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

sofic groups and direct finiteness abstract we construct an analogue of von neumann s affiliated algebras for sofic group algebras over arbitrary fields consequently we settle kaplansky s direct finiteness conjecture for sofic groups

sofic groups and diophantine approximation we prove the algebraic eigenvalue conjecture of j dodziuk p linnell v mathai t schick and s yates see 2 for sofic groups moreover we give restrictions on the spectral measure of elements in the integral group ring finally we define integer operators and prove a quantization of the operator norm below 2 to the knowledge of the author there is no group known that is not sofic

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

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

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

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

auditory intensity perception successive versus simultaneous across channel discriminations this study measures the ability of observers to compare the intensities of two stimuli occupying different frequency regions it includes three experiments each experiment having two conditions in one condition the two stimuli to be compared were presented simultaneously within each interval this condition has been called profile analysis in the other condition the two stimuli were presented successively within each interval because the overall level of the stimuli was randomized between intervals the observers were encouraged to compare the intensities of the two stimuli within each observation interval rather than between intervals the stimuli were two simple tones in experiment 1 and two tonal complexes in both experiments 2 and 3 the stimuli used in experiments 2 and 3 differed in frequency the results show that simultaneous comparisons are superior to successive comparisons for simple tones the difference in threshold is about 8 db for complexes with 10 to 11 components the difference

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

convergence and limits of linear representations of finite groups motivated by the theory of graph limits we introduce and study the convergence and limits of linear representations of finite groups over finite fields the limit objects are infinite dimensional representations of free groups in continuous algebras we show that under a certain integrality condition the algebras above are skew fields our main result is the extension of schramm s characterization of hyperfiniteness to linear representations

informational processing of complex sound ii cross dimensional analysis a series of experiments investigated listeners ability simultaneously to process information across different acoustic dimensions on each trial the listener heard a pair of brief n tone sequences n 1 to 12 the frequency intensity and duration of each tone in the sequence varied randomly from trial to trial on average the values of these three parameters were greater for one sequence the target than the other the nontarget the listener s task was to identify the target on each trial for an ideal observer in this task d performance grows as the square root n obtained d grew at a rate slightly less than the square root of n close to cube root of n growth was observed when the average difference occurred in only one of the three tone parameter values within a block of trials although performance fell short of ideal optimum weights were consistently given to each tone and each parameter the results are consistent with a model in which performance depends predominantly on the information content of the sounds regardless of how the information is packaged in the stimulus transmitted information is estimated to be 0 9 2 0 bits within a single acoustic dimension 2 1 3 0 bits when distributed across dimensions

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

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

approximating l2 invariants and the atiyah conjecture let g be a torsion free discrete group and let denote the field of algebraic numbers in we prove that g fulfills the atiyah conjecture if g lies in a certain class of groups d which contains in particular all groups that are residually torsion free elementary amenable or are residually free this result implies that there are no nontrivial zero divisors in g the statement relies on new approximation results for l2 betti numbers over g which are the core of the work done in this paper another set of results in the paper is concerned with certain number theoretic properties of eigenvalues for the combinatorial laplacian on l2 cochains on any normal covering space of a finite cw complex we establish the absence of eigenvalues that are transcendental numbers whenever the covering transformation group is either amenable or in the linnell class we also establish the absence of eigenvalues that are liouville transcendental numbers whenever the covering transformation group is either residually finite or more generally in a certain large bootstrap class 2003 wiley periodicals inc

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

material identification of real impact sounds effects of size variation in steel glass wood and plexiglass plates identification of the material of struck objects of variable size was investigated previous studies on this issue assumed recognition to be based on acoustical measures of damping this assumption was tested comparing the power of a damping measure in explaining identification data with that of several other acoustical descriptors listeners performance was perfect with respect to gross material categories steel glass and wood plexiglass comprising materials of vastly different mechanical properties impaired performance was observed for materials within the same gross category identification being based on the size of the objects alone the damping descriptor accounted for the identification of the gross categories however other descriptors such as signal duration explained the results equally well materials within the same gross category were identified mainly on the basis of signal frequency overall poor support for the relevance of damping to material perception was found an analysis of the acoustical support for perfect material identification was carried out sufficient acoustical information for perfect performance was found thus procedural biases for the origin of the effects of size could be discarded pointing toward their cognitive rather than methodological nature identification performance was explained in terms of the regularities of the everyday acoustical environment

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

wave propagation in nonlinear and hysteretic media a numerical study abstract this paper considers the problem of one dimensional wave propagation in nonlinear hysteretic media the constitutive law in the media is prescribed by an integral relationship based on the duhem model of hysteresis it is found that the well known nonlinear elastic stress strain relationship is a special case of this integral relationship it is also shown that the stress strain relationship from the mccall and guyer model of hyesteretic materials can also be derived from this integral stress strain relationship the first part of this paper focuses on a material with a quadratic stress strain relationship where the initial value problem is formulated into a system of conservation laws analytical solutions to the riemann problem are obtained by solving the corresponding eigenvalue problem and serve as reference for the verification and illustration of the accuracy obtained using the applied numerical scheme proposed by kurganov and tadmor the second part of this research is devoted to wave propagation in hysteretic media several types of initial excitations are presented in order to determine special characteristics of the wave propagation due to material nonlinearity and hysteresis the results of this paper demonstrate the accuracy and the robustness of this numerical scheme to analyze wave propagation in nonlinear materials

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

matching measure benjamini schramm convergence and the monomer dimer free energy we define the matching measure of a lattice l as the spectral measure of the tree of self avoiding walks in l we connect this invariant to the monomer dimer partition function of a sequence of finite graphs converging to l this allows us to express the monomer dimer free energy of l in terms of the matching measure exploiting an analytic advantage of the matching measure over the mayer series then leads to new rigorous bounds on the monomer dimer free energies of various euclidean lattices while our estimates use only the computational data given in previous papers they improve the known bounds significantly

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

normal generation and ell 2 betti numbers of groups the normal rank of a group is the minimal number of elements whose normal closure coincides with the group we study the relation between the normal rank of a group and its first ell 2 betti number and conjecture the inequality beta 1 2 g le mathrm nrk g 1 for torsion free groups the conjecture is proved for limits of left orderable amenable groups on the other hand for every n ge 2 and every varepsilon 0 we give an example of a simple group q with torsion such that beta 1 2 q ge n 1 varepsilon these groups also provide examples of simple groups of rank exactly n for every n ge 2 existence of such examples for n 3 was unknown until now

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

mathematical models for hysteresis the various existing classical models for hysteresis preisach ishlinskii duhem madelung are surveyed as well a more modern treatments by contemporary workers the emphasis is on a clear mathematical description of the formulation and properties of each model in addition the authors try to make the reader aware of the many open questions in the study of hysteresis

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

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

group ring elements with large spectral density given delta 0 we construct a group g and a group ring element s in mathbb z g such that the spectral measure mu of s fulfils mu 0 varepsilon frac c log varepsilon 1 delta for small varepsilon in particular the novikov shubin invariant of any such s is 0 the constructed examples show that the best known upper bounds on mu 0 varepsilon are not far from being optimal

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

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

level dominance for the detection of changes in level distribution in sound streams sound streams were generated by randomly choosing the levels of tone pips from two different distributions a and b of the 18 tone pips the first nine were drawn from distribution a and the second nine from distribution b or the opposite the listeners task was to indicate order a b or b a in two conditions the a and b distributions differed in mean condition 1 or variance condition 2 in contrast to an ideal observer listeners strategies were consistent across the two conditions analyses suggest that listeners relied primarily on the more intense tone pips in making their decisions

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

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

on turing dynamical systems and the atiyah problem main theorems of the article concern the problem of atiyah on possible values of l 2 betti numbers it is shown that all non negative real numbers are l 2 betti numbers and that many for example all non negative algebraic real numbers are l 2 betti numbers of simply connected manifolds with respect to a free cocompact action also an explicit example is constructed which leads to a simply connected manifold with a transcendental l 2 betti number with respect to an action of the threefold direct product of the lamplighter group mathbb z 2 mathbb z wr mathbb z the main new idea is embedding turing machines into integral group rings the main tool developed generalizes known techniques of spectral computations for certain random walk operators to arbitrary operators in groupoid rings of discrete measured groupoids

hyperlinearity essentially free actions and l2 invariants the sofic property we prove that connes embedding conjecture holds for the von neumann algebras of sofic groups that is sofic groups are hyperlinear hence we provide some new examples of hyperlinearity we also show that the determinant conjecture holds for sofic groups as well we introduce the notion of essentially free actions and amenable actions and study their properties

auditory streaming of tones of uncertain frequency level and duration stimulus uncertainty is known to critically affect auditory masking but its influence on auditory streaming has been largely ignored standard aba aba tone sequences were made increasingly uncertain by increasing the sigma of normal distributions from which the frequency level or duration of tones were randomly drawn consistent with predictions based on a model of masking by lutfi gilbertson chang and stamas j acoust soc am 134 2160 2170 2013 the frequency difference for which a and b tones formed separate streams increased as a linear function of sigma in tone frequency but was much less affected by sigma in tone level or duration

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

discrimination of frequency variance for tonal sequences real world auditory stimuli are highly variable across occurrences and sources the present study examined the sensitivity of human listeners to differences in global stimulus variability in a two interval forced choice task variance discrimination was measured using sequences of five 100 ms tone pulses the frequency of each pulse was sampled randomly from a distribution that was gaussian in logarithmic frequency in the non signal interval the sampled distribution had a variance of stan2 while in the signal interval the variance of the sequence was sig2 with sig2 stan2 the listener s task was to choose the interval with the larger variance to constrain possible decision strategies the mean frequency of the sampling distribution of each interval was randomly chosen for each presentation psychometric functions were measured for various values of stan2 although the performance was remarkably similar across listeners overall performance was poorer than that of an ideal observer io which perfectly compares interval variances however like the io weber s law behavior was observed with a constant ratio of sig2 stan2 to stan2 yielding similar performance a model which degraded the io with a frequency resolution noise and a computational noise provided a reasonable fit to the real data

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

discrimination of the spectral density of multitone complexes spectral density d defined as the number of partials comprising a sound divided by its bandwidth has been suggested as cue for the identification of the size and shape of sound sources few data are available however on the ability of listeners to discriminate differences in spectral density in a cue comparison forced choice procedure with feedback three highly practiced listeners discriminated differences in the spectral density of multitone complexes varying in bandwidth w 500 1500 hz center frequency fc 500 2000 hz and number of tones n 6 31 to reduce extraneous cues for discrimination the overall level of the complexes was roved and the frequencies were drawn at random uniformly over a fixed bandwidth and center frequency for each presentation psychometric functions were obtained relating percent correct discrimination to d in each condition for d 0 02 hz 1 they increased with d

two dimensional wave propagation in an elastic half space with quadratic nonlinearity a numerical study this study investigates two dimensional wave propagation in an elastic half space with quadratic nonlinearity the problem is formulated as a hyperbolic system of conservation laws which is solved numerically using a semi discrete central scheme these numerical results are then analyzed in the frequency domain to interpret the nonlinear effects specifically the excitation of higher order harmonics to quantify and compare the nonlinearity of different materials a new parameter is introduced which is similar to the acoustic nonlinearity parameter for one dimensional longitudinal waves by using this new parameter it is found that the nonlinear effects of a material depend on the point of observation in the half space both the angle and the distance to the excitation source furthermore it is illustrated that the third order elastic constants have a linear effect on the acoustic nonlinearity of a material

successive versus simultaneous comparison in auditory intensity discrimination the ability to discriminate between two brief sounds having identical frequency components but differing in the intensity of one or more of the components is studied the stimulus manipulations include randomizing the overall intensity of the sounds varying the number and spacing of the components and varying the interval of time between the sounds the results from the experiment in which interstimulus interval is manipulated clearly support a profile analysis mechanism that computes two rough spectral analyses stores a classification of these spectra in memory and compares the two stores this profile mechanism involves a simultaneous comparison of different components of the complex some remote from the signal frequency rather than a successive comparison of the difference in intensity at the signal frequency the simultaneous comparison process is more sensitive when the profile is composed of many components spaced over a wide frequency range

sofic mean length abstract given a length function l on the r modules of a unital ring r for each sofic group we define a mean length for every locally l finite r module relative to a bigger r module we establish an addition formula for the mean length we give two applications the first one shows that for any unital left noetherian ring r r is stably direct finite the second one shows that for any z module m the mean topological dimension of the induced action on the pontryagin dual of m coincides with the von neumann luck rank of m

spectral and temporal cues for perception of material and action categories in impacted sound sources in two experiments similarity ratings and categorization performance with recorded impact sounds representing three material categories wood metal glass being manipulated by three different categories of action drop strike rattle were examined previous research focusing on single impact sounds suggests that temporal cues related to damping are essential for material discrimination but spectral cues are potentially more efficient for discriminating materials manipulated by different actions that include multiple impacts e g dropping rattling perceived similarity between material categories across different actions was correlated with the distribution of long term spectral energy spectral centroid similarity between action categories was described by the temporal distribution of envelope energy temporal centroid or by the density of impacts moreover perceptual similarity correlated with the pattern of confusion in categorization judgments listeners tended to confuse materials with similar spectral centroids and actions with similar temporal centroids and onset densities to confirm the influence of these different features spectral cues were removed by applying the envelopes of the original sounds to a broadband noise carrier without spectral cues listeners retained sensitivity to action categories but not to material categories conversely listeners recognized material but not action categories after envelope scrambling that preserved long term spectral content

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

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

sample discrimination of frequency differences with distracters this study examined the effect of the type and frequency range of remote frequency distracters on sample discrimination of frequency differences sd f for baseline sd f conditions normal hearing listeners judged frequency differences between pairs of target tones drawn from gaussian frequency distributions near 2000 hz in experiment 1 the distracters were pairs of random frequency tones fixed frequency tones or noise bands with one distracter above and one below the target region three frequency separations of targets and distracters were tested none overlapping the target region effects of fixed frequency or noise band distracters were small compared to that of random frequency distracters which drove performance to near chance in experiment 2 dominance of the low frequency distracter was supported by the effects of changing distracter level by presenting only the higher or lower frequency distracter and by the pattern of weights derived from trial by trial responses performance recovered only when the lower frequency distracter was attenuated 40 50 db relative to the targets in experiment 3 all stimulus distributions were shifted 2 octaves higher in frequency the stronger influence of the distracter frequency below the target remained the results demonstrate the importance of both stimulus variability and frequency relationships in the interaction of targets and distracters for sd f

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

sample discrimination of frequency by hearing impaired and normal hearing listeners in a multiple observation sample discrimination experiment normal hearing nh and hearing impaired hi listeners heard two multitone complexes each consisting of six simultaneous tones with nominal frequencies spaced evenly on an erbn logarithmic scale between 257 and 6930hz on every trial the frequency of each tone was sampled from a normal distribution centered near its nominal frequency in one interval of a 2ifc task all tones were sampled from distributions lower in mean frequency and in the other interval from distributions higher in mean frequency listeners had to identify the latter interval decision weights were obtained from multiple regression analysis of the between interval frequency differences for each tone and listeners responses frequency difference limens an index of sensorineural resolution and decision weights for each tone were used to predict the sensitivity of different decision theoretic models results indicate that low frequency tones were given much greater perceptu

sensory constraints on auditory identification of the material and geometric properties of struck bars a computational formula is derived for estimating the constraints limited auditory sensitivity imposes on auditory identification of the material and geometric properties of struck bars the formula combines a model of the transverse motion of the bar with empirical psychometric functions to map out null regions in the bar s physical parameter space where changes in the frequency amplitude and decay of partials are likely below threshold for detection parameters of the physical space include bar density young s modulus fluid and viscoelastic damping factors bar length and bar cross sectional area as related to bar shape and hollowness the formula is used to estimate the possible effect of limited sensitivity in past studies on the auditory identification of bar attributes the results suggest that sensitivity may indeed have played a role in some studies and that apparent discrepancies in results may be understood based on whether the predominant source of damping was internal or external to the bar the formula identifies conditions representing an expected bound on identification performance and thereby may be used to aid in the design of future studies for which the struck bar is the sound source of choice

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