bluuebunny/crossref_metadata_2025 huggingface dataset:
The Alignment Shift Formation Mechanism of Thin Film Based DWDM Module With Solder Assembly Packaging
Authors: Lin Samuel I-En
Published: October 2004

Thermal residual plastic deformation of bond joints on thin film based DWDM module under thermal cycles loading was investigated using three-dimensional finite element analysis. Finite element simulations were carried out to investigate the effect of the 4 and 6 solder-joint designs for the metal tube with 0.1 mm alignment offset. It was found that 6-solder joint requires more thermal cycles to arrive a stable tilt angle. The transverse movement of metal tube under thermal loading was also examined to determine the influence of solder volume imperfections and solder materials. Favorable results were obtained for 80Au20Sn solder as compared to 63Sn37Pb solder. From the thermal-elasto-plastic analysis, the solder volume control has great impact on the metal tube movement and tilt angle during thermal loadings. If adequate solder volume is provided in four solder joints, the minimum alignment shift of the metal tube is projected to be comparable to an optimally designed bond joint geometry.
The Thermoelastic Analysis of Chip-Substrate System
Authors: Wu Linzhi
Published: October 2004

The presence of dissimilar material systems and thermal gradients introduces thermal stresses in multi-layered electronic assemblies and packages during fabrication and operation. The thermal stresses of the chip-substrate structure near free edges play an important role in determining the reliability of electronic packaging structures. Therefore, it is important to provide designers a good estimate of free edge stresses. According to the heat conduction mechanism of integrated circuits, the temperature field distribution in the chip and substrate is derived and solved when the chip works in a steady state. Taking the temperature field in the chip and substrate as the heat source, we solve the thermal stress field in the chip and substrate by using the technique of Fourier’s series expansion. The effects of geometric parameters of the chip and substrate on thermal stresses are analyzed. From the analysis of thermal stresses in the chip-substrate structure, it can be found that the stress concentration near free edges is more prominent. In the design of electronic packagings, the stress concentration near free edges which may cause cracking and delamination leading to the failure or malfunction of electronic assemblies and packages should be taken into account in details.
Analytical Thermo-Mechanical Model for Non-Underfilled Area Array Flip Chip Assemblies
Authors: Vandevelde Bart , Beyne Eric , Vandepitte Dirk , Baelmans Martine
Published: October 2004

An analytical model is derived for the calculation of thermo-mechanical induced stresses in area array flip chip assemblies. This analytical model is based on structural mechanics and has the ability to characterize the nature and to estimate the magnitude of the induced stresses. The extension of this model compared to existing procedures is its applicability to area array systems, which behave significantly different from peripheral assemblies. The model is compared to finite element simulations. The model calculates accurately the forces and bending moments acting on the flip chip connections. The transformation of these forces and moments into stresses is less accurate as the model does not include stress concentrations near the corners. The model simulates very well the different parameter trends such as chip size and is therefore well suited for understanding parameter sensitivity studies.
Behavior of Lead-Free Solder Under Thermomechanical Loading
Authors: Wei Y. , Chow C. L. , Lau K. J. , Vianco P. , Fang H. E.
Published: October 2004

This paper presents an investigation of lead-free Sn-Ag base alloy, 95.5Sn-3.9Ag-0.6Cu, both experimentally and analytically. Experimentally, the deformation behavior of the material was measured for different temperatures (25°C and 1000°C) over a range of strain rates (10−5 to 10−3/s) under isothermal and thermomechanical conditions. Development of a unified viscoplastic constitutive model followed, taking into account the effects of the measured strain rate and temperature changes. The temperature rate effects are considered in the evolution equation of back stress. In order to include material degradation in the solder, the theory of damage mechanics is applied by introducing two damage variables in the viscoplastic constitutive model. Finally, the constitutive model is coded into a general-purpose finite element computer program (ABAQUS) through its user-defined material subroutine (UMAT). The damage-coupled finite element analysis (FEA) is then employed to monitor the condition of failure of a notched component. The predicted and measured maximum loads have been compared and found to be satisfactory. In addition, the calculated damage distribution contours enable the identification of potential failure site for failure analysis.
Environmental Aging and Deadhesion of Polyimide Dielectric Films
Authors: Murray Steven , Hillman Craig , Pecht Michael
Published: October 2004

One possible failure mechanism of products containing polyimide dielectric is deadhesion of polyimide from neighboring metallization. Deadhesion usually occurs due to the combined damage mechanisms of environmental aging and fatigue. In this paper, the rate of aging of Kapton-E polyimide is quantified as a function of temperature and humidity exposure using peel and tensile tests. An accelerated test methodology that accounts for both aging and fatigue and that can be used to evaluate the resistance of electronic products to polyimide deadhesion is then proposed.
Multi-Physics Simulation of a Microprocessor Package Under Water Cooling
Authors: Bao-Min Liu , Y. C. Mui
Published: October 2004

Simulation tools today are well developed and make it possible to study more than one physical phenomena in the engineering processes. In this paper, a multi-physics simulation was performed to investigate the thermal, hydraulic and stress behavior of a flip-chip microprocessor package and a water-cooling thermal system. The distribution of the temperature, velocity, pressures, and stress inside the integrated circuit (IC) package and the water jacket was predicted and analyzed. The thermal resistance, Rjw, was defined and calculated to evaluate the overall thermal performance. The difference between the numerically predicted Rjw and the experimental result is within 10%. Thermal and hydraulic parametric studies were performed on the parameters such as the water flow rate, the die size, the channel height, and the base thickness of the water jacket. The impact of heater was also investigated to optimize the heater efficiency under different thermal contact between the IC package and the thermal head. Stress simulation was performed on the heater plate and the IC package subject to the temperature profile. The thermal stress and deformation were found to be at safe level under the given conditions. The results show that the use of multi-physics simulation and analysis can provide a deeper insight of complex processes, as well as to investigate the key parameters for system optimization. The numerical approach can reduce the risk and uncertainties at design stage as well as improve the system performance at the production stage.
A neural network model of the articulatory-acoustic forward mapping trained on recordings of articulatory parameters
Authors: Kello Christopher T. , Plaut David C.
Published: October 2004

Three neural network models were trained on the forward mapping from articulatory positions to acoustic outputs for a single speaker of the Edinburgh multi-channel articulatory speech database. The model parameters (i.e., connection weights) were learned via the backpropagation of error signals generated by the difference between acoustic outputs of the models, and their acoustic targets. Efficacy of the trained models was assessed by subjecting the models’ acoustic outputs to speech intelligibility tests. The results of these tests showed that enough phonetic information was captured by the models to support rates of word identification as high as 84%, approaching an identification rate of 92% for the actual target stimuli. These forward models could serve as one component of a data-driven articulatory synthesizer. The models also provide the first step toward building a model of spoken word acquisition and phonological development trained on real speech.
Long-range propagation of finite-amplitude acoustic waves in an ocean waveguide
Authors: Castor Kaëlig , Gerstoft Peter , Roux Philippe , Kuperman W. A. , McDonald B. E.
Published: October 2004

A hybrid method coupling nonlinear and linear propagation codes is used to study the nonlinear signature of long-range acoustic propagation for high-amplitude sources in an ocean waveguide. The differences between linear and nonlinear propagation are investigated in deep and shallow water environments. The spectral reshaping that occurs in nonlinear propagation induces two main effects: in shallow water, an unusual arrival time structure in the lowest order modes is observed, and in both shallow and deep water environments, there is a tendency to have acoustic energy more uniformly distributed across modes. Further, parametric low-frequency generation in deep water is a candidate for the coupling between water and sediments for T-wave formation.
Compressional- and shear-wave velocities and attenuation in deep-sea sediment during laboratory compaction
Authors: Leurer Klaus C.
Published: October 2004

Velocities and attenuation of compressional (50 kHz) and shear waves (100 kHz) in two deep-sea sediment samples are investigated as a function of effective pressure up to 20 MPa with simultaneous measurement of porosity, density, and permeability. In both samples, the compressional-wave velocities show a strong increase with pressure, ranging from 1683 m/s at 1 MPa to 2128 m/s at 20 MPa in a silty clay and from 1840 m/s to 2462 m/s in a foraminiferal mud. Shear wave propagation is strongly restricted at pressures below 4 and 9 MPa in the respective sample, indicating a structural change in the sediment material at critical porosity values of 0.430 and 0.397, respectively. The compressional-wave attenuation, in terms of 1/QP, varies between 0.03 and 0.08, and 0.04 and 0.07, respectively. A result previously not reported in laboratory studies is a maximum in 1/QP as a function of effective pressure observed in both samples. The shear-wave attenuation is nearly constant as a function of pressure, having average values of about 0.07. The maximum of compressional-wave attenuation occurs at the respective critical porosity for each sample. Velocities and attenuation from this experiment exhibit a systematic pattern in a QP/QS vs (VP/VS)2 representation.
Geographic variation and acoustic structure of the underwater vocalization of harbor seal (Phoca vitulina) in Norway, Sweden and Scotland
Authors: Bjørgesæter Anders , Ugland Karl Inne , Bjørge Arne
Published: October 2004

The male harbor seal (Phoca vitulina) produces broadband nonharmonic vocalizations underwater during the breeding season. In total, 120 vocalizations from six colonies were analyzed to provide a description of the acoustic structure and for the presence of geographic variation. The complex harbor seal vocalizations may be described by how the frequency bandwidth varies over time. An algorithm that identifies the boundaries between noise and signal from digital spectrograms was developed in order to extract a frequency bandwidth contour. The contours were used as inputs for multivariate analysis. The vocalizations’ sound types (e.g., pulsed sound, whistle, and broadband nonharmonic sound) were determined by comparing the vocalizations’ spectrographic representations with sound waves produced by known sound sources. Comparison between colonies revealed differences in the frequency contours, as well as some geographical variation in use of sound types. The vocal differences may reflect a limited exchange of individuals between the six colonies due to long distances and strong site fidelity. Geographically different vocal repertoires have potential for identifying discrete breeding colonies of harbor seals, but more information is needed on the nature and extent of early movements of young, the degree of learning, and the stability of the vocal repertoire. A characteristic feature of many vocalizations in this study was the presence of tonal-like introductory phrases that fit into the categories pulsed sound and whistles. The functions of these phrases are unknown but may be important in distance perception and localization of the sound source. The potential behavioral consequences of the observed variability may be indicative of adaptations to different environmental properties influencing determination of distance and direction and plausible different male mating tactics.
Lamb mode conversion in a plate with a delamination
Authors: Shkerdin G. , Glorieux C.
Published: October 2004

A theoretical study of Lamb mode propagation through a part of a plate containing a finite-length, delamination parallel with the surface is presented. In the delamination boundary region, which is taken parallel with the free plate surface, noncontact boundary conditions are assumed. The calculation is based on a modal decomposition method. As a result of diffraction on a delamination the incident Lamb mode is efficiently converted into Lamb modes with wave numbers close to the wave number of incident mode. The transmission coefficient of a Rayleigh wave incident on a delamination located near the surface has an oscillating dependence on the delamination parameters and has a pronounced minimum where there is a strong conversion into transmitted Lamb modes. Inversely, using the method of phase conjugation, a proper incident Lamb mode combination can be efficiently converted into a single transmitted Lamb or Rayleigh wave.
A phenomenological model of peripheral and central neural responses to amplitude-modulated tones
Authors: Nelson Paul C. , Carney Laurel H.
Published: October 2004

A phenomenological model with time-varying excitation and inhibition was developed to study possible neural mechanisms underlying changes in the representation of temporal envelopes along the auditory pathway. A modified version of an existing auditory-nerve model [Zhang et al., J. Acoust. Soc. Am. 109, 648–670 (2001)] was used to provide inputs to higher hypothetical processing centers. Model responses were compared directly to published physiological data at three levels: the auditory nerve, ventral cochlear nucleus, and inferior colliculus. Trends and absolute values of both average firing rate and synchrony to the modulation period were accurately predicted at each level for a wide range of stimulus modulation depths and modulation frequencies. The diversity of central physiological responses was accounted for with realistic variations of model parameters. Specifically, enhanced synchrony in the cochlear nucleus and rate-tuning to modulation frequency in the inferior colliculus were predicted by choosing appropriate relative strengths and time courses of excitatory and inhibitory inputs to postsynaptic model cells. The proposed model is fundamentally different than others that have been used to explain the representation of envelopes in the mammalian midbrain, and it provides a computational tool for testing hypothesized relationships between physiology and psychophysics.
Acoustic concentration of particles in piezoelectric tubes: Theoretical modeling of the effect of cavity shape and symmetry breaking
Authors: Kogan Shulim , Kaduchak Gregory , Sinha Dipen N.
Published: October 2004

A new class of simple, highly efficient, cylindrical acoustic concentration devices has been developed based upon cylindrical (or near cylindrical) geometries [Kaduchak et al., Rev. Sci. Instrum. 73, 1332–1336 (2002)] for aerosol concentration applications. The concentrators are constructed from single PZT tubes driven at or near the breathing mode resonance. Acoustic concentration of aerosols is performed within the tube cavity. It has been found that slight modifications to the cylindrical cavity geometry can significantly increase the collection efficiency and assist in precise particle positioning. This paper analyzes the theoretical framework for the acoustic concentration of particles in these devices for various geometrical perturbations. The cavity geometries studied are (1) hollow cylindrical piezoelectric tube, (2) hollow piezoelectric tube with an inner concentric solid cylinder insert, (3) a hollow piezoelectric tube with a concentric elliptic insert which breaks the circular-cylindrical symmetry, and (4) a hollow elliptic cylindrical piezoelectric tube. It is shown that breaking the circular symmetry within the cavity localizes the particles in small spatial regions within the cavity. This localization of particles may be very useful in applications requiring aerosol collection or particle stream positioning.
Nonlinear acoustic simulations using direct simulation Monte Carlo
Authors: Danforth Amanda L. , Long Lyle N.
Published: October 2004

In the simulation of fluid dynamics, one can either treat the fluid as a continuum or as discrete particles. Although popular for acoustics, the continuum model is limited to small Knudsen numbers (the ratio of mean free path to a length scale). Particle methods are necessary for, but not limited to, problems with Knudsen numbers greater than 0.1, which can occur in shockwaves, microdevices, high frequency sound or rarefied gases. Some well known particle methods include Monte Carlo, cellular automata, discrete velocity, lattice Boltzmann, and molecular dynamics. The direct simulation Monte Carlo (DSMC) method describes gas flows through direct physical modeling of particle motions and collisions. DSMC can model problems for the entire range of Knudsen numbers. In particular, DSMC is capable of simulating nonlinear acoustics, as well as the details of viscous dissipation, dispersion, nonequilibrium effects, and other physical properties. A DSMC method has been implemented for one-dimensional nonlinear acoustics problems on parallel computers using object-oriented C++ and the message passing interface (MPI). DSMC results will be shown and compared with continuum theory and continuum simulations.
Adhesion and nonlinear scattering by rough surfaces in contact: Beyond the phenomenology of the Preisach–Mayergoyz framework
Authors: Pecorari Claudio
Published: October 2004

Phenomenological models reproducing the elasticity and acoustic properties of geomaterials and materials with damage have been successfully developed. These models yield macroscopic stress–strain constitutive equations featuring hysteresis with end-point memory, and predict the efficient generation of higher harmonics accompanying the propagation of monochromatic waves. The assumption common to these models is that the material’s microstructure is characterized by nonlinear compliant components of an unspecified nature which can exist in two states: “open” or “closed.” The density of the compliant units is defined on a mathematical continuum (the Preisach–Mayergoyz space) whose elements identify the dynamic behavior of the components. In this work, adhesion is shown to introduce hysteresis with end-point memory in the macroscopic behavior of an interface between two rough surfaces in contact, and, upon scattering, to generate higher harmonics bearing a striking similarity to those observed in wave propagation phenomena in media with distributed damage and in geomaterials. It appears, therefore, that two rough surfaces interacting via adhesion forces offer a meaningful example of macroscopic interface or bond with dynamics resembling that of the fictitious elements of the Preisach–Mayergoyz space, and acoustic nonlinear properties similar to those of rocks and damaged materials.
Radial reflection diffraction tomography
Authors: Lehman Sean K. , Norton Stephen J.
Published: October 2004

A wave-based tomographic imaging algorithm based upon a single rotating radially outward oriented transducer is developed. At successive angular locations at a fixed radius, the transducer launches a primary field and collects the backscattered field in a “pitch/catch” operation. The hardware configuration, operating mode, and data collection method are identical to that of most medical intravascular ultrasound (IVUS) systems. IVUS systems form images of the medium surrounding the probe based upon ultrasonic B scans, using a straight-ray model of sound propagation. The goal of this research is to develop a wave-based imaging algorithm using diffraction tomography techniques. Given the hardware configuration and the imaging method, this system is referred to as “radial reflection diffraction tomography.” Two hardware configurations are considered: a multimonostatic mode using a single transducer as described above, and a multistatic mode consisting of a single transmitter and an aperture formed by multiple receivers. In this latter case, the entire source/receiver aperture rotates about the fixed radius. Practically, such a probe is mounted at the end of a catheter or snaking tube that can be inserted into a part or medium with the goal of forming images of the plane perpendicular to the axis of rotation. An analytic expression for the multimonostatic inverse is derived, but ultimately the new Hilbert space inverse wave (HSIW) algorithm is used to construct images using both operating modes. Applications include improved IVUS imaging, bore hole tomography, and nondestructive evaluation (NDE) of parts with existing access holes.
Bayesian model selection applied to self-noise geoacoustic inversion
Authors: Battle David J. , Gerstoft Peter , Hodgkiss William S. , Kuperman W. A. , Nielsen Peter L.
Published: October 2004

Self-noise geoacoustic inversion involves the estimation of bottom parameters such as sound speeds and densities by analyzing towed-array signals whose origin is the tow platform itself. As well as forming inputs to more detailed assessments of seabed geology, these parameters enable performance predictions for sonar systems operating in shallow-water environments. In this paper, Gibbs sampling is used to obtain joint and marginal posterior probability distributions for seabed parameters. The advantages of viewing parameter estimation problems from such a probabilistic perspective include better quantified uncertainties for inverted parameters as well as the ability to compute Bayesian evidence for a range of competing geoacoustic models in order to judge which model explains the data most efficiently.
Microparticle concentration in short path length ultrasonic resonators: Roles of radiation pressure and acoustic streaming
Authors: Kuznetsova Larisa A. , Coakley W. Terence
Published: October 2004

Acoustic streaming in ultrasonic (1.4–3.0 MHz) circular and rectangular resonators of path length approximately one-half or one quarter wavelength (λ) has been characterized by particle image velocimetry (PIV) using fluorescent 1 μm diam latex markers. Particles of all diameters examined (1, 24, 80 μm) moved into pressure node planes within 4 s of initiation of sonication. The larger particles then moved within that plane to one or more preferred positions. 1 μm particles in a λ/2 cylindrical resonator with a single nodal concentration region for larger particles were convected by Rayleigh-type streaming from the center of the node plane to its edge. In contrast, particles concentrated at many loci in two planes of a second cylindrical and a rectangular chamber. Small scale wall-associated Rayleigh-type vortices occurred in a λ/4 chamber. More unexpectedly, wall-independent bulk suspension vortices, with circulation planes parallel to the transducer radiating surface, were recorded in both resonators. Tracer particles experienced radial forces that drove them towards or away from the center of the vortices to be concentrated at its center or entrained in a vortex perimeter ring. These different outcomes are discussed in terms of lateral radiation force distribution in the node planes.
Scattering matrix properties with evanescent modes for waveguides in fluids and solids
Authors: Pagneux V. , Maurel A.
Published: October 2004

Reciprocity, energy conservation, and time-reversal invariance are three general properties of the wave fields that imply algebraic scattering matrix properties. In this paper, these scattering matrix properties are established for waveguides when evanescent modes are taken into account. The situations correspond to guided acoustic pressure waves in fluids and Lamb waves in solids treated with the same formalism. The relations between the three properties verified by the scattering matrix are then discussed, and it is found that, as soon as two properties are verified, the third is also verified.
Testing low/very low frequency acoustic sources for basin-wide propagation in the Indian Ocean
Authors: Blackman Donna K. , de Groot-Hedlin Catherine , Harben Phil , Sauter Allan , Orcutt John A.
Published: October 2004

Low/very low frequency acoustic signals were transmitted to distant receivers in the Indian Ocean. The aim was to test methods for characterizing the hydroacoustic capability of the International Monitoring System (IMS) that discriminates for nuclear tests in the region. Several acoustic sources were deployed between Seychelles and Fremantle, Australia, and the IMS receivers comprised a network of hydrophones off Diego Garcia and Australia. Two of the three acoustic sources tested produced basin-scale propagation of impulsive signals. Single glass spheres imploded within the sound channel produced a clear signal at frequencies above ∼40 Hz, at ranges of hundreds to a thousand kilometers. Five-sphere glass implosions were recorded at ranges up to 4400 km. Near-sea surface shots from a large airgun array were recorded in several cases at ranges of hundreds to thousands of kilometers, the frequency of the highest signal-to-noise ratio arrivals varied within the 5–100 Hz band. High background noise level was a key factor at IMS stations that did not detect the airgun signals in the 5–15 Hz band. In a few cases, details of bathymetric features that are not well represented in the digital elevation model contributed to unexpected variation in relative signal levels between IMS stations.
The effects of single and double hearing protection on the localization and segregation of spatially-separated speech signals (L)
Authors: Brungart Douglas S. , Kordik Alexander J. , Simpson Brian D.
Published: October 2004

Recent results have shown that auditory localization in the horizontal plane is dramatically worse for listeners wearing double hearing protection (earplugs and earmuffs) than it is for listeners wearing single hearing protection (earplugs or earmuffs alone). This suggests that double hearing protection might also impair the spatial unmasking that normally occurs when two simultaneous talkers are spatially separated in azimuth (the so-called “cocktail party” effect). In this experiment, normal hearing listeners wearing no hearing protection, single hearing protection (earmuffs), or double hearing protection were asked to perform a speech intelligibility task that required them to segregate two simultaneous talkers who were either presented from the same loudspeaker or spatially separated by 90° in azimuth. The listeners were also asked to determine the location of the target talker in each trial. The results show that the listeners were unable to reliably determine the location of the target talker when they wore double hearing protection, but that they were still able to benefit from the spatial separation of the competing talkers. This suggests that the use of double hearing protection causes spatially separated sound sources to be heard at locations that are inaccurate but still distinct enough to enhance the segregation of speech.
Hybrid passive–active absorption using microperforated panels
Authors: Cobo Pedro , Pfretzschner Jaime , Cuesta Marı́a , Anthony David K.
Published: October 2004

A theoretical and experimental study of a proposed hybrid passive–active plane-wave system to provide broadband acoustic absorption is presented. The passive absorber consists of a microperforated panel (MPP), used in place of conventional fibrous materials, in front of an air layer. The active system uses an active transducer (a loudspeaker), an error sensor (a microphone), and an adaptive controller. MPPs are thinner than fibrous materials and provide a better solution in hygienic environments. For two such systems, the dependence of performance on MPP parameters is studied for two control strategies: impedance matching and pressure release. The first condition is found to be better for cases where the acoustic impedance of the system approaches that of air. Otherwise, the pressure-release condition is better, and a wideband solution is the implementation of the active control system up to a frequency where the natural band of the passive system provides higher absorption. Therefore, the use of a low-pass filter in the error signal is implemented to afford hybrid passive–active wideband absorption. The control effort of active system is also considered. Experimental verification shows good agreement with theory, and an average absorption coefficient of 0.82 in the frequency bandwidth 100 to 1600 Hz was achieved.
Development of local volume displacement sensors for vibrating plates
Authors: Zahui Marcellin , Wendt Ronald
Published: October 2004

Development of local volume displacement sensors is presented. This development supports the implementation of noise control techniques that are based on minimization of local volume displacements, velocities, or accelerations of a vibrating structure. In this paper, a general methodology for the development of local volume displacement sensors for vibrating plates using p_olyv_ynilid_ene f_luoride (PVDF) is presented. This methodology was verified experimentally for a clamped plate. The local volume displacement measured using a PVDF sensor matched the local volume displacement found using multiple accelerometer measurements. The resulting sensor spans the entire x-length of the plate and covers the width of the area of interest. The sensor is composed of several strips of PVDF whose width varies with x quadratically on the local area and linearly elsewhere. Design issues for a clamped plate, a simply supported plate and a plate with arbitrary boundary conditions are discussed along with a presentation of some sample sensor shapes.
Masker phase effects in normal-hearing and hearing-impaired listeners: Evidence for peripheral compression at low signal frequencies
Authors: Oxenham Andrew J. , Dau Torsten
Published: October 2004

The presence of cochlear-based compression at low frequencies was investigated by measuring phase effects in harmonic maskers. In normal-hearing listeners, the amount of masking produced depends strongly on the phase relationships between the individual masker components. This effect is thought to be determined primarily by properties of the cochlea, including the phase dispersion and compressive input–output function of the basilar membrane. Thresholds for signals of 250 and 1000 Hz were measured in harmonic maskers with fundamental frequencies of 12.5 and 100 Hz as a function of the masker phase curvature. Results from 12 listeners with sensorineural hearing loss showed reduced masker phase effects, when compared with data from normal-hearing listeners, at both 250- and 1000-Hz signal frequencies. The effects of hearing impairment on phase-related masking differences were not well simulated in normal-hearing listeners by an additive white noise, suggesting that the effects of hearing impairment are not simply due to reduced sensation level. Maximum differences in masked threshold were correlated with auditory filter bandwidths at the respective frequencies, suggesting that both measures are affected by a common underlying mechanism, presumably related to cochlear outer hair cell function. The results also suggest that normal peripheral compression remains strong even at 250 Hz.
The effect of onset asynchrony on profile analysis by normal-hearing and hearing-impaired listeners
Authors: Lentz Jennifer J. , Leek Marjorie R. , Molis Michelle R.
Published: October 2004

The effect of onset asynchrony on discrimination of spectral shape was evaluated for hearing-impaired and normal-hearing listeners. Stimuli were the sum of four tones equally spaced on a logarithmic frequency scale. The standard stimulus had tones of equal amplitude, and the signal stimulus had two adjacent components increased in level, and the other two components decreased in level. Thresholds for discrimination between the standard and signal stimuli were measured as a function of an onset asynchrony among the components of 0, 50, and 200 ms. Hearing-impaired and normal-hearing listeners had similar thresholds when the stimulus components were widely spaced in frequency, but hearing-impaired listeners had much higher thresholds for narrowly spaced components. Excitation pattern analyses indicated that listeners may use spectral peaks in the stimulus rather than the change in excitation across the full stimulus bandwidth for spectral shape discrimination tasks. Increasing temporal asynchrony of components resulted in increased thresholds for both groups of listeners to a greater extent in the wide span than the narrow span. Reduced effects of onset asynchrony in the narrow span suggest that spectral resolvability of components plays an important role in the processing of onset asynchrony across frequency.
Measurements of directional properties of reverberant sound fields in rooms using a spherical microphone array
Authors: Gover Bradford N. , Ryan James G. , Stinson Michael R.
Published: October 2004

The directional variation of sound at a point has been studied in three rooms, using a measurement system described previously [J. Acoust. Soc. Am. 112, 1980–1991 (2002)]. The system uses a pair of 32-element spherical microphone arrays to obtain directional impulse responses in each of 60 steering directions, with an angular resolution of 28°, covering all directions in the whole solid angle. Together, the array measurements span the frequency range from 300 to 3300 Hz. The angular distribution of incident sound energy is visualized on a three-dimensional plot, and quantified by computing the directional diffusion and the directional peak-to-average level difference (“anisotropy index”) of the sound field. The small-to-medium-sized rooms had reverberation times of 360, 400, and 600 ms. Measurements were made for several source and receiver locations in each, and were analyzed over several time ranges (full decay time of room, late time decay, 2-ms windows throughout the decay). All measured sound fields were found to be highly directional, the distribution of arriving energy at a point greatly influenced by the early specular reflections. The directions and arrival times of these reflections were identified from the measurements, giving excellent agreement with those expected from knowledge of the room geometry. It was observed that as time progressed, the sound fields initially exhibited increasing isotropy, followed by increasing anisotropy, due to nonuniform absorption in the rooms. The measurement system is capable of yielding detailed information about the reverberant sound field in a room, and is easily modified to be able to analyze ambient or time-varying fields.
The dynamics and tuning of orchestral crotales
Authors: Deutsch Bradley M. , Ramirez Cherie L. , Moore Thomas R.
Published: October 2004

An experimental and theoretical investigation of the acoustic and vibrational properties of orchestral crotales within the range C6 to C8 is reported. Interferograms of the acoustically important modes of vibration are presented and the frequencies are reported. It is shown that the acoustic spectra of crotales are not predicted by assuming that they are either thin circular plates or annular plates clamped at the center, despite the physical resemblance to these objects. Results from finite element analysis are presented that demonstrate how changing the size of the central mass affects the tuning of the instruments, and it is concluded that crotales are not currently designed to ensure optimal tuning. The possibility of using annular plates as crotales is also investigated and the physical parameters for such a set of instruments are presented.
The influence of sexual orientation on vowel production (L)
Authors: Pierrehumbert Janet B. , Bent Tessa , Munson Benjamin , Bradlow Ann R. , Bailey J. Michael
Published: October 2004

Vowel production in gay, lesbian, bisexual (GLB), and heterosexual speakers was examined. Differences in the acoustic characteristics of vowels were found as a function of sexual orientation. Lesbian and bisexual women produced less fronted /u/ and /ɑ/ than heterosexual women. Gay men produced a more expanded vowel space than heterosexual men. However, the vowels of GLB speakers were not generally shifted toward vowel patterns typical of the opposite sex. These results are inconsistent with the conjecture that innate biological factors have a broadly feminizing influence on the speech of gay men and a broadly masculinizing influence on the speech of lesbian/bisexual women. They are consistent with the idea that innate biological factors influence GLB speech patterns indirectly by causing selective adoption of certain speech patterns characteristic of the opposite sex.
Talker differences in clear and conversational speech: Vowel intelligibility for normal-hearing listeners
Authors: Hargus Ferguson Sarah
Published: October 2004

Several studies have shown that when a talker is instructed to speak as though talking to a hearing-impaired person, the resulting “clear” speech is significantly more intelligible than typical conversational speech. While variability among talkers during speech production is well known, only one study to date [Gagné et al., J. Acad. Rehab. Audiol. 27, 135–158 (1994)] has directly examined differences among talkers producing clear and conversational speech. Data from that study, which utilized ten talkers, suggested that talkers vary in the extent to which they improve their intelligibility by speaking clearly. Similar variability can be also seen in studies using smaller groups of talkers [e.g., Picheny, Durlach, and Braida, J. Speech Hear. Res. 28, 96–103 (1985)]. In the current paper, clear and conversational speech materials were recorded from 41 male and female talkers aged 18 to 45 years. A listening experiment demonstrated that for normal-hearing listeners in noise, vowel intelligibility varied widely among the 41 talkers for both speaking styles, as did the magnitude of the speaking style effect. While female talkers showed a larger clear speech vowel intelligibility benefit than male talkers, neither talker age nor prior experience communicating with hearing-impaired listeners significantly affected the speaking style effect.
Acoustic scattering from finite cylindrical shells: Influence of end-caps (L)
Authors: Haumesser L. , Touraine N. , Décultot D. , Maze G.
Published: October 2004

By using an experimental approach, the acoustic backscattering from air-filled cylindrical shells, immersed in water, is investigated. The targets considered in this work are ended either by hemispherical caps or by flat circular lids. Given the 1% shell thickness and the frequency window of this study, only echoes resulting from the propagation of S0 and T0 waves (respectively, quasi-compressional and quasi-shear waves of lowest order) are observable. On both types of objects, measurements are carried out at various aspect angles of incidence over the broadside of the target. The influence of the type of end-caps on the propagation of helical waves (i.e. waves initially generated on the cylindrical part of the objects) is studied using incidence-angle/time representations.
Perfect harmony: A mathematical analysis of four historical tunings
Authors: Page Michael F.
Published: October 2004

In Western music, a musical interval defined by the frequency ratio of two notes is generally considered consonant when the ratio is composed of small integers. Perfect harmony or an “ideal just scale,” which has no exact solution, would require the division of an octave into 12 notes, each of which would be used to create six other consonant intervals. The purpose of this study is to analyze four well-known historical tunings to evaluate how well each one approximates perfect harmony. The analysis consists of a general evaluation in which all consonant intervals are given equal weighting and a specific evaluation for three preludes from Bach’s “Well-Tempered Clavier,” for which intervals are weighted in proportion to the duration of their occurrence. The four tunings, 5-limit just intonation, quarter-comma meantone temperament, well temperament (Werckmeister III), and equal temperament, are evaluated by measures of centrality, dispersion, distance, and dissonance. When all keys and consonant intervals are equally weighted, equal temperament demonstrates the strongest performance across a variety of measures, although it is not always the best tuning. Given C as the starting note for each tuning, equal temperament and well temperament perform strongly for the three “Well-Tempered Clavier” preludes examined.
Secant lines in a preliminary study of phonetic reduction of / ɪ / and /ε /
Authors: McGowan Richard S.
Published: October 2004

Two subjects from the X-Ray Microbeam Speech Production Database were examined in their production of the vowels /ɪ/ and /ε/ in alveolar and dental consonant contexts. Secant lines, or first-order splines, between the three most anterior pellets were examined at vowel critical times. These critical times were zero crossings in the tangential acceleration of the midpoints of the secant lines. We expected and found, in general, that vowel reduction occurred as a function of vowel duration in measures of the secant line midpoint-to-palate distance and secant line orientation at vowel critical times. The shorter the vowel, the smaller the distance of the secant line midpoints to the palate and the less downward the orientation of the secant lines at the vowel critical times. Phonetic reduction was also apparent in the formant frequencies. There were differences between the speakers in terms of the range of vowel duration and degree of reduction. The subjects differed in the functional parts of the tongue spanned by the secant lines and the shape of their palates. These differences were factors in the observed relations between formant frequencies and the articulatory, secant line measures for each subject.
Using statistical decision theory to predict speech intelligibility. III. Effect of audibility on speech recognition sensitivity
Authors: Müsch Hannes , Buus Søren
Published: October 2004

The speech recognition sensitivity (SRS) model [H. Müsch and S. Buus, J. Acoust. Soc. Am. 109, 2896–2909 (2001)] is a macroscopic model for predicting speech intelligibility. The present study proposes a modification to the relation between the SRS model’s audibility-noise variance and the signal-excitation to noise-excitation ratio (SNRE) in the auditory periphery. The modified relation is derived from data obtained in nine studies that measured normal-hearing listeners’ consonant-recognition performance at several levels of speech-spectrum shaped noise. When the audibility-noise variance is directly proportional to the relative power of the noise excitation in the auditory periphery, the SRS model yields good predictions of the data. Four of the nine studies also reported consonant-recognition performance in various filtering conditions. Good predictions of these data were achieved with SRS model parameters that were consistent with the model parameters fitting the speech-in-noise data and with the model parameters used in the original SRS papers.
Leaky Rayleigh and Scholte waves at the fluid–solid interface subjected to transient point loading
Authors: Zhu Jinying , Popovics John S. , Schubert Frank
Published: October 2004

The analysis of acoustic waves generated by a transient normal point load applied on a fluid–solid interface is presented. The closed-form exact solution of the wave motion is obtained by using integral transform techniques. The obtained analytical solution provides necessary theoretical background for optimization of fluid-coupled ultrasonic and acoustic wave detection in experiments. Numerical simulation (elastodynamic finite integration technique) is performed to verify the obtained analytical solution. Detailed descriptions of leaky Rayleigh and Scholte wave solutions are presented. A simplified solution to isolate the contributions of leaky Rayleigh and Scholte waves generated by a transient point load is proposed, and closed-form formulations for displacement and stress components are then presented. The simplified solution is compared to the exact solution for two configurations: water/concrete and air/concrete. The excitation effectiveness of leaky Rayleigh waves for the air/concrete configuration is studied, which has practical significance to air-coupled sensing in civil engineering structures.
Transcriptional Response of
Candida albicans
upon Internalization by Macrophages
Authors: Lorenz Michael C. , Bender Jennifer A. , Fink Gerald R.
Published: October 2004

The opportunistic fungal pathogen
Candida albicans
is both a benign gut commensal and a frequently fatal systemic pathogen. The interaction of
C. albicans
with the host's innate immune system is the primary factor in this balance; defects in innate immunity predispose the patient to disseminated candidiasis. Because of the central importance of phagocytic cells in defense against fungal infections, we have investigated the response of
C. albicans
to phagocytosis by mammalian macrophages using genomic transcript profiling. This analysis reveals a dramatic reprogramming of transcription in
C. albicans
that occurs in two successive steps. In the early phase cells shift to a starvation mode, including gluconeogenic growth, activation of fatty acid degradation, and downregulation of translation. In a later phase, as hyphal growth enables
C. albicans
to escape from the macrophage, cells quickly resume glycolytic growth. In addition, there is a substantial nonmetabolic response imbedded in the early phase, including machinery for DNA damage repair, oxidative stress responses, peptide uptake systems, and arginine biosynthesis. Further, a surprising percentage of the genes that respond specifically to macrophage contact have no known homologs, suggesting that the organism has undergone substantial evolutionary adaptations to the commensal or pathogen lifestyle. This transcriptional reprogramming is almost wholly absent in the related, but nonpathogenic, yeast
Saccharomyces cerevisiae
, suggesting that these large-scale and coordinated changes contribute significantly to the ability of this organism to survive and cause disease in vivo.