correlation factors describing primary and spatial sensations of sound fields abstract the theory of subjective preference of the sound field in a concert hall is established based on the model of human auditory brain system the model consists of the autocorrelation function acf mechanism and the interaural crosscorrelation function iacf mechanism for signals arriving at two ear entrances and the specialization of human cerebral hemispheres this theory can be developed to describe primary sensations such as pitch or missing fundamental loudness timbre and in addition duration sensation which is introduced here as a fourth these four primary sensations may be formulated by the temporal factors extracted from the acf associated with the left hemisphere and spatial sensations such as localization in the horizontal plane apparent source width and subjective diffuseness are described by the spatial factors extracted from the iacf associated with the right hemisphere any important subjective responses of sound fields may be described by both temporal and spatial factors

on the stability margin of networked dynamical systems this paper is concerned with the stability gain and phase margin of networked dynamical systems e g vehicles in formation each of which has access to the state of its neighbors and subsequently uses a state feedback gain f for a certain global objective such as attitude synchronization here the network topology is directed and described by a generalized laplacian matrix l an individual dynamical system can adopt its own state feedback control law such as a linear quadratic regulator controller for an ample stability margin but it may lose the stability margin to a great extent when the same control strategy utilizing relative state information is used after being interconnected with other dynamical systems this paper reveals and elaborates upon the following four facts first the stability margin after interconnection is quantified via the minimum singular value of a frequency dependent matrix made up of f and l second the stability margin of a networked dynamical system having a pole at the origin is at most the inverse of the zero eigenvalue sensitivity of l third there exists an upper bound of the stability margin that has a computational merit and asymptotically converges to the exact margin with respect to network size probability of link existence and control gain in a random network setting and finally l can be designed to maximize the stability margin numerical examples are provided to demonstrate the elaboration

distributed static output feedback control for state synchronization in networks of identical lti systems this paper studies state synchronization of multi agent systems with disturbances using distributed static output feedback opfb control the bounded l 2 gain synchronization problem using distributed static opfb is defined and solved the availability of only output measurements restricts the local controls design while the communication graph topology restricts global information flow among the agents it is shown here that these two types of restriction can be dealt with in a symmetric manner and lead to two similar conditions guaranteeing the existence of bounded l 2 gain static opfb one condition is on the output measurement matrix on a local scale and the other on the graph laplacian matrix on a global scale under additional conditions a distributed two player zero sum game using static opfb is also solved and leads to distributed nash equilibrium on the communication graph as a special case the static opfb globally optimal control is given a new class of digraphs satisfying the above condition on the graph laplacian is studied the synchronizing region for distributed static opfb control is exposed and found to be conical different than the infinite right half plane synchronizing region for distributed state feedback

subjective diffuseness of music signals convolved with binaural impulse responses abstract the spatial impression of sound in a hall can be quantified using sound field factors such as the interaural cross correlation coefficient iacc calculated from binaural impulse response bir henceforth denoted by iaccir the subjective diffuseness for the listener is a spatial attribute which depends on factors associated both with the source signal and with the actual sound field and is quantified using the iacc of the signal received by the listener henceforth denoted by iaccsr therefore the subjective diffuseness in a given hall may change with the music the aims of this study are to estimate the iaccsr from the iaccir and the factors which is obtained from autocorrelation function acf of music signal and to evaluate the subjective diffuseness by these factors first the relationship between the iaccir and iaccsr was investigated second subjective diffuseness was measured by a psycho acoustical experiment as a result the iaccsr could be estimated from the iaccir of the bir and the effective duration e from the acf of music signal it was found that the effects of birs on subjective diffuseness could be evaluated by iaccir for almost all subjects while the effects of music signals could be evaluated by the e and the width of the peak at 0 w 0 of the acf

objective measures of listener envelopment this paper reports the results of subjective studies to determine objective predictors of perceived listener envelopment in concert halls subjects seated in an anechoic room were exposed to simulated sound fields that were expected to have varied listener envelopment as independent variables the reverberation time the early to late sound ratio the overall sound level and the angular distribution of the late arriving sound levels were varied all of these factors had statistically significant effects on perceived listener envelopment the results indicate however that the angular distribution of the late arriving sound and the overall level would have the largest effects in real concert halls thus listener envelopment depends on having strong lateral reflections arriving at the listener 80 ms or more after the direct sound several objective measures correlated significantly with listener envelopment however a new measure the late lateral sound level as measured using a figure of eight microphone was found to be both conceptually simple and a very good predictor of the perceived listener envelopment of the sound fields in this experiment

nonlinear response in evaluating the subjective diffuseness of sound fields tests were conducted to determine which horizontal reflection angles are most effective in stimulating subjective diffuseness for a listener in a room paired comparison tests were carried out where subjects were asked to judge in which of two sound fields they perceived more diffuseness results show that the most effective horizontal angle depends on the frequency of the one third octave band noise as is indicated by the interaural cross correlation the remarkable finding in this investigation is that the scale value of subjective diffuseness may be formulated in terms of the 3 2 power of the magnitude of interaural cross correlation iacc and that the scale value does not vary with the frequency of the bandpass noise source

coordination of multi agent systems on interacting physical and communication topologies abstract a new framework is given for coordination of multi agent systems that are interconnected by a physical coupling digraph the edges of this graph represent physical couplings between agents that are fixed due to dynamical interactions on top of the physical graph distributed control protocols are designed where the allowed communications between agents for control purposes are prescribed by a second fixed communication digraph the physical and communication digraphs are generally different and the combination of these two graphs forms a cyber physical system the interactions between physical and communication graphs are the focus of this paper we consider different interactions between two graphs including the case when their pinned laplacian commutes the case of the communication graph with diagonalizable pinned laplacian and the case of two general graphs moreover within each graph the relations between the agents can be either collaborative or antagonistic to capture this the theory of bipartite consensus is used coordination protocols for different cases are designed that are distributed with respect to the communication graph and overcome the detrimental effects of the signed physical graph the proposed control methods are illustrated by simulation examples

optimal design for synchronization of cooperative systems state feedback observer and output feedback this technical note studies synchronization of identical general linear systems on a digraph containing a spanning tree a leader node or command generator is considered which generates the desired tracking trajectory a framework for cooperative tracking control is proposed including full state feedback control observer design and dynamic output feedback control the classical system theory notion of duality is extended to networked systems it is shown that unbounded synchronization regions that achieve synchronization on arbitrary digraphs containing a spanning tree can be guaranteed by using linear quadratic regulator based optimal control and observer design methods at each node

numerical evidence of mixing in rooms using the free path temporal distribution the ergodic propriety of a room has strong effects on its reverberation if the room is ergodic the reverberation can be broken up in two steps a deterministic process followed by a stochastic one the late reverberation can be then modeled by a reverberation algorithm instead of more computationally consuming methods in this study the free path temporal distribution obtained by ray tracing is used as an indicator of the room s mixing the energetic average of the path lengths is computed at each time step ergodic rooms are thus characterized by rapidly convergent distributions the free path value becomes independent of time on the other hand path selection mechanism and orbits are observed in non ergodic rooms the transition time from the deterministic process to the stochastic one is also studied through the evaluation of the room s time constant it is shown that its value depends only on the mean free path and the boundaries scattering value an empirical expression is obtained which agrees well with simulations carried out in a concert hall this transition time from a deterministic model to a stochastic one can be used to speed up the acoustical predictions and auralizations in ergodic rooms

detection of static and dynamic changes in interaural correlation this study examines the relation between a static and a dynamic measure of interaural correlation discrimination 1 the just noticeable difference jnd in interaural correlation and 2 the minimum detectable duration of a fixed interaural correlation change embedded within a single noise burst of a given reference correlation for the first task jnds were obtained from reference interaural correlations of 1 1 and from 0 interaural correlation in either the positive or negative direction for the dynamic task duration thresholds were obtained for a brief target noise of 1 1 and 0 interaural correlation embedded in reference marker noise of 1 1 and 0 interaural correlation performance with a reference interaural correlation of 1 was significantly better than with a reference correlation of 1 similarly when the reference noise was interaurally uncorrelated discrimination was significantly better for a target correlation change towards 1 than towards 1 thus for both static and dynamic tasks interaural correlation discrimination in the positive range was significantly better than in the negative range using the two measures the length of a binaural temporal window was estimated its equivalent rectangular duration erd was approximately 86 ms and independent of the interaural correlation configuration

on the subjective responses based on the auditory brain model in relation to the factors extracted from the interaural cross correlation mechanism and the auto correlation mechanism of sound fields based on the auditory brain model for subjective responses the author investigated the relationship between several important subjective attributes of the sound field and the orthogonal factors that are extracted from both of the interaural cross correlation function and the autocorrelation function there are three significant findings 1 the apparent source width asw is described by two orthogonal spatial factors the iacc and the width of the interaural cross correlation function wiacc the scale value of asw is formulated by superpositioning two terms the 3 2 power of the iacc and the 1 2 power of the wiacc 2 the most preferred delay time of a single reflection for a cello soloist can be calculated by the amplitude of the reflection and the minimum value of the effective duration of the running autocorrelation function of the music motifs played by the cellist 3 from subjective preference tests by paired comparison method for different source locations on the stage in an actual concert

effects of frequency characteristics of reverberation time on listener envelopment spatial impression perceived in a listening space comprises at least two components one is auditory apparent source width asw and the other is listener envelopment lev both asw and lev are affected not only by temporal but also by spatial structures of reflections it has been clarified that asw for symphony music is significantly affected by low frequency components of source signals and reflections but not by their high frequency components the objective of this work is to investigate whether lev is affected by the frequency characteristics of source signals and reverberation sounds which are known to contribute to the creation of lev in this study three experiments were performed to clarify the effects of reverberation time rt and its frequency characteristics on lev in contrast to the case of asw the experimental results show that rts both at high and low frequencies affect lev

key node selection in minimum cost control of complex networks abstract finding the key node set that is connected with a given number of external control sources for driving complex networks from initial state to any predefined state with minimum cost known as minimum cost control problem is critically important but remains largely open by defining an importance index for each node we propose revisited projected gradient method extension r pgme in monte carlo scenario to determine key node set it is found that the importance index of a node is strongly correlated to occurrence rate of that node to be selected as a key node in monte carlo realizations for three elementary topologies erd s renyi and scale free networks we also discover the distribution patterns of key nodes when the control cost reaches its minimum specifically the importance indices of all nodes in an elementary stem show a quasi periodic distribution with high peak values in the beginning and end of a quasi period while they approach to a uniform distribution in an elementary cycle we further point out that an elementary dilation can be regarded as two elementary stems whose lengths are the closest and the importance indices in each stem present similar distribution as in an elementary stem our results provide a better understanding and deep insight of locating the key nodes in different topologies with minimum control cost

numerical simulations of piano strings i a physical model for a struck string using finite difference methods the first attempt to generate musical sounds by solving the equations of vibrating strings by means of finite difference methods fdm was made by hiller and ruiz j audio eng soc 19 462 472 1971 it is shown here how this numerical approach and the underlying physical model can be improved in order to simulate the motion of the piano string with a high degree of realism starting from the fundamental equations of a damped stiff string interacting with a nonlinear hammer a numerical finite difference scheme is derived from which the time histories of string displacement and velocity for each point of the string are computed in the time domain the interacting force between hammer and string as well as the force acting on the bridge are given by the same scheme the performance of the model is illustrated by a few examples of simulated string waveforms a brief discussion of the aspects of numerical stability and dispersion with reference to the proper choice of sampling parameters is also included

spatial mapping of intracranial auditory events for various degrees of interaural coherence the broadening and splitting of auditory events in dichotic listening conditions with various degrees of interaural coherence are discussed by using a psychoacoustical mapping method it has been possible to observe broadening and splitting for a wide range of stimuli including broadband pink noise as well as bandpass noises with different relative bandwidths and center frequencies the spatial extents of the auditory events decrease with increasing center frequencies for bandpass stimuli of constant relative bandwidth the number of partial events for bandpass stimuli decreases with increasing degrees of interaural coherence these results are for example of interest with respect to auditory spaciousness in architectural acoustics

interaural cross correlation lateral fraction and low and high frequency sound levels as measures of acoustical quality in concert halls interaural cross correlation coefficient iacc and lateral efficiency lf as correlates with subjective ratings see companion paper l beranek determination of categories of acoustical quality in concert halls this session were analyzed to make iacc sensitive to quality ratings a multi octave band average was developed based on blauert et al acustica 59 292 and on a subjectively derived set of equal asw contours that showed the 0 5 1 0 and 2 0 octave bands to be of equal importance this iacc3 was divided into iacce3 integrated over first 0 08 s after arrival of the direct sound and iaccl 3 same 0 08 to 1 s subjective judgments were also made to determine the effects of increased sound levels of symphonic music at frequencies above and below 355 hz on apparent source width asw iacce3 and gl both appear important for determining asw the measured quantity 1 iacce3 alone was found to separate the 17 concert halls of this study for which iacc data were available into the same three category groups as those determined from the interviews lateral fraction lf was found to extend over a very small range and there were so many overlaps among halls when separation into three rating groups was attempted that lf was judged not to be suitable for rating acoustical quality

pinning control of scale free dynamical networks abstract recently it has been demonstrated that many large complex networks display a scale free feature that is their connectivity distributions have the power law form in the present work control of a scale free dynamical network by applying local feedback injections to a fraction of network nodes is investigated the specifically and randomly pinning schemes are considered the specifically pinning of the most highly connected nodes is shown to require a significantly smaller number of local controllers as compared to the randomly pinning scheme the method is applied to an array of chua s oscillators as an example

a new definition of boundary point between early reflections and late reverberation in room impulse responses the early reflections in the room impulse response are usually defined as those observed within the initial 80ms after the arrival of the direct sound after which time the sound field is called reverberant this number was chosen from measurements of other functions in a limited number of halls in order to give an objective foundation to this time separation and to establish a physical indicator for it a new method is proposed that defines a transition time tl which is the time at which the energy correlation between the direct plus initial sound and the subsequent decaying sound first achieves a specified low value for various halls this number is shown and its relevance as a new parameter is discussed

energy conserving schemes for the simulation of musical instrument contact dynamics abstract collisions are an innate part of the function of many musical instruments due to the nonlinear nature of contact forces special care has to be taken in the construction of numerical schemes for simulation and sound synthesis finite difference schemes and other time stepping algorithms used for musical instrument modelling purposes are normally arrived at by discretising a newtonian description of the system however because impact forces are non analytic functions of the phase space variables algorithm stability can rarely be established this way this paper presents a systematic approach to deriving energy conserving schemes for frictionless impact modelling the proposed numerical formulations follow from discretising hamilton s equations of motion generally leading to an implicit system of nonlinear equations that can be solved with newton s method the approach is first outlined for point mass collisions and then extended to distributed settings such as vibrating strings and beams colliding with rigid obstacles stability and other relevant properties of the proposed approach are discussed and further demonstrated with simulation examples the methodology is exemplified through a case study on tanpura string vibration with the results confirming the main findings of previous studies on the role of the bridge in sound generation with this type of string instrument

cooperative optimal control for multi agent systems on directed graph topologies this note brings together stability and optimality theory to design distributed cooperative control protocols that guarantee consensus and are globally optimal with respect to a positive semi definite quadratic performance criterion a common problem in cooperative optimal control is that global optimization problems generally require global information which is not available to distributed controllers optimal control for multi agent systems is complicated by the fact that the communication graph topology interplays with the agent system dynamics in the note we use an inverse optimality approach together with partial stability to consider the cooperative consensus and pinning control agents with identical linear time invariant dynamics are considered communication graphs are assumed directed and having fixed topology structured quadratic performance indices are derived that capture the topology of the graph which allows for global optimal control that is implemented using local distributed protocols a new class of digraphs is defined that admits a distributed solution to the global optimal control problem namely those with simple graph laplacian matrices

comparison of concert hall measurements of spatial impression two different types of measures of spatial impression lateral energy fractions and interaural cross correlations were measured at a number of locations in 14 different concert halls the mean and range of the hall average values of these quantities give an indication of typical conditions to be expected in other larger concert halls comparisons of hall average values of the two types of quantities showed them to be significantly related at medium and lower frequencies in good agreement with theoretical expectations individual position measurements were less well related and showed that other factors had a major influence on the individual position measurements in some halls the two types of quantities varied quite differently with increasing source receiver distance at a particular seat location the two types of measures cannot always give similar indications of expected spatial impression calculating hall average values from a small number of measurement locations is shown to introduce significant errors

relation of acoustical parameters with and without audiences in concert halls and a simple method for simulating the occupied state six acoustical parameters rt edt c80 d g and iacce3 were measured with and without audiences at six concert and opera halls the range in volume was 3576 to 15 300 m3 the upholstering of the chairs ranged from light to heavy comparisons were made of these parameters before and after addition of the audience the conclusions are 1 predictions of the occupied reverberation times were found inaccurate when the measured unoccupied values were adjusted by using unoccupied versus occupied data for the chairs obtained in a reverberation chamber if diffuse sound conditions are assumed it would be possible to predict edt c80 d and g from the occupied rt values whether measured or calculated as above such predictions are also inaccurate 2 plots of the six parameters i e unoccupied versus occupied values are nearly straight lines with correlations generally in excess of 0 9 these high correlations permit the use of empirical equations to predict these parameters for occupied halls from meas

piano string excitation vi nonlinear modeling accurate modeling of the piano string hammer interaction requires that the nonlinearity of the force displacement relation for the hammer be recognized and included two models that accomplish this with numerical integration are described and sample results are presented the first model is valid for a perfectly flexible string where nondispersive traveling waves can be conveniently followed with a digital delay line the second model uses standing waves instead to describe the vibrations of a stiff string with the stiffness itself justifying truncation of what would otherwise be a poorly converging normal mode summation predictions with these models give significantly better agreement with data than did previous calculations with completely linear models

perception of coloration in sound fields in relation to the autocorrelation function the perception of coloration was investigated in a sound field composed of a strong primary sound and a time shifted t1 weak sound as source signal a continuous bandpass noise was used subjects judged the sensation level of the weak sound in comparison to the situation in which only the primary sound was presented the results are interpreted by means of the autocorrelation function of the bandpass noise signal

discrimination of interaural envelope correlation and its relation to binaural unmasking at high frequencies listeners sensitivity to interaural correlation of the envelope of high frequency waveforms and whether such sensitivity might account for detectability in a masking level difference paradigm were assessed thresholds of interaural envelope decorrelation from a reference correlation of 1 0 were measured for bands of noise centered at 4 khz and bandwidths ranging from 50 1600 hz decorrelation of the envelope was achieved by mixing two independent narrow band noises separately with the same listeners noso and nos detection thresholds were measured for maskers of the same center frequency and bandwidths for bandwidths of noise up to about 400 hz listeners were similarly sensitive to interaural decorrelation in both types of task however for bandwidths greater than 400 hz or so while sensitivity in the discrimination task was unaffected sensitivity was reduced in the nos conditions additional data suggested that listeners were able to maintain their sensitivity independent of bandwidth in the discrimination task by focusing on binaural information within select spectral regions of the stimuli

consensus rate regulation for general linear multi agent systems under directed topology recently optimization in distributed multi agent coordination has been studied concerning convergence speed the optimal convergence speed of consensus for multi agent systems consisting of general linear node dynamics is still an open problem this paper aims to design optimal distributed consensus protocols for general identical linear continuous time cooperative systems which not only minimize some local quadric performances but also regulate the consensus rate including convergence rate and damping rate for the multi agent systems the graph topology is assumed to be fixed and directed the inverse optimal design method is utilized and the resulting optimal distributed protocols place part of close loop poles of the global disagreement systems at specified locations asymptotically while the remains far from the imaginary axis enough it turns out that for the identical linear continuous time multi agent systems the convergence speed has no upper bound the main advantages of the developed method over the lqr design method are that the resulting multi agent systems can achieve specified consensus rate asymptotically and the resulting protocols have the whole right half complex plane as its asymptotical consensus region numerical examples are given to illustrate the effectiveness of the proposed design procedures

parameter fitting for piano sound synthesis by physical modeling a difficult issue in the synthesis of piano tones by physical models is to choose the values of the parameters governing the hammer string model in fact these parameters are hard to estimate from static measurements causing the synthesis sounds to be unrealistic an original approach that estimates the parameters of a piano model from the measurement of the string vibration by minimizing a perceptual criterion is proposed the minimization process that was used is a combination of a gradient method and a simulated annealing algorithm in order to avoid convergence problems in case of multiple local minima the criterion based on the tristimulus concept takes into account the spectral energy density in three bands each allowing particular parameters to be estimated the optimization process has been run on signals measured on an experimental setup the parameters thus estimated provided a better sound quality than the one obtained using a global energetic criterion both the sound s attack and its brightness were better preserved this quality gain was obtained for parameter values very close to the initial ones showing that only slight deviations are necessary to make synthetic sounds closer to the real ones

frequency dependency of the relationship between perceived auditory source width and the interaural cross correlation coefficient for time invariant stimuli previous research has indicated that the relationship between the interaural cross correlation coefficient iacc of a narrow band sound and its perceived auditory source width is dependent on its frequency however this dependency has not been investigated in sufficient detail for researchers to be able to properly model it in order to produce a perceptually relevant iacc based model of auditory source width a series of experiments has therefore been conducted to investigate this frequency dependency in a controlled manner and to derive an appropriate model three main factors were discovered in the course of these experiments first the nature of the frequency dependency of the perceived auditory source width of stimuli with an iacc of 1 was determined and an appropriate mathematical model was derived second the loss of perceived temporal detail at high frequencies caused by the breakdown of phase locking in the ear was found to be relevant and the model was modified accordingly using rectification and a low pass filter finally it was found that there was a further frequency dependency at low frequencies and a method for modeling this was derived the final model was shown to predict the experimental data well

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

analysis of sabine and eyring equations and their application to concert hall audience and chair absorption historically two equations have been used for predicting reverberation times sabine and eyring a precise means is presented for determining eyring absorption coefficients eyring when the sabine coefficients sabine are known and vice versa thus either formula can be used provided the absorption coefficients for the sabine formula are allowed to exceed 1 0 the sabine formula is not an approximation to the eyring equation and is not a shortcoming given low reverberation times the ratio of sabine to eyring may become greater than 2 0 it is vital that for correct prediction of reverberation times the absorption coefficients used in either formula must have been determined in spaces similar in size and shape with similar locations of high absorption audience areas and with similar reverberation times for concert halls it is found that when the audience area fully occupied and midfrequency reverberation time are postulated the hall volume is directly proportional to the audience absorpt

the influence of late arriving energy on spatial impression new subjective experiments using sound fields simulated in an anechoic room confirm that spatial impression in concert halls is composed of at least two distinct aspects apparent source width and listener envelopment previously published research has shown that apparent source width is related to the relative level of early lateral reflections this new work demonstrates that listener envelopment is related to the level direction of arrival and temporal distribution of late arriving reflections it is further shown that increased amounts of listener envelopment decrease the subject s sensitivity to changes in the apparent source width of the sound field listener envelopment is related to objective acoustical measures and the implications for concert hall design are discussed

on the relationship between the autocorrelation function of continuous brain waves and the subjective preference of the sound field in change of the iacc this study analyzed the range of waves 8 13 hz of continuous brain waves cbw and compared them with the scale value of the subjective preference of the sound field in a change of the interaural cross correlation function iacc ando concert hall acoustics springer verlag heidelberg 1985 the source signal was sinfonietta opus 48 third movement composed by arnold the scale value of the subjective preference and the cbws to a paired stimuli i e reference stimuli iacc 1 0 and test stimuli iacc 0 3 or 0 65 which were presented alternatively were compared it is found that the value of the effective duration e of the autocorrelation function acf of the waves from only the right hemisphere corresponds well to the subjective preference it is considered therefore that e is an objective measure reflecting the subjective preference chen and ando unpublished

detection of early reflections using multifractals early reflections are not always strong and sparse enough on the timeline to be easily identified when reviewing the impulse response diagram this paper presents a method for the detection of early reflection in the room impulse response using multifractals the proposed method uses the distribution of holder s exponent calculated for the acoustic impulse response for early reflection detection the obtained results confirm the assumption that impulse response signals exhibit self similarity and that fractal theory can be used for the detection of early reflections