global target aggregation and state agreement of nonlinear multi agent systems with switching topologies in this paper we discuss coordination problems of a group of autonomous agents including the target aggregation to a convex set and the state agreement the aggregation of the whole agent group consisting of leaders informed agents and followers to a given set is investigated with switching interconnection topologies described by the connectivity assumptions on the joint topology in the time interval t for any time t and then the state agreement problem is studied in a similar way an approach based on set stability and limit set analysis is given to study the multi agent convergence problems with the help of graph theory and convex analysis coordination conditions are obtained in some important cases and the results show that simple local rules can make the networked agents with first order nonlinear individual dynamics achieve desired collective behaviors

auditory filter nonlinearity in mild moderate hearing impairment sensorineural hearing loss has frequently been shown to result in a loss of frequency selectivity less is known about its effects on the level dependence of selectivity that is so prominent a feature of normal hearing the aim of the present study is to characterize such changes in nonlinearity as manifested in the auditory filter shapes of listeners with mild moderate hearing impairment notched noise masked thresholds at 2 khz were measured over a range of stimulus levels in hearing impaired listeners with losses of 20 50 db growth of masking functions for different notch widths are more parallel for hearing impaired than for normal hearing listeners indicating a more linear filter level dependent filter shapes estimated from the data show relatively little change in shape across level the loss of nonlinearity is also evident in the input output functions derived from the fitted filter shapes reductions in nonlinearity are clearly evident even in a listener with only 20 db hearing loss

speech perception in gated noise the effects of temporal resolution previous investigations have suggested that hearing impaired hi listeners have reduced masking release mr compared to normal hearing listeners nh when they listen in modulated noise the current study examined the following questions that have not been clearly answered first when hi listeners are amplified so that their performance is equal to that of nh listeners in quiet and in steady noise do hi listeners still show reduced mr with modulated noise when compared to nh listeners second is the masking release the same for sentences and cv syllables third does forward masking significantly contribute to the variability in performance among hi listeners to compensate for reduced hearing sensitivity for hi listeners the spectrum levels of both speech and noise were adjusted based on the individual hearing loss there was no significant difference between the performance of nh listeners and that of hi listeners in steady noise and in quiet however the amount of mr for sentences and for cv syllables was significantly reduced for hi listeners for sentence recognition the amount of mr seemed to be more related to hearing sensitivity for low to mid frequencies than to forward masking in contrast forward masking thresholds appear to be a major contributor to the amount of mr for syllable recognition

distributed subgradient methods for convex optimization over random networks we consider the problem of cooperatively minimizing the sum of convex functions where the functions represent local objective functions of the agents we assume that each agent has information about his local function and communicate with the other agents over a time varying network topology for this problem we propose a distributed subgradient method that uses averaging algorithms for locally sharing information among the agents in contrast to previous works on multi agent optimization that make worst case assumptions about the connectivity of the agents such as bounded communication intervals between nodes we assume that links fail according to a given stochastic process under the assumption that the link failures are independent and identically distributed over time possibly correlated across links we provide almost sure convergence results for our subgradient algorithm

effect of variability in level on forward masking and on increment detection in the first of four experiments all with the same four subjects varying the level of a forward masker from interval to interval in a two interval forced choice 2ifc adaptive procedure had little effect on threshold in the second experiment the signal level was fixed and performance was measured in units of d varying the level of the forward masker again had little effect analyses of trial by trial data indicated that subjects did not vote for the interval with the higher level masker as would an energy detector performance was better on trials where the masker level in the interval with the signal was lower and was relatively independent of masker level in the nonsignal interval in the third experiment these results were replicated for a wider range of masker variability and with maskers lower in frequency than the signal in the fourth experiment the same range of variability from interval to interval was imposed on the level of the pedestal in an increment detection task results were sim

short term temporal integration evidence for the influence of peripheral compression thresholds for a 6 5 khz sinusoidal signal temporally centered in a 400 ms broadband noise masker were measured as a function of signal duration for normally hearing listeners and listeners with cochlear hearing loss over a range of masker levels for the normally hearing listeners the slope of the function relating signal threshold to signal duration integration function was steeper at medium masker levels than at low or high levels by a factor of nearly 2 for signal durations between 2 and 10 ms while no significant effect of level was found for signal durations of 20 ms and more no effect of stimulus level was found for the hearing impaired listeners at any signal duration for signal durations greater than 10 ms consistent with many previous studies the slope of the integration function was shallower for the hearing impaired listeners than for the normally hearing listeners however for shorter durations there was no significant difference in slope between the results from the hearing impaired listeners and those from the normally hearing listeners in the high and low level masker conditions a model incorporating a compressive nonlinearity representing the effect of basilar membrane bm compression and a short term temporal integrator postulated to be a more central process can account well for changes in the short term integration function with level if it is assumed that the compression is greater at medium levels than at low or high levels by a factor of about 4 this is in reasonable agreement with physiological measurements of bm compression and with previous psychophysical estimates

recovery from on and off frequency forward masking in listeners with normal and impaired hearing the aim of this study was to investigate the possible mechanisms underlying an effect reported earlier wojtczak m and oxenham a j 2009 j acoust soc am 125 270 281 in normal hearing listeners whereby recovery from forward masking can be slower for off frequency tonal maskers than for on frequency tonal maskers that produce the same amount of masking at a 0 ms masker signal delay to rule out potential effects of confusion between the tonal signal and tonal masker one condition used a noise band forward masker to test whether the effect involved temporal build up another condition used a short duration 30 ms forward masker to test whether the effect is dependent on normal cochlear function conditions were tested in five listeners with sensorineural hearing loss for the 150 ms noise maskers the data from normal hearing listeners replicated the findings from the previous study that used tonal maskers in contrast no significant difference in recovery from on and off frequency masking was observed for the 30 ms tonal maskers in normal hearing listeners or for the 150 ms tonal maskers in hearing impaired listeners overall the results are consistent with a mechanism based on efferent feedback that affects the recovery from forward masking in the normal auditory system

learning by canonical smooth estimation i simultaneous estimation this paper examines the problem of learning from examples in a framework that is based on but more general than valiant s probably approximately correct pac model for learning in our framework the learner observes examples that consist of sample points drawn and labeled according to a fixed unknown probability distribution based on this empirical data the learner must select from a set of candidate functions a particular function or hypothesis that will accurately predict the labels of future sample points the expected mismatch between a hypothesis prediction and the label of a new sample point is called the hypothesis generalization error following the pioneering work of vapnik and chervonenkis others have attacked this sort of learning problem by finding hypotheses that minimize the relative frequency based empirical error estimate we generalize this approach by examining the simultaneous estimation problem we demonstrate how one can learn from such a simultaneous error estimate and propose a new class of estimators called smooth estimators we characterize the class of simultaneous estimation problems solvable by a smooth estimator

distributed computation of linear matrix equations an optimization perspective this paper investigates the distributed computation of the well known linear matrix equation in the form of axb f with the matrices a b x and f of appropriate dimensions over multiagent networks from an optimization perspective in this paper we consider the standard distributed matrix information structures where each agent of the considered multiagent network has access to one of the subblock matrices of a b and f to be specific we first propose different decomposition methods to reformulate the matrix equations in standard structures as distributed constrained optimization problems by introducing substitutional variables we show that the solutions of the reformulated distributed optimization problems are equivalent to least squares solutions to original matrix equations and we design distributed continuous time algorithms for the constrained optimization problems even by using augmented matrices and a derivative feedback technique moreover we prove the exponential convergence of the algorithms to a least squares solution to the matrix equation for any initial condition

temporal integration and compression near absolute threshold in normal and impaired ears the decrease in absolute threshold with increasing stimulus duration often referred to as temporal integration is greater for listeners with normal hearing than for listeners with sensorineural hearing loss it has been suggested that the difference is related to reduced basilar membrane bm compression in the impaired group the present experiment tested this hypothesis by comparing temporal integration and bm compression in normal and impaired ears at low levels absolute thresholds were measured for 4 24 and 44 ms pure tone signals with frequencies f s of 2 and 4 khz the difference between the absolute thresholds for the 4 and 24 ms signals was used as a measure of temporal integration compression near threshold was estimated by measuring the level of a 100 ms off frequency 0 45f s pure tone forward masker required to mask a 44 ms pure tone signal presented at sensation levels of 5 and 10 db there was a significant negative correlation between amount of temporal integration and absolute threshold however there was no correlation between absolute threshold and compression at low levels both normal and impaired ears showed a nearly linear response the results suggest that the differences in integration between normal and impaired ears cannot be explained by differences in bm compression

effects of peripheral nonlinearity on psychometric functions for forward masked tones psychometric functions pfs for forward masked tones were obtained for conditions in which signal level was varied to estimate threshold at several masker levels variable signal condition and in which masker level was varied to estimate threshold at several signal levels variable masker condition the changes in pf slope across combinations of masker frequency masker level and signal delay were explored in three experiments in experiment 1 a 2 khz 10 ms tone was masked by a 50 70 or 90 db spl 20 ms on frequency forward masker with signal delays of 2 20 or 40 ms in a variable signal condition pf slopes decreased in conditions where signal threshold was high in experiments 2 and 3 the signal was a 4 khz 10 ms tone and the masker was either a 4 or 2 4 khz 200 ms tone in experiment 2 on frequency maskers were presented at 30 to 90 db spl in 10 db steps and off frequency maskers were presented at 60 to 90 db spl in 10 db steps with signal delays of 0 10 or 30 ms in a variable signal condition pf slopes decreased as signal level increased and this trend was similar for on and off frequency maskers in experiment 3 variable masker conditions with on and off frequency maskers and 0 ms signal delay were presented in general the results were consistent with the hypothesis that peripheral nonlinearity is reflected in the pf slopes the data also indicate that masker level plays a role independent of signal level an effect that could be accounted for by assuming greater internal noise at higher stimulus levels

word recognition in noise at higher than normal levels decreases in scores and increases in masking under certain conditions speech recognition in noise decreases above conversational levels when signal to noise ratio is held constant the current study was undertaken to determine if nonlinear growth of masking and the subsequent reduction in effective signal to noise ratio accounts for this decline nine young adults with normal hearing listened to monosyllabic words at three levels in each of three levels of a masker shaped to match the speech spectrum an additional low level noise equated audibility by producing equivalent masked thresholds for all subjects if word recognition was determined entirely by signal to noise ratio and was independent of overall speech and masker levels scores at a given signal to noise ratio should remain constant with increasing level masked pure tone thresholds measured in the speech shaped maskers increased linearly with increasing masker level at lower frequencies but nonlinearly at higher frequencies consistent with nonlinear growth of upward spread of masking that followed the peaks in the spectrum of the speech shaped masker word recognition declined significantly with increasing level when signal to noise ratio was held constant which was attributed to nonlinear growth of masking and reduced effective signal to noise ratio at high speech shaped masker levels as indicated by audibility estimates based on the articulation index

distributed continuous time convex optimization on weight balanced digraphs this technical note studies the continuous time distributed optimization of a sum of convex functions over directed graphs contrary to what is known in the consensus literature where the same dynamics works for both undirected and directed scenarios we show that the consensus based dynamics that solves the continuous time distributed optimization problem for undirected graphs fails to converge when transcribed to the directed setting this study sets the basis for the design of an alternative distributed dynamics which we show is guaranteed to converge on any strongly connected weight balanced digraph to the set of minimizers of a sum of convex differentiable functions with globally lipschitz gradients our technical approach combines notions of invariance and cocoercivity with the positive definiteness properties of graph matrices to establish the results

input output functions for stimulus frequency otoacoustic emissions in normal hearing adult ears input output i o functions for stimulus frequency sfoae and distortion product dpoae otoacoustic emissions were recorded in 30 normal hearing adult ears using a nonlinear residual method sfoaes were recorded at half octaves from 500 8000 hz in an l1 l2 paradigm with l2 0 to 85 db spl and in a paradigm with l1 fixed and l2 varied dpoaes were elicited with primary levels of kummer et al j acoust soc am 103 3431 3444 1998 at f2 frequencies of 2000 and 4000 hz interpretable sfoae responses were obtained from 1000 6000 hz in the equal level paradigm sfoae levels were larger than dpoaes levels signal to noise ratios were smaller and i o functions were less compressive a two slope model of sfoae i o functions predicted the low level round trip attenuation the breakpoint between linearity and compression and compressive slope in ear but not coupler recordings the noise at the sfoae frequency increased with increasing level above 60 db spl whereas noise at adjacent frequencies did no

correspondence between behavioral and individually optimized otoacoustic emission estimates of human cochlear input output curves previous studies have shown a high within subject correspondence between distortion product otoacoustic emission dpoae input output i o curves and behaviorally inferred basilar membrane bm i o curves for frequencies above 2 khz for lower frequencies dpoae i o curves contained notches and plateaus that did not have a counterpart in corresponding behavioral curves it was hypothesized that this might improve by using individualized optimal dpoae primary levels here data from previous studies are re analyzed to test this hypothesis by comparing behaviorally inferred bm i o curves and dpoae i o curves measured with well established group average primary levels and two individualized primary level rules one optimized to maximize dpoae levels and one intended for primaries to evoke comparable bm responses at the f2 cochlear region test frequencies were 0 5 1 and 4 khz behavioral i o curves were obtained from temporal forward masking curves results showed high within subject correspondence between behavioral and dpoae i o curves at 4 khz only regardless of the primary level rule plateaus and notches were equally common in low frequency dpoae i o curves for individualized and group average dpoae primary levels at 0 5 and 1 khz results are discussed in terms of the adequacy of dpoae i o curves for inferring individual cochlear nonlinearity characteristics

detection and intensity discrimination of gaussian shaped tone pulses as a function of duration j acoust soc am 105 3425 3435 1999 proposed that the auditory system partitions the spectro temporal domain into frequency time f t windows and that the characteristics of these windows could be explored by measuring intensity discrimination for gaussian shaped tone pulses presented just above their detection threshold in noise they reasoned that for a long duration tone pulse the auditory representation would be maximally compact in the frequency domain but would spread across several f t windows in the time domain for a very short duration tone pulse the auditory representation would be maximally compact in the time domain but would spread across several f t windows in the frequency domain there should be some intermediate duration at which the auditory representation is compact in both the time and frequency domains and for which intensity discrimination performance should worsen due to the limited opportunity for multiple looks their data for signal frequencies of 1 and 4 khz were consistent with this expectation intensity discrimination was poorest at a duration of about 3 5 ms at 1 khz and 1 ms at 4 khz durations are specified between 6 8 db down points on the envelope this experiment attempted to replicate those results and to extend them to a wider range of frequencies and levels intensity discrimination of gaussian shaped tone pulses was measured at three levels 10 db above absolute threshold or above masked threshold in a pink noise with a spectrum level of either 15 or 40 db at 1 khz the signal frequency was 0 25 khz durations from 2 to 320 ms 1 khz durations from 0 5 to 80 ms or 4 khz durations from 0 1 to 20 ms three normally hearing subjects were tested at 1 and 4 khz performance was poorest overall for the 15 db pink noise level and thresholds showed a peak at intermediate durations about 3 5 ms at 1 khz and 1 ms at 4 khz such peaks were still apparent but smaller in the no noise condition and were almost absent at the higher noise level for the 0 25 khz signal frequency peaks were not observed consistently at any level although two subjects showed small peaks for durations around 10 ms an explanation is offered for the results in terms of the level and frequency dependence of basilar membrane input output functions

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

on distributed convex optimization under inequality and equality constraints we consider a general multi agent convex optimization problem where the agents are to collectively minimize a global objective function subject to a global inequality constraint a global equality constraint and a global constraint set the objective function is defined by a sum of local objective functions while the global constraint set is produced by the intersection of local constraint sets in particular we study two cases one where the equality constraint is absent and the other where the local constraint sets are identical we devise two distributed primal dual subgradient algorithms based on the characterization of the primal dual optimal solutions as the saddle points of the lagrangian and penalty functions these algorithms can be implemented over networks with dynamically changing topologies but satisfying a standard connectivity property and allow the agents to asymptotically agree on optimal solutions and optimal values of the optimization problem under the slater s condition

additivity of auditory masking using gaussian shaped tones both temporal and spectral masking have been studied extensively in the literature mostly they have been regarded as separate phenomena very little is known about the interaction between these two effects i e masking in the time frequency domain data on the time frequency spread of masking evoked by a single gaussian shaped tone pulse are presented in an accompanying study at the same conference necciari et al the current study gathers data on the additivity of masking by up to four approximately equally effective gaussian maskers erb 600 hz separated either along the time or the frequency axis for temporal separation the amount of masking increases with the number of maskers with excess masking exceeding linear additivity of up to 25 db for frequency separation preliminary data excess masking amounts up to 15 db and the higher frequency masker relative to the target contributes more to the additivity than the lower frequency maskers experiments with multiple maskers combining both temporal and frequency separation are underway combined with the single maker data these data may serve as a basis for modeling time frequency masking effects in complex signals work partly supported by oead wtz project amadeus and anr

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

models of the additivity of masking three models of masking additivity are reviewed which are referred to as the high compression model m j penner j acoust soc am 67 608 616 1980 m j penner and r m shiffrin j acoust soc am 67 617 627 1980 the power law model r a lutfi j acoust soc am 73 262 267 1983 80 422 428 1986 and the modified power law model with compressed internal noise humes et al j acoust soc am 83 188 202 1988 while the high compression model was derived from data for two or more nonsimultaneous maskers and the power law model was derived from data for two or more simultaneous maskers the modified power law model can be applied to both cases the modified power law model assumes that the threshold in quiet is equivalent to a masked threshold resulting from an internal noise that is continually present additional assumptions concern the interaction of two maskers prior to the addition of the masking effects most of the data on the additivity of masking are well described b

distributed constrained optimal consensus of multi agent systems we study a distributed optimal consensus problem of continuous time multi agent systems with a common state set constraint each agent is assigned with an individual cost function which is coercive and convex a distributed control protocol is to be designed to guarantee a consensus and in the meanwhile reach the minimizer of the aggregate cost functions within the constraint set three terms are included in the protocol local averaging local projection and local subgradient with a diminishing but persistent gain it is shown that the constrained optimal consensus can be achieved under a uniformly jointly connected communication network with bounded time varying edge weights

learning by canonical smooth estimation ii learning and choice of model complexity this paper analyzes the properties of a procedure for learning from examples this canonical learner is based on a canonical error estimator developed in part i in learning problems one can observe data that consists of labeled sample points and the goal is to find a model or hypothesis from a set of candidates that will accurately predict the labels of new sample points the expected mismatch between a hypothesis prediction and the actual label of a new sample point is called the hypothesis generalization error we compare the canonical learner with the traditional technique of finding hypotheses that minimize the relative frequency based empirical error estimate it is shown that for a broad class of learning problems the set of cases for which such empirical error minimization works is a proper subset of the cases for which the canonical learner works we derive bounds to show that the number of samples required by these two methods is comparable we also address the issue of how to determine the appropriate complexity for the class of candidate hypotheses

forward masking as a function of frequency masker level and signal delay the forward masking of a sinusoidal signal by a sinusoid of the same frequency was investigated for frequencies ranging from 125 to 4000 hz forward masking in db is proportional to both masker level and log signal delay at each frequency more forward masking occurs at very low frequencies than at high frequencies given equal sensation level maskers and masked thresholds are greater at low frequencies than at high frequencies given equal spl maskers the data can be described equally well by assuming that the difference in forward masking as a function of frequency is due to a change in the time course of recovery from masking or to a change in the growth of masking at each signal delay the frequency effect is not large enough to change the interpretation of forward masking data in studies of suppression or psychophysical tuning curves

distributed continuous time optimization nonuniform gradient gains finite time convergence and convex constraint set in this paper a distributed optimization problem with general differentiable convex objective functions is studied for continuous time multi agent systems with single integrator dynamics the objective is for multiple agents to cooperatively optimize a team objective function formed by a sum of local objective functions with only local interaction and information while explicitly taking into account nonuniform gradient gains finite time convergence and a common convex constraint set first a distributed nonsmooth algorithm is introduced for a special class of convex objective functions that have a quadratic like form it is shown that all agents reach a consensus in finite time while minimizing the team objective function asymptotically second a distributed algorithm is presented for general differentiable convex objective functions in which the interaction gains of each agent can be self adjusted based on local states a corresponding condition is then given to guarantee that all agents reach a consensus in finite time while minimizing the team objective function asymptotically third a distributed optimization algorithm with state dependent gradient gains is given for general differentiable convex objective functions it is shown that the distributed continuous time optimization problem can be solved even though the gradient gains are not identical fourth a distributed tracking algorithm combined with a distributed estimation algorithm is given for general differentiable convex objective functions it is shown that all agents reach a consensus while minimizing the team objective function in finite time fifth as an extension of the previous results a distributed constrained optimization algorithm with nonuniform gradient gains and a distributed constrained finite time optimization algorithm are given it is shown that both algorithms can be used to solve a distributed continuous time optimization problem with a common convex constraint set numerical examples are included to illustrate the obtained theoretical results

auditory temporal integration and the power function model the auditory temporal integration function was studied with the objective of improving both its quantitative description and the specification of its principle independent variable stimulus duration in sec i temporal integration data from 20 studies were subjected to uniform analyses using standardized definitions of duration and two models of temporal integration analyses revealed that these data were best described by a power function model used in conjunction with a definition of duration termed assigned duration that de emphasized the rise fall portions of the stimuli there was a strong effect of stimulus frequency and in general the slope of the temporal integration function was less than 10 db per decade of duration i e a power function exponent less than 1 0 in sec ii an experimental study was performed to further evaluate the models and definitions detection thresholds were measured in 11 normal hearing human subjects using a total of 24 single burst and multiple burst acoustic stimuli of 3 125 khz the issues addressed are the quantitative description of the temporal integration function the definition of stimulus duration the similarity of the integration processes for single burst and multiple burst stimuli and the contribution of rise fall time to the integration process a power function in conjunction with the assigned duration definition was again most effective in describing the data single and multiple burst stimuli both seemed to be integrated by the same central mechanism with data for each type of stimulus being described by a power function exponent of approximately 0 6 at 3 125 khz it was concluded that the contribution of the rise fall portions of the stimuli can be factored out from the rest of the temporal integration process in sec iii the conclusions that emerged from the review of published work and the present experimental work suggested that auditory temporal integration is best described by a power function in conjunction with the assigned duration definition the exponent for the power function is typically less than 1 0 and varies with frequency and hearing level second a means of empirically assaying the contribution of the rise fall portions of the stimuli is presented and evaluated finally properties of a central auditory integrator are hypothesized abstract truncated at 250 words

a behavioral measure of basilar membrane nonlinearity in listeners with normal and impaired hearing this paper examines the possibility of estimating basilar membrane bm nonlinearity using a psychophysical technique the level of a forward masker required to mask a brief signal was measured for conditions where the masker was either at or one octave below the signal frequency the level of the forward masker at masked threshold provided an indirect measure of the bm response to the signal as follows consistent with physiological studies it was assumed that the bm responds linearly to frequencies well below the characteristic frequency cf thus the ratio of the slopes of the masking functions between a masker at the signal frequency and a masker well below the signal frequency should provide an estimate of bm compression at cf results obtained from normally hearing listeners were in quantitative agreement with physiological estimates of bm compression furthermore differences between normally hearing listeners and listeners with cochlear hearing impairment were consistent with the physiological effects of damage to the cochlea the results support the hypothesis that bm nonlinearity governs the nonlinear growth of the upward spread of masking and suggest that this technique provides a straightforward method for estimating bm nonlinearity in humans

estimating peripheral gain and compression using fixed duration masking curves estimates of human basilar membrane gain and compression obtained using temporal masking curve tmc and additivity of forward masking afm methods with long duration maskers or long masker signal silent intervals may be affected by olivocochlear efferent activation which reduces basilar membrane gain the present study introduces a fixed duration masking curve fdmc method which involves a comparison of off and on frequency forward masker levels at threshold as a function of masker and signal duration with the total masker signal duration fixed at 25 ms to minimize efferent effects gain and compression estimates from the fdmc technique were compared with those from tmc 104 ms maskers and afm 10 and 200 ms maskers methods compression estimates over an input masker range of 40 60 db sound pressure level were similar for the four methods maximum compression occurred at a lower input level for the fdmc compared to the tmc method estimates of gain were similar for tmc and fdmc methods the fdmc

constrained consensus and optimization in multi agent networks we present distributed algorithms that can be used by multiple agents to align their estimates with a particular value over a network with time varying connectivity our framework is general in that this value can represent a consensus value among multiple agents or an optimal solution of an optimization problem where the global objective function is a combination of local agent objective functions our main focus is on constrained problems where the estimates of each agent are restricted to lie in different convex sets to highlight the effects of constraints we first consider a constrained consensus problem and present a distributed projected consensus algorithm in which agents combine their local averaging operation with projection on their individual constraint sets this algorithm can be viewed as a version of an alternating projection method with weights that are varying over time and across agents we establish convergence and convergence rate results for the projected consensus algorithm we next study a constrained optimization problem for optimizing the sum of local objective functions of the agents subject to the intersection of their local constraint sets we present a distributed projected subgradient algorithm which involves each agent performing a local averaging operation taking a subgradient step to minimize its own objective function and projecting on its constraint set we show that with an appropriately selected stepsize rule the agent estimates generated by this algorithm converge to the same optimal solution for the cases when the weights are constant and equal and when the weights are time varying but all agents have the same constraint set

memory universal prediction of stationary random processes we consider the problem of one step ahead prediction of a real valued stationary strongly mixing random process xi sub i spl infin sup spl infin the best mean square predictor of x sub 0 is its conditional mean given the entire infinite past x sub i sub i spl infin sup 1 given a sequence of observations x sub 1 x sub 2 x sub n we propose estimators for the conditional mean based on sequences of parametric models of increasing memory and of increasing dimension for example neural networks and legendre polynomials the proposed estimators select both the model memory and the model dimension in a data driven fashion by minimizing certain complexity regularized least squares criteria when the underlying predictor function has a finite memory we establish that the proposed estimators are memory universal the proposed estimators which do not know the true memory deliver the same statistical performance rates of integrated mean squared error as that delivered by estimators that know the true memory furthermore when the underlying predictor function does not have a finite memory we establish that the estimator based on legendre polynomials is consistent

temporal integration at 6 khz as a function of masker bandwidth thresholds were measured for a 6 khz sinusoidal signal presented within a 500 ms masker the masker was either a bandpass gaussian noise of varying bandwidth or a sinusoid of the same frequency as the signal the spectrum level of the noise masker was kept constant at 20 db spl and the level of the sinusoidal masker was 40 db spl thresholds for signal durations between 2 and 300 ms were measured for masker bandwidths ranging from 60 to 12 000 hz the masker was spectrally centered around 6 khz for masker bandwidths less than 600 hz the slope of the temporal integration function decreased with decreasing masker bandwidth the results are not consistent with current models of temporal integration or temporal resolution it is suggested that the results at narrow bandwidths can be understood in terms of changes in the power spectrum of the stimulus envelope or modulation spectrum according to this view the onset and offset ramps of the signal introduce detectable high frequency components into the modulation spectrum which provide a salient cue in narrowband maskers for broadband maskers these high frequency components are masked by the inherent rapid fluctuations in the masker envelope additionally for signal durations between 7 and 80 ms signal thresholds decreased by up to 5 db as the masker bandwidth increased from 1200 to 12 000 hz the mechanisms underlying this effect are not yet fully understood

use of psychometric function slopes for forward masked tones to investigate cochlear nonlinearity schairer et al 2003 effects of peripheral nonlinearity on psychometric functions for forward masked tones j acoust soc am 133 1560 1573 demonstrated that cochlear nonlinearity is reflected in psychometric function pf slopes for 4 khz forward masked tones the goals of the current study were to use pf slopes to compare the degree of compression between signal frequencies of 0 25 and 4 khz in listeners with normal hearing lnh and between lnh and listeners with cochlear hearing loss lhl forward masked thresholds were estimated in lnh and lhl using on and off frequency maskers and 0 25 and 4 khz signals in three experiments pfs were reconstructed from adaptive procedure data for each subject in each condition trends in pf slopes across conditions suggest comparable compression at 0 25 and 4 khz and potentially a wider bandwidth of compression in relative frequency at 0 25 khz this is consistent with other recent behavioral studies that revise earlier estimates of less compression at lower frequencies the preliminary results in lhl demonstrate that pf slopes are abnormally steep at frequencies with hl but are similar to those for lnh at frequencies with nh overall the results are consistent with the notion that pf slopes reflect degree of cochlear nonlinearity and can be used as an additional measure of compression across frequency

growth of masking as a measure of response growth in hearing impaired listeners growth of masking functions were obtained from 19 normal and 5 hearing impaired listeners using a simultaneous masking paradigm when masker and probe frequency are identical the slope of masking approximates 1 0 for both normal hearing and impaired listeners for masker frequencies less than or greater than probe frequency the slopes for impaired listeners are shallower than those of normals these findings are consistent with previously reported physiological data single fiber rate versus level and ap masking functions for animals with induced cochlear lesions results are discussed in terms of a potential masking technique to estimate the growth of response in normal and impaired ears

comparison of distortion product otoacoustic emission growth rates and slopes of forward masked psychometric functions slopes of forward masked psychometric functions fm pfs were compared with distortion product otoacoustic emission dpoae input output i o parameters at 1 and 6 khz to test the hypothesis that these measures provide similar estimates of cochlear compression implicit in this hypothesis is the assumption that both dpoae i o and fm pf slopes are functionally related to basilar membrane bm response growth fm pf slope decreased with signal level but this effect was reduced or reversed with increasing hearing loss there was a trend of decreasing psychometric function pf slope with increasing frequency consistent with greater compression at higher frequencies dpoae i o functions at 6 khz exhibited an increase in the breakpoint of a two segment slope as a function of hearing loss with a concomitant decrease in the level of the distortion product ld results of the comparison between fm pf and dpoae i o parameters revealed only a weak correlation suggesting that one or both of these measures may p

existence properties and trajectory specification of generalised multi agent flocking a class of flocking algorithms for second order multi agent networks with single virtual leaders are developed by including more weighting and navigating matrices in this paper flocking existence

a compressive gammachirp auditory filter for both physiological and psychophysical data a gammachirp auditory filter was developed by irino and patterson j acoust soc am 101 412 419 1997 to provide a level dependent version of the linear gammatone auditory filter with which to explain the level dependent changes in cochlear filtering observed in psychophysical masking experiments in this analytical gammachirp filter the chirp varied with level and there was no explicit representation of the change in filter gain or compression with level subsequently carney et al j acoust soc am 105 2384 2391 1999 reviewed carney and yin s j neurophysiol 60 1653 1677 1988 reverse correlation revcor data and showed that the frequency glide of the chirp does not vary with level in their data in this article the architecture of the analytical gammachirp is reviewed with respect to cochlear physiology and a new form of gammachirp filter is described in which the magnitude response the gain and the compression vary with level but the chirp does not this new compressive gammachirp filter is used to fit the level dependent revcor data reported by carney et al 1999 and the level dependent masking data reported by rosen and baker hear res 73 231 243 1994

on decentralized negotiation of optimal consensus a consensus problem consists of finding a distributed control strategy that brings the state or output of a group of agents to a common value a consensus point in this paper we propose a negotiation algorithm that computes an optimal consensus point for agents modeled as linear control systems subject to convex input constraints and linear state constraints by primal decomposition and incremental subgradient methods it is shown that the algorithm can be implemented such that each agent exchanges only a small amount of information per iteration with its neighbors

similarity in loudness and distortion product otoacoustic emission input output functions implications for an objective hearing aid adjustment the aim of the present study was to compare distortion product otoacoustic emissions dpoaes to loudness with regard to the potentiality of dpoaes to determine characteristic quantities of the cochlear impaired ear and to derive objective hearing aid parameters recently neely et al j acoust soc am 114 1499 1507 2003 compared dpoae input output functions to the fletcher and munson j acoust soc am 5 82 108 1933 loudness function finding a close resemblance in the slope characteristics of both measures the present study extended their work by performing both loudness and dpoae measurements in the same subject sample and by developing a method for the estimation of gain needed to compensate for loss of cochlear sensitivity and compression dpoaes and loudness exhibited similar behavior when plotted on a logarithmic scale and slope increased with increasing hearing loss confirming the findings of neely et al to compensate for undesired nonpathological impacts on the magnitude of dpoae level normalization of dpoae data was implemented a close resemblance between gain functions based on loudness and normalized dpoae data was achieved these findings suggest that dpoaes are able to quantify the loss of cochlear sensitivity and compression and thus might provide parameters for a noncooperative hearing aid adjustment

auditory filter nonlinearity across frequency using simultaneous notched noise masking psychoacoustic masking experiments have been widely used to investigate cochlear function in human listeners here we use simultaneous notched noise masking experiments in normal hearing listeners to characterize the changes in auditory filter shape with stimulus level over the frequency range 0 25 6khz at each frequency a range of fixed signal levels 30 70db spl and fixed masker levels 20 50db spl spectrum level are used in order to obtain accurate descriptions of the filter shapes in individual listeners the notched noise data for individual listeners are fitted with two filter shape models a rounded exponential roex shape in which the filter skirt changes as a linear function of probe tone level and the other in which the gain of the tip filter relative to the filter tail changes as a function of signal level glasberg and moore j acoust soc am 108 2318 2328 2000 the parameters for these fitted models are then described with a simple set of equations that quantify the changes in aud

two experiments on the temporal boundaries for the nonlinear additivity of masking the present paper describes the results from two experiments which explored the temporal boundary between overlapping and nonoverlapping maskers and its effects on the additivity of masking in the first experiment detection thresholds for a short duration 1000 hz signal were measured in the presence of two equal duration broadband maskers which varied in degree of temporal overlap following complete overlap of maskers the temporal separation of masker onsets was systematically varied to create conditions ranging from partially overlapping simultaneous masking to combined forward and backward masking the signal was always temporally centered between the onset of the first masker and the offset of the second masker nonlinear additivity of masking occurred for the majority of subjects when maskers and signal did not overlap whereas linear additivity resulted for all subjects when the maskers and signal overlapped in the second experiment two separate forward maskers were used so that masker masker overlap could be manipulated independent from masker signal overlap maskers were changed gradually from temporally overlapping or concurrent forward maskers to sequential forward maskers results for all subjects showed nonlinear additivity for all combined masker conditions together these two experiments indicated that nonlinear masking additivity is observed when the signal does not overlap temporally with the maskers however when maskers and signal overlap temporally and spectrally linear additivity is observed

basilar membrane nonlinearity and loudness loudness matching functions for tones for persons with one shifted threshold ear hearing loss and noise shifted thresholds and one ear within normal limits were used to derive the presumed basilar membrane bm input output i o function in a normal ear the comparison was made by assuming that the bm i o function for the ear with the cochlear threshold shift has a slope of one a linearized cochlea the function for the normal ear was derived from the loudness matching function based on this assumption comparisons were made for archival basilar membrane data m a ruggero n c rich a recio s s narayan and l robles j acoust soc am 101 2151 2163 1997 for chinchilla and archival loudness matches for long duration tones for persons with various degrees of cochlear hearing loss f miskolczy fodor j acoust soc am 32 486 492 1960 comparisons were made also between bm i o functions and ones derived from loudness matches for persons with unilateral hearing loss simulated by broa

a multi agent system with a proportional integral protocol for distributed constrained optimization this technical note presents a continuous time multi agent system for distributed optimization with an additive objective function composed of individual objective functions subject to bound equality and inequality constraints each individual objective function is assumed to be convex in the region defined by its local bound constraints only without the need to be globally convex all agents in the system communicate using a proportional integral protocol with their output information instead of state information to reduce communication bandwidth it is proved that all agents with any initial state can reach output consensus at an optimal solution to the given constrained optimization problem provided that the graph describing the communication links among agents is undirected and connected it is further proved that the system with only integral protocol is also convergent to the unique optimal solution if each individual objective function is strictly convex simulation results are presented to substantiate the theoretical results

characterizing auditory processing and perception in individual listeners with sensorineural hearing loss this study considered consequences of sensorineural hearing loss in ten listeners the characterization of individual hearing loss was based on psychoacoustic data addressing audiometric pure tone sensitivity cochlear compression frequency selectivity temporal resolution and intensity discrimination in the experiments it was found that listeners with comparable audiograms can show very different results in the supra threshold measures in an attempt to account for the observed individual data a model of auditory signal processing and perception jepsen et al j acoust soc am 124 422 438 2008 was used as a framework the parameters of the cochlear processing stage of the model were adjusted to account for behaviorally estimated individual basilar membrane input output functions and the audiogram from which the amounts of inner hair cell and outer hair cell losses were estimated as a function of frequency all other model parameters were left unchanged the predictions showed a reasonably good agreement with the measured individual data in the frequency selectivity and forward masking conditions while the variation of intensity discrimination thresholds across listeners was underestimated by the model the model and the associated parameters for individual hearing impaired listeners might be useful for investigating effects of individual hearing impairment in more complex conditions such as speech intelligibility in noise

pattern recognition for conditionally independent data in this work we consider the task of relaxing the i i d assumption in pattern recognition or classification aiming to make existing learning algorithms applicable to a wider range of tasks pattern recognition is guessing a discrete label of some object based on a set of given examples pairs of objects and labels we consider the case of deterministically defined labels traditionally this task is studied under the assumption that examples are independent and identically distributed however it turns out that many results of pattern recognition theory carry over a weaker assumption namely under the assumption of conditional independence and identical distribution of objects while the only assumption on the distribution of labels is that the rate of occurrence of each label should be above some positive threshold we find a broad class of learning algorithms for which estimations of the probability of the classification error achieved under the classical i i d assumption can be generalized to the similar estimates for case of conditionally i i d examples

on and off frequency compression estimated using a new version of the additivity of forward masking technique on and off frequency compression at the 4000 and 8000 hz cochlear places were estimated using a new version of the additivity of forward masking afm technique that measures the effects of combining two non overlapping forward maskers instead of measuring signal thresholds to estimate compression of the signal as in the original afm technique the decrease in masker threshold in the combined masker condition compared to the individual masker conditions is used to estimate compression of the masker at the signal place by varying masker frequency it is possible to estimate off frequency compression the maskers were 500 hz wide bands of noise and the signal was a brief pure tone compression at different levels was estimated using different overall signal levels or different masker signal intervals it was shown that the new afm technique and the original afm technique produce consistent results considerable compression was observed for maskers well below the signal frequency suggesting that the assumption of off frequency linearity used in other techniques may not be valid reducing the duration of the first masker from 200 to 20 ms reduced the compression exponent in some cases suggesting a possible influence of olivocochlear efferent activity

forward masking adaptation or integration the aim of this study was to attempt to distinguish between neural adaptation and persistence or temporal integration as possible explanations of forward masking thresholds were measured for a sinusoidal signal as a function of signal duration for conditions where the delay between the masker offset and the signal offset the offset offset interval was fixed the masker was a 200 ms broadband noise presented at a spectrum level of 40 db re 20 pa and the signal was a 4 khz sinusoid gated with 2 ms ramps the offset offset interval was fixed at various durations between 4 and 102 ms and signal thresholds were measured for a range of signal durations at each interval a substantial decrease in thresholds was observed with increasing duration for signal durations up to about 20 ms at short offset offset intervals the amount of temporal integration exceeded that normally found in quiet the results were simulated using models of temporal integration the temporal window model and adaptation for both models the inclusion of a peripheral nonlinearity similar to that observed physiologically in studies of the basilar membrane was essential in producing a good fit to the data both models were about equally successful in accounting for the present data however the temporal window model provided a somewhat better account of similar data from a simultaneous masking experiment using the same parameters this suggests that the linear time invariant properties of the temporal window approach are appropriate for modeling forward masking overall the results confirm that forward masking can be described in terms of peripheral nonlinearity followed by linear temporal integration at higher levels in the auditory system however the difference in predictions between the adaptation and integration models is relatively small meaning that influence of adaptation cannot be ruled out

extension of the pac framework to finite and countable markov chains we consider a model of learning in which the successive observations follow a certain markov chain the observations are labeled according to a membership to some unknown target set for a markov chain with finitely many states we show that if the target set belongs to a family of sets with a finite vapnik chervonenkis 1995 dimension then probably approximately correct pac learning of this set is possible with polynomially large samples specifically for observations following a random walk with a state space spl xscr and uniform stationary distribution the sample size required is no more than spl omega t sub 0 1 spl lambda sub 2 log t sub 0 spl chi 1 spl delta where spl delta is the confidence level spl lambda sub 2 is the second largest eigenvalue of the transition matrix and t sub 0 is the sample size sufficient for learning from independent and identically distributed i i d observations we then obtain similar results for markov chains with countably many states using lyapunov function technique and results on mixing properties of infinite state markov chains

comparing different estimates of cochlear compression in listeners with normal and impaired hearing a loss of cochlear compression may underlie many of the difficulties experienced by hearing impaired listeners two behavioral forward masking paradigms that have been used to estimate the magnitude of cochlear compression are growth of masking gom and temporal masking tm the aim of this study was to determine whether these two measures produce within subjects results that are consistent across a range of signal frequencies and if so to compare them in terms of reliability or efficiency gom and tm functions were measured in a group of five normal hearing and five hearing impaired listeners at signal frequencies of 1000 2000 and 4000 hz compression values were derived from the masking data and confidence intervals were constructed around these estimates both measures produced comparable estimates of compression but both measures have distinct advantages and disadvantages so that the more appropriate measure depends on factors such as the frequency region of interest and the degree of hearing loss because of the long testing times needed neither measure is suitable for clinical use in its current form

suppression and comodulation masking release in normal hearing and hearing impaired listeners the detectability of a sinusoidal signal embedded in a masker at the signal frequency can be improved by simultaneously presenting additional maskers in off frequency regions if the additional maskers and the on frequency masker component have the same temporal envelope this effect is commonly referred to as comodulation masking release cmr recently it was hypothesized that peripheral nonlinear processes such as suppression may play a role in cmr over several octaves when the level of the off frequency masker component is higher than the level of the on frequency masker component the aim of the present study was to test this hypothesis by measuring suppression and cmr within the same subjects for various frequency level combinations of the off frequency masker component experimental data for normal hearing listeners show a large overlap between the existence regions for suppression and cmr hearing impaired subjects with a sensorineural hearing loss show on average negligible suppression and cmr the data support the hypothesis that part of the cmr in experiments with large spectral distances and large level differences between the masker components is due to the nonlinear processing at the level of the cochlea

cochlear compression estimates from measurements of distortion product otoacoustic emissions evidence of the compressive growth of basilar membrane displacement can be seen in distortion product otoacoustic emission dpoae levels measured as a function of stimulus level when the levels of the two stimulus tones f1 and f2 are related by the formula l1 39 db 0 4 l2 kummer et al j acoust soc am 103 3431 3444 1998 the shape of the function relating dpoae level to l2 is similar up to an l2 of 70 db spl to the classic fletcher and munson j acoust soc am 9 1 10 1933 loudness function when plotted on a logarithmic scale explicit estimates of compression have been derived based on recent dpoae measurements from the laboratory if dpoae growth rate is defined as the slope of the dpoae i o function in db db then a cogent definition of compression is the reciprocal of the growth rate in humans with normal hearing compression varies from about 1 at threshold to about 4 at 70 db spl with hearing loss compression is still about 1 at threshold but grows more slowly above thresh

comparison of the roex and gammachirp filters as representations of the auditory filter although the rounded exponential roex filter has been successfully used to represent the magnitude response of the auditory filter recent studies with the roex p w t filter reveal two serious problems the fits to notched noise masking data are somewhat unstable unless the filter is reduced to a physically unrealizable form and there is no time domain version of the roex p w t filter to support modeling of the perception of complex sounds this paper describes a compressive gammachirp cgc filter with the same architecture as the roex p w t which can be implemented in the time domain the gain and asymmetry of this parallel cgc filter are shown to be comparable to those of the roex p w t filter but the fits to masking data are still somewhat unstable the roex p w t and parallel cgc filters were also compared with the cascade cgc filter patterson et al j acoust soc am 114 1529 1542 2003 which was found to provide an equivalent fit with 25 fewer coefficients moreover the fits were stable the advantage of the cascade cgc filter appears to derive from its parsimonious representation of the high frequency side of the filter it is concluded that cgc filters offer better prospects than roex filters for the representation of the auditory filter

a chernoff bound for random walks on expander graphs we consider a finite random walk on a weighted graph g we show that the fraction of time spent in a set of vertices a converges to the stationary probability pi a with error probability exponentially small in the length of the random walk and the square of the size of the deviation from pi a the exponential bound is in terms of the expansion of g and improves previous results of d aldous probab engrg inform sci 1 1987 pp 33 46 l lovasz and m simonovits it random structures algorithms 4 1993 pp 359 412 m ajtai j komlos and e szemeredi deterministic simulation of logspace in proc 19th acm symp on theory of computing 1987 we show that taking the sample average from one trajectory gives a more efficient estimate of pi a than the standard method of generating independent sample points from several trajectories using this more efficient sampling method we improve the algorithms of jerrum and sinclair for approximating the number of perfect matchings in a dense graph and for approximating the partition function of a ferromagnetic ising system and we give an efficient algorithm to estimate the entropy of a random walk on an unweighted graph

categorical loudness scaling and equal loudness contours in listeners with normal hearing and hearing loss this study describes procedures for constructing equal loudness contours elcs in units of phons from categorical loudness scaling cls data and characterizes the impact of hearing loss on these estimates of loudness additionally this study developed a metric level dependent loudness loss which uses cls data to specify the deviation from normal loudness perception at various loudness levels and as function of frequency for an individual listener with hearing loss cls measurements were made in 87 participants with hearing loss and 61 participants with normal hearing an assessment of the reliability of cls measurements was conducted on a subset of the data cls measurements were reliable there was a systematic increase in the slope of the low level segment of the cls functions with increase in the degree of hearing loss elcs derived from cls measurements were similar to standardized elcs international organization for standardization iso 226 2003 the presence of hearing loss decreased the vertical spacing of the elcs reflecting loudness recruitment and reduced cochlear compression representing cls data in phons may lead to wider acceptance of cls measurements like the audiogram that specifies hearing loss at threshold level dependent loudness loss describes deficit for suprathreshold sounds such information may have implications for the fitting of hearing aids

temporal integration frequency resolution and off frequency listening in normal hearing and cochlear impaired listeners temporal integration for a 1000 hz signal was determined for normal hearing and cochlear hearing impaired listeners in quiet and in masking noise of variable bandwidth critical ratio and 3 db critical band measures of frequency resolution were derived from the masking data temporal integration for the normal hearing listeners was markedly reduced in narrow band noise when contrasted with temporal integration in quiet or in wideband noise the effect of noise bandwidth on temporal integration was smaller for the hearing impaired group hearing impaired subjects showed both reduced temporal integration and reduced frequency resolution for the 200 ms signal however a direct relation between temporal integration and frequency resolution was not indicated frequency resolution for the normal hearing listeners did not differ from that of the hearing impaired listeners for the 20 ms signal it was suggested that some of the frequency resolution and temporal integration differences between normal hearing and hearing impaired listeners could be accounted for by off frequency listening

influence of primary level and primary frequency ratios on human distortion product otoacoustic emissions the combined influence of primary level differences l1 l2 and primary frequency ratio f2 f1 on distortion product otoacoustic emission dpoae level was investigated in 20 normal hearing subjects dpoaes were recorded with continuously varying stimulus levels neely et al j acoust soc am 117 1248 1259 2005 for the following stimulus conditions f2 1 2 4 and 8 khz and f2 f1 1 05 to 1 4 various l1 l2 including one individually optimized to produce the largest dpoae for broadly spaced primary frequencies at low l2 levels the largest dpoaes were recorded when l1 was much higher than l2 with l1 remaining relatively constant as l2 increased as f2 fl decreased the largest dpoaes were observed when l1 was closer to l2 and increased as l2 increased optimal values for l1 l2 and f2 f1 were derived from these data in general average dpoae levels for the new l1 l2 and f2 f1 were equivalent to or larger than those observed for other stimulus combinations including the l1 l2 described by kummer et al j acoust soc am 103 3431 3444 1998 and those defined by neely et al in which l1 l2 was evaluated but f2 f1 was fixed at 1 2

behavioral measures of cochlear compression and temporal resolution as predictors of speech masking release in hearing impaired listeners hearing impaired hi listeners often show less masking release mr than normal hearing listeners when temporal fluctuations are imposed on a steady state masker even when accounting for overall audibility differences this difference may be related to a loss of cochlear compression in hi listeners behavioral estimates of compression using temporal masking curves tmcs were compared with mr for band limited 500 4000 hz speech and pure tones in hi listeners and age matched noise masked normal hearing nmnh listeners compression and pure tone mr estimates were made at 500 1500 and 4000 hz the amount of mr was defined as the difference in performance between steady state and 10 hz square wave gated speech shaped noise in addition temporal resolution was estimated from the slope of the off frequency tmc no significant relationship was found between estimated cochlear compression and mr for either speech or pure tones nmnh listeners had significantly steeper off frequency temporal masking recovery slopes than did hi listeners and a small but significant correlation was observed between poorer temporal resolution and reduced mr for speech the results suggest either that the effects of hearing impairment on mr are not determined primarily by changes in peripheral compression or that the tmc does not provide a sufficiently reliable measure of cochlear compression

cooperative optimal control for lipschitz nonlinear systems over generally directed topologies abstract this paper studies the cooperative optimal control for multi agent systems mass with lipschitz nonlinearities over general digraphs the leader following consensus model consisting of multiple followers and one leader is constructed distributed optimal control protocols using the linear quadratic regulator approach are designed under the proposed protocols the performance index of the mas is optimized by solving the algebraic riccati equation are the weighting matrices of performance index rely on the lipschitz nonlinearities leading to optimal performance simulation studies are finally reported to illustrate the effectiveness of presented protocols

reaching an optimal consensus dynamical systems that compute intersections of convex sets in this paper multi agent systems minimizing a sum of objective functions where each component is only known to a particular node is considered for continuous time dynamics with time varying interconnection topologies assuming that each node can observe a convex solution set of its optimization component and the intersection of all such sets is nonempty the considered optimization problem is converted to an intersection computation problem by a simple distributed control rule the considered multi agent system with continuous time dynamics achieves not only a consensus but also an optimal agreement within the optimal solution set of the overall optimization objective directed and bidirectional communications are studied respectively and connectivity conditions are given to ensure a global optimal consensus in this way the corresponding intersection computation problem is solved by the proposed decentralized continuous time algorithm we establish several important properties of the distance functions with respect to the global optimal solution set and a class of invariant sets with the help of convex and non smooth analysis

simulation based uniform value function estimates of markov decision processes the value function of a markov decision process mdp assigns to each policy its expected discounted reward this expected reward can be estimated as the empirical average of the reward over many independent simulation runs we derive bounds on the number of runs needed for the uniform convergence of the empirical average to the expected reward for a class of policies in terms of the vapnik chervonenkis or p dimension of the policy class further we show through a counterexample that whether we get uniform convergence or not for an mdp depends on the simulation method used uniform convergence results are also obtained for the average reward case for partially observed markov decision processes and can be easily extended to markov games the results can be viewed as a contribution to empirical process theory and as an extension of the probably approximately correct pac learning theory for partially observable mdps and markov games

the role of envelope fluctuations in spectral masking two experiments are reported in this study in the first experiment the masking effect of five different types of narrow band maskers was compared the masker was either a tone a narrow band gaussian noise or a multiplication noise obtained by multiplying a sinusoid with a low pass gaussian noise the noise maskers had a bandwidth of either 20 or 100 hz in all cases the masker had a center frequency of 1 3 khz and a duration of 500 ms five point growth of masking functions were measured using a 2 khz tonal target with a duration of 400 ms temporally centered in the masker six subjects participated in the experiment although considerable intersubject differences were observed the data of all subjects showed several common trends first the tonal maskers produced more masking than the noise maskers second gaussian noise maskers produced more masking than multiplication noise maskers of the same bandwidth finally 100 hz wide noise maskers produced more masking than 20 hz wide maskers of the same

exponential convergence of distributed primal dual convex optimization algorithm without strong convexity abstract this paper establishes exponential convergence rates for a class of primal dual gradient algorithms in distributed optimization without strong convexity the convergence analysis is based on a carefully constructed lyapunov function by evaluating metric subregularity of the primal dual gradient map we present a general criterion under which the algorithm achieves exponential convergence to facilitate practical applications of this criterion several simplified sufficient conditions are derived we also prove that although these results are developed for the continuous time algorithms they carry over in a parallel manner to the discrete time algorithms constructed by using euler s approximation method

fine structure of hearing threshold and loudness perception hearing thresholds measured with high frequency resolution show a quasiperiodic change in level called threshold fine structure or microstructure the effect of this fine structure on loudness perception over a range of stimulus levels was investigated in 12 subjects three different approaches were used individual hearing thresholds and equal loudness contours were measured in eight subjects using loudness matching paradigms in addition the loudness growth of sinusoids was observed at frequencies associated with individual minima or maxima in the hearing threshold from five subjects using a loudness matching paradigm at low levels loudness growth depended on the position of the test or reference tone frequency within the threshold fine structure the slope of loudness growth differs by 0 2 db db when an identical test tone is compared with two different reference tones i e a difference in loudness growth of 2 db per 10 db change in stimulus finally loudness growth was measured for the same f

generalization performance of least square regularized regression algorithm with markov chain samples abstract the previously known works describing the generalization of least square regularized regression algorithm are usually based on the assumption of independent and identically distributed i i d samples in this paper we go far beyond this classical framework by studying the generalization of least square regularized regression algorithm with markov chain samples we first establish a novel concentration inequality for uniformly ergodic markov chains then we establish the bounds on the generalization of least square regularized regression algorithm with uniformly ergodic markov chain samples and show that least square regularized regression algorithm with uniformly ergodic markov chains is consistent