grid generation techniques in computational fluid dynamics revue des differentes methodes on montre que les regions tridimensionnelles sont mieux traitees par fragmentation du champ en sous regions avec generation de grilles dans chaque sous region interet des grilles adaptatives couplees a des solutions physiques

alternating direction adaptive grid generation an alternating direction method has been developed to adaptively resolve numerical solutions to physical problems by moving the points of a coordinate grid with the solution or with the salient quantities derived from it a surface grid is defined over the grid on the physical region grid movement is computed on this abstractly defined solution surface with the use of pointwise weights and is then projected back to determine new locations in the physical region the weights cause clustering relative to the uniform conditions of surface arc length and are formed with magnitudes of quantities that are used for point attraction when the salient quantities have been used to form the surface the gradients are implicitly revolved and surface curvature becomes the primary remaining quantity in each coordinate direction the magnitude of normal curvature is used with arbitrary weights a movement cycle generally consists of a sweep through the coordinate curves in a given direction on a curve by curve basis and then in alternating directions to do the same thing until all directions have been covered

on the complexity of computing the volume of a polyhedron we show that computing the volume of a polyhedron given either as a list of facets or as a list of vertices is as hard as computing the permanent of a matrix

relations between auditory functions in impaired hearing relations between auditory functions as expressed by coefficients of correlation were studied for a group of 22 sensorineurally hearing impaired subjects with moderate losses in addition to the audiogram we measured frequency resolution temporal resolution and speech reception in quiet and in noise frequency resolution was derived from masking with comb filtered noise and from the psychophysical tuning curve for both paradigms in simultaneous and in nonsimultaneous masking the critical ratio was also determined temporal resolution was determined with intensity modulated noise and from backward and forward masking all tests were performed at 1000 hz correlations among tests were gathered in a matrix and subjected to a principal components analysis it turned out that tests on frequency resolution form a cluster and are approximately independent of audiometric loss furthermore hearing loss for speech in noise is closely allied to frequency resolution whereas hearing loss for speech in quiet is governed by audiometric loss

polytope volume computation a combinatorial form of gram s relation for convex polytopes can be adapted for use in computing polytope volume we present an algorithm for volume computation based on this observation this algorithm is useful in finding the volume of a polytope given as the solution set of a system of linear inequalities p x e r ax b as an illustration we compute a formula for the volume of a projective image of the n cube from this formula we deduce that when a and b have rational entries so that the volume of p is also a rational number the number of binary digits in the denominator of the volume cannot be bounded by a polynomial in the total number of digits in the numerators and denominators of entries of a and b this settles a question posed by dyer and frieze

streamwise computation of three dimensional incompressible potential flows abstract a new method for the computation of three dimensional incompressible potential flows is presented the dependent variables of this method are the streamwise velocity along a set of chosen streamlines and the coordinates of the chosen streamlines in the cross stream plane since the method computes streamline coordinates directly it can be easily used to generate boundary fitted grids for the computation of three dimensional viscous flows sample computations are presented for i flow through a rectangular diffuser with an offset and with a change in the aspect ratio and ii flow through a duct whose cross section changes from a square to a rhombus

relations between intelligibility of narrow band speech and auditory functions both in the 1 khz frequency region relations between perception of suprathreshold speech and auditory functions were examined in 24 hearing impaired listeners and 12 normal hearing listeners the speech intelligibility index sii was used to account for audibility the auditory functions included detection efficiency temporal and spectral resolution temporal and spectral integration and discrimination of intensity frequency rhythm and spectro temporal shape all auditory functions were measured at 1 khz speech intelligibility was assessed with the speech reception threshold srt in quiet and in noise and with the speech reception bandwidth threshold srbt previously developed for investigating speech perception in a limited frequency region around 1 khz the results showed that the elevated srt in quiet could be explained on the basis of audibility audibility could only partly account for the elevated srt values in noise and the deviant srbt values suggesting that suprathreshold deficits affected intelligibility in these conditions sii predictions for the srbt improved significantly by including the individually measured upward spread of masking in the sii model reduced spectral resolution reduced temporal resolution and reduced frequency discrimination appeared to be related to speech perception deficits loss of peripheral compression appeared to have the smallest effect on the intelligibility of suprathreshold speech

psychometric functions for level discrimination in cochlearly impaired and normal listeners with equivalent threshold masking the purpose of this study was to determine whether the form of the psychometric functions for level discrimination also known as intensity discrimination measured in a two interval two alternative forced choice paradigm changes with hearing impairment measurements of sensitivity d as a function of delta l 20 log p delta p lp where p is pressure were obtained in six listeners with cochlear impairments five normal listeners tested in the quiet and two masked normal listeners stimuli were chosen to encompass a wide range of conditions and difference limens results show that the d is nearly proportional to delta l over the entire range of stimuli this simple relationship is not changed by cochlear impairments or masking noise these findings indicate that if the transformation from stimulus intensity to decision variable is affected by hearing impairment or masking the change affects both the mean and the standard deviation in the same manner i e the standard deviation may be proportional to the derivative of the transformation as was suggested by zwislocki and jordan j acoust soc am 79 772 780 1986 the results also lend support to the notion that delta l plotted on a logarithmic scale is an appropriate representation of level discrimination performance

use of streamline coordinates in the numerical solution of compressible flow problems abstract iterative correction of streamline geometry is used as the basis of a numerical method for subsonic isentropic steady flow problems direct solution of coupled ordinary differential equations is applicable to the corresponding supersonic problem the method is formulated in three dimensions but for illustrative purposes is applied to a two dimensional jet involving a free surface condition the method may be particularly economical where intuition or experience provides a good starting guess for streamline geometry

general curvilinear coordinate systems the basic ideas of the construction and use of numerically generated boundary fitted coordinate systems for the numerical solution of partial differential equations are discussed with such coordinate systems all computation can be done on a fixed square grid in the rectangular transformed region regardless of the shape or movement of the physical boundaries a number of different types of configurations for the transformed region and the basic transformation relations from a cartesian system to a general curvilinear system are given the material of this paper is applicable to all types of coordinate system generation

boundary fitted coordinate systems for numerical solution of partial differential equations a review a comprehensive review of methods of numerically generating curvilinear coordinate systems with coordinate lines coincident with all boundary segments is given some general mathematical framework and error analysis common to such coordinate systems is also included the general categories of generating systems are those based on conformal mapping orthogonal systems nearly orthogonal systems systems produced as the solution of elliptic and hyperbolic partial differential equations and systems generated algebraically by interpolation among the boundaries also covered are the control of coordinate line spacing by functions embedded in the partial differential operators of the generating system and by subsequent stretching transformation dynamically adaptive coordinate systems coupled with the physical solution and time dependent systems that follow moving boundaries are treated references reporting experience using such coordinate systems are reviewed as well as those covering the system development

a numerical approach for computing flows by local transformations and domain decomposition using an optimization algorithm this paper presents theoretical information for numerical simulation of two and three dimensional flows based on the concepts of streamlines and local transformation functions associated with domain decomposition in this approach in addition to the pressure the primary unknowns are the local mapping functions between the physical sub domains and transformed domains where the mapped streamlines are parallel straight lines this makes it easy to handle time dependent constitutive equations for complex fluids to solve the governing equations that also involve compatibility equations between sub domains an optimization algorithm is set up in order to compute the unknowns related to the streamlines iteratively applications are given for two dimensional flows between eccentric cylinders using different constitutive equations

effects of degradation of intensity time or frequency content on speech intelligibility for normal hearing and hearing impaired listeners many hearing impaired listeners suffer from distorted auditory processing capabilities this study examines which aspects of auditory coding i e intensity time or frequency are distorted and how this affects speech perception the distortion sensitivity model is used the effect of distorted auditory coding of a speech signal is simulated by an artificial distortion and the sensitivity of speech intelligibility to this artificial distortion is compared for normal hearing and hearing impaired listeners stimuli speech plus noise are wavelet coded using a complex sinusoidal carrier with a gaussian envelope 14 octave bandwidth intensity information is distorted by multiplying the modulus of each wavelet coefficient by a random factor temporal and spectral information are distorted by randomly shifting the wavelet positions along the temporal or spectral axis respectively measured were 1 detection thresholds for each type of distortion and 2 speech reception thresholds for various degrees

relations between frequency selectivity temporal fine structure processing and speech reception in impaired hearing frequency selectivity temporal fine structure tfs processing and speech reception were assessed for six normal hearing nh listeners ten sensorineurally hearing impaired hi listeners with similar high frequency losses and two listeners with an obscure dysfunction od tfs processing was investigated at low frequencies in regions of normal hearing through measurements of binaural masked detection tone lateralization and monaural frequency modulation fm detection lateralization and fm detection thresholds were measured in quiet and in background noise speech reception thresholds were obtained for full spectrum and lowpass filtered sentences with different interferers both the hi listeners and the od listeners showed poorer performance than the nh listeners in terms of frequency selectivity tfs processing and speech reception while a correlation was observed between the monaural and binaural tfs processing deficits in the hi listeners no relation was found between tfs processing and frequency selectivity the effect of noise on tfs processing was not larger for the hi listeners than for the nh listeners finally tfs processing performance was correlated with speech reception in a two talker background and lateralized noise but not in amplitude modulated noise the results provide constraints for future models of impaired auditory signal processing

speech reception in quiet and in noisy conditions by individuals with noise induced hearing loss in relation to their tone audiogram tone thresholds and speech reception thresholds were measured in 200 individuals 400 ears with noise induced hearing loss the speech reception thresholds were measured in a quiet condition and in noise with a speech spectrum at levels of 35 50 65 and 80 dba the tone audiograms could be described by three principal components hearing loss in the regions above 3 khz from 1 to 3 khz and below 1 khz the speech thresholds could be described by two components speech reception in quiet and speech reception in noise at 50 80 dba hearing loss above 1 khz was related to speech reception in noise hearing loss at and below 1 khz to speech reception in quiet the correlation between the speech thresholds in quiet and in noise was only r 0 45 an adequate predictor of the speech threshold in noise the primary factor in the hearing handicap was the pure tone average at 2 and 4 khz pta2 4 r 0 72 the minimum value of the prediction error for any tone audiometric predictor of this speech threshold was 1 2 db standard deviation the prediction could not be improved by taking into account the critical ratio for low frequency noise nor by its upward spread of masking the prediction error is due to measurement error and to a factor common to both ears the latter factor is ascribed to cognitive skill in speech reception hearing loss above 10 to 15 db hl hearing level already shows an effect on the speech threshold in noise a noticeable handicap is found at pta2 4 30 db hl

modeling speech intelligibility in quiet and noise in listeners with normal and impaired hearing the speech intelligibility index sii is an often used calculation method for estimating the proportion of audible speech in noise for speech reception thresholds srts measured in normally hearing listeners using various types of stationary noise this model predicts a fairly constant speech proportion of about 0 33 necessary for dutch sentence intelligibility however when the sii model is applied for srts in quiet the estimated speech proportions are often higher and show a larger inter subject variability than found for speech in noise near normal speech levels 65 db sound pressure level spl the present model attempts to alleviate this problem by including cochlear compression it is based on a loudness model for normally hearing and hearing impaired listeners of moore and glasberg 2004 hear res 188 70 88 it estimates internal excitation levels for speech and noise and then calculates the proportion of speech above noise and threshold using similar spectral weighting as used in the sii the present model and the standard sii were used to predict sii values in quiet and in stationary noise for normally hearing and hearing impaired listeners the present model predicted siis for three listener types normal hearing noise induced and age induced hearing loss with markedly less variability than the standard sii

lattice points in simple polytopes in terms of fp h q x dx where the polytope p h is obtained from p by independent parallel motions of all facets this extends to simple lattice polytopes the eulermaclaurin summation formula of khovanskii and pukhlikov 8 valid for lattice polytopes such that the primitive vectors on edges through each vertex of p form a basis of the lattice as a corollary we recover results of pommersheim 9 and kantor khovanskii 6 on the coefficients of the ehrhart polynomial of p our proof is elementary in a subsequent article we will show how to adapt it to compute the equivariant todd class of any complete toric variety with quotient singularities the euler maclaurin summation formula for simple lattice polytopes has been obtained independently by ginzburg guillemin karshon 4 they used the dictionary between convex polytopes and projective toric varieties with an ample divisor class in combination with the riemann roch kawasaki formula 1 7 for complex manifolds with quotient singularities a counting formula for lattice points in lattice simplices has been announced by cappell and shaneson 2 as a consequence of their computation of the todd class of toric varieties with quotient singularities

additivity of masking in normally hearing and hearing impaired subjects the effects of combining two equally effective maskers were studied in normally hearing and elderly hearing impaired subjects the additivity of nonsimultaneous masking was investigated by measuring thresholds for a brief 4 khz signal in the presence of a broadband noise forward masker a backward masker and a combination of both for the normally hearing subjects combining two equally effective nonsimultaneous maskers resulted in up to a 15 db greater increase in threshold than the 3 db predicted by an energy summation model excess masking however the hearing impaired subjects showed little or no excess masking the difference between the two groups is consistent with a theory linking excess masking to the compressive transfer function measured on the basilar membrane bm in the hearing impaired subjects the transfer function is more linear accounting for the lack of excess masking the additivity of simultaneous masking was investigated by measuring thresholds for a 100 ms 4 khz signal in the presence of either a 400 ms broadband noise masker or a 400 ms sinusoidal masker at the same frequency as the signal and then combining two equally effective maskers a noise and a tone the maximum amount of excess masking 3 to 4 db was similar across the two groups of subjects consistent with an explanation based on the use of different detection cues for the tonal and noise maskers it is argued that while peripheral compression may underlie excess masking for pairs of nonsimultaneous maskers it is unlikely that in simultaneous masking where the maskers are close in frequency to the signal the two maskers are compressed individually before their effects are combined it is further suggested that bm nonlinearity may underlie the effects of the upward spread of masking and the nonlinear growth of forward masking as well as accounting for the additivity of simultaneous masking when the masker frequencies are well below that of the signal

intensity discrimination of gaussian windowed tones indications for the shape of the auditory frequency time window the just noticeable difference in intensity jnd i was measured for 1 khz tones with a gaussian shaped envelope as a function of their spectro temporal shape the stimuli with constant energy and a constant product of bandwidth and duration ranged from a long duration narrow band tone to a short duration broadband click the jnd i was measured in three normal hearing listeners at sensation levels of 0 10 20 and 30 db in 35 db a spl pink noise at intermediate sensation levels jnd i depends on the spectro temporal shape at the extreme shapes tones and clicks intensity discrimination performance is best whereas at intermediate shapes the jnd i is larger similar results are observed at a higher overall sound level and at a higher carrier frequency the maximum jnd i is observed for stimuli with an effective bandwidth of about 1 3 octave and an effective duration of 4 ms at 1 khz 1 ms at 4 khz a generalized multiple window model is proposed that assumes that the spectro temporal domain is partitioned into internal auditory frequency time windows the model predicts that intensity discrimination thresholds depend upon the number of windows excited by a signal jnd i is largest for stimuli covering one window

the effect of intensity perturbations on speech intelligibility for normal hearing and hearing impaired listeners hearing impaired listeners are known to suffer from reduced speech intelligibility in noise even if sounds are above their hearing thresholds this study examined the possible contribution of reduced acuity of intensity coding to this problem the distortion sensitivity model was used the effect of reduced acuity of auditory intensity coding on intelligibility was mimicked by an artificial distortion of the speech intensity coding and the sensitivity to this distortion for hearing impaired listeners was compared with that for normal hearing listeners stimuli speech plus noise were wavelet coded using a gaussian wavelet 1 4 octave bandwidth the intensity coding was distorted by multiplying the modulus of each wavelet coefficient by a random factor speech reception thresholds srts were measured for various degrees of intensity perturbation hearing impaired listeners were classified as suffering from suprathreshold deficits if intelligibility of undistorted speech was worse than predicted from audibility by the speech intelligibility index model ansi ansi s3 5 1997 1997 hearing impaired listeners without suprathreshold deficits were as sensitive to the intensity distortion as the normal hearing listeners hearing impaired listeners with suprathreshold deficits appeared to be less sensitive results indicate that reduced acuity of auditory intensity coding may be a factor underlying reduced speech intelligibility in noise for the hearing impaired hearing impaired listeners are known to suffer from reduced speech intelligibility in noise even if sounds are above their hearing thresholds this study examined the possible contribution of reduced acuity of intensity coding to this problem the distortion sensitivity model was used the effect of reduced acuity of auditory intensity coding on intelligibility was mimicked by an artificial distortion of the speech intensity coding and the sensitivity to this distortion for hearing impaired listeners was compared with that for normal hearing listeners stimuli speech plus noise were wavelet coded using a gaussian wavelet 1 4 octave bandwidth the intensity coding was distorted by multiplying the modulus of each wavelet coefficient by a random factor speech reception thresholds srts were measured for various degrees of intensity perturbation hearing impaired listeners were classified as suffering from suprathreshold deficits if intelligibility of undistorted speech was worse than predicted from

how to integrate a polynomial over a simplex this paper starts by settling the computational complexity of the problem of integrating a polynomial function f over a rational simplex we prove that the problem is np hard for arbitrary polynomials via a generalization of a theorem of motzkin and straus on the other hand if the polynomial depends only on a fixed number of variables while its degree and the dimension of the simplex are allowed to vary we prove that integration can be done in polynomial time as a consequence for polynomials of fixed total degree there is a polynomial time algorithm as well we explore our algorithms with some experiments we conclude the article with extensions to other polytopes and discussion of other available methods 1

psychoacoustic and phonetic temporal processing in normal and hearing impaired listeners four measures of auditory temporal processing were obtained from 16 normals and 16 individuals with a hearing loss of heterogeneous origin these measures were 1 temporal integration the difference in detection thresholds between signals of 10 and 1000 ms duration which was determined to provide an estimate of the ability to integrate energy over time 2 gap detection the shortest duration of silence between two noise bursts that can be discriminated from an uninterrupted noise 3 temporal difference limen the increment in duration necessary to detect a difference in the duration of a noise burst 4 gap difference limen the increment in duration necessary to detect a difference in the duration of a silent interval between two noise bursts each measure was obtained for stimuli centered both at 500 and at 4000 hz using a three alternative forced choice procedure in addition measures of identification and discrimination were obtained for two sets of synthetic speech syllables varying chiefly in a temporal parameter voice onset time from ba to pa and from bi to pi finally speech identification in noise was measured with the faaf test most of the hearing impaired listeners displayed poorer temporal analysis than the normals on all of the psychoacoustical tasks regardless of whether the two groups were compared at similar sound pressure levels or at similar sensation levels although the hearing impaired listeners displayed a reduction in the ability to discriminate subphonemic cues for the voiced voiceless distinction their identification of that distinction in stop consonants appeared to be normal the hearing impaired group made about twice as many errors as did the normals on each of the consonant features of place manner and voicing when identifying speech in noise increased temporal difference limen and longer gap detection thresholds were found to correlate significantly with reduced speech intelligibility in noise even when the effects of the pure tone threshold loss were partialed out

multiplicities of classical varieties the j multiplicity plays an important role in the intersec tion theory of stuckrad vogel cycles while recent developments confirm the connections between the e multiplicity and equisingularity theory in this paper we establish under some constraints a relation ship between the j multiplicity of an ideal and the degree of its fiber cone as a conse quence we are able to compute the j multiplicity of all the ideals defin ing rational normal scrolls by using the standard monomial theory we can also compute the j and e multiplicity of ideals defining determinan tal varieties the found quantities are integrals which qu ite surprisingly are central in random matrix theory

three dimensional grid generation using poisson equations a method for constructing a boundary fitted grid system for arbitrary three dimensional 3 d configurations is presented the grid generation procedure is formulated through the poison equations a feature of the scheme is that grid lines in the grid system are smothly interconnected between the boundary co ordinates the control of the grid distributions in the interior of the system has implemented by the forcing functions appearing in the poisson equations and by the boundary coordinates reasonable cell sizes and shapes are obtained even for extreme boundary shapes which normally tend to cause poorly controlled grid distributions

algebraic grid generation three methods are described for transforming grids in bounded two and three dimensional physical domains into a uniform grid in a rectangular computational domain the methods are based on mathematical interpolation functions and do not require the solution of differential equations or the use of complex variables they are simply referred to as algebraic methods and are called transfinite interpolation the multisurface method and the two boundary technique the primary advantage of the methods is that they provide explicit control of physical grid shape and physical grid spacing secondly they require relatively few computations consequently the application of inter active computer graphics in conjunction with the methods is advocated for rapid generation of grids the basic mathematical structure of each method is described and particular attention is given to surface representation parameter variable generation and control function generation physical boundary topology and grid derivative requirements are presented

solution of viscous internal flows on curvilinear grids generated by the schwarz christoffel transformation abstract a method is presented for combining an accurate orthogonal curvilinear coordinate generation procedure with a fast accurate and stable forward marching viscous flow solution technique to solve for the flow field in arbitrary axisymmetric ducts in this method the coordinates are generated from the plane potential flow streamlines and potential lines using the schwarz christoffel transformation with a composite finite difference formula which is valid everywhere and which treats the poles exactly by analytic integration since the coordinate streamlines approximate the actual streamlines the equations of motion for viscous compressible flow can be parabolized so as to solve for both the boundary layers and core flow in a single streamwise pass the versatility of the method is demonstrated by two examples of viscous compressible swirling flow through complex radial gas turbine passages author

an efficient full potential implicit method based on characteristics for supersonic flows la methode utilise la theorie de la propagation de signal caracteristique pour simuler avec precision la structure de l ecoulement qui inclut des ondes de choc et un ecoulement transversal mixte elliptique hyperbolique

measuring the threshold for speech reception by adaptive variation of the signal bandwidth ii hearing impaired listeners in a previous study noordhoek et al j acoust soc am 105 2895 2902 1999 an adaptive test was developed to determine the speech reception bandwidth threshold srbt i e the width of a speech band around 1 khz required for a 50 intelligibility score in this test the band filtered speech is presented in complementary bandstop filtered noise in the present study the performance of 34 hearing impaired listeners was measured on this srbt test and on more common srt speech reception threshold tests namely the srt in quiet the standard srt in noise standard speech spectrum and the spectrally adapted srt in noise fitted to the individual s dynamic range the aim was to investigate to what extent the performance on these tests could be explained simply from audibility as estimated with the sii speech intelligibility index model or require the assumption of suprathreshold deficits for most listeners an elevated srt in quiet or an elevated standard srt in noise could be explained on the basis of audibility for the spectrally adapted srt in noise and especially for the srbt the data of most listeners could not be explained from audibility suggesting that the effects of suprathreshold deficits may be present possibly such a deficit is an increased downward spread of masking

the use of solution adaptive grids in solving partial differential equations the grid point distribution used in solving a partial differential equation using a numerical method has a substantial influence on the quality of the solution an adaptive grid which adjusts as the solution changes provides the best results when the number of grid points available for use during the calculation is fixed basic concepts used in generating and applying adaptive grids are reviewed in this paper and examples illustrating applications of these concepts are presented

the deterioration of hearing with age frequency selectivity the critical ratio the audiogram and speech threshold the frequency selectivity of the auditory system was measured by masking a sinusoidal signal 0 5 2 0 or 4 0 khz or a filtered speech signal with a wideband noise having a notch or stopband centered on the signal as the notch was widened performance improved for both types of signal but the rate of improvement decreased as the age of the 16 listeners increased from 23 to 75 years indicating a loss in frequency selectivity with age auditory filter shapes derived from the tone in noise data show a that the passband of the filter broadens progressively with age and b that the dynamic range of the filter ages like the audiogram that is the range changes little with age before 55 but beyond this point there is an accelerating rate of loss the speech experiment shows comparable but smaller effects the filter width measurements show that the critical ratio is a poor estimator of frequency selectivity because it confounds the tuning of the system with the efficiency of the signal detection and speech processing mechanisms that follow the filter an alternative one point measure of frequency selectivity which is both sensitive and reliable is developed via the filter shape model of masking

on the number of channels needed to understand speech recent studies have shown that high levels of speech understanding could be achieved when the speech spectrum was divided into four channels and then reconstructed as a sum of four noise bands or sine waves with frequencies equal to the center frequencies of the channels in these studies speech understanding was assessed using sentences produced by a single male talker the aim of experiment 1 was to assess the number of channels necessary for a high level of speech understanding when sentences were produced by multiple talkers in experiment 1 sentences produced by 135 different talkers were processed through n 2 n 16 number of channels synthesized as a sum of n sine waves with frequencies equal to the center frequencies of the filters and presented to normal hearing listeners for identification a minimum of five channels was needed to achieve a high level 90 of speech understanding asymptotic performance was achieved with eight channels at least for the speech material used in this study the outcome of experiment 1 demonstrated that the number of channels needed to reach asymptotic performance varies as a function of the recognition task and or need for listeners to attend to fine phonetic detail in experiment 2 sentences were processed through 6 and 16 channels and quantized into a small number of steps the purpose of this experiment was to investigate whether listeners use across channel differences in amplitude to code frequency information particularly when speech is processed through a small number of channels for sentences processed through six channels there was a significant reduction in speech understanding when the spectral amplitudes were quantized into a small number 8 of steps high levels 92 of speech understanding were maintained for sentences processed through 16 channels and quantized into only 2 steps the findings of experiment 2 suggest an inverse relationship between the importance of spectral amplitude resolution number of steps and spectral resolution number of channels

conformal mappings for internal viscous flow problems abstract isolated occlusions in a straight channel or pipe can be described analytically in a fashion that allows efficient accurate computation of nonlinear flow fields through conformal transformations

marginal likelihood integrals for mixtures of independence models inference in bayesian statistics involves the evaluation of marginal likelihood integrals we present algebraic algorithms for computing such integrals exactly for discrete data of small sample size our methods apply to both uniform priors and dirichlet priors the underlying statistical models are mixtures of independent distributions or in geometric language secant varieties of segre veronese varieties

streamwise computation of three dimensional parabolic flows a new approach to calculate three dimensional parabolic flows is presented the flow field is computed by calculating velocity along a set of streamlines the dependent variables commonly used in the computation of three dimensional flows are the three velocity components in contrast the dependent variables in the present approach are the streamwise velocity and the two coordinates in the cross stream plane of the chosen streamlines the streamwise velocity is calculated from the finite difference equations obtained by applying euler s momentum theorem to streamtubes constructed around the chosen streamlines the streamline coordinates are calculated from the conservation of mass results of the calculations based on the present approach are compared with the experimental data for flow through rectangular ducts the agreement is satisfactory

frequency discrimination of complex signals frequency selectivity and speech perception in hearing impaired subjects frequency discrimination of spectral envelopes of complex stimuli frequency selectivity measured with psychophysical tuning curves and speech perception were determined in hearing impaired subjects each having a relatively flat sensory neural loss both the frequency discrimination and speech perception measures were obtained in quiet and noise most of these subjects showed abnormal susceptibility to ambient noise with regard to speech perception frequency discrimination in quiet and frequency selectivity did not correlate significantly at low signal to noise ratios frequency discrimination correlated significantly with frequency selectivity speech perception in noise correlated significantly with frequency selectivity and with frequency discrimination at low signal to noise ratios the frequency discrimination data are discussed in terms of an excitation pattern model however they neither support nor refute the model

effects of spectral smearing and temporal fine structure degradation on speech masking release this study assessed the effects of spectral smearing and temporal fine structure tfs degradation on masking release mr the improvement in speech identification in amplitude modulated compared to steady noise observed for normal hearing listeners syllables and noise stimuli were processed using either a spectral smearing algorithm or a tone excited vocoder the two processing schemes simulated broadening of the auditory filters by factors of 2 and 4 simulations of the early stages of auditory processing showed that the two schemes produced comparable excitation patterns however fundamental frequency f0 information conveyed by tfs was degraded more severely by the vocoder than by the spectral smearing algorithm both schemes reduced mr but for each amount of spectral smearing the vocoder produced a greater reduction in mr than the spectral smearing algorithm consistent with the effects of each scheme on f0 representation moreover the effects of spectral smearing on mr produced by the two schemes were different for manner and voicing finally mr data for listeners with moderate hearing loss were well matched by mr data obtained for normal hearing listeners with vocoded stimuli suggesting that impaired frequency selectivity alone may not be sufficient to account for the reduced mr observed for hearing impaired listeners