published: August 2013

A 63-year-old woman with no medical history underwent an abdominal surgery with hysterectomy and bilateral salpingo-oophorectomy for a 10 cm peritoneal cyst with increased cancer antigene-125. A large suspicious tumour of the Douglas space, with contact to the uterus and the rectal wall was described. The rest of the exploration was normal, specially the rest of the peritoneum. Histopathology revealed a malignant transformation of a superficial peritoneal endometriosis. Secondary surgery was thus completed by laparoscopy with bilateral pelvic and para-aortic lymph node dissections, omentectomy and multiple peritoneal biopsies. All staging samples were free of cancer; therefore no complementary therapy was administered. After 18 months of follow-up, consisting of clinical examination and pelvis magnetic resonance imaging every 6 months, we did not observe any recurrence. Malignant transformation of superficial peritoneal endometriosis is a rare disease and surgical management seems to be the main treatment.
Bizarre cause for avulsion of permanent maxillary lateral incisor tooth
Authors: Kiran Shital , Bargale Seema Dinesh , Sikligar Smit , Shanthraj Srinivas L
Published: August 2013

A 9-year-old boy presented with a missing upper front tooth after an accident involving kite flying. Diagnosis of avulsion of the upper right lateral incisor (22) was made after examination of his socket as well as by radiological investigations. A removable partial denture was given for the aesthetic purpose. The patient is under follow-up. The present case illustrates the management of avulsion.
Exercise- and resveratrol-mediated alterations in adipose tissue metabolism
Authors: Wright David C.
Published: August 2013

Owing to its obligatory role in locomotion and the fact that it accounts for the vast majority of whole-body glucose and lipid oxidation, much work has focused on studying the biochemical adaptations that occur in skeletal muscle in response to exercise. However, over the past several years there has been a growing appreciation that adipose tissue is an important player in regulating systemic carbohydrate and lipid homeostasis. Despite this, the examination of how exercise alters adipose tissue function and metabolism is, when compared with skeletal muscle, in its infancy. The purpose of the current review is to highlight some of the recent findings from our laboratory and others that focus on the emerging area of adipose tissue exercise biochemistry. Specifically, the role of exercise on the induction of mitochondrial and glyceroneogenic enzymes will be examined and will be compared with the well-characterized effects of thiazolidinediones, which are insulin-sensitizing drugs. A particular emphasis will be placed on the role of interleukin-6 in mediating the effects of exercise. Finally, we will discuss recent data from our laboratory demonstrating beneficial effects of resveratrol supplementation on adipose tissue metabolism.
Experimental testing and finite element modeling on continuous concrete beams reinforced with fibre reinforced polymer bars and stirrups
Authors: El-Mogy Mostafa , El-Ragaby Amr , El-Salakawy Ehab
Published: August 2013

Continuous concrete beams are common elements in structures such as parking garages and overpasses, which might be exposed to extreme weather. Using the non-corrodible fibre reinforced polymer (FRP) bars is a viable alternative to avoid steel corrosion problems. Due to the linear-elastic behaviour of FRP materials, the possibility of moment redistribution in FRP-reinforced beams is questionable. In this paper, the experimental results of ten full-scale continuous concrete beams are summarized followed by a finite element parametric study using ANSYS software. Steel, glass fibre reinforced polymer, and carbon fibre reinforced polymer bars were used in different combinations as longitudinal and transverse reinforcement. The main investigated parameters were the ratio and type of longitudinal and transverse reinforcement. Results showed that moment redistribution in such beams is possible if the reinforcement configuration is chosen properly. The developed finite element model predicted the response of tested beams with a reasonable degree of accuracy and was used to expand the range of investigated parameters.