temporal integration and multiple looks revisited weights as a function of time this study tests the hypothesis that temporal integration for detection of tone bursts with various durations can be explained by optimally combining multiple looks of brief signal segments whose contribution to detection increases over time detectability was measured for signals consisting of six consecutive 25 ms 1 khz tone pulses presented in a 50 hz wide masker or in maskers consisting of seven 50 hz wide noises one critical band apart with either coherent or incoherent envelopes the level of each signal pulse varied randomly around masked threshold according to a gaussian distribution the slopes of conditional psychometric functions plotted in terms of d 2 as a function of the squared signal pulse intensity for pulses in a particular temporal position yielded estimates of the contribution to detection provided by each pulse results for three normal listeners showed a small but significant effect of the temporal location of the pulse multiple looks predictions of temporal integration functio

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

relative contributions of specific frequency bands to the loudness of broadband sounds listeners with normal hearing nh and sensorineural hearing loss snhl were asked to compare pairs of noise stimuli and choose the louder noise in each pair each noise was made up of 15 two erbn equivalent rectangular bandwidth wide frequency bands that varied independently over a 12 db range from one presentation to the next mean levels of the bands followed the long term average speech spectrum ltass or were set to 43 51 or 59 db sound pressure level spl the relative contribution of each band to the total loudness of the noise was determined by computing the correlation between the difference in levels for a given band on every trial and the listener s decision on that trial weights for snhl listeners were governed by audibility and the spectrum of the noise stimuli with bands near the spectral peak of the ltass noise receiving greatest weight nh listeners assigned greater weight to the lowest and highest bands an effect that increased with overall level but did not assign greater weight to bands near the ltass peak additional loudness matching and paired comparison studies using stimuli missing one of the 15 bands showed a significant contribution by the highest band but properties other than loudness may have contributed to the decisions

spectral shape discrimination by hearing impaired and normal hearing listeners the ability to discriminate between sounds with different spectral shapes was evaluated for normal hearing and hearing impaired listeners listeners discriminated between a standard stimulus and a signal stimulus in which half of the standard components were decreased in level and half were increased in level in one condition the standard stimulus was the sum of six equal amplitude tones equal spl and in another the standard stimulus was the sum of six tones at equal sensation levels re audiometric thresholds for individual subjects equal sl spectral weights were estimated in conditions where the amplitudes of the individual tones were perturbed slightly on every presentation sensitivity was similar in all conditions for normal hearing and hearing impaired listeners the presence of perturbation and equal sl components increased thresholds for both groups but only small differences in weighting strategy were measured between the groups depending on whether the equal spl or equal sl condition was tested the average data suggest that normal hearing listeners may rely more on the central components of the spectrum whereas hearing impaired listeners may have been more likely to use the edges however individual weighting functions were quite variable especially for the hi listeners perhaps reflecting difficulty in processing changes in spectral shape due to hearing loss differences in weighting strategy without changes in sensitivity suggest that factors other than spectral weights such as internal noise or difficulty encoding a reference stimulus also may dominate performance

discriminating coherence in spectro temporal patterns this study examined the ability of trained listeners to discriminate coherent components in randomly varying spectral patterns in each observation interval the listener was presented with a sequence of bursts of multitone complexes having a fixed number of tones m in each burst in the standard interval the frequency of each tone in every burst was chosen randomly between 200 and 5000 hz in the signal interval the frequencies of n tones were repeated throughout the burst sequence while the remaining m n tones were chosen at random the n tones were coherent in the sense that they were perceived as sticking together to form a pattern the listener s task was to discriminate which burst sequence contained the n components the results indicated that discrimination improved with increasing n m with increasing number of bursts per interval and declined as the coherent components were increasingly perturbed in frequency further for a fixed value of the ratio n m discriminability was relatively independent of m a model incorporating multichannel filtering and an optimum decision rule was reasonably successful in accounting for the experimental results

adaptive localized replay an efficient integration scheme for accurate simulation of coarsening dynamical systems coarsening dynamical systems cds of ordinary differential equations odes have as a defining feature the presence of discontinuities in the governing equations due to the removal of vanishing elements from the system simple commonly used integration strategies for odes neglect these discontinuities resulting in large errors in contrast available methods to resolve discontinuities exhibit total running times that scale like o n 2 as the number of elements n the resulting need to choose between either speed or accuracy frustrates attempts to gather well converged statistical data from large ensembles of elements a common goal in studies of coarsening in this work we introduce a numerical scheme called adaptive localized replay alr which overcomes this dilemma provided the underlying system has sparse neighbor dependence by analyzing the system after each timestep and then selectively re simulating only those small parts of the system that were affected by discontinuities we attain high order accuracy while maintaining running times of o n using a reference implementation of our algorithm applied to a sample problem from the field of faceted surface evolution we obtain convergence and runtime results for the alr method which compares favorably with existing methods

variation in spectral shape discrimination weighting functions at different stimulus levels and signal strengths this study evaluated whether weights for spectral shape discrimination depend on overall stimulus level and signal strength the degree of spectral shape change between two stimuli five listeners discriminated between standard stimuli that were the sum of six equal amplitude tones and signal stimuli created by decreasing the amplitudes of three low frequency components and increasing the amplitudes of three high frequency components weighting functions were influenced by stimulus level in that the relative contribution of the low frequency decremented components to the high frequency incremented components decreased with increasing stimulus level although individual variability was present a follow up experiment suggested that the level dependence was due to greater reliance on high frequency components rather than incremented components excitation pattern analyses indicated that the level dependence is primarily but not solely driven by cochlear factors in general different signal strengths had no effect on the weighting functions when normalized but two of the five listeners showed variability in the shape of the weighting function across signal strengths results suggest that the effects of stimulus level on weighting functions and individual variability in the shapes of the weighting functions should be considered when comparing weighting functions across conditions and groups that might require different stimulus levels and signal strengths

measuring decision weights in recognition experiments with multiple response alternatives comparing the correlation and multinomial logistic regression methods psychophysical reverse correlation methods allow researchers to gain insight into the perceptual representations and decision weighting strategies of individual subjects in perceptual tasks although these methods have gained momentum until recently their development was limited to experiments involving only two response categories recently two approaches for estimating decision weights in m alternative experiments have been put forward one approach extends the two category correlation method to m 2 alternatives the second uses multinomial logistic regression mlr in this article the relative merits of the two methods are discussed and the issues of convergence and statistical efficiency of the methods are evaluated quantitatively using monte carlo simulations the results indicate that for a range of values of the number of trials the estimated weighting patterns are closer to their asymptotic values for the correlation method than for the mlr method moreover for the mlr method weight estimates for different stimulus components can exhibit strong correlations making the analysis and interpretation of measured weighting patterns less straightforward than for the correlation method these and other advantages of the correlation method which include computational simplicity and a close relationship to other well established psychophysical reverse correlation methods make it an attractive tool to uncover decision strategies in m alternative experiments

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

a level set method for the evolution of faceted crystals a level set formulation for the motion of faceted interfaces is presented the evolving surface of a crystal is represented as the zero level of a phase function the crystal is identified by its orientation and facet speeds accuracy is tested on a single crystal by comparison with the exact evolution the method is extended to study the evolution of a polycrystal numerical examples in two and three dimensions are presented

model for coarsening froths and foams the coarsening process of froths and foams is described statistically in two dimensions by a random neighbor model this nonlinear dynamical model contains no free parameters all rates are determined dynamically it describes normal growth agrees with experimental results throws light on old data and hopefully inspires new simulations and measurements lewis s law anat rec 38 341 1928 am j bot 30 74 1943 and some other properties can be derived analytically from the model

spectral weights for overall level discrimination in listeners with sensorineural hearing loss a conditional on a single stimulus coss analysis procedure b g berg j acoust soc am 86 1743 1746 1989 was used to measure the weight or relative reliance that normal hearing and hearing impaired listeners give to different frequencies in the discrimination of the overall level of a multitone complex on each trial two multitone tone complexes comprised of six octave frequencies from 250 to 8000 hz were presented to subjects the levels of the frequencies for each complex were randomly varied the listeners task was to identify the complex with the higher overall intensity level normal hearing listeners used a variety of listening strategies to perform the task showing no general preference to weight one component over another hearing impaired listeners however showed a general tendency to give greatest weight to the spectral information in the region of their hearing loss thirteen of the 14 hearing impaired listeners all of whom had a high frequency sensorineural hearing loss weighted one or more of the high frequency components in the complex the greatest

a fifth order interpolant for the dornand and prince runge kutta method abstract a family of fifth order interpolants for the fifth order solution provided by the dormand and prince runge kutta pair rk5 4 7m which requires two additional function evaluations per step is presented an optimal interpolant in this family has been determined by choosing the parameters to minimize the leading coefficients of the local truncation error of the continuous solution some numerical experiments with the nonstiff detest problems show that the proposed optimal method has a good interpolatory behavior

models of auditory masking a molecular psychophysical approach gilkey et al j acoust soc am 78 1207 1219 1985 measured hit proportions and false alarm proportions for detecting a 500 hz tone at each of four starting phase angles in each of 25 reproducible noise samples in the present paper their results are modeled by fitting the general form of the electrical analog model of jeffress j acoust soc am 48 480 488 1967 to the diotic data the best fitting configurations of this model do not correspond to energy detectors or to envelope detectors a detector composed of a 50 hz wide single tuned filter followed by a half wave rectifier and an integrator with an integration time of 100 to 200 ms fits the data of all four subjects relatively well linear combinations of the outputs of several detectors that differ in center frequency or integration window provide even better fits to the data these linear combinations assign negative weights to some frequencies or to some time intervals suggesting that a subject s decision is based on a comparison of

observer efficiency and weights in a multiple observation task a sequence of seven tones sampled from one of two distributions differing in mean frequency is presented to observers who try to report which distribution was sampled estimates are obtained of the weight or importance given to each tone as a function of its temporal position in five experiments the reliability of the information is varied by changing the variance of the distributions tones with high reliability are sampled from distributions with relatively small variance whereas tones with low reliability are sampled from distributions with relatively large variance results show that the observations are weighted more efficiently when the tones have equal rather than unequal reliability and when the most reliable tones have the greater intensity additional results show that the most intense tones often receive the greatest weight even when those tones have the least reliability

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

effects of a limited class of nonlinearities on estimates of relative weights perturbation analyses have been applied in recent years to determine the relative contribution of individual stimulus components in detection and discrimination tasks responses to stimulus samples are compared to stimulus parameters to determine the details of the decision rule often a linear model is assumed and it is of interest to determine the relative contribution of different stimulus elements to the decision here biases in estimated relative weights are considered for the case where the decision variable is given by d ixin k m and the stimulus components the xi are normally distributed of equal variance and mutually independent the i are the true combination weights and n k and m are positive reals the method used to estimate relative weights is the correlation coefficient between the xi and the observer s responses estimates of relative i do not depend on m but may depend on the mean values of the xi and the values of n and k a dependence on the variance i2 holds even fo

intensity discrimination in the presence of random frequency multicomponent maskers and broadband noise this study examined the effects of multicomponent random frequency maskers and broadband noise maskers on intensity discrimination at 1000 hz maskers and signals were 200 ms presented simultaneously in the first set of conditions thresholds were measured for the detection of a 1000 hz tone in the presence of 40 or 60 db spl random frequency or noise maskers with extensive training of listeners with the random frequency masker to assure stable effects of masker frequency uncertainty the random frequency maskers had two six or ten components chosen at random from a large frequency range 300 3000 hz excluding a 160 hz band around 1000 hz for these maskers performance across the four listeners was very similar showing large effects of masker frequency uncertainty for noise maskers performance matched predictions for energy based masking in the second and third sets of conditions intensity discrimination was measured at 1000 hz for pedestals ranging from 40 to 80 db spl first in isolation and then in the presence of the maskers the pattern of results for intensity discrimination in quiet showed the expected near miss to weber s law but poorer performance than typically observed the addition of broadband noise maskers had little effect on performance however random frequency maskers degraded performance in nearly all conditions with the size of the effect dependent on the level of the pedestal relative to the masker considering the pedestal as a tonal masker the data were fitted with various models of combined masking a simple power law model provided excellent fits with exponents ranging from 0 24 to 0 35 for the multicomponent maskers but 1 0 linear for the noise the results support models positing that the effects of individual maskers undergo nonlinear transformation before they are added independent of the mechanisms which produce these effects because random frequency maskers presumably produce informational uncertainty based masking the nonlinearity in this case appears central rather than peripheral

nonmonotonicity of informational masking neff and green percept psychophys 41 409 415 1987 report that the masking of single tones by random frequency multitone maskers varies nonmonotonically with number of masker components peaking at 10 50 components in this paper it is shown that such results are well predicted by a model the component relative entropy model core wherein thresholds increase linearly with the ensemble variance of masker spectra smoothed by peripheral auditory filters r a lutfi j acoust soc am 94 748 758 1993 three experiments were conducted in the first the nonmonotonic relation was replicated for 9 of 11 listeners in conditions similar to those of neff and green in the second the frequencies of masker components were fixed and the levels of components were varied randomly across presentations to simulate gaussian noise in this case the nonmonotonicity and the total amount of masking for these listeners were shown to be significantly reduced in the third experiment masked thresholds for the signal were found to vary monotonically with the frequency spacing of masker components for a fixed number of masker components large individual differences among listeners were obtained in some experimental conditions individual as well as mean thresholds were well predicted by the core model with an appropriate selection of the values of the two free parameters of the model for each listener

correlational analysis of acoustic cues for the discrimination of auditory motion the sound of a source moving in a straight path and passing directly in front of the listener on the azimuthal plane was synthesized over headphones to include three dynamic cues for motion doppler effect overall intensity and interaural time difference discriminability of a change in displacement velocity and acceleration of this source was measured using a standard two interval forced choice procedure in each case the relative reliance or weight given to the three acoustic cues was estimated from correlations of the listener s response with small independent perturbations imposed on cues from trial to trial group estimates of threshold agreed well with results from past studies while the obtained pattern of weights depended on the individual starting velocity and discrimination task for the discrimination of displacement at moderate velocity 10 m s responses were most highly correlated with intensity or interaural time difference for the discrimination of velocity and to a lesser extent acceleration responses were most highly correlated with doppler effect at higher velocity 50 m s responses in all discrimination tasks were most strongly correlated with doppler effect with few exceptions randomizing source spectrum or roving distance of the source from trial to trial did not significantly affect the pattern of results the results suggest that motion perception is mutable and not in all cases based on a single invariant acoustic cue

auditory discrimination of force of impact the auditory discrimination of force of impact was measured for three groups of listeners using sounds synthesized according to first order equations of motion for the homogenous isotropic bar morse and ingard 1968 theoretical acoustics pp 175 191 the three groups were professional percussionists nonmusicians and individuals recruited from the general population without regard to musical background in the two interval forced choice procedure listeners chose the sound corresponding to the greater force of impact as the length of the bar varied from one presentation to the next from the equations of motion a maximum likelihood test for the task was determined to be of the form log a log f 0 where a and f are the amplitude and frequency of any one partial and 0 5 relative decision weights on log f were obtained from the trial by trial responses of listeners and compared to percussionists generally outperformed the other groups however the obtained decision weights of all listeners deviated significantly from and showed variability within groups far in excess of the variability associated with replication providing correct feedback after each trial had little effect on the decision weights the variability in these measures was comparable to that seen in studies involving the auditory discrimination of other source attributes

dynamics and self similarity in min driven clustering we study a mean field model for a clustering process that may be described informally as follows at each step a random integer k is chosen with probability p k and the smallest cluster merges with k randomly chosen clusters we prove that the model determines a continuous dynamical system on the space of probability measures supported in 0 oo and we establish necessary and sufficient conditions for the approach to self similar form we also characterize eternal solutions for this model via a levy khintchine formula the analysis is based on an explicit solution formula discovered by gallay and mielke extended using a careful choice of time scale

spectral weights for sample discrimination as a function of overall level doherty and lutfi 1996 spectral weights for overall level discrimination in listeners with sensorineural hearing loss j acoust soc am 99 1053 1058 examined the weights assigned to individual components of a six tone complex during a sample discrimination task and reported that hearing impaired subjects gave the most weight to components in the region of their high frequency hearing loss in contrast weighting patterns varied for normal hearing subjects in the current study the same six tone complex comprised of the octave frequencies from 0 25 to 8 khz was presented to three subjects with normal hearing in high pass noise in low pass noise and in quiet at two overall levels consistent with doherty and lutfi subjects assigned more weight to the 4 khz component in the high pass noise condition but roughly equal weight to all components in the lower level quiet condition weights in the low pass noise and higher level quiet conditions however were similar to those in the high pass no

the extent to which a position based explanation accounts for binaural release from informational masking detection was measured for a 500hz tone masked by noise an energetic masker or sets of ten randomly drawn tones an informational masker presenting the maskers diotically and the target tone with a variety of interaural differences interaural amplitude ratios and or interaural time delays resulted in reduced detection thresholds relative to when the target was presented diotically binaural release from masking thresholds observed when time and amplitude differences applied to the target were reinforcing favored the same ear resulting in a lateralized position for the target were not significantly different from thresholds obtained when differences were opposing favored opposite ears resulting in a centered position for the target this irrelevance of differences in the perceived location of the target is a classic result for energetic maskers but had not previously been shown for informational maskers however this parallellism between the patterns of binaural release for energet

a molecular description of profile analysis decision weights and internal noise systematic inefficiencies and internal noise in a spectral profile discrimination task were investigated listeners detected a 1000 hz sinusoid added in phase to the central component of a complex consisting of 11 equal intensity sinusoids parameters for a channel model that employs decision weights and internal noise were estimated with molecular psychophysical techniques maximum likelihood predictions of the model were generally within a few decibels of observed thresholds the degree to which an assumption of ideal weights leads to overestimation of internal noise was also assessed

effect of temporal position proportional variance and proportional duration on decision weights in temporal pattern discrimination two experiments investigated how listeners allocate their attention to different segments of a temporal pattern the experiments allowed a direct test of the predictions of the proportion of total duration ptd rule and the component relative entropy core model listeners had to decide whether two sequences of nine tones had the same or different temporal patterns tone duration 25 ms tone frequency 1000 hz a sequence s temporal pattern was determined by the time intervals between each tone s offset and the next tone s onset on same trials the time intervals at corresponding temporal positions in the two sequences were identical on different trials the corresponding time intervals were randomly varied listener attention to different temporal positions within a sequence was assessed by calculating the decision weights at each position the results supported the core model and were inconsistent with the ptd rule manipulating the mean of the time intervals within the sequence had no consistent ef

estimates of internal templates for the detection of sequential tonal patterns in this experiment listeners detected sequential tonal patterns embedded in multitone multiburst random maskers the maskers consisted of eight 30ms bursts of random frequency tones the signal when present occupied the central six bursts and was centered at 1000hz the six sequential signal tones formed several spectro temporal patterns an equal frequency pattern three ascending patterns with frequency ranges spanning 0 5 1 and 2 equivalent rectangular bandwidths erbs and a random pattern with frequencies drawn at random from the range of 925 1075hz the total number of tones in each burst m was varied to determine detection threshold the detectability of the signal pattern declined as the frequency range of the signal pattern increased and when the signal was random relative weights as a function of time and frequency interpreted as listeners internal templates depended systematically on the properties of the signal pattern tested the templates indicated that when sensitivity was po

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

frequency correlation functions for the detection of a tone added to modulated noise maskers psychophysical experiments using reproducible stimuli were completed for the detection of a 1000 hz tone added to a masker the noise masker was either sinusoidally amplitude modulated or not and masker bandwidths of 100 300 and 900 hz were tested the masker was centered at 1000 hz and the rate of amplitude modulation when present was 29 hz on average comodulation masking release values of 10 and 16 db were obtained for the 300 and 900 hz wide maskers respectively no release from masking was obtained for the 100 hz wide maskers data analysis consisted of computing the correlation coefficient between the level of each spectral component of each stimulus token and the observers responses to that token the resulting correlation functions estimate the relative contribution or weight of different frequency regions to the observers responses while the correlation functions for the modulated and unmodulated maskers share some features differences in both the pattern and quality of fit are apparent for wideband maskers for two of the observers however restricting the region of comparison to the region surrounding the signal frequency led to increased similarity of the correlation functions

temporal limits of level dominance in a sample discrimination task level dominance refers to the effect where attention is automatically directed to the loudest part of an auditory display in a sample discrimination task the frequencies of five 50ms tones were sampled from normal distributions with means of 1000 and 1100hz and presented sequentially with the tones alternating in intensity observers decide from which distribution the sample was drawn the informativeness of the even numbered tones d 2 was greater than the informativeness of the odd numbered tones d 1 estimates of decision weights and performance levels d show that when the more informative tones were less intense observers attended to the louder tones rather than the more informative tones this effect extends well beyond the temporal limits expected from forward masking studies

a new embedded pair of runge kutta formulas of orders 5 and 6 a new pair of embedded runge kutta rk formulas of orders 5 and 6 is presented it is derived from a family of rk methods depending on eight parameters by using certain measures of accuracy and stability numerical tests comparing its efficiency to other formulas of the same order in current use are presented with an extra function evaluation per step a c 1 continuous interpolant of order 5 can be obtained

auditory detection of hollowness the airborne sounds produced by freely vibrating hollow and solid bars were synthesized according to the equations of bar motion from theoretical acoustics and were presented to listeners over headphones in a two interval forced choice task listeners were asked to distinguish between the hollow and solid bar sounds as bar length was varied at random from one presentation to the next all other physical properties of the bar were held constant across trials listener decision strategies for detecting hollowness in iron aluminum and wood bars were determined from regression weights describing the relation between the listener s response and the frequency intensity and decay modulus of the individual partials comprising these sounds the obtained weights were compared to those of a hypothetical listener that bases judgments on the acoustic relations intrinsic to hollowness as determined from the equations for motion results indicate that listeners adopt roughly one of two decision strategies either basing judgments on the appropriate acoustic relations or basing judgments predominantly on frequency alone the decision strategy of some listeners also changed from one type to the other with a change in bar material or upon replication of the same condition the results are interpreted in terms of the vulnerability of the intrinsic acoustic relations to small perturbations in acoustic parameters as would be associated with listener internal noise they demonstrate that basic limits of human sensitivity can have a profound effect on the identification of rudimentary source attributes from sound even in conditions where acoustic variation is largely dictated by physical variation in the source

level dominance in sound source identification impact sounds were synthesized according to standard textbook equations given for the motion of simply supported metal plates in a two interval forced choice procedure highly practiced listeners identified from these sounds a predefined class of target plates based on their particular material and geometric properties the effects of two factors on identification were examined the relative level of partials comprising the sounds and the relative amount of information given as the difference in d each partial provided for identification in different conditions one factor was fixed while the other either increased or decreased with frequency the effect on listener identification in each case was determined from a logistic discriminant analysis of trial by trial responses yielding a vector of listener decision weights on the frequency and decay of individual partials the weights increased proportionally with relative level but were largely uninfluenced by relative information content a result exactly opposite to that expected from a maximum likelihood observer the dominant effect of relative level was replicated for other sound sources clamped bars and stretched membranes and was not diminished by randomizing the relative level of partials across trials the results are taken to underscore the importance of relative level in the identification of rudimentary sound sources

emergent parabolic scaling of nano faceting crystal growth nano faceted crystals answer the call for self assembled physico chemically tailored materials with those arising from a kinetically mediated response to free energy disequilibria thermokinetics holding the greatest promise the dynamics of slightly undercooled crystal melt interfaces possessing strongly anisotropic and curvature dependent surface energy and evolving under attachment detachment limited kinetics offer a model system for the study of thermokinetic effects the fundamental non equilibrium feature of this dynamics is explicated through our discovery of one dimensional convex and concave translating fronts solitons whose constant asymptotic angles provably deviate from the thermodynamically expected wulff angles in direct proportion to the degree of undercooling these thermokinetic solitons induce a novel emergent facet dynamics which is exactly characterized via an original geometric matched asymptotic analysis we thereby discover an emergent parabolic symmetry of its coarsening facet ensembles which naturally implies the universal scaling law l t 1 2 for the growth in time t of the characteristic length l

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

level discrimination of single tones in a multitone complex by normal hearing and hearing impaired listeners a conditional on a single stimulus coss analysis procedure j acoust soc am 86 1743 1746 1989 was used to estimate how well normal hearing and hearing impaired listeners selectively attend to individual spectral components of a broadband signal in a level discrimination task on each trial two multitone complexes consisting of six octave frequencies from 250 to 8000 hz were presented to listeners the levels of the individual tones were chosen independently and at random on each presentation the target tone was selected within a block of trials as the 250 1000 or 4000 hz component on each trial listeners were asked to indicate which of the two complex sounds contained the higher level target as a group normal hearing listeners exhibited greater selectivity than hearing impaired listeners to the 250 hz target while hearing impaired listeners showed greater selectivity than normal hearing listeners to the 4000 hz target which is in the region of their hearing loss both groups of listeners displayed large variability in their ability to selectively weight the 1000 hz target trial by trial analysis showed a decrease in weighting efficiency with increasing frequency for normal hearing listeners but a relatively constant weighting efficiency across frequency for hearing impaired listeners interestingly hearing impaired listeners selectively weighted the 4000 hz target which was in the region of their hearing loss more efficiently than did the normal hearing listeners

fourth and fifth order scaled rungs kutta algorithms for treating dense output new runge kutta algorithms are developed which determine the solution of a system of ordinary differential equations at any point within a given integration step as well as at the end of each step

spectral weights in profile listening the coss analysis suggested by berg b g berg j acoust soc am 86 1743 1746 1989 is applied to a profile listening task the listener s task is to detect an increment in the level of the middle component of an n component spectrum the overall level of the components is randomly selected from a 20 db range on each presentation thus the detection task is essentially one of detecting a change in spectral shape to implement the coss analysis a small perturbation in level is added to each component of the complex coss functions are generated from these perturbations and the spectral weight that the listener assigns to each component is estimated data are reported for n 3 5 and 11 components and for perturbations with standard deviations of 0 5 1 and 2 db the estimated weights are similar to those derived for an optimum detector namely the level at the signal component is compared with the average level of the nonsignal components this result supports the view that profile analysis invol

discrimination of random time varying spectra with statistical constraints in the present study a sample discrimination procedure is used to examine how various statistical constraints on random time varying spectra might aid listeners in discriminating among these signals time varying spectra were constructed by adding five sequences of tones five tones in each sequence centered at the octave frequencies from 250 to 4000 hz the levels frequencies and durations of the tones varied randomly from one presentation to the next the signal to be detected was an increment in the level of tones comprising the sequence centered at 1000 hz the target sequence three main conditions were examined in which the parameter values of tones varied independently of one another equal variance condition covaried across tone sequences cross channel covariance condition or covaried among themselves for each tone cross parameter covariance condition for the latter two conditions two special cases were examined in which the target sequence varied independently of nontarget sequence

a new method for derivation of continuous runge kutta formulas abstract a technique is introduced for the derivation of continuously embedded runge kutta formulas the method is illustrated in detail for the fourth order case a sixth order formula is presented which was derived by the technique it has two fifth order formulas continuously embedded one of which is c 1 the other is for error estimation an additional fifth order approximation is provided which usually gives error bounds for sufficiently small step sizes

mean field theory for coarsening faceted surfaces a mean field theory is developed for the scale invariant length distributions observed during the coarsening of generic one dimensional faceted surfaces this theory closely follows the lifshitz slyozov wagner theory of ostwald ripening in two phase systems but the mechanism of coarsening in faceted surfaces requires the addition of convolution terms recalling work on particle coalescence and induces an unexpected coupling between the convolution and the rate of facet loss as a generic framework the theory concisely illustrates how the universal processes of facet removal and neighbor merger are moderated by the system specific mean field velocity describing average rates of length change for a simple example facet dynamics associated with the directional solidification of a binary alloy agreement between the predicted scaling state and that observed after direct numerical simulation of 40 000 000 facets is reasonable given the limiting assumption of noncorrelation between neighbors relaxing this assumption is a clear path forward toward improved quantitative agreement with data in the future

decision strategies of hearing impaired listeners in spectral shape discrimination the ability to discriminate between sounds with different spectral shapes was evaluated for normal hearing and hearing impaired listeners listeners detected a 920 hz tone added in phase to a single component of a standard consisting of the sum of five tones spaced equally on a logarithmic frequency scale ranging from 200 to 4200 hz an overall level randomization of 10 db was either present or absent in one subset of conditions the no perturbation conditions the standard stimulus was the sum of equal amplitude tones in the perturbation conditions the amplitudes of the components within a stimulus were randomly altered on every presentation for both perturbation and no perturbation conditions thresholds for the detection of the 920 hz tone were measured to compare sensitivity to changes in spectral shape between normal hearing and hearing impaired listeners to assess whether hearing impaired listeners relied on different regions of the spectrum to discriminate between sounds spectral weights were estimated from the perturbed standards by correlating the listener s responses with the level differences per component across two intervals of a two alternative forced choice task results showed that hearing impaired and normal hearing listeners had similar sensitivity to changes in spectral shape on average across frequency correlation functions also were similar for both groups of listeners suggesting that as long as all components are audible and well separated in frequency hearing impaired listeners can use information across frequency as well as normal hearing listeners analysis of the individual data revealed however that normal hearing listeners may be better able to adopt optimal weighting schemes this conclusion is only tentative as differences in internal noise may need to be considered to interpret the results obtained from weighting studies between normal hearing and hearing impaired listeners

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

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

perceptual weights for loudness judgments of six tone complexes subjects with normal hearing nh and with sensorineural hearing loss snhl judged the overall loudness of six tone complexes comprised of octave frequencies from 0 25 to 8 khz the level of each tone was selected from a normal distribution with a standard deviation of 5 db and subjects judged which of two complexes was louder overall level varied across conditions in the loudness task there was no difference in mean level across the two stimuli in the sample discrimination task the two complexes differed by an average of 5 db for both tasks perceptual weights were derived by correlating the differences in level between matched frequency tones in the complexes and the loudness decision on each trial weights obtained in the two tasks showed similar shifts from low to high frequency components with increasing overall level simulation of these experiments using a model of loudness perception moore and glasberg 2004 hear res 188 70 88 yielded predicted weights for these stimuli that were highly correlated with predicted specific loudness but not with the observed weights

high order embedded runge kutta formulae abstract the criteria to be satisfied by embedded runge kutta pairs of formulae are reviewed two new formulae of orders 6 and 8 are presented together with tests on their efficiency relative to other high order formulae in current use

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

sensitivity to changes in overall level and spectral shape an evaluation of a channel model two experiments involving level and spectral shape discrimination which test an optimal channel model developed by durlach et al j acoust soc am 80 63 72 1986 are described the model specifies how the auditory system compares and or combines intensity information in different frequency channels in the first experiment psychometric functions were obtained for the discrimination of changes in level and discrimination of changes in spectral shape for an eight tone complex sound a variety of different base spectral shapes were tested in some conditions level randomization was introduced to reduce the reliability of across interval changes in level increasing the amount of level variation degraded performance for the level discrimination task but had no effect on the shape discrimination task in all conditions sensitivity to changes in spectral shape was superior to sensitivity to changes in level consequently two models of central noise are evaluated in an attempt to explain these results one in which central noise acts prior to the formation of the likelihood ratio and one in which central noise degrades the likelihood ratio the former model is more successful in accounting for the data in a second experiment the detectability of a level increment to one component of a multitone complex was measured the frequency content of the complex was varied by systematically removing six components from a 23 component complex thresholds were measured for increments at three different signal frequencies a common trend in the data was that when there was a spectral gap directly above the signal frequency thresholds were lowest this result differs from the predictions of a simple channel model and contrasts with results presented by green and berg q j exp psychol 43a 449 458 1991

molecular analysis of the effect of relative tone level on multitone pattern discrimination molecular psychophysics attempts to model the observer s response to stimuli as they vary from trial to trial the approach has gained popularity in multitone pattern discrimination studies as a means of estimating the relative reliance or decision weight listeners give to different tones in the pattern various factors affecting decision weights have been examined but one largely ignored is the relative level of tones in the pattern in the present study listeners detected a level increment in a sequence of 5 100 ms 2 0 khz tone bursts alternating in level between 40 and 80db spl the level increment was made largest on the 40 db tones yet despite this all four highly practiced listeners gave near exclusive weight to the 80 db tones the effect was the same when the tones were replaced by bursts of broadband gaussian noise alternating in level it was reduced only when the level differences were made 10db and it was entirely reversed only when the low level tones alternated with louder bursts of ga

coarsening dynamics of a one dimensional driven cahn hilliard system we study the one dimensional cahn hilliard equation with an additional driving term representing say the effect of gravity we find that the driving field e has an asymmetric effect on the solution for a single stationary domain wall or kink the direction of the field determining whether the analytic solutions found by leung j stat phys 61 345 1990 are unique the dynamics of a kink antikink pair bubble is then studied the behavior of a bubble is dependent on the relative sizes of a characteristic length scale mathit e mathrm ensuremath 1 where e is the driving field and the separation l of the interfaces for el ensuremath gg 1 the velocities of the interfaces are negligible while in the opposite limit a traveling wave solution is found with a velocity v ensuremath propto e l for this latter case el ensuremath ll 1 a set of reduced equations describing the evolution of the domain lengths is obtained for a system with a large number of interfaces and implies a characteristic length scale growing as et 1 2 numerical results for the domain size distribution and structure factor confirm this behavior and show that the system exhibits dynamical scaling from very early times textcopyright 1996 the american physical society

relative weights for frequency glide detection using narrowband noise narrowband noise stimuli were used to derive relative weights for detecting frequency glides in a yes no procedure one stimulus set was restricted to the duration of the glide for the second stimulus set there were fringe noise bands preceding and following the glide for both sets the center frequency of the linear glide was either fixed at 1000hz or randomly chosen on each trial from the range of 800 1200hz relative weights as a function of time were derived using a linear model and the linear classification method a ahumada j vis 2 121 131 2002 sensitivity was better for the fixed than random frequency conditions and weight patterns from the random frequency conditions were less reliable than those obtained from the fixed frequency conditions the magnitudes of the relative weights tended to be larger for the second half of the stimulus suggesting that subjects paid more attention to the later than the earlier parts of stimuli in the random frequency conditions the linear model failed to account for subjects performance unless the stimuli were expressed in terms of relative changes in frequency rather than absolute frequency

distribution of auditory filter bandwidths at 2 khz in young normal listeners auditory filter shapes at 2 khz were estimated for 95 young normally hearing subjects using a notched noise masker with spectrum level of 45 db excluding two subjects with a recent history of noise exposure the equivalent rectangular bandwidths erbs of the filters were approximately normally distributed but the distribution had a slight positive skew the mean erb was 308 hz and the standard deviation was 32 hz the two noise exposed subjects had erbs of 404 and 497 hz

auditory discrimination of material changes in a struck clamped bar the principles of theoretical acoustics were applied to approximately reconstruct the sound pressure waveform at the ear as would be generated by an idealized struck clamped bar the result is an inharmonic sum of damped sinusoids whose individual acoustic parameters frequency intensity and decay modulus are for a fixed geometry and fixed driving force uniquely determined by the material composition of the bar in the standard 2ifc procedure listeners were asked to discriminate changes in material composition based on their perception of the acoustic waveform listener strategies for discriminating such changes were estimated by perturbing slightly the individual acoustic parameters from trial to trial and computing correlations with the listener s response cf r a lutfi and e oh j acoust soc am 95 2963 a 1994 in general the correlations reveal that listeners fail to make optimal use of the information in the acoustic waveform by tending to give undue weight for a given material change to changes in component frequency in some case the accompanying reduction in performance efficiency amounted to 80

informational processing of complex sound i intensity discrimination this paper reports on some initial experiments using the sample discrimination paradigm to investigate normal hearing listeners ability to process information in complex nonspeech sounds an important feature of the sample discrimination experiment is that the value of the d i f f e r e n c e to be discriminated randomly varies from trial to trial it is this variation that yields potential information in the present study listeners heard a pair of multitone complexes or sequences on each trial the individual levels of the tones were drawn from two normal distributions differing only in mean the listener s task was to identify the sound having the higher mean tone level for an ideal observer in these experiments performance in d grows as the square root n where n is the number of tones obtained d grew more nearly as the cube root of n regardless of whether the tones were played sequentially or simultaneously or whether they were increased in number from high frequencies to low or from low frequencies to high a preliminary model is proposed in which discrimination performance depends predominantly on the information content of the sounds and is largely independent of the physical dimensions along which the sounds vary information content is defined in terms of the variance of the underlying stimulus distributions and a stimulus equivocation factor that is derived from the data based on this model transmitted information is estimated to be between 1 0 and 2 6 bits

continuous approximate solution of ordinary differential equations and their systems abstract the solution of initial value problems in ordinary differential equations are continuously differentiable functions yet all effective methods presently used for the numerical solution of these problems either in scalar or vector form are discrete processes they yield a finite set of approximate values of the solution the process derived in this paper yields a continuously differentiable function a polynomial which gives fourth order runge kutta approximations at all interior points of each interval of application and a fifth order approximation at each end point like conventional fifth order runge kutta algorithms the process requires only six evaluations of the given directional function per application or step it is endowed with an imbedding property for step size control and provides valuable information about committed local truncation errors it may be called a continuous imbedded runge kutta process of maximum order five it is valid for both scalar and vector cases

psychometric functions for level discrimination to determine the form of psychometric functions for 2i 2afc level discrimination ten increment levels were presented in random order within blocks of 100 trials stimuli were chosen to encompass a wide range of conditions and difference limens eight 10 ms tones had frequencies of 0 25 1 8 or 14 khz and levels of 30 60 or 90 db spl two 500 ms stimuli also were tested a 1 khz tone at 90 db spl and a white noise at 63 db spl for each condition at least 20 blocks were presented in mixed order results for three normal listeners show that the sensitivity d is nearly proportional to l 20 log p p p where p is pressure over the entire range of difference limens when d is plotted against weber fractions for pressure p p or intensity i i exponents of the best fitting power functions decrease with increasing difference limens and are less than one for large difference limens these results indicate that the transformation from stimulus intensity to decision variable may be approximately lo

spectral and temporal weights in spectral shape discrimination the coss analysis b g berg j acoust soc am 86 1743 1746 1989 was used to estimate spectral and temporal weights of a three component amplitude modulated stimulus in a spectral shape discrimination task in all experiments the task of the observer was to detect an increment in the level of the center component a spectral temporal weight quantifies the relative influence of a spectral component on the decisions of an observer during a specified segment of the total stimulus duration in the first two experiments the signal was added to all three temporal segments of the center component the ideal weights for each component should be the same across temporal segments spectral temporal weights were obtained for four conditions with different stimulus durations in general the estimated weights for each component were not equal at different temporal segments in the third experiment the signal was added to only one of three segments of the center component ideally weight patterns should have changed when the temporal position of the signal segment was altered two stimulus durations 300 and 15 ms were used for the 300 ms condition the signal was added to only the end segment and for all three observers the weight patterns are different from that obtained in experiment 1 with the signal added to all segments for the 15 ms conditions altering the signal position changed the estimated weights for only one observer

a measure of internal noise based on sample discrimination internal noise is often inferred from the difference between observed performance and optimum performance in detection and discrimination tasks it can be measured directly in some cases by observing the extent to which a change in external variability impacts performance in the studies reported here external variability was added to an intensity discrimination task by adding a gaussian random variable with zero mean to the overall level presented in each interval of a two interval forced choice task the standard deviation of the random variable was set to half the mean difference between the levels in the two intervals resulting in d ideal 2 as the mean difference and the corresponding standard deviation of the random variable decreased in size performance was increasingly limited by internal noise permitting a reliable estimate of internal noise to be obtained this can be viewed as a sample discrimination task with one component per sample in the first study performance was measured using 2 khz tones presented at an average level of 70 db spl with mean differences between distributions ranging from 0 1 to 2 2 db in steps of 0 3 db the distributions were either gaussian in level or in power conditions with no external variability were used to obtain a psychometric function in the second study performance was measured using 2 khz tones presented at average levels of 50 and 90 db spl with mean differences ranging from 0 4 to 2 2 db in steps of 0 6 db in both studies the measure of internal noise was highly reliable and in good agreement with the intensity difference limen dl estimated from the psychometric function analyses suggest that this measure could be used to estimate the mean difference between the decision distributions as well as the amount of internal noise in cases where the mean difference between the distributions is unknown

decision rules of listeners in spectral shape discrimination with or without signal frequency uncertainty a correlation technique was used to assess the decision rules of three listeners in two cases of spectral shape discrimination tasks in one case the signal frequency was fixed and in the other it was randomly varied within each block of trials in order to estimate the decision rule of the listeners the experimenter superimposed random level perturbations on each frequency component upon each stimulus presentation over many trials correlation coefficients were computed between the random perturbations and the binary responses of the listeners and were expressed as a function of signal level for both the fixed and random signal cases the measured correlation functions were in reasonably good agreement with those predicted based on the likelihood ratio decision rules thus the listeners appeared to use information nearly optimally in discriminating spectral shapes this investigation demonstrated that the correlation technique can be used to reveal the decision rules for cases where the decision statistics are nonlinear functions of the observations

coarsening dynamics of the convective cahn hilliard equation abstract we characterize the coarsening dynamics associated with a convective cahn hilliard equation cch in one space dimension first we derive a sharp interface theory through a matched asymptotic analysis two types of phase boundaries kink and anti kink arise due to the presence of convection and their motions are governed to leading order by a nearest neighbors interaction coarsening dynamical system cds theoretical predictions on cds include the characteristic length l m for coarsening exhibits the temporal power law scaling t1 2 provided l m is appropriately small with respect to the peclet length scale l p binary coalescence of phase boundaries is impossible ternary coalescence only occurs through the kink ternary interaction two kinks meet an anti kink resulting in a kink direct numerical simulations performed on both cds and cch confirm each of these predictions a linear stability analysis of cds identifies a pinching mechanism as the dominant instability which in turn leads to kink ternaries we propose a self similar period doubling pinch ansatz as a model for the coarsening process from which an analytical coarsening law for the characteristic length scale l m emerges it predicts both the scaling constant c of the t1 2 regime i e l m ct 1 2 as well as the crossover to logarithmically slow coarsening as l m crosses l p our analytical coarsening law stands in good qualitative agreement with large scale numerical simulations that have been performed on cch

informational processing of complex sound iii interference in this study theoretical results from information theory and detection theory are applied to provide a formal analysis of the interaction of target and context uncertainty on the discrimination of brief multitone sequences the experiments employ a sample discrimination task in which the performance of an ideal observer is held constant while the relative variability of the target t and context c is varied listener performance in these experiments was less than ideal but increased monotonically with t c whether the task was to discriminate the frequency or the intensity of the target performance was also constant for a constant t c regardless of the target s position in the sequence the results are consistent with a class of models in which the decision variable is a weighted sum of the tone values comprising the sequence weighting functions computed from the trial by trial data suggest that limits in performance result from trial by trial variability in the weights the decision variable also

the decision process in forward masked intensity discrimination evidence from molecular analyses in a two interval forced choice intensity discrimination task presenting a fixed increment the level of the forward masker in interval 1 and interval 2 was sampled independently from the same normal distribution on each trial mean and standard deviation of the distribution were varied correlational analyses of the trial by trial data revealed different decision strategies depending on the relation between mean masker level and standard level if the two levels were identical listeners tended to select the interval containing the higher level masker behaving like an energy detector at the output of a temporal window of integration for mean masker level higher than the standard level most listeners showed a negative correlation between the masker level in a given interval and the probability of selecting this interval indicating a strategy of comparing the masker loudness and the target loudness in each of the two observation intervals and voting for the interval where the loudness difference was s