bluuebunny/crossref_metadata_2025 huggingface dataset:
Wildfires and animal extinctions at the Cretaceous/Tertiary boundary
Authors: Adair Robert K.
Published: May 2010

Persuasive models of the ejection of material at high velocities from the Chicxulub asteroid impact marking the Cretaceous/Tertiary boundary have led to the conclusion that upon return, that material, heated in passage through the upper atmosphere, generated a high level of infrared energy density over the Earth’s surface. That radiant energy has been considered to be a direct source of universal wildfires, which were presumed to be a major cause of plant and animal species extinctions. The extinction of many animal species, especially the dinosaurs, has also been attributed to the immediate lethal effects of the radiation. I find that the absorption of the radiation by the atmosphere, by cloud formations, and by ejecta drifting in the lower atmosphere reduced the radiation at the surface to a level that cannot be expected to have generated universal fires. Although the reduced radiation will have likely caused severe injuries to many animals, such insults alone seem unlikely to have generated the overall species extinctions that have been deduced.
The falling raindrop, revisited
Authors: Sokal Alan D.
Published: May 2010

I reconsider the problem of a raindrop falling through mist, collecting mass, and generalize it to allow an arbitrary power-law form for the accretion rate. I show that the coupled differential equations can be solved by the simple trick of temporarily eliminating time in favor of the raindrop’s mass as the independent variable.
Simulating a one-dimensional plasma
Authors: Boozer A. D.
Published: May 2010

We describe a dynamical model of a one-dimensional plasma and present a simple algorithm for simulating the model on a computer. We use the algorithm to perform several numerical experiments that illustrate collective effects in plasma physics such as Debye screening and plasma oscillations.
Gauge transformation through an accelerated frame of reference
Authors: Shukla Ashish , Bhattacharya Kaushik
Published: May 2010

The Schrödinger equation of a charged particle in a uniform electric field can be specified in either a time-independent or a time-dependent gauge. The wave functions in these two gauges are related by a phase factor reflecting the gauge symmetry of the problem. We show that the effect of such a gauge transformation connecting the two wave functions can be mimicked by the effect of two successive extended Galilean transformations. An extended Galilean transformation connects two reference frames such that one is accelerating with respect to the other.
Strain in layered zinc blende and wurtzite semiconductor structures grown along arbitrary crystallographic directions
Authors: Yoo K. H. , Albrecht J. D. , Ram-Mohan L. R.
Published: May 2010

We present a simple approach to the evaluation of strain in zinc blende and in wurtzite layered semiconductor structures. These crystallographic structures are of particular interest because of their importance in optoelectronic device applications. The composite layered materials are currently grown pseudomorphically on substrates, which dictate the strain in the layers. Components of the strain are derived for arbitrary crystallographic growth directions. The strain in the layer determines the piezoelectric field in each layer in the structure. The strain and the strain-induced electric field are important in designing layered heterostructures with specific electronic energy levels for device applications. The methods presented are more generally applicable to other crystallographic structures and composite pseudomorphically grown materials. Illustrative problems and solutions are included.
Energy flow lines and the spot of Poisson–Arago
Authors: Gondran Michel , Gondran Alexandre
Published: May 2010

We show how energy flow lines answer the question about diffraction phenomena posed in 1818 by the French Academy: “Deduce by mathematical induction the movements of the rays during their crossing near the bodies.” The use of energy flow lines provides a complementary answer to Fresnel’s wave theory of light. A numerical simulation of the energy flow lines shows that they can reach the bright spot of Poisson–Arago in the shadow center of a circular opaque disk. For a monochromatic wave in vacuum, these energy flow lines correspond to the diffracted rays of Newton’s Opticks.
Derivation of the Boltzmann principle
Authors: Campisi Michele , Kobe Donald H.
Published: May 2010

We derive the Boltzmann principle SB=kB ln W based on classical mechanical models of thermodynamics. The argument is based on the heat theorem and can be traced back to the second half of the 19th century in the works of Helmholtz and Boltzmann. Despite its simplicity, this argument has remained almost unknown. We present it in a contemporary, self-contained, and accessible form. The approach constitutes an important link between classical mechanics and statistical mechanics.
On a concavity property of the ground state in quantum mechanics
Authors: Gartner Paul , Baer Norman , Ritter Sandra
Published: May 2010

The concavity of the ground-state energy as a function of the coupling constant of the perturbation is shown using Ritz’s variational principle. The derivation is simple and general, and the result is a useful tool for checking the accuracy of standard approximations such as perturbation theory and variational methods.
Large scale scanning probe microscope: Making the shear-force scanning visible
Authors: Bosma E. , Offerhaus H. L. , van der Veen J. T. , Segerink F. B. , van Wessel I. M.
Published: May 2010

We describe a demonstration of a scanning probe microscope with shear-force tuning fork feedback. The tuning fork is several centimeters long, and the rigid fiber is replaced by a toothpick. By scaling this demonstration to visible dimensions the accessibility of shear-force scanning and tuning fork feedback is increased.
Binaural interference in the free field
Authors: Croghan Naomi B. H. , Grantham D. Wesley
Published: May 2010

In an anechoic chamber the minimum audible angle (MAA) was measured in seven normal-hearing adults for a narrow band of noise centered at 4000 Hz (target). In the absence of an interfering stimulus, the average MAA was 2.1°. When a low-frequency interferer (a narrow band of noise centered at 500 Hz) was pulsed on and off with the target from directly in front of the subject, the average MAA was significantly elevated (13.4°). However, if the interferer was continuously present, or if it consisted of two independent noises presented from ±90°, interference was much reduced. The interference effect was asymmetric: a high-frequency interferer did not result in elevation of MAA threshold for a low-frequency target. These results are similar to those that have been extensively reported for stimuli under headphones [Bernstein and Trahiotis (1995). J. Acoust. Soc. Am. 98, 155–163]. These data are consistent with the notion that interference from a spectrally remote low-frequency interferer occurs in the free field to the extent that the target and interferer are fused into a single perceptual object. If cues are provided that promote perceptual segregation (such as temporal onset differences or spatial location differences), the interference is reduced or eliminated.
Measuring inter-pulse intervals in sperm whale clicks: Consistency of automatic estimation methods
Authors: Antunes Ricardo , Rendell Luke , Gordon Jonathan
Published: May 2010

Sperm whale clicks are characterized by a multi-pulsed structure. The time lag between consecutive pulses, i.e., the inter-pulse interval (IPI), is related to the size of the sound production organ such that its measurement provides a means to acoustically estimate the size of individual whales. Due to off-axis effects the identification of pulses is, however, not always straightforward, and automatic measurement methods provide not only more objective estimation, but may also facilitate IPI estimation in cases where single click measurements are ambiguous. In particular, averaging measurements over a time series of clicks from the same whale could enhance the discrimination of time invariant pulses. The authors developed two automatic methods of automatic IPI measurement based on waveform and autocorrelation averaging and compared their accuracy and consistency with other previously used methods. Manual measurement by an experienced operator provided the most self-consistent estimates. The autocorrelation averaging technique had the best overall performance of the automated methods achieving a very similar performance to manual measurement. On some recordings cepstrum averaging methods converged when autocorrelation did not. Therefore, applying both of these automated methods and choosing the best of the two are recommended.
Air-borne sound generated by sea waves
Authors: Bolin Karl , Åbom Mats
Published: May 2010

This paper describes a semi-empiric model and measurements of air-borne sound generated by breaking sea waves. Measurements have been performed at the Baltic Sea. Shores with different slopes and sediment types have been investigated. Results showed that the sound pressure level increased from 60 dB at 0.4 m wave height to 78 dB at 2.0 m wave height. The 1/3 octave spectrum was dependent on the surf type. A scaling model based on the dissipated wave power and a surf similarity parameter is proposed and compared to measurements. The predictions show satisfactory agreement to the measurements.
Robust passive range estimation using the waveguide invariant
Authors: Cockrell Kevin L. , Schmidt Henrik
Published: May 2010

The waveguide invariant principle is used to estimate the range to a broadband acoustic source in a shallow-water waveguide using a single acoustic receiver towed along a path directly toward the acoustic source. A relationship between the signal processing parameters and the ocean-acoustic environmental parameters is used to increase the effective signal-to-noise ratio without requiring detailed knowledge of the environment. Heuristics are developed to estimate the minimum source bandwidth and minimum horizontal aperture required for range estimation. A range estimation algorithm is tested on experimental and simulated data for source ranges of 500–2200 m and frequencies from 350 to 700 Hz. The algorithm is accurate to within approximately 25% for the cases tested and requires only a minimal amount of a priori environmental knowledge.
Evidence for basal distortion-product otoacoustic emission components
Authors: Martin Glen K. , Stagner Barden B. , Lonsbury-Martin Brenda L.
Published: May 2010

Distortion-product otoacoustic emissions (DPOAEs) were measured with traditional DP-grams and level/phase (L/P) maps in rabbits with either normal cochlear function or unique sound-induced cochlear losses that were characterized as either low-frequency or notched configurations. To demonstrate that emission generators distributed basal to the f2 primary-tone contribute, in general, to DPOAE levels and phases, a high-frequency interference tone (IT) was presented at 1/3 of an octave (oct) above the f2 primary-tone, and DPOAEs were re-measured as “augmented” DP-grams (ADP-grams) and L/P maps. The vector difference between the control and augmented functions was then computed to derive residual DP-grams (RDP-grams) and L/P maps. The resulting RDP-grams and L/P maps, which described the DPOAEs removed by the IT, supported the notion that basal DPOAE components routinely contribute to the generation of standard measures of DPOAEs. Separate experiments demonstrated that these components could not be attributed to the effects of the 1/3-oct IT on f2, or DPOAEs generated by the addition of a third interfering tone. These basal components can “fill in” the lesion estimated by the commonly employed DP-gram. Thus, ADP-grams more accurately reveal the pattern of cochlear damage and may eventually lead to an improved DP-gram procedure.
Higher harmonic generation in nonlinear waveguides of arbitrary cross-section
Authors: Srivastava Ankit , Bartoli Ivan , Salamone Salvatore , Lanza di Scalea Francesco
Published: May 2010

This article concerns the generation and properties of double harmonics in nonlinear isotropic waveguides of complex cross-section. Analytical solutions of nonlinear Rayleigh–Lamb waves and rod waves have been known for some time. These solutions explain the phenomenon of cumulative double harmonic generation of guided waves. These solutions, however, are only applicable to simple geometries. This paper combines the general approach of the analytical solutions with semi-analytical finite element models to generalize the method to more complex geometries, specifically waveguides with arbitrary cross-sections. Supporting comparisons with analytical solutions are presented for simple cases. This is followed by the study of the case of a rail track. One reason for studying nonlinear guided waves in rails is the potential measurement of thermal stresses in welded rail.
Derivation of a Ritz series modeling technique for acoustic cavity-structural systems based on a constrained Hamilton’s principle
Authors: Ginsberg Jerry H.
Published: May 2010

Hamilton’s principle for dynamic systems is adapted to describe the coupled response of a confined acoustic domain and an elastic structure that forms part or all of the boundary. A key part of the modified principle is the treatment of the surface traction as a Lagrange multiplier function that enforces continuity conditions at the fluid-solid interface. The structural displacement, fluid velocity potential, and traction are represented by Ritz series, where the usage of the velocity potential as the state variable for the fluid assures that the flow is irrotational. Designation of the coefficients of the potential function series as generalized velocities leads to corresponding series representations of the particle velocity, displacement, and pressure in the fluid, which in turn leads to descriptions of the mechanical energies and virtual work. Application of the calculus of variations to Hamilton’s principle yields linear differential-algebraic equations whose form is identical to those governing mechanical systems that are subject to nonholonomic kinematic constraints. Criteria for selection of basis functions for the various Ritz series are illustrated with an example of a rectangular cavity bounded on one side by an elastic plate and conditions that change discontinuously on other sides.
Room acoustic transition time based on reflection overlap
Authors: Jeong Cheol-Ho , Brunskog Jonas , Jacobsen Finn
Published: May 2010

A transition time is defined based on the temporal overlap of reflected pulses in room impulse responses. Assuming specular reflections only, the temporal distance between adjacent reflections, which is proportional to the volume of a room, is compared with the characteristic width of a pulse at time t, which is mainly controlled by the absorption characteristics of the boundary surfaces of the room. Scattering, diffuse reflections, and diffraction, which facilitate the overlapping process, have not been taken into account. Measured impulse responses show that the transition occurs earlier in a room with nonuniform absorption and furniture than in a room that satisfies the underlying assumptions.
A real-time method for autonomous passive acoustic detection-classification of humpback whales
Authors: Abbot Ted A. , Premus Vincent E. , Abbot Philip A.
Published: May 2010

This paper describes a method for real-time, autonomous, joint detection-classification of humpback whale vocalizations. The approach adapts the spectrogram correlation method used by Mellinger and Clark [J. Acoust. Soc. Am. 107, 3518–3529 (2000)] for bowhead whale endnote detection to the humpback whale problem. The objective is the implementation of a system to determine the presence or absence of humpback whales with passive acoustic methods and to perform this classification with low false alarm rate in real time. Multiple correlation kernels are used due to the diversity of humpback song. The approach also takes advantage of the fact that humpbacks tend to vocalize repeatedly for extended periods of time, and identification is declared only when multiple song units are detected within a fixed time interval. Humpback whale vocalizations from Alaska, Hawaii, and Stellwagen Bank were used to train the algorithm. It was then tested on independent data obtained off Kaena Point, Hawaii in February and March of 2009. Results show that the algorithm successfully classified humpback whales autonomously in real time, with a measured probability of correct classification in excess of 74% and a measured probability of false alarm below 1%.
Effects of background noise level on behavioral estimates of basilar-membrane compression
Authors: Gregan Melanie J. , Nelson Peggy B. , Oxenham Andrew J.
Published: May 2010

Hearing-impaired (HI) listeners often show poorer performance on psychoacoustic tasks than do normal-hearing (NH) listeners. Although some such deficits may reflect changes in suprathreshold sound processing, others may be due to stimulus audibility and the elevated absolute thresholds associated with hearing loss. Masking noise can be used to raise the thresholds of NH to equal the thresholds in quiet of HI listeners. However, such noise may have other effects, including changing peripheral response characteristics, such as the compressive input-output function of the basilar membrane in the normal cochlea. This study estimated compression behaviorally across a range of background noise levels in NH listeners at a 4 kHz signal frequency, using a growth of forward masking paradigm. For signals 5 dB or more above threshold in noise, no significant effect of broadband noise level was found on estimates of compression. This finding suggests that broadband noise does not significantly alter the compressive response of the basilar membrane to sounds that are presented well above their threshold in the noise. Similarities between the performance of HI listeners and NH listeners in threshold-equalizing noise are therefore unlikely to be due to a linearization of basilar-membrane responses to suprathreshold stimuli in the NH listeners.
Closed-form analytical solutions of the time difference of arrival source location problem for minimal element monitoring arrays
Authors: Spencer Steven J.
Published: May 2010

Closed-form analytical solutions are found for the time difference of arrival (TDOA) source location problem. Solutions are found for both two-dimensional (2D) and three-dimensional (3D) source location by formulating the TDOA equations in, respectively, polar and spherical coordinate systems, with the radial direction coincident with the assumed geodesic path of signal propagation to a reference sensor. Quadratic equations for TDOA 2D and 3D source location based on the spherical intersection (SX) scheme, in some cases permitting dual physical solutions, are found for three and four sensor element monitoring arrays, respectively. A method of spherical intersection subarrays (SXSAs) is developed to derive from these quadratic equations globally unique closed-form analytical solutions for TDOA 2D and 3D source location, for four and five sensor element monitoring arrays, respectively. Errors in 2D source location for introduced bias in time differences of arrival are shown to have a strong geometrical dependence. The SXSA and SX methods perform well in terms of accuracy and precision at high levels of arrival time bias for both 2D and 3D source location and are much more efficient than nonlinear least-squares schemes. The SXSA scheme may have particular applicability to accurately solving source location problems in demanding real-time situations.
Measurement of the binaural auditory filter using a detection task
Authors: Kolarik Andrew J. , Culling John F.
Published: May 2010

The spectral resolution of the binaural system was measured using a tone-detection task in a binaural analog of the notched-noise technique. Three listeners performed 2-interval, 2-alternative, forced choice tasks with a 500-ms out-of-phase signal within 500 ms of broadband masking noise consisting of an “outer” band of either interaurally uncorrelated or anticorrelated noise, and an “inner” band of interaurally correlated noise. Three signal frequencies were tested (250, 500, and 750 Hz), and the asymmetry of the filter was measured by keeping the signal at a constant frequency and moving the correlated noise band relative to the signal. Thresholds were taken for bandwidths of correlated noise ranging from 0 to 400 Hz. The equivalent rectangular bandwidth of the binaural filter was found to increase with signal frequency, and estimates tended to be larger than monaural bandwidths measured for the same listeners using equivalent techniques.
Third- and fourth-order constants of incompressible soft solids and the acousto-elastic effect
Authors: Destrade Michel , Gilchrist Michael D. , Saccomandi Giuseppe
Published: May 2010

Acousto-elasticity is concerned with the propagation of small-amplitude waves in deformed solids. Results previously established for the incremental elastodynamics of exact non-linear elasticity are useful for the determination of third- and fourth-order elastic constants, especially in the case of incompressible isotropic soft solids, where the expressions are particularly simple. Specifically, it is simply a matter of expanding the expression for ρv2, where ρ is the mass density and v the wave speed, in terms of the elongation e of a block subject to a uniaxial tension. The analysis shows that in the resulting expression: ρv2=a+be+ce2, say, a depends linearly on μ; b on μ and A; and c on μ, A, and D, the respective second-, third, and fourth-order constants of incompressible elasticity, for bulk shear waves and for surface waves.
Lingual kinematics and coarticulation for alveolopalatal and velar consonants in Catalan
Authors: Recasens Daniel , Espinosa Aina
Published: May 2010

Vertical lingual movement data for the alveolopalatal consonants /ʃ/ and /ɲ/ and for the dorsovelar consonant /k/ in Catalan /aCa/ sequences produced by three speakers reveal that the tongue body travels a smaller distance at a slower speed and in a longer time during the lowering period extending from the consonant into the following vowel (CV) than during the rising period extending from the preceding vowel into the consonant (VC). For two speakers, two-phase trajectories characterized by two successive velocity peaks occur more frequently during the former period than during the latter, whether associated with tongue blade and dorsum (for alveolopalatals) or with the tongue dorsum articulator alone (for velars). Greater tongue dorsum involvement for /ɲ/ and /k/ than for /ʃ/ accounts for a different kinematic relationship between the four articulatory phases. The lingual gesture for alveolopalatals and, less so, that for velars may exert more prominent spatial and temporal effects on V2 than on V1 which is in agreement with the salience of the C-to-V carryover component associated with these consonants according to previous coarticulation studies. These kinematic and coarticulation data may be attributed to tongue dorsum biomechanics to a large extent.
A finite difference method for a coupled model of wave propagation in poroelastic materials
Authors: Zhang Yang , Song Limin , Deffenbaugh Max , Toksöz M. Nafi
Published: May 2010

A computational method for time-domain multi-physics simulation of wave propagation in a poroelastic medium is presented. The medium is composed of an elastic matrix saturated with a Newtonian fluid, and the method operates on a digital representation of the medium where a distinct material phase and properties are specified at each volume cell. The dynamic response to an acoustic excitation is modeled mathematically with a coupled system of equations: elastic wave equation in the solid matrix and linearized Navier–Stokes equation in the fluid. Implementation of the solution is simplified by introducing a common numerical form for both solid and fluid cells and using a rotated-staggered-grid which allows stable solutions without explicitly handling the fluid-solid boundary conditions. A stability analysis is presented which can be used to select gridding and time step size as a function of material properties. The numerical results are shown to agree with the analytical solution for an idealized porous medium of periodically alternating solid and fluid layers.
Spatio-temporal invariants of the time reversal operator
Authors: Robert Jean-Luc , Fink Mathias
Published: May 2010

The decomposition of the time reversal operator, known by the French acronym DORT, is a technique to extract point scatterers’ monochromatic Green’s functions from a medium. It is used to detect, locate, and focus on scatterers in various domains such as underwater acoustics, medical ultrasound, and nondestructive evaluation. A limitation of the method arises from its single-frequency nature, when the signals used in acoustics are often broadband. Reconstruction of the broadband Green’s functions from the single-frequency Green’s functions can be very difficult when numerous scatterers are present in the medium. Moreover, the method does not take advantage of the axial resolution associated with broadband signals. Time domain methods are investigated here as an answer to these problems. It is shown that the time reversal operator in the time domain takes the form of a tensor. The properties of the invariants are discussed. It is shown they do not have all the expected properties. Another method is proposed that requires a priori information on the medium.
Growth and recovery of temporary threshold shift at 3 kHz in bottlenose dolphins: Experimental data and mathematical models
Authors: Finneran James J. , Carder Donald A. , Schlundt Carolyn E. , Dear Randall L.
Published: May 2010

Measurements of temporary threshold shift (TTS) in marine mammals have become important components in developing safe exposure guidelines for animals exposed to intense human-generated underwater noise; however, existing marine mammal TTS data are somewhat limited in that they have typically induced small amounts of TTS. This paper presents experimental data for the growth and recovery of larger amounts of TTS (up to 23 dB) in two bottlenose dolphins (Tursiops truncatus). Exposures consisted of 3-kHz tones with durations from 4 to 128 s and sound pressure levels from 100 to 200 dB re 1 μPa. The resulting TTS data were combined with existing data from two additional dolphins to develop mathematical models for the growth and recovery of TTS. TTS growth was modeled as the product of functions of exposure duration and sound pressure level. TTS recovery was modeled using a double exponential function of the TTS at 4-min post-exposure and the recovery time.
Temporal pitch perception at high rates in cochlear implants
Authors: Kong Ying-Yee , Carlyon Robert P.
Published: May 2010

A recent study reported that a group of Med-El COMBI 40+CI (cochlear implant) users could, in a forced-choice task, detect changes in the rate of a pulse train for rates higher than the 300 pps “upper limit” commonly reported in the literature [Kong, Y.-Y., et al. (2009). J. Acoust. Soc. Am. 125, 1649–1657]. The present study further investigated the upper limit of temporal pitch in the same group of CI users on three tasks [pitch ranking, rate discrimination, and multidimensional scaling (MDS)]. The patterns of results were consistent across the three tasks and all subjects could follow rate changes above 300 pps. Two subjects showed exceptional ability to follow temporal pitch change up to about 900 pps. Results from the MDS study indicated that, for the two listeners tested, changes in pulse rate over the range of 500–840 pps were perceived along a perceptual dimension that was orthogonal to the place of excitation. Some subjects showed a temporal pitch reversal at rates beyond their upper limit of pitch and some showed a reversal within a small range of rates below the upper limit. These results are discussed in relation to the possible neural bases for temporal pitch processing at high rates.
On the variations of acoustic absorption peak with particle velocity in micro-perforated panels at high level of excitation
Authors: Tayong Rostand , Dupont Thomas , Leclaire Philippe
Published: May 2010

The acoustic behavior of micro-perforated panels (MPP) is studied theoretically and experimentally at high level of pressure excitation. A model based on Forchheimer’s regime of flow velocity in the perforations is proposed. This model is valid at relatively high Reynolds numbers and low Mach numbers. The experimental method consists in measuring the acoustical pressure at three different positions in an impedance tube, the two measurement positions usually considered in an impedance tube and one measurement in the vicinity of the rear surface of the MPP. The impedance tube is equipped with a pressure driver instead of the usual loudspeaker and capable of delivering a high sound pressure level up to 160 dB. MPP specimens made out of steel, dural and polypropylene were tested. Measurements using random noise or sinusoidal excitation in a frequency range between 200 and 1600 Hz were carried out on MPPs backed by air cavities. It was observed that the maximum of absorption can be a positive or a negative function of the flow velocity in the perforations. This suggests the existence of a maximum of absorption as a function of flow velocity. This behavior was predicted by the model and confirmed experimentally.
The binaural intelligibility level difference in hearing-impaired listeners: The role of supra-threshold deficits
Authors: Goverts S. Theo , Houtgast Tammo
Published: May 2010

Reduced binaural performance of hearing-impaired listeners may not only be caused by raised hearing thresholds (reduced audibility), but also by supra-threshold coding deficits in signal cues. This question was investigated in the present study using binaural intelligibility level difference (BILD) comparisons: the improvement of speech-reception threshold scores for N0Sπ relative to N0S0 presentation conditions. Investigated was what types of supra-threshold deficits play a role in reducing BILDs in hearing-impaired subjects. BILDs were investigated for 25 mild to moderate sensorineural hearing-impaired listeners, under conditions where optimal audibility was assured. All stimuli were bandpass filtered (250–4000 Hz). A distortion-sensitivity approach was used to investigate the sensitivity of subjects BILDs to external stimulus perturbations in the phase, frequency, time, and intensity domains. The underlying assumption of this approach was that an auditory coding deficit occurring in a signal cue in a particular domain will result in a low sensitivity to external perturbations applied in that domain. Compared to reference data for listeners with normal BILDs, distortion-sensitivity data for a subgroup of eight listeners with reduced BILDs suggests that these reductions in BILD were caused by coding deficits in the phase and time domains.
A simulation study of harmonics regeneration in noise reduction for electric and acoustic stimulation
Authors: Hu Yi
Published: May 2010

Recent research results show that combined electric and acoustic stimulation (EAS) significantly improves speech recognition in noise, and it is generally established that access to the improved F0 representation of target speech, along with the glimpse cues, provide the EAS benefits. Under noisy listening conditions, noise signals degrade these important cues by introducing undesired temporal-frequency components and corrupting harmonics structure. In this study, the potential of combining noise reduction and harmonics regeneration techniques was investigated to further improve speech intelligibility in noise by providing improved beneficial cues for EAS. Three hypotheses were tested: (1) noise reduction methods can improve speech intelligibility in noise for EAS; (2) harmonics regeneration after noise reduction can further improve speech intelligibility in noise for EAS; and (3) harmonics sideband constraints in frequency domain (or equivalently, amplitude modulation in temporal domain), even deterministic ones, can provide additional benefits. Test results demonstrate that combining noise reduction and harmonics regeneration can significantly improve speech recognition in noise for EAS, and it is also beneficial to preserve the harmonics sidebands under adverse listening conditions. This finding warrants further work into the development of algorithms that regenerate harmonics and the related sidebands for EAS processing under noisy conditions.
Correction of ultrasonic array images to improve reflector sizing and location in inhomogeneous materials using a ray-tracing model
Authors: Connolly G. D. , Lowe M. J. S. , Temple J. A. G. , Rokhlin S. I.
Published: May 2010

The use of ultrasonic arrays has increased dramatically within recent years due to their ability to perform multiple types of inspection and to produce images of the structure through post-processing of received signals. Phased arrays offer many advantages over conventional transducers in the inspection of materials that are inhomogeneous with spatially varying anisotropic properties. In this paper, the arrays are focused on austenitic steel welds as a representative inhomogeneous material. The method of ray-tracing through a previously developed model of an inhomogeneous weld is shown, with particular emphasis on the difficulties presented by material inhomogeneity. The delay laws for the structure are computed and are used to perform synthetic focusing at the post-processing stage of signal data acquired by the array. It is demonstrated for a simulated austenitic weld that by taking material inhomogeneity and anisotropy into account, superior reflector location (and hence, superior sizing) results when compared to cases where these are ignored. The image is thus said to have been corrected. Typical images are produced from both analytical data in the frequency domain and data from finite element simulations in the time domain in a variety of wave modes, including cases with mode conversion and reflections.
Multi-microphone adaptive noise reduction strategies for coordinated stimulation in bilateral cochlear implant devices
Authors: Kokkinakis Kostas , Loizou Philipos C.
Published: May 2010

Bilateral cochlear implant (BI-CI) recipients achieve high word recognition scores in quiet listening conditions. Still, there is a substantial drop in speech recognition performance when there is reverberation and more than one interferers. BI-CI users utilize information from just two directional microphones placed on opposite sides of the head in a so-called independent stimulation mode. To enhance the ability of BI-CI users to communicate in noise, the use of two computationally inexpensive multi-microphone adaptive noise reduction strategies exploiting information simultaneously collected by the microphones associated with two behind-the-ear (BTE) processors (one per ear) is proposed. To this end, as many as four microphones are employed (two omni-directional and two directional) in each of the two BTE processors (one per ear). In the proposed two-microphone binaural strategies, all four microphones (two behind each ear) are being used in a coordinated stimulation mode. The hypothesis is that such strategies combine spatial information from all microphones to form a better representation of the target than that made available with only a single input. Speech intelligibility is assessed in BI-CI listeners using IEEE sentences corrupted by up to three steady speech-shaped noise sources. Results indicate that multi-microphone strategies improve speech understanding in single- and multi-noise source scenarios.
Gender differences in children’s singing voices: Acoustic analyses and results of a listening test
Authors: Mecke Ann-Christine , Sundberg Johan
Published: May 2010

This study tested the hypothesis that acoustic parameters exist which are specific to gender in children’s singing voices, and that these parameters are relevant to listeners’ identification of gender of children’s singing voices. A listening test was run with examples of singing produced by children belonging to different singing cultures, six boys and six girls from a Swedish music school and six boys from an elite German boys’ choir. Sustained vowels were analyzed with regard to formants and voice source properties (jitter, shimmer and glottal-to-noise-excitation rate, closed quotient, and normalized amplitude quotient). Most of the measured parameters differed significantly between the boys belonging to the two different singing cultures. Regarding boys and girls from the same choir, only the closed quotient and the fourth formant frequency differed significantly. The listening test was carried out by an expert panel. The listeners correctly identified the gender of the singer in 66.0% of the cases, i.e., far better than chance. A multiple linear regression analysis revealed that the listener’s answers correlated well with the formant frequencies, with the fourth formant showing the highest correlation.
Temporary threshold shift in a bottlenose dolphin (Tursiops truncatus) exposed to intermittent tones
Authors: Finneran James J. , Carder Donald A. , Schlundt Carolyn E. , Dear Randall L.
Published: May 2010

Temporary threshold shift (TTS) was measured in a bottlenose dolphin exposed to a sequence of four 3-kHz tones with durations of 16 s and sound pressure levels (SPLs) of 192 dB re 1 μPa. The tones were separated by 224 s of silence, resulting in duty cycle of approximately 7%. The resulting growth and recovery of TTS were compared to experimentally measured TTS in the same subject exposed to single, continuous tones with similar SPLs. The data confirm the potential for accumulation of TTS across multiple exposures and for recovery of hearing during the quiet intervals between exposures. The degree to which various models could predict the growth of TTS across multiple exposures was also examined.
Some characteristics of the concert harp’s acoustic radiation
Authors: Le Carrou Jean-Loic , Leclere Quentin , Gautier Francois
Published: May 2010

The way a musical instrument radiates plays an important part in determining the instrument's sound quality. For the concert harp, the soundboard has to radiate the string’s vibration over a range of 7 octaves. Despite the effort of instrument makers, this radiation is not uniform throughout this range. In a recent paper, Waltham and Kotlicki [J. Acoust. Soc. Am. 124, 1774–1780 (2008)] proposed an interesting approach for the study of the string-to-string variance based on the relationship between the string attachment position and the operating deflection shapes of the soundboard. Although the soundboard vibrational characteristics determine a large part of the instrument’s radiation, it is also important to study directly its radiation to conclude on the origins of the string-to-string variation in the sound production. This is done by computing the equivalent acoustical sources on the soundboard from the far field sound radiation measured around the harp, using the acoustic imaging technique inverse frequency response function. Results show that the radiated sound depends on the correlation between these sources, and the played string’s frequency and location. These equivalent sources thus determine the magnitude and directivity of each string’s partial in the far field, which have consequences on the spectral balance of the perceived sound for each string.
Modeling power law absorption and dispersion for acoustic propagation using the fractional Laplacian
Authors: Treeby Bradley E. , Cox B. T.
Published: May 2010

The efficient simulation of wave propagation through lossy media in which the absorption follows a frequency power law has many important applications in biomedical ultrasonics. Previous wave equations which use time-domain fractional operators require the storage of the complete pressure field at previous time steps (such operators are convolution based). This makes them unsuitable for many three-dimensional problems of interest. Here, a wave equation that utilizes two lossy derivative operators based on the fractional Laplacian is derived. These operators account separately for the required power law absorption and dispersion and can be efficiently incorporated into Fourier based pseudospectral and k-space methods without the increase in memory required by their time-domain fractional counterparts. A framework for encoding the developed wave equation using three coupled first-order constitutive equations is discussed, and the model is demonstrated through several one-, two-, and three-dimensional simulations.
Guided wave phase velocity measurement using multi-emitter and multi-receiver arrays in the axial transmission configuration
Authors: Minonzio Jean-Gabriel , Talmant Marilyne , Laugier Pascal
Published: May 2010

This paper is devoted to a method of extraction of guided waves phase velocities from experimental signals. Measurements are performed using an axial transmission device consisting of a linear arrangement of emitters and receivers placed on the surface of the inspected specimen. The technique takes benefit of using both multiple emitters and receivers and is validated on a reference wave guide. The guided mode phase velocities are obtained using a projection in the singular vectors basis. The singular vectors are determined by the singular values decomposition (SVD) of the response matrix between the two arrays in the frequency domain. This technique enables to recover accurately guided wave phase velocity dispersion curves. The SVD based approach was designed to overcome limitations of spatio-temporal Fourier transform for receiver array of limited spatial extent as in the case of clinical assessment of cortical bone in axial transmission.
Perceptual interactions in the loudness of combined auditory and vibrotactile stimuli
Authors: Wilson E. Courtenay , Braida Louis D. , Reed Charlotte M.
Published: May 2010

The loudness of auditory (A), tactile (T), and auditory-tactile (A+T) stimuli was measured at supra-threshold levels. Auditory stimuli were pure tones presented binaurally through headphones; tactile stimuli were sinusoids delivered through a single-channel vibrator to the left middle fingertip. All stimuli were presented together with a broadband auditory noise. The A and T stimuli were presented at levels that were matched in loudness to that of the 200-Hz auditory tone at 25 dB sensation level. The 200-Hz auditory tone was then matched in loudness to various combinations of auditory and tactile stimuli (A+T), and purely auditory stimuli (A+A). The results indicate that the matched intensity of the 200-Hz auditory tone is less when the A+T and A+A stimuli are close together in frequency than when they are separated by an octave or more. This suggests that A+T integration may operate in a manner similar to that found in auditory critical band studies, further supporting a strong frequency relationship between the auditory and somatosensory systems.
A highly accurate plucking mechanism for acoustical measurements of stringed instruments
Authors: Smit Thorsten , Türckheim Friedrich , Mores Robert
Published: May 2010

This paper introduces a fully automated plucking apparatus for stringed instruments. The basic idea of the proposed mechanism is to make use of the constant tensile strength of bare wires. It defines the plucking intensity of a clasped string by pulling the wire until it breaks. The main components of the apparatus are bare wires for the string plucking, solenoids for the transmission of traction, bipolar transistors for the electric circuit switching, and a signal generator for the trigger settings. The mean average of the correlation coefficients between several individual excitations is well above 99%.
Higher order differential-integral microphone arrays
Authors: Abhayapala Thushara D. , Gupta Aastha
Published: May 2010

This paper develops theory to design higher order directional microphone arrays. The proposed higher order designs have similar inter sensor spacings as traditional first and second order differential arrays. The Jacobi–Anger expansion is used to exploit the underlying structure of microphone signals from pairs of closely spaced sensors. Specifically, the difference and sum of these microphone signals are processed to design the novel directional array.
Comment on “Detection of an Infectious Retrovirus, XMRV, in Blood Cells of Patients with Chronic Fatigue Syndrome”
Authors: Lloyd Andrew , White Peter , Wessely Simon , Sharpe Michael , Buchwald Dedra
Published: May 2010

Lombardi
et al
. (Reports, 23 October 2009, p. 585) reported a significant association between the human retrovirus XMRV and chronic fatigue syndrome (CFS). However, the cases with CFS and the control subjects in their study are poorly described and unlikely to be representative. Independent replication is a critical first step before accepting the validity of this finding.
Response to Comments on “Detection of an Infectious Retrovirus, XMRV, in Blood Cells of Patients with Chronic Fatigue Syndrome”
Authors: Mikovits Judy A. , Ruscetti Francis W.
Published: May 2010

We reported the detection of the human gammaretrovirus XMRV in 67% of 101 patients with chronic fatigue syndrome (CFS) and in 3.7% of 218 healthy controls, but we did not claim that XMRV causes CFS. Here, we explain why the criticisms of Sudlow
et al
., Lloyd
et al
., and van der Meer
et al
. regarding the selection of patients and controls in our study are unwarranted.
Erosion of Lizard Diversity by Climate Change and Altered Thermal Niches
Authors: Sinervo Barry , Méndez-de-la-Cruz Fausto , Miles Donald B. , Heulin Benoit , Bastiaans Elizabeth , Villagrán-Santa Cruz Maricela , Lara-Resendiz Rafael , Martínez-Méndez Norberto , Calderón-Espinosa Martha Lucía , Meza-Lázaro Rubi Nelsi , Gadsden Héctor , Avila Luciano Javier , Morando Mariana , De la Riva Ignacio J. , Sepulveda Pedro Victoriano , Rocha Carlos Frederico Duarte , Ibargüengoytía Nora , Puntriano César Aguilar , Massot Manuel , Lepetz Virginie , Oksanen Tuula A. , Chapple David G. , Bauer Aaron M. , Branch William R. , Clobert Jean , Sites Jack W.
Published: May 2010

Demise of the Lizards

Despite pessimistic forecasts from recent studies examining the effects of global climate change on species, and observed extinctions in local geographic areas, there is little evidence so far of global-scale extinctions.

Sinervo
et al.

(p.
894
; see the Perspective by

Huey
et al.

) find that extinctions resulting from climate change are currently reducing global lizard diversity. Climate records during the past century were synthesized with detailed surveys of Mexican species at 200 sites over the past 30 years. Temperature change has been so rapid in this region that rates of adaptation have not kept pace with climate change. The models were then extended to all families of lizards at >1000 sites across the globe, and suggest that climate change-induced extinctions are currently affecting worldwide lizard assemblages.
That Was Then But This Is Now: Malaria Research in the Time of an Eradication Agenda
Authors: Kappe Stefan H. I. , Vaughan Ashley M. , Boddey Justin A. , Cowman Alan F.
Published: May 2010

The global research community must take up the challenge to work toward the eradication of malaria. In the past, malaria research has focused on drugs and vaccines that target the blood stage of infection, and mainly on the most deadly species,
Plasmodium falciparum
, all of which is justified by the need to prevent and treat the disease. This work remains critically important today. However, an increased research focus is now being placed on potential interventions that aim to kill the parasite stages transmitted to and by the mosquito vector because they may represent more vulnerable targets to stop the spread of malaria. Here, we highlight some of the research into malaria parasite biology that has the potential to provide new intervention targets for antimalarial drugs and vaccines.