estimates of effective frequency selectivity based on the detection of a tone added to complex maskers in experiment 1 the validity of parameters associated with the roex p r auditory filter shape was examined for three different types of maskers a a noise masker b a random 12 tone masker whose frequencies varied on a burst by burst basis multiple burst different mbd and c a random 12 tone masker whose frequencies were the same across bursts multiple burst same mbs first the power spectrum model of masking was used to estimate auditory filter shapes for four observers second the resulting auditory filter shapes were used in a computer simulation that provided an estimate of internal noise for each observer third relative weights across frequency were estimated for each observer and each masker type for the noise masker these analyses provided predictions and relative weights that were consistent across the three analyses for the mbd and mbs maskers there was little consistency neither the estimated internal noise nor the estimated relative weights reliably supported a single f

the runge phenomenon and spatially variable shape parameters in rbf interpolation many studies mostly empirical have been devoted to finding an optimal shape parameter for radial basis functions rbf when exploring the underlying factors that determine what is a good such choice we are led to consider the runge phenomenon rp best known in cases of high order polynomial interpolation as a key error mechanism this observation suggests that it can be advantageous to let the shape parameter vary spatially rather than assigning a single value to it benefits typically include improvements in both accuracy and numerical conditioning still another benefit arises if one wishes to improve local accuracy by clustering nodes in selected areas this idea is routinely used when working with splines or finite element methods however local refinement with rbfs may cause rp type errors unless we use a spatially variable shape paremeter with this enhancement rbf approximations combine freedom from meshes with spectral accuracy on irregular domains and furthermore permit local node clustering to improve the resolution wherever this might be needed

examination of a linear model in an informational masking study when multitone maskers are used in a two interval forced choice experiment the amount of masking is larger when the masker is randomly chosen on each presentation interval compared to on each trial the same masker in the two listening intervals these conditions are referred to as having within versus between trial randomization if it is assumed that an observer s ultimate detection decision depends on a single decision variable dv it is probable that the dv s variance will be substantially larger in the within trial randomization condition compared to the between trial randomization condition the goal of the current experiment is to evaluate the degree to which this stimulus based change in dv variance can account for the difference in thresholds in the within versus between trial randomization conditions thresholds are measured for the detection of a tone added to a six component masker in between and within trial randomization conditions the slopes of the psychometric functions provide an estimate of the variance in the dv for the between and within trial randomization conditions additionally a channel model is fitted to the psychophysical results in the within trial randomization condition the resulting model is then used to predict the value of the dv for each trial and ultimately to estimate the proportion of the total variance in the within trial randomization condition that is attributable to changes in maskers across intervals the variance of the dv in the between trial randomization condition accounted for approximately 65 of the total variance in the dv in the within trial randomization condition stimulus based interval by interval masker randomization accounted for approximately 20 of the total variance of the within trial randomization dv the remaining 15 of the dv variance in the within trial randomization condition remained unaccounted for this result is fairly stable whether the maskers are drawn from a small versus large pool of potential maskers

dependence of post masking on masker duration and its relation to temporal effects in loudness temporal masking of tones by noise was investigated using a post forward masking paradigm the masker level and duration were varied for every masker level employed the rate of decay of masking was found to depend on the duration of the masker specific loudness values were computed from the forward masking functions and an electronic device which simulates these loudness functions is presented in the simulation a series of integrators or a single integration with one long time constant was utilized the effect of the proposed integrators on loudness meters is discussed

informational masking for simultaneous nonspeech stimuli psychometric functions for fixed and randomly mixed maskers sensitivity d and response bias were measured as a function of target level for the detection of a 1000 hz tone in multitone maskers using a one interval two alternative forced choice 1i 2afc paradigm ten such maskers each with eight randomly selected components in the region 200 5000 hz with 800 1250 hz excluded to form a protected zone were presented under two conditions the fixed condition in which the same eight component masker is used throughout an experimental run and the random condition in which an eight component masker is chosen randomly trial to trial from the given set of ten such maskers differences between the results obtained with these two conditions help characterize the listener s susceptibility to informational masking im the d results show great intersubject variability but can be reasonably well fit by simple energy detector models in which internal noise and filter bandwidth are used as fitting parameters in contrast the results are not well fit by these models in addition to presentation of new data and its relation to energy detector models this paper provides comments on a variety of issues problems and research needs in the im area 2005 acoustical society of america doi 10 1121 1 2032748

similarity uncertainty and masking in the identification of nonspeech auditory patterns this study examined whether increasing the similarity between informational maskers and signals would increase the amount of masking obtained in a nonspeech pattern identification task the signals were contiguous sequences of pure tone bursts arranged in six narrow band spectro temporal patterns the informational maskers were sequences of multitone bursts played synchronously with the signal tones the listener s task was to identify the patterns in a 1 interval 6 alternative forced choice procedure three types of multitone maskers were generated according to different randomization rules for the least signal like informational masker the components in each multitone burst were chosen at random within the frequency range of 200 6500 hz excluding a protected region around the signal frequencies for the intermediate masker the frequency components in the first burst were chosen quasirandomly but the components in successive bursts were constrained to fall in narrow frequency bands around the frequencies of the components in the initial burst within the narrow bands the frequencies were randomized this masker was considered to be more similar to the signal patterns because it consisted of a set of narrow band sequences any one of which might be mistaken for a signal pattern the most signal like masker was similar to the intermediate masker in that it consisted of a set of synchronously played narrow band sequences but the variation in frequency within each sequence was sinusoidal completing roughly one period in a sequence this masker consisted of discernible patterns but not patterns that were part of the set of signals in addition masking produced by gaussian noise bursts thought to produce primarily peripherally based energetic masking was measured and compared to the informational masking results for the three informational maskers more masking was produced by the maskers comprised of narrow band sequences than for the masker in which the frequencies were not constrained to narrow bands also the slopes of the performance level functions for the three informational maskers were much shallower than for the gaussian noise masker or for no masker the findings provided qualified support for the hypothesis that increasing the similarity between signals and maskers or parts of the maskers causes greater informational masking however it is also possible that the greater masking was a consequence of increasing the number of perceptual streams that had to be evaluated by the listener

the role of masker fringes for the detection of coherent tone pips three experiments investigated the role of pre post exposure to a masker in a detection task with complex random spectro temporal maskers in the first experiment the masker was either continuously presented or pulsed on and off with the signal for most listeners thresholds were lower when the masker was continuously presented despite the fact that there was more uncertainty about the timing of the signal in the second experiment the signal bearing portion of the masker was preceded and followed by masker fringes of different durations consistent with the findings of experiment 1 for some listeners shorter duration fringes led to higher thresholds than long duration fringes in the third experiment the masker fringe a preceded b followed or c both preceded and followed the signal relative to the middle signal conditions a late signal yielded lower thresholds and the early signal yielded higher thresholds these results indicate that listeners can use features of an ongoing sound to extract an added signal and that listeners differ in the importance of pre exposure for efficient signal extraction however listeners do not appear to perform this comparison retrospectively after the signal potentially indicating a form of backward masking

role of attention in overshoot frequency certainty versus uncertainty overshoot the elevation in the threshold for a brief signal that comes on close to masker onset was measured with signal frequency certain same frequency on every trial or uncertain randomized over trials in broadband noise thresholds were higher 2ms after masker onset than 200ms later by 9db with frequency certainty by 6 7db with uncertainty in narrowband noise centered on the signal frequency thresholds at 2ms were not elevated with certainty but were elevated 4 5db with uncertainty thus frequency uncertainty leads to less overshoot in broadband noise to more overshoot in narrowband noise reduced overshoot in broadband noise may come about because the masker given its many frequencies disrupts focusing at onset as much under certainty as uncertainty once the initial disruption dissipates threshold is lower with certainty so overshoot is greater in contrast a narrowband noise with frequencies only near the signal does not disrupt focusing when the signal frequency is known beforeha

excitation based and informational masking of a tonal signal in a four tone masker this study examined contributions of peripheral excitation and informational masking to the variability in masking effectiveness observed across samples of multi tonal maskers detection thresholds were measured for a 1000 hz signal presented simultaneously with each of 25 four tone masker samples using a two interval forced choice adaptive task thresholds were measured with each sample fixed throughout trial blocks for ten listeners average thresholds differed by as much as 26 db across samples an excitation based model of partial loudness moore b c j et al 1997 j audio eng soc 45 224 237 was used to predict thresholds these predictions accounted for a significant portion of variance in the data of several listeners but no relation between the model and data was observed for many listeners moreover substantial individual differences on the order of 41 db were observed for some maskers the largest individual differences were found for maskers predicted to produce minimal excitat

individual differences in simultaneous masking with random frequency multicomponent maskers individual differences were examined for 49 listeners in a simultaneous masking task with random frequency multicomponent maskers and a 1000 hz signal across conditions the maskers were broadband noise or complexes of 2 100 sinusoids whose frequencies were randomly chosen with each presentation maskers were equal rms waveforms presented at 60 db spl thresholds for the multicomponent maskers spanned a range of up to 59 db across listeners within conditions without distinct groupings when divided into quartiles mean thresholds for listeners in the lowest quartile increased monotonically with the number of masker components and peaked below values produced by broadband noise listeners in the upper quartile had nonmonotonic functions with a broad peak around 10 20 components with values above those produced by broadband noise quiet thresholds and masked thresholds for the broadband noise masker did not distinguish high from low threshold groups lowering masker uncertainty frequencies randomized between but not within trials or introducing temporal differences by shortening the signal both improved performance by as much as 40 db dependent on the masking produced with maximum uncertainty training effects within experiment excluding an initial training period were examined for all listeners and for five listeners across two consecutive experiments eleven of forty nine listeners 22 showed systematic improvement averaging 12 db within experiment independent of high or low original thresholds for the five tested longer four improved by 5 db or more in at least one condition but the change in performance occurred primarily during initial training for the second experiment the large individual differences documented present a challenge to the development of models for masking produced by masker frequency uncertainty

signal uncertainty and psychometric functions in profile analysis experiment 1 was conducted to compare the effects of signal frequency uncertainty on the detection of a change in spectral shape and on the detection of a tone in wideband noise results indicate that for both tasks the uncertainty effect was small being on average about 3 db in a second experiment psychometric functions were measured for the detection of changes in the spectral shape of multicomponent complexes psychometric functions for profile tasks have a 25 db range and are similar to those measured for the detection of an increment in the level of a single sinusoid these psychometric functions are different from those found when detecting a signal in noise which typically have a 10 db range three equations for the shape of the psychometric functions were compared the difference in the resulting fits was small thus preventing an unambiguous choice of functional form

strategies used to detect auditory signals in small sets of random maskers detection performance for a masked auditory signal of fixed frequency can be substantially degraded if there is uncertainty about the frequency content of the masker a quasimolecular psychophysical approach was used to examine response strategies in masker uncertainty conditions and to investigate the influence of uncertainty when the number of different masker samples was limited to ten or fewer the task of the four listeners was to detect a 1000 hz signal that was presented simultaneously with one of ten ten tone masker samples the masker sample was either fixed throughout a block of two interval forced choice trials or was randomized across or within trials the primary results showed that 1 when the signal level was low and the masker sample differed between the two intervals of a trial most listeners based their responses more on the presence of specific masker samples than on the signal 2 the detrimental effect of masker uncertainty was clearly evident when only four maskers were randomly presented and grew as the size of the masker set was increased from two to ten 3 the slopes of psychometric functions measured with the same masker samples differed among the fixed and two random masker conditions 4 there were large differences in the influence of masker uncertainty across masker samples and listeners these data demonstrate the great susceptibility of human listeners to the influence of masker uncertainty and the ability of quasimolecular investigations to reveal important aspects of behavior in uncertainty condition

a model of auditory pattern analysis based on component relative entropy recently results from detection and information theory have been used to predict performance of human observers in experiments involving the discriminability of changes in individual components of unfamiliar or uncertain tone patterns r a lutfi j acoust soc am 91 3391 3401 1992 in this paper the theoretical analysis is expanded to yield a general rule of pattern analysis that accounts for nearly all of the major results of such experiments conducted over the last 18 years the rule can be stated as follows component discriminability in an unfamiliar tone pattern profile or sequence is a linearly increasing function of the component s relative entropy core in the pattern ancillary the threshold for detection of a change decreases by one order of magnitude factor of 10 for each one bit increase in core this precise relation of threshold to core is demonstrated repeatedly in a review of past studies and is shown to account for the relative effects of a variety of important variables and their interactions such variables include the total duration of the pattern the number of tones in the pattern the number of tones subject to change the relative level and duration of individual tones in the pattern the relative variability and the physical dimension of the tones parameters that are subject to change the number and position of targets in the pattern the psychophysical procedure used method of adjustment versus same different the type of discrimination task frequency versus intensity discrimination and the manner of presentation of the tones simultaneous or sequential the core rule seems to reflect a general property of auditory analysis wherein the perception of patterns in an ensemble is dominated by those features that dominate the variance of the ensemble

correlation coefficients and correlation ratios as estimates of observer weights in multiple observation tasks advantages of correlational methods are described for estimating the relative reliance or weight observers give to different elements of a complex display when performing auditory or visual discriminations correlational methods differ from other such methods by providing a least squares estimate of weights rather than a maximum likelihood estimate based on a presumed model the main benefit is that these methods can be generally applied in cases where the statistical properties of elements are unknown where correlations exist between elements or where it is necessary to evaluate decision models that are inherently nonlinear

spline interpolation techniques applied to the study of geophysical data abstract this work is devoted to the study of geophysical data by using different spline interpolation techniques a spatial analysis of the california earthquakes geological data was performed some of the methods proved to be more efficient than others depending on the number of data points considered overall this class of interpolation surface proved to be a very powerful tool for analyzing geophysical data

effective properties of multicomponent simultaneous maskers under conditions of uncertainty when more than one sinusoid is used as a masker more masking is observed than would be predicted by a simple combination of their individual effects this masking is dramatically increased when the masker components vary in frequency and intensity with each presentation these studies manipulated several masker parameters under conditions of high masker uncertainty examining the effect of excluding critical band components fixing or randomizing component amplitudes and frequencies and narrowing the frequency range of the components the signal was always a 200 ms 1000 hz sinusoid presented simultaneously with the 200 ms masker removing critical band components reduced the amount of masking but considerable masking remained that appears to be nonperipheral in origin fixing masker frequencies across the two intervals of a trial greatly reduced the masking observed whereas fixing masker amplitudes had no effect reducing the frequency range from 5000 to 2700 hz generally increased the masking obser

a multilevel algorithm for the biharmonic problem a finite element discretization of the mixed variable formulation of the biharmonic problem is considered a multilevel algorithm for the numerical solution of the discrete equations is described convergence is proved under the assumption ofh 3 regularity

cuing effects for informational masking the detection of a tone added to a random frequency multitone masker can be very poor even when the maskers have little energy in the frequency region of the signal this paper examines the effects of adding a pretrial cue to reduce uncertainty for the masker or the signal the first two experiments examined the effect of cuing a fixed frequency signal as the number of masker components and presentation methods were manipulated cue effectiveness varied across observers but could reduce thresholds by as much as 20 db procedural comparisons indicated observers benefited more from having two masker samples to compare with or without a signal cue than having a single interval with one masker sample and a signal cue the third experiment used random frequency signals and compared no cue signal cue and masker cue conditions and also systematically varied the time interval between cue offset and trial onset thresholds with a cued random frequency signal remained higher than for a cued fixed frequency signal for time intervals between the cue and trial of 50 ms or longer thresholds were approximately the same with a signal or a masker cue and lower than when there was no cue without a cue or with a masker cue analyses of possible decision strategies suggested observers attended to the potential signal frequencies particularly the highest signal frequency with a signal cue observers appeared to attend to the frequency of the subsequent signal

relative estimates of combination weights decision criteria and internal noise based on correlation coefficients a means by which relative combination weights may be determined is described for a signal detection model in which the decision variable is a weighted linear combination of several independent normally distributed random variables xi s the first theorem presents the correlation between the binary response variables signal versus no signal and the component xi the second theorem presents a parallel result for the case that additive internal noise is present thus in psychophysical experiments the relative combination weights may be obtained by correlating the observers responses and the input random variables third three numerical methods which allow the evaluation of the relative magnitude of the decision criterion and the variance of a hypothetical additive internal noise are considered

informational masking by everyday sounds tone in noise detection is severely degraded when only a few spectral components of the noise are presented at random on each trial neff and green percept psychophys 41 409 415 1987 the elevations in threshold are attributed to uncertainty regarding the noise caused by sparse sampling of noise components informational masking is the term used to describe the result the present experiment was undertaken to determine how informational masking is affected when sparse sampling is from a set of common everyday sounds instead of noise on each presentation a different masker waveform of constant total power was synthesized from the magnitude and phase of a fixed number m of spectral components m 2 921 across blocks of trials the components were selected at random from 1 of 50 common environmental sounds e g baby crying door slamming phone ringing or 1 of 50 samples of gaussian noise masked thresholds for a 1 0 khz signal in the presence of both types of maskers were obtained using an adaptive two interval forced choice procedure results with noise replicated earlier results showing largest elevations in threshold for 10 20 sampled components results with everyday sounds showed a similar pattern with thresholds elevated above those for noise by as much as 10 db at the larger values of m the differences in masked thresholds were systematically related to differences in the ensemble variance of masker spectra as predicted by a model previously applied to noise lutfi j acoust soc am 94 748 758 1993 not predicted was the result of a subsequent trial by trial analysis in which 9 11 db less masking was observed for samples from everyday sounds rated as easily recognized by listeners the results suggest that listeners fail to exploit lawful dependencies among spectral components of everyday sounds to aid detection unless enough information is available for the sound to be easily recognized

growth of forward masking for sinusoidal and noise maskers as a function of signal delay implications for suppression in noise the first two experiments were designed to determine whether mutual suppression in broadband noise increases in strength with increasing overall level in experiment i masking functions signal threshold versus masker level were measured in forward masking as a function of the delay time of a 10 ms signal both for a broadband noise masker low pass filtered at 8 khz and for sinusoidal maskers at 1 2 and 4 khz in the latter case the signal frequency equaled the masker frequency for short signal delays the masking functions were steeper for the sinusoidal masker than for the noise masker at longer delays the slopes for both masker types decreased and the slopes for the two masker types became more nearly equal in experiment ii we investigated the effect of gating a low level noise cue with the sinusoidal masker at the longer signal delays the masking functions had equal slopes for the broadband noise masker and the sinusoidal masker with cue at short signal delays the masking functions for sinuso