bluuebunny/crossref_metadata_2025 huggingface dataset:
Lack of an osmotic constraint on intake rate of the eastern curlew Numenius madagascariensis
Authors: Blakey Rachel , Zharikov Yuri , A. Skilleter Greg
Published: June 2006

Rates of food intake in animals consuming abundant prey can be constrained by the rates of digestion or excretion of ingested substances, such as salt, particularly so in the animals that regularly migrate between freshwater and saltwater environments. We tested this hypothesis in a long‐distance migrant shorebird, the eastern curlew Numenius madagascariensis (suborder Charadrii), foraging on intertidal decapods in eastern Australia. We predicted that if food intake rates are constrained osmotically, individuals with access to freshwater and less saline prey (FW group) would have higher rates of food and water intake than individuals with seawater‐only access (SW group). Food intake rates did not differ between the FW and SW groups (0.14 g ash‐free dry mass min−1), nor did the water influx rates (0.75 g min−1). Salt intake rates were lower at FW sites (19.3 versus 23.3 mg NaCl min−1) and overall they were similar to those of marine birds. Food intake rate in the eastern curlew appeared limited by digestive rather than by osmoregulatory capacity.
Measuring the off-axis angle and the rotational movements of phonating sperm whales using a single hydrophone
Authors: Laplanche Christophe , Adam Olivier , Lopatka Maciej , Motsch Jean-François
Published: June 2006

The common use of the bent-horn model of the sperm whale sound generator describes sperm whale clicks as the pulse series {p0,p1,p2,p3,…}. Clicks, however, deviate from this standard when recorded using off-axis hydrophones. The existence of additional pulses within the {p0,p1,p2,p3,…} series can be explained still using the bent-horn model. Multiple reflections on the whale’s frontal and distal sacs of the p0 pulse lead to additional sets of pulses detectable using a farfield, off-axis hydrophone. The travel times of some of these additional pulses depend on the whale’s orientation. The authors propose a method to estimate the off-axis angle of sperm whale clicks. They also propose a method to determine the nature of the movement (if it is pitch, yaw, or roll) of phonating sperm whales. The application of both methods requires the measurement of the travel time differences between pulses composing a sperm whale click. They lead, using a simple apparatus consisting of a single hydrophone at an unknown depth, to new measurements of the underwater movements of sperm whales. Using these methods shows that sperm whales would methodically scan seawater while searching for prey, by making periodic pitch and yaw movements in sync with their acoustic activity.
Sound absorption by viscoelastic coatings with periodically distributed cavities
Authors: Ivansson Sven M.
Published: June 2006

Thin rubber layers with air-filled cavities can be used as anechoic submarine coatings. Normally incident sonar energy is redistributed in the lateral direction and absorbed. In this paper, the anechoic effect is studied theoretically and numerically by adapting techniques used in electron scattering and band-gap computations for photonic and phononic crystals. Reflection and transmission matrices are computed recursively, from basic ones for layers containing periodic arrays of spherical cavities. A method to locate zeroes of analytical functions is applied to prove the existence of, and to specify, thin coatings with vanishing reflectance at isolated frequencies. Coatings much thinner than quarter-wavelength ones are found. Most of the absorption loss takes place close to the cavities and scattering of compressional spherically symmetric waves is important. The viscoelastic shear-wave properties of the rubber are crucial for generating this loss. The requirements for vanishing reflectance are specified using a simplified model with normal plane waves and spherically symmetric waves, that includes effects of multiple scattering among the cavities. An energy relation is derived, relating the anelastic loss in the rubber coating to loss by monopole resonance scattering from isolated cavities. The noticeable effects of multiple scattering are incorporated by a modulating factor.
The directionality of acoustic T-phase signals from small magnitude submarine earthquakes
Authors: Chapman N. R. , Marrett R.
Published: June 2006

Acoustic transients radiated from small magnitude undersea earthquakes were studied in an experiment carried out using a towed horizontal line array operating in the South Fiji Basin. The transient signals consisted of P, S, and T phases, with the T-phase signal from each earthquake lasting up to 7min. The directionality of the T-phase signal was determined by processing the array hydrophone data with a conventional beamformer. The weakest part of the signal arrived first on a direct bearing between the earthquake source and the array. However, subsequent stronger components arrived from different directions farther south of the source, in a region where a number of seamounts and ridges rose within the sound channel. A simple model based on ray path travel times for elastic wave travel in the earth and acoustic wave propagation in the water suggests that the later components of the T-phase signal were radiated into the water by downslope propagation from the seamounts and ridges. The initial weaker components may be scattered into the sound channel by leakage from the P and S phases relatively close to the array.
The effect of reflector geometry on the acoustic field and bubble dynamics produced by an electrohydraulic shock wave lithotripter
Authors: Zhou Yufeng , Zhong Pei
Published: June 2006

A theoretical model for the propagation of shock wave from an axisymmetric reflector was developed by modifying the initial conditions for the conventional solution of a nonlinear parabolic wave equation (i.e., the Khokhlov–Zabolotskaya–Kuznestsov equation). The ellipsoidal reflector of an HM-3 lithotripter is modeled equivalently as a self-focusing spherically distributed pressure source. The pressure wave form generated by the spark discharge of the HM-3 electrode was measured by a fiber optic probe hydrophone and used as source conditions in the numerical calculation. The simulated pressure wave forms, accounting for the effects of diffraction, nonlinearity, and thermoviscous absorption in wave propagation and focusing, were compared with the measured results and a reasonably good agreement was found. Furthermore, the primary characteristics in the pressure wave forms produced by different reflector geometries, such as that produced by a reflector insert, can also be predicted by this model. It is interesting to note that when the interpulse delay time calculated by linear geometric model is less than about 1.5μs, two pulses from the reflector insert and the uncovered bottom of the original HM-3 reflector will merge together. Coupling the simulated pressure wave form with the Gilmore model was carried out to evaluate the effect of reflector geometry on resultant bubble dynamics in a lithotripter field. Altogether, the equivalent reflector model was found to provide a useful tool for the prediction of pressure wave form generated in a lithotripter field. This model may be used to guide the design optimization of reflector geometries for improving the performance and safety of clinical lithotripters.
Comparison of Levitt- and Zwislocki-type adaptive procedures for stimulus placement in human listeners
Authors: Rowan Daniel , Hinton Kathryn , Mackenzie Emma
Published: June 2006

The “3-down, 1-up” adaptive stimulus placement rules attributed to Levitt and Zwislocki were compared in the context of human interaural time difference discrimination, employing otherwise commonly used procedures (e.g., averaging reversals to estimate threshold). The Zwislocki rule typically accumulated over three more reversals than the Levitt rule but the rules were approximately equally efficient. This may be because the additional reversals did not provide additional information or that any additional information was countered by other factors, such as the lower theoretical asymptotic response probability (0.75 vs 0.794). Relative bias between rules was also explored with the aid of a simulation.
Auditory-visual speech perception and synchrony detection for speech and nonspeech signals
Authors: Conrey Brianna , Pisoni David B.
Published: June 2006

Previous research has identified a “synchrony window” of several hundred milliseconds over which auditory-visual (AV) asynchronies are not reliably perceived. Individual variability in the size of this AV synchrony window has been linked with variability in AV speech perception measures, but it was not clear whether AV speech perception measures are related to synchrony detection for speech only or for both speech and nonspeech signals. An experiment was conducted to investigate the relationship between measures of AV speech perception and AV synchrony detection for speech and nonspeech signals. Variability in AV synchrony detection for both speech and nonspeech signals was found to be related to variability in measures of auditory-only (A-only) and AV speech perception, suggesting that temporal processing for both speech and nonspeech signals must be taken into account in explaining variability in A-only and multisensory speech perception.
Speech categorization in context: Joint effects of nonspeech and speech precursors
Authors: Holt Lori L.
Published: June 2006

The extent to which context influences speech categorization can inform theories of pre-lexical speech perception. Across three conditions, listeners categorized speech targets preceded by speech context syllables. These syllables were presented as the sole context or paired with nonspeech tone contexts previously shown to affect speech categorization. Listeners’ context-dependent categorization across these conditions provides evidence that speech and nonspeech context stimuli jointly influence speech processing. Specifically, when the spectral characteristics of speech and nonspeech context stimuli are mismatched such that they are expected to produce opposing effects on speech categorization the influence of nonspeech contexts may undermine, or even reverse, the expected effect of adjacent speech context. Likewise, when spectrally matched, the cross-class contexts may collaborate to increase effects of context. Similar effects are observed even when natural speech syllables, matched in source to the speech categorization targets, serve as the speech contexts. Results are well-predicted by spectral characteristics of the context stimuli.
In-plane vibration of thin circular structures submitted to pulsed microwave
Authors: Hadj Henni Anis Redha , Bacon C. , Hosten B.
Published: June 2006

The absorption of microwaves by material induces a temperature rise that generates a mechanical deformation in the irradiated structure by thermoelastic effect. As a continuous development of this recent generation technique, the present study investigates the in-plane mechanical vibration of disks and rings submitted to pulsed microwaves in order to develop a contactless evaluation method. The vibration of a disk submitted to microwave irradiations depends on the distribution of the electromagnetic field in the sample. If the irradiation is axisymmetric, the purely radial eigenmode is generated. On the contrary, if the irradiation field is not axisymmetric, the vibration is angular dependent. Consequently, one can choose to use various eigenfrequencies for determining the geometrical properties of a circular plate and the mechanical properties of the material. A semi-analytic model is presented to predict the in-plane vibration eigenfrequencies of thin rings and disks. Wave equations are solved by taking into account the angular dependence in order to estimate the maximum number of disk or ring eigenfrequencies. The model is validated by comparison between the theoretical and the experimental results and applied for the evaluation of rings and disks geometries and their constitutive material properties using the microwave excitation technique.
Low-frequency acoustic propagation loss in the Arctic Ocean: Results of the Arctic climate observations using underwater sound experiment
Authors: Gavrilov Alexander N. , Mikhalevsky Peter N.
Published: June 2006

Acoustic data from the Arctic climate observations using underwater sound (ACOUS) experiment are analyzed to determine the correlation between acoustic propagation loss and the seasonal variability of sea ice thickness. The objective of this research is to provide long-term synoptic monitoring of sea ice thickness, an important global climate variable, using acoustic remote sensing. As part of the ACOUS program an autonomous acoustic source deployed northwest of Franz Josef Land transmitted tomographic signals at 20.5Hz once every four days from October 1998 until December 1999. These signals were received on a vertical array in the Lincoln Sea 1250km away. Two of the signals transmitted in April 1999 were received on a vertical array at ice camp APLIS in the Chukchi Sea north of Point Barrow, Alaska, at a distance of approximately 2720km from the source. Temporal variations of the modal propagation loss are examined. The influence of ice parameters, variations of the sound speed profile, and mode-coupling effects on the propagation losses of individual modes is studied. The experimental results are compared to the results of the earlier experiments and the theoretical prediction using numerical modeling.
Natural resonance frequencies, wave blocking, and energy localization in an elastic half-space and waveguide with a crack
Authors: Glushkov Evgeny , Glushkova Natalia , Golub Michael , Boström Anders
Published: June 2006

Sharp stopping of time-harmonic wave transmission in elastic structures with defects is considered as a manifestation of the well-known trapped mode effect. It is associated with natural resonance poles lying close to the real axis in the complex frequency plane. Nonresonant wave blocking may also occur due to antiphase combination of the incident and scattered waves. The present paper is aimed to give an insight into such phenomena using an analytically based computer model which strictly takes into account all wave interactions in a cracked structure. Numerical examples are restricted to the case of a line horizontal crack in a half-plane or in a layer (2D in-plane motion), that is, nevertheless, quite enough to demonstrate two kinds of the Rayleigh wave stopping mechanisms (resonant and nonresonant) as well as a possibility of pure real natural resonance frequencies and of a full blocking effect with energy localization.
Correlation analysis of the beam angle dependence for elastography
Authors: Rao Min , Varghese Tomy
Published: June 2006

Signal decorrelation is a major source of error in the displacements estimated using correlation techniques for elastographic imaging. Previous papers have addressed the variation in the correlation coefficient as a function of the applied compression for a finite window size and an insonification angle of zero degrees. The recent use of angular beam-steered radio-frequency echo signals for spatial angular compounding and shear strain estimation have demonstrated the need for understanding signal decorrelation artifacts for data acquired at different beam angles. In this paper, we provide both numerical and closed form theoretical solutions of the correlation between pre- and post-compression radio-frequency echo signals acquired at a specified beam angle. The expression for the correlation coefficient obtained is a function of the beam angle and the applied compression for a finite duration window. Accuracy of the theoretical results is verified using tissue-mimicking phantom experiments on a uniformly elastic phantom using beam-steered data acquisitions on a linear array transducer. The theory predicts a faster decorrelation with changes in the beam or insonification angle for longer radio-frequency echo signal segments and at deeper locations in the medium. Theoretical results provide useful information for improving angular compounding and shear strain estimation techniques for elastography.
A method for modeling polymer viscoelastic data and the temperature shift function
Authors: Madigosky Walter M. , Lee Gilbert F. , Niemiec Jan M.
Published: June 2006

Dynamic viscoelastic polymer data is traditionally time-temperature shifted to obtain a temperature shift function (TSF) and then fitted to various analytical models. The process of obtaining the TSF can introduce considerable procedural or operator bias. Nevertheless the Havriliak and Negami (HN) model using the TSF methodology can generally describe polymers that are rheologically simple. In this paper the “wicket” plot is utilized as an important tool in analyzing data, as it is completely independent of time-temperature shifting (TTS). Using the wicket plot the data is fit to the HN equation to determine the four material HN constants independent of TTS. Having obtained the complete spectra of dynamic properties the specific relaxation time (frequency) at each temperature is obtained by matching the HN curve to the experimental data at that temperature thus determining the TSF. The procedure is illustrated by analyzing computer-generated data with random error in modulus and loss and finally real data on a standard material.
Steerable frequency-invariant beamforming for arbitrary arrays
Authors: Parra Lucas C.
Published: June 2006

Frequency-invariant beamforming aims to parameterize array filter coefficients such that the spectral and spatial response profiles of the array can be adjusted independently. Solutions to this problem have been presented for specific sensor configurations often requiring a larger number of sensors. However, in practical applications, the number and location of sensors are often restricted. This paper proposes to find an optimal linear basis transformation that decouples the frequency response from the spatial response. A least-squares optimal basis transform can be computed numerically for arbitrary sensor configurations, for which typically no exact analytical solutions are available. This transform can be further combined with a spherical harmonics basis resulting in readily steerable broadband beams. This solution to broadband beamforming effectively decouples the array geometry from the steering geometry. Furthermore, for frequency-invariant beams, this approach results in a significant reduction in the number of beam-design parameters. Here, the method is demonstrated for an optimal design of far-field response for an irregular linear array with as few as three sensors.
Design of an underwater Tonpilz transducer with 2-2 mode piezocomposite materials
Authors: Roh Yongrae , Lu Xiaoguang
Published: June 2006

The performance of a transducer is determined by the properties of constituent materials and the effects of many structural parameters. In this study, the use of 2-2 piezocomposite materials in an underwater Tonpilz transducer was investigated. Through finite element analyses, the relationship between the piezocomposite material properties and the performance of the transducer was investigated, i.e., operation frequency, bandwidth, and sound pressure. Based on the analysis result, the geometry of the Tonpilz transducer that could provide the highest sound pressure for a given electric field amplitude while satisfying requirements such as bandwidth and operation frequency was optimized. The optimization result was compared with that of a traditional piezoceramic transducer to confirm the superiority of the piezocomposite transducer; a Tonpilz transducer made of 2-2 mode piezocomposite plates could provide a higher effective coupling factor and thus a wider bandwidth at a desired operation frequency with a smaller size than a traditional piezoceramic transducer.
Hybrid measurement of auditory steady-state responses and distortion product otoacoustic emissions using an amplitude-modulated primary tone
Authors: Oswald Johann A. , Rosner Thomas , Janssen Thomas
Published: June 2006

A maximum auditory steady-state response (ASSR) amplitude is yielded when the ASSR is elicited by an amplitude-modulated tone (fc) with a fixed modulation frequency (fm=40Hz), whereas the maximum distortion product otoacoustic emission (DPOAE) level is yielded when the DPOAE is elicited using a fixed frequency ratio of the primary tones (f2∕f1=1.2). When eliciting the DPOAE and ASSR by the same tone pair, optimal stimulation is present for either DPOAE or ASSR and thus adequate simultaneous DPOAE/ASSR measurement is not possible across test frequency f2 or fc, respectively. The purpose of the present study was to determine whether the ASSR and DPOAE can be measured simultaneously without notable restrictions using a DPOAE stimulus setting in which one primary tone is amplitude modulated. A DPOAE of frequency 2f1-f2 and ASSR of modulation frequency 41Hz were measured in ten normal hearing subjects at a test frequency between 0.5 and 8kHz (f2=fc). The decrease in the DPOAE level and the loss in ASSR amplitude during hybrid mode stimulation amounted, on average, to only 2.60dB [standard deviation (SD)=1.38dB] and 1.83dB (SD=2.38dB), respectively. These findings suggest simultaneous DPOAE and ASSR measurements to be feasible across all test frequencies when using a DPOAE stimulus setting where the primary tone f2 is amplitude modulated.
Adjoint-based acoustic inversion for the physical characterization of a shallow water environment
Authors: Hermand Jean-Pierre , Meyer Matthias , Asch Mark , Berrada Mohamed
Published: June 2006

Recently the concept of adjoint modeling has been introduced in shallow water acoustics for solving inverse problems. Analytical adjoints have been derived for normal modes and for both the standard parabolic equation and Claerbout’s wide-angle approximation (WAPE). This paper proposes the application of a semiautomatic adjoint approach that has been successfully applied in the past for multidimensional variational data assimilation in meteorological and climate modeling. Starting from a modular graph representation of the underlying forward model, a programming tool facilitates the generation and coding of both the tangent linear and the adjoint models. The potential of this numerical adjoint approach for the physical characterization of a shallow water environment is illustrated with two applications for geoacoustic inversion and ocean acoustic tomography using Claerbout’s WAPE in combination with nonlocal boundary conditions. Furthermore, the adjoint optimization is extended to multiple frequencies and it is shown how a broadband approach can enhance the performance of the inversion process. For a sparse array geometry in particular, the generalization of the adjoint-based approach to a joint optimization across multiple frequencies is necessary to compensate for the lack of vertical sampling of the propagation modes. Results with test data synthesized from geoacoustic inversion experiments in the Mediterranean show that with the numerical adjoint approach the acoustic field, the sound speed profile in the water column and the bottom properties can be efficiently retrieved.
Analysis and design of composite/folded variable area perforated tube resonators for low frequency attenuation
Authors: Kar T. , Sharma P. P. R. , Munjal M. L.
Published: June 2006

Variable area concentric-tube-resonator mufflers may be used effectively for attenuating the odd harmonics. This ensures a broad-band transmission loss (TL) spectrum. In this paper, configurations that consist of variable area resonators within a uniform area muffler shell for enhancing the low-frequency noise attenuation are investigated. The variable area resonator elements within a muffler allow multiple elements, where the sum of their acoustic lengths is more than the geometric length of the muffler. This shifts the overall TL spectrum toward lower frequency. The underlying idea of incorporating the extended inlets and outlets in these resonators, is to reproduce the broadband attenuation. It has the effectiveness of dissipative ducts without the use of any absorptive materials. The results have been validated by means of three-dimensional finite element analysis.
Approximations for the scattered field potential from higher mode transmission in rectangular apertures
Authors: Horner J. L. , Peat K. S.
Published: June 2006

This paper considers the wave fields that result when a plane wave impinges at an arbitrary angle on a rectangular aperture in a rigid, thick wall. A nondimensional form of a prior Fourier transform solution of this problem is derived, from which it is more easy to appreciate the relationship between the physical attributes of the aperture and incoming wave and the resultant acoustic fields. The scattered field from the aperture is examined in detail, in particular the modal contributions to the driving function for the amplitude of the velocity potential. Although the full scattered field contains both modal sum and modal coupling effects, it is shown that neglect of the modal coupling effects introduces minimal error to the solution in certain situations. An approximate analytical solution to the uncoupled analysis is then developed, which is accurate provided that the aperture is acoustically large, such that there are several cut-on modes within the aperture. The full nature of the scattered field can be easily interpreted from the nondimensional, analytical solution. In particular, an error analysis is given from which one can determine the required number of modes in a solution for given accuracy.
Vibrational modes of partly filled wine glasses
Authors: Jundt Gregor , Radu Adrian , Fort Emmanuel , Duda Jan , Vach Holger , Fletcher Neville
Published: June 2006

Time-average holographic interferometry has been employed to study how the vibrational modes of a singing wine glass change when it is filled with a liquid. While the liquid clearly lowers the resonance frequencies, it does not change the vibrational mode structure in a first approximation. A more detailed analysis, however, reveals that the presence of the liquid causes the simultaneous excitation of two orthogonal modes that are well resolved for the empty glass.
Characterization of impedance boundary as damped harmonic oscillators via impulse reflection
Authors: Fung K.-Y. , Jing Xiaodong
Published: June 2006

This paper demonstrates that various sound-absorbing/reflective materials or structures can be effectively characterized over a wide band of frequency by the sum of only a few damped harmonic oscillators. This method is physically sound in the sense that each damped harmonic oscillator corresponds to the natural resonance of the impedance boundary as it is numerically advantageous to afford a simple, recursive, efficient, and unconditionally stable boundary algorithm for computational aero-acoustics applications. The time-domain damped-harmonic-oscillator impedance characterization method is finally validated by accurate predictions of reflected pulses from impedance boundaries physically formed of Helmholtz resonators or various exits of a circular pipe.
Real time decomposition of speech into modulated components
Authors: Wang Yadong , Kumaresan Ramdas
Published: June 2006

Motivated by the active process of the outer hair cell (OHC) in the mammalian inner ear, a real time decomposition of speech into modulated components is presented. A generalized phase lock loop (GPLL) was applied to decompose the speech signal into its envelope and positive instantaneous frequency (PIF) parts, which can be further processed and represented by timing information alone. A log-derivative operator is applied to the bandpass signal. Analytic and antianalytic components occupying non overlapping frequency bands are separated by filtering. The proposed algorithms are used to represent speech signals processed through a bandpass filter bank.
Reducing reflected contributions to ear-canal distortion product otoacoustic emissions in humans
Authors: Johnson Tiffany A. , Neely Stephen T. , Kopun Judy G. , Gorga Michael P.
Published: June 2006

Distortion product otoacoustic emission (DPOAE) fine structure has been attributed to the interaction of two cochlear-source mechanisms (distortion and reflection sources). A suppressor presented near the 2f1-f2 frequency reduces the reflection-source contribution and, therefore, DPOAE fine structure. Optimal relationships between stimulus and suppressor conditions, however, have not been described. In this study, the relationship between suppressor level (L3) and stimulus level (L2) was evaluated to determine the L3 that was most effective at reducing fine structure. Subjects were initially screened to find individuals who produced DPOAE fine structure. A difference in the prevalence of fine structure in two frequency intervals was observed. At 2kHz, 11 of 12 subjects exhibited fine structure, as compared to 5 of 22 subjects at 4kHz. Only subjects demonstrating fine structure participated in subsequent measurements. DPOAE responses were evaluated in 1∕3-octave intervals centered at 2 or 4kHz, with 4 subjects contributing data at each interval. Multiple L3’s were evaluated for each L2, which ranged from 20to80dB SPL. The results indicated that one or more L3’s at each L2 were roughly equally effective at reducing DPOAE fine structure. However, no single L3 was effective at all L2’s in every subject.
Spectral fine-structures of low-frequency modulated distortion product otoacoustic emissions
Authors: Bian Lin
Published: June 2006

Biasing of the cochlear partition with a low-frequency tone can produce an amplitude modulation of distortion product otoacoustic emissions (DPOAEs) in gerbils. In the time domain, odd- versus even-order DPOAEs demonstrated different modulation patterns depending on the bias tone phase. In the frequency domain, multiple sidebands are presented on either side of each DPOAE component. These sidebands were located at harmonic multiples of the biasing frequency from the DPOAE component. For odd-order DPOAEs, sidebands at the even-multiples of the biasing frequency were enhanced, while for even-order DPOAEs, the sidebands at the odd-multiples were elevated. When a modulation in DPOAE magnitude was presented, the magnitudes of the sidebands were enhanced and even greater than the DPOAEs. The amplitudes of these sidebands varied with the levels of the bias tone and two primary tones. The results indicate that the maximal amplitude modulations of DPOAEs occur at a confined bias and primary level space. This can provide a guide for optimal selections of signal conditions for better recordings of low-frequency modulated DPOAEs in future research and applications. Spectral fine-structure and its unique relation to the DPOAE modulation pattern may be useful for direct acquisition of cochlear transducer nonlinearity from a simple spectral analysis.
Prediction method for tire air-pumping noise using a hybrid technique
Authors: Kim Sungtae , Jeong Wontae , Park Yonghwan , Lee Soogab
Published: June 2006

Air-pumping noise from a car tire is investigated with a hybrid technique composed of three stages: (1) small-scale air-pumping noise generation process is modeled as a piston-like movement of the base-side of the tire groove and then numerically simulated; (2) the flow properties in the tire groove are used as air-pumping sources and noise propagation is simulated with emphasis placed on scattering process with full tire/road geometry; (3) the far-field acoustic pressure is predicted from a Kirchhoff integral method by using unsteady flow data in space and time which is provided by the computational fluid dynamics (CFD) calculation of full tire-road domain. The comparison of predicted results shows that the nonlinearity of the air-pumping noise generation mechanism affects not only noise characteristics in frequency domain but also in the directivity pattern. It seems that this approach can overcome the weakness of the acoustic monopole theory which stems from the usual assumption of a small amplitude acoustic wave equation while using nonlinear governing equation for the CFD calculation. Furthermore, through the use of a computational domain which covers tire and road surface, the geometric effects on air-pumping noise generation and propagation are taken into account in the source modeling process.
Interaural fluctuations and the detection of interaural incoherence: Bandwidth effects
Authors: Goupell Matthew J. , Hartmann William M.
Published: June 2006

One-hundred left-right noise-pairs were generated, all with a fixed value of long-term interaural coherence, 0.9922. The noises had a center frequency of 500Hz, a bandwidth of 14Hz, and a duration of 500ms. Listeners were required to discriminate between these slightly incoherent noises and diotic noises, with a coherence of 1.0. It was found that the value of interaural coherence itself was an inadequate predictor of discrimination. Instead, incoherence was much more readily detected for those noise-pairs with the largest fluctuations in interaural phase or level differences (as measured by the standard deviations). One-hundred noise-pairs with the same value of coherence, 0.9922, and geometric mean frequency of 500Hz were also generated for bandwidths of 108 and 2394Hz. It was found that for increasing bandwidth, fluctuations in interaural differences varied less between different noise-pairs and that detection performance varied less as well. The results suggest that incoherence detection is based on the size of interaural fluctuations and that the value of coherence itself predicts performance only in the wideband limit.
A helical biosonar scanning pattern in the Chinese Noctule, Nyctalus plancyi
Authors: Müller Rolf , Lu Hongwang , Zhang Shuyi , Peremans Herbert
Published: June 2006

Directivity and sound diffraction of the pinna of the Chinese Noctule (Nyctalus plancyi) have been studied numerically. The pinna was found capable of generating a periodic helical scanning pattern over frequency, if the tragus and the thickened lower ledge of the pinna rim were in an appropriate position. During the helical scan, a directivity pattern with a strong mainlobe alternated with a pattern dominated by a conical sleeve of sidelobes. This alternation was present, even when an unfavorable arrangement of the pinna disrupted the overall helical scanning pattern. In the fully formed helical scan, the orientation of main and sidelobes for different frequencies revealed a spatial ordering which extends volume coverage. Five different pinna parts have been removed from the digital pinna-shape representations in turn to assess their influence on the directivity. Of these parts, the tragus stem and the thickened lower ledge of the pinna rim were found to have the largest overall impact. The anatomical prominence of these structures was hence in agreement with their acoustic functionality. In the near-field, tragus stem and lower ledge were seen to act primarily through large shifts in the wavefield phase in both directions.
No adaptation in the amplitude modulation domain in trained listeners
Authors: Bruckert Laetitia , Herrmann Marion , Lorenzi Christian
Published: June 2006

The present study shows that on average, exposure to a 15min, 5kHz tone modulated sinusoidally in amplitude at 16Hz with a 100% depth does not affect significantly amplitude modulation (AM) detection thresholds measured between 4 and 64Hz when listeners are extensively trained to the AM detection task, with and without adaptor before data collection. These results are compatible with previous work given that a clear 6-dB adaptation effect was observed during the first pilot trials. However, the results reveal that adaptation effects are not robust, and suggest that the mechanisms underlying adaptation to AM must be reevaluated.
Temporal and cross-range coherence of sound traveling through shallow-water nonlinear internal wave packets
Authors: Duda Timothy F.
Published: June 2006

Expressions governing coherence scales of sound passing through a moving packet of nonlinear internal waves in a continental shelf environment are presented. The expressions describe the temporal coherence scale at a point, and the horizontal coherence scale in a plane transverse to the acoustic path, respectively. Factors in the expressions are the wave packet propagation speed, wave packet propagation direction, the fractional distance from the packet to the source, and the spatial scale S of packet displacement required to cause acoustic field decorrelation. The scale S is determined by the details of coupled mode propagation within the packet and the waveguide. Here, S is evaluated as a function of frequency for one environment, providing numerical values for the coherence scales of this environment. Coherence scales derived from numerical simulation of coupled mode acoustic propagation through moving wave packets substantiate the expressions.
Dugong (Dugong dugon) vocalization patterns recorded by automatic underwater sound monitoring systems
Authors: Ichikawa Kotaro , Tsutsumi Chika , Arai Nobuaki , Akamatsu Tomonari , Shinke Tomio , Hara Takeshi , Adulyanukosol Kanjana
Published: June 2006

To quantitatively examine the diurnal, or tidal, effects on dugong behavior, we employed passive acoustic observation techniques to monitor the animals. Automatic underwater sound monitoring systems for dugongs (AUSOMS-D) were deployed on the sea floor at depths of about 5m south of Talibong Island, Thailand. The AUSOMS-D recorded underwater sound in stereo at a sampling frequency of 44.1kHz for more than 116 consecutive hours. Dugong calls were automatically detected by newly developed software with a detection rate of 36.1% and a false alarm rate of 2.9%. In total, 3453 calls were detected during the 164h of recording. The autocorrelation of the call rate indicated an attendance cycle of about 24 or 25h, and the most frequent vocalizations were observed from 0300 to 0500h. The calculated bearings of the sound sources, i.e., dugongs, were used as an indicator to track the relative numbers of dugongs during the monitoring periods.
The perception of Mandarin tone contrasts: A cross-linguistic study
Authors: Chang Yueh-chin , Halle Pierre , Best Catherine T.
Published: June 2006

Previous studies of the perception of tone continua found that Mandarin listeners perceive tones more categorically than French listeners, whose performance is essentially psychophysically motivated. In this study, we examined native-language effects on the perception of Mandarin tone continua by Cantonese, Thai, and Japanese listeners. Cantonese distinguishes six tones: high-rising, low-rising, low-falling, and high-, mid-, and low level. Thai has five tones: rising, falling, and high-, mid-, and low level. Standard Japanese has a word pitch accent with at most one LH and one HL pitch movement per word. Listeners of these languages were tested on three Mandarin tone continua constructed from natural utterances within carrier sentences. Listeners were run on AXB identification and discrimination tests on isolated syllables. Japanese, Thai, and Cantonese listeners, in that order, perceived tones increasingly categorically. Cantonese and Thai listeners were more sensitive to tone-contour differences than Japanese listeners, although less than Mandarin listeners. The Cantonese and Thai data show that both phonological and phonetic properties of the native language affect the perception of the non-native Mandarin tones. The findings are compared with prior cross-linguistic research, and discussed with reference to the suprasegmental phonological differences across languages.
Contextual effects on the continuancy of /■/
Authors: Zhao Sherry
Published: June 2006

This research examined the segmental-contextual effects on the continuancy of the voiced dental /■/ in American-English and whether certain acoustic attributes were preserved despite possible modification. Word-initial /■/ cases, extracted from continuous speech of 146 speakers from the TIMIT database, were frequently (averaging 65%) stoplike when it was in utterance-initial position or when its preceding phoneme was voiceless and/or [-continuant]. This stoplike modification occurred less frequently (averaging 39%) when /■/ was preceded by a voiced fricative and rarely (averaging 13%) when preceded by a vowel or liquid consonant. A comparison of stoplike /■/ and /d/ cases under similar contexts showed that the burst peak location, burst spectrum shape, and F2 at vowel onset averages were all statistically different between the two groups. In addition, the acoustic data suggested that the dental place of articulation was preserved for the modified /■/. Preliminary automatic classification experiments involving salient acoustic attributes seemed to indicate that F2 at vowel onset may be a reliable cue for the dental place of articulation in /■/. [Work supported by NIH DC02978 and T32DC00038.]
Differences in heart rate variability between Asian and Caucasian children living in the same Canadian community
Authors: Reed Katharine E , Warburton Darren E.R , Whitney Crystal L , McKay Heather A
Published: June 2006

Heart rate variability (HRV) is an umbrella term for a variety of measures that assess autonomic influence on the heart. Reduced beat-to-beat variability is found in individuals with a variety of cardiac abnormalities. A reduced HRV positively correlates with obesity, poor aerobic fitness, and increasing age. Racial (black-white) differences are apparent in adults and adolescents. We aimed to evaluate (i) Asian-Caucasian differences in HRV and (ii) differences in HRV between girls and boys. Sixty-two children (30 male (15 Caucasian, 15 Asian) and 32 female (15 Caucasian, 17 Asians)) with a mean age of 10.3 ± 0.6 y underwent 5 min resting HRV recording, fitness testing (Leger's 20 m shuttle), and self-assessed maturity. Outcome HRV measures were a ratio of low to high frequency power (LF:HF), standard deviation of R-R intervals (SDRR) and root mean square of successive R-R intervals (RMSSD). Data were compared between groups using analysis of covariance (ANCOVA). There were no race or sex differences for time domain variables, mean R-R, body mass index, or blood pressure. Compared with Caucasian children, Asian children displayed a higher adjusted (fitness, R-R interval) LF:HF ratio (72.9 ± 59.4 vs. 120.6 ± 85.3, p < 0.05). Girls demonstrated a higher adjusted LF:HF power than boys (117.2 ± 85.1 vs. 76.6 ± 62.4, p = < 0.05). In conclusion, Asian and Caucasian children display different frequency domain components of heart rate variability.Key words: autonomic nervous system, sympathetic, vagal, race, aerobic fitness, sex.
Excess post-exercise oxygen consumption in untrained males: effects of intermittent durations of arm ergometry
Authors: Lyons Scott , Richardson Mark , Bishop Phillip , Smith Joe , Heath Hank , Giesen Judy
Published: June 2006

The purpose of this study was to investigate excess post-exercise oxygen consumption (EPOC) following a continuous 30 min bout of upper-body exercise (UBE) compared with 3 consecutive 10 min bouts of UBE. Ten male subjects (age (mean ± standard deviation), 25.7 ± 5.83 years; arm VO2 peak, 2.2 ± 0.25 L·min-1), on separate days (48 h between trials) and in counterbalanced order, performed a continuous 30 min bout of arm exercise at 60% of arm VO2 peak and 3 separate 10 min bouts of arm exercise at 60% of arm VO2 peak. Subjects reported to the laboratory rested and after a 12 h fast. Each test was preceded by a 30 min baseline test to determine resting metabolic rate. Post-exercise VO2 was continuously monitored until baseline was re-established. Results showed that the combined magnitude of the EPOCs from the intermittent exercise sessions was significantly (p > .05) greater (4.47 ± 1.58 L O2) than that elicited from the continuous exercise session (1.54 ± 1.25 L O2). These data indicate that separating a continuous 30 min arm exercise into 3 equal 10 min arm exercises will elicit a small but significantly higher EPOC, and thus result in greater post-exercise energy expenditure. This could be beneficial for those unable to perform lower-body exercise (LBE), or for those with limited exercise capacities.Key words: upper-body exercise, EPOC, magnitude, recovery.
Cold pressor test protocol to evaluate cardiac autonomic function
Authors: Wirch Jennifer L , Wolfe Larry A , Weissgerber Tracey L , Davies Gregory A.L
Published: June 2006

The primary objective of this study was to develop a cold pressor test (CPT) protocol to evaluate cardiac autonomic function. Secondary objectives were to assess CPT protocol reliability and to examine gender differences in response to orthostatic stress and the CPT. Healthy, normotensive men and women (n = 12 per group) completed 2 trials on different days in the left lateral decubitus and standing postures and during a 6 min CPT (hand immersion while seated). Measurements included R-R interval, blood pressure, ventilatory responses, spontaneous baroreflex sensitivity, and heart rate variability indices. During the CPT, blood pressure and the sympathetic nervous system (SNS) indicator increased significantly and low-frequency power, high-frequency power (normalized for tidal volume), and the parasympathetic nervous system (PNS) indicator decreased significantly. Standing caused significant increases in the SNS indicator and decreases in the R-R interval in both genders. The PNS indicator was higher in women than in men in the left lateral decubitus posture. The 6 min hand-immersion CPT provoked cardiac sympathetic activation and parasympathetic withdrawal; however, it is best suited to studies with a repeated measures design, as analysis of reliability suggests that responses are highly variable between individuals. Performing the CPT in the left lateral decubitus position may prevent vasovagal responses.Key words: cold pressor test, sympathetic nervous system, parasympathetic nervous system, gender, posture.
Breathing strategy in master athletes and untrained elderly subjects according to the incremental protocol
Authors: Deruelle Fabien , Nourry Cédric , Mucci Patrick , Bart Frédéric , Grosbois Jean-Marie , Lensel Ghislaine , Fabre Claudine
Published: June 2006

To analyze the influence of step-duration protocol (1 vs. 3 min) on breathing strategy according to the physical fitness of healthy elderly subjects, this study compared the ventilatory responses and exercise tidal flow-volume loops (ETFVL) at the first and second ventilatory thresholds (VT1and VT2). Nineteen master athletes (mean age (± SD), 63.1 ± 3.2 y; [Formula: see text]O2 max, 41.5 mL·(min·kg)-1) and 8 untrained elderly subjects (age, 65.5 ± 2.3 y; [Formula: see text]O2 max, 25.8 mL·(min·kg)-1) performed 2 exhaustive exercise tests on a cycle ergometer. In untrained subjects, at VT1and VT2, no significant difference was measured in ventilatory responses and ETFVL between protocols. Master athletes, at VT2, presented a significantly higher [Formula: see text]CO2(P < 0.01), ventilation ([Formula: see text]E; P < 0.01), breathing frequency (fb; P < 0.05), tidal volume relative to inspiratory capatcity (Vt/IC) (P < 0.01),Vtrelative to forced vital capacity (Vt/FVC; P < 0.05), and lower inspiratory reserve volume relative to FVC (IRV/FVC; P < 0.01) during the 1 min protocol than during the 3 min protocol. Master athletes, at maximal exercise, expressed significantly higher [Formula: see text]CO2(P < 0.01) and dyspnea (P < 0.05) with the shorter protocol. We concluded that, in untrained subjects, neither incremental exercise test had an impact on respiratory responses during exercise. Nevertheless, in master athletes, breathing strategy seems to be protocol dependent. The short test induced higher mechanical ventilatory constraints and dyspneic feeling than the long protocol, which could be explained by a higher [Formula: see text]E itself linked to a greater [Formula: see text]CO2and a higher blood lactate concentration.Key words: exercise flow-volume loops, master athletes, submaximal exercise, mechanical ventilatory constraints.