Monika Rychtarikova - Academia.edu (original) (raw)

Papers by Monika Rychtarikova

The Journal of the Acoustical Society of America, 2015

Acoustic scattering audibility thresholds are needed for the efficient design of performance spac... more Acoustic scattering audibility thresholds are needed for the efficient design of performance spaces and to increase the accuracy of geometric room acoustic models. This paper focuses on the evaluation of the perceptual thresholds of the scattering coefficient through listening tests in simulated concert halls. It also deals with an investigation on the sensitivity of room acoustic parameters to scattering coefficients. A rectangular concert hall has been simulated with three prediction models, in which scattering coefficients of 0.1, 0.3, 0.5, 0.6, 0.7, and 0.9 were applied to the ceiling and walls in six different configurations. The analysis was performed comparing the results of the three-alternative forced choice listening tests and considering the objective parameters T30, early decay time (EDT), C80, and G. An increase in EDT and a decrease in C80 have been observed for increasing scattering coefficient values for all three types of software, while no similar trend was observed for the other parameters. The perceptual evaluation has shown that differences of ∼0.4, relative to an anchor value of 0.9 of the scattering coefficient, were perceived in the listening test conducted with one of the three kinds of software, while no clear differences in auralizations were perceived with the other two kinds.

From the acoustical point of view, spaces like open plan offices, restaurants or railway stations... more From the acoustical point of view, spaces like open plan offices, restaurants or railway stations can be understood as multi-source environments. The acoustical quality depends on the situation. Sometimes, speech privacy is of interest, in other cases speech intelligibility is desired, but in any case too high sound levels should be avoided. Higher sound levels can be acceptable in a railway station or a students' restaurant, but in an open plan office, the global masking noise is preferably lower than (50?)48 dB(A). In many ray-tracing programs an auralization method is incorporated.. In our research this method is used to demonstrate the acoustical quality in an office space to architects and future users. In the example of this paper a U-shaped open plan office is analyzed. Measured and simulated results are compared and the influence of several architectural set-ups is expressed in acoustical quantities and is made audible. The result is an interactive demon-stration set-up ...

This paper presents proposal of the methodology for the multidisciplinary assessment of urban pub... more This paper presents proposal of the methodology for the multidisciplinary assessment of urban public places which can be understood as an initial steps in territorial development policies on the scale of design and renovation of urban public space towards sustainable cities. Proposed method is based on transversal actions between different research fields, such a urban density, mobility, microclimate and pollution, vegetation and biodiversity, artificial lighting, water, acoustics and users, summarized and evaluated in a "transversality matrix". Our network deals with the problematic of public space on a national scale as it includes four interdisciplinary teams from all three regions of Belgium. This research is financed by the Belgian Federal Government (SPP-Politique Scientifique Fédérale) through the project "Development of the Urban Public Spaces Towards Sustainable Cities" (DRUPSSuC).

The scattering coefficient is one of the most important input parameters in room acoustics simula... more The scattering coefficient is one of the most important input parameters in room acoustics simulations. Together with the absorption coefficient they belong to the main descriptors of interior surface properties in a calculation process based on ray or radiosity method algorithms. This contribution deals with the comparison of three predicting software and objective assessment of scattered sound in the example of a virtual concert hall. The influence of scattered sound on the objective room acoustical parameters like T30, EDT, C80, D50 and G, is investigated. Six different alternatives were simulated, where scattering coefficient values s = 10, 30, 50, 60, 70 and 90% respectively, were applied to the interior surfaces of the ceiling, side and rear walls. Analysis has been performed by studying the results of objective room acoustical parameters predicted by simulations done with the software Odeon® 10.1, Catt-Acoustic® v 8.0. and Raven.

This contribution deals with the comparison of three prediction software, and objective and subje... more This contribution deals with the comparison of three prediction software, and objective and subjective assessment of scattered sound in the example of a virtual concert hall. The influence of scattered sound on the objective room acoustical parameters, like T30, EDT, C80, D50 and G, is investigated. Six different alternatives were simulated, where scattering coefficients values s = 10, 30, 50, 60, 70 and 90 % respectively were applied to the interior surfaces of the ceiling, side and rear walls. Analysis has been performed by comparing the results of objective room acoustical parameters predicted by simulations done in the software Odeon® 10.1, Catt-Acoustic® v 8.0. and Raven on one hand, and by investigation of subjective perception of scattered sound on the other hand. Listening tests applying the 3AFC method were performed, with stimuli presented to subjects via headphones by using signals auralized in one of the software (Odeon® 10.1).

Known in the past for its spectacular acoustic characteristics, the ancient theatre keeps today a... more Known in the past for its spectacular acoustic characteristics, the ancient theatre keeps today an important role as a modern stage: during the summer season many important theatrical events are organized in the frame of its ancient ruins, keeping alive a tradition that attracts people all around the world. But, without doubts, the actual conditions for the audience are deeply changed, affected by “modern” noises and damaged situation of the theatre itself. The insertion of the scenery elements has also to be considered as a variable that can modify the sound propagation in the theatre, with better or maybe worst results. In this article a research conducted on the acoustic perception of the audience of the Greek theatre of Syracuse is presented. A parametric study realized through a technical software (Odeon ® version 12.1) has been performed considering different scenery conditions, from the empty theatre and by adding different scenic elements to evaluate their influence on passi...

The complex sound field in performance spaces, characterized by multiple sound reflections from v... more The complex sound field in performance spaces, characterized by multiple sound reflections from various surfaces with different absorptive and diffusive characteristics, makes it difficult to deduce the effect of the single interior surface on the room impulse response. In order to obtain more knowledge on this topic, laboratory experiments were performed in a semi-anechoic room. Three different conditions were studied by monaural and binaural room impulse response measurements. Three types of surfaces with different absorptive and diffusive characteristics (flat surface and two differently absorbing concrete blocks with the same geometrical pattern) were placed on the floor during the experiments. The measurements were performed at the same distance from the surface sample at three different distances from the source position. Moreover, for each microphone position eight different orientations of the artificial head were considered. The monaural and binaural impulse responses have ...

Inclusive design is increasingly receiving attention from researchers and educators in architectu... more Inclusive design is increasingly receiving attention from researchers and educators in architecture and urban planning. Often, however, it is associated with improvement of living environments for people with reduced mobility. The rapidly growing number of older persons who suffer from reduced visual abilities, together with people who are visually impaired represent a considerable percentage of the population. This group raises new questions not only for the medical sector, but also for architectural design and acoustics, where the currently used normative values are optimized for people with “normal” visual abilities. This article discusses questions related to perception of sound and soundscape by people with a visual impairment by combining (1) findings about their superior ability in auditory perception from objective listening test experiments, magnetic resonance imaging and positron emission tomography with (2) insights gained through indepth interviews with and testimonies w...

This paper reports on the application of a recently developed deterministic prediction technique ... more This paper reports on the application of a recently developed deterministic prediction technique called the Wave Based Method (WBM) for the analysis of an interior room acoustics problem. The WBM has been developed as an alternative simulation technique for steady-state dynamic problems. It is based on a Trefftz approach in that exact solution functions of the governing differential equation are used as underlaying shape functions. Its superior convergence rate and lower computational load as compared to other deterministic methods such as the finite element method and the boundary element method, make it applicable also for mid-frequency analysis as has been reported already for various mechanical applications. In this paper, the WBM is applied for the acoustic analysis of an L-shaped room, and prediction results are compared with Fast Multipole BEM predictions, ray tracing results and measurements.

Journal of Sound and Vibration, 2015

ABSTRACT Structural details and workmanship can cause considerable differences in sound insulatio... more ABSTRACT Structural details and workmanship can cause considerable differences in sound insulation properties of timber frame partitions. In this study, the influence of panel fastening is investigated experimentally by means of standardized sound reduction index measurements, supported by detailed scanning laser Doppler vibrometry. In particular the effect of the number of screws used to fasten the panels to the studs, and the tightness of the screws, is studied using seven different configurations of lightweight timber frame building elements. In the frequency range from 300 to 4000 Hz, differences in the weighted sound reduction index RW as large as 10 dB were measured, suggesting that the method of fastening can have a large impact on the acoustic performance of building elements. Using the measured vibrational responses of the element, its acoustic radiation efficiency was computed numerically by means of a Rayleigh integral. The increased radiation efficiency partly explains the reduced sound reduction index. Loosening the screws, or reducing the number of screws, lowers the radiation efficiency, and significantly increases the sound reduction index of the partition.

Journal of Sound and Vibration, 2015

ABSTRACT This paper introduces a methodology that makes use of laser Doppler vibrometry to assess... more ABSTRACT This paper introduces a methodology that makes use of laser Doppler vibrometry to assess the acoustic insulation performance of a building element. The sound power radiated by the surface of the element is numerically determined from the vibrational pattern, offering an alternative for classical microphone measurements. Compared to the latter the proposed analysis is not sensitive to room acoustical effects. This allows the proposed methodology to be used at low frequencies, where the standardized microphone based approach suffers from a high uncertainty due to a low acoustic modal density.

Applied Acoustics, 2015

ABSTRACT A global estimator of the uncertainty of the average frequency response function in mult... more ABSTRACT A global estimator of the uncertainty of the average frequency response function in multi-channel spectral analysis measurements is proposed. The proposed global estimator is a generalization of the random error estimator of the frequency response function magnitude of a single-input–single-output system. In principle, the signal-to-noise ratio (and thus the quality of the frequency response function estimation) is increasing with increasing number of averages M , according to M. However, in the situation that, for practical reasons, there is a maximum imposed upon the total measurement time TmaxTmax, it is clear that there is a trade-off between the number of averages M and the record length T (s) that is used to obtain an estimate of a single-average-frequency-response-function. There is a choice between a few long records or many short records, with the requirement that, assuming zero overlap, the number of averages M times the record length T may not exceed the total available measurement time, i.e. M×T⩽TmaxM×T⩽Tmax. In addition to the existence of such an optimum, a minimum record length is required as well which is related to the reverberation time of the system. The newly proposed global estimator is used to determine the optimal record length of a multi-channel system, such that a minimum error of the average frequency response function is obtained. It is also shown by experimental results that indeed the minimum allowable record length is related to the reverberation time of the system being measured.

Building Acoustics, 2014

ABSTRACT Acoustic scattering has become an important input parameter in geometric models, and in ... more ABSTRACT Acoustic scattering has become an important input parameter in geometric models, and in research concerning the enhancement of auralized sound. This contribution deals with a comparison of four scaled prediction models of the same concert hall and a study of scattering coefficient prominence in simulations, while the size of the concert hall doubled. The hall has is fan shaped with an aspect ratios of about 4.5:2.8:1 and has typical auditorium features, such as a stage and a raked audience area. The influence of a volume scale-factor on the scattered sound effects on the prediction of the objective room acoustic parameters, that is, EDT, C80, D50, LF80 and G, has been investigated. Five different alternatives, in which scattering coefficient percentage values of 10, 30, 50, 70, and 90%, respectively, were applied separately and combined to the interior surfaces of the ceiling, side and rear walls, have been simulated. An analysis has been performed studying the results of the objective room acoustical parameters predicted, through simulations carried out with two kinds of software: Odeon 11.00 and CATT-Acoustic v 8.0.

Applied Acoustics, 2015

ABSTRACT The front-back sound localization performance of human subjects was investigated in 3 vi... more ABSTRACT The front-back sound localization performance of human subjects was investigated in 3 virtual rooms with different acoustic characteristics, and in an anechoic chamber. The three chosen rectangular rooms had the same width-length-height ratio. Their size and reverberation time were systematically varied in order to disentangle the respective effects on the localization cues, perceived during listening tests. The sound absorption was distributed equally over all surfaces. The head related transfer function (HRTF) used in simulation of the receiver was based on measurements on an artificial head. Four stimuli, with different spectra and time domain structure, were presented to the listeners: broadband noise, orchestra legato sound, orchestra staccato sound, and noise containing two one-third octave band components around 0.5 and 3.15 kHz. Significant differences in localization performance were found between sounds presented in the smallest room and the large rooms, and between the anechoic room and the two large rooms. People's localization performance was significantly different between staccato and legato sound stimuli, and it was significantly worse for the noise containing two one-third octave band components compared to the other stimuli. Also learning effects were observed.

The Journal of the Acoustical Society of America, 2015

Acoustic scattering audibility thresholds are needed for the efficient design of performance spac... more Acoustic scattering audibility thresholds are needed for the efficient design of performance spaces and to increase the accuracy of geometric room acoustic models. This paper focuses on the evaluation of the perceptual thresholds of the scattering coefficient through listening tests in simulated concert halls. It also deals with an investigation on the sensitivity of room acoustic parameters to scattering coefficients. A rectangular concert hall has been simulated with three prediction models, in which scattering coefficients of 0.1, 0.3, 0.5, 0.6, 0.7, and 0.9 were applied to the ceiling and walls in six different configurations. The analysis was performed comparing the results of the three-alternative forced choice listening tests and considering the objective parameters T30, early decay time (EDT), C80, and G. An increase in EDT and a decrease in C80 have been observed for increasing scattering coefficient values for all three types of software, while no similar trend was observed for the other parameters. The perceptual evaluation has shown that differences of ∼0.4, relative to an anchor value of 0.9 of the scattering coefficient, were perceived in the listening test conducted with one of the three kinds of software, while no clear differences in auralizations were perceived with the other two kinds.

From the acoustical point of view, spaces like open plan offices, restaurants or railway stations... more From the acoustical point of view, spaces like open plan offices, restaurants or railway stations can be understood as multi-source environments. The acoustical quality depends on the situation. Sometimes, speech privacy is of interest, in other cases speech intelligibility is desired, but in any case too high sound levels should be avoided. Higher sound levels can be acceptable in a railway station or a students' restaurant, but in an open plan office, the global masking noise is preferably lower than (50?)48 dB(A). In many ray-tracing programs an auralization method is incorporated.. In our research this method is used to demonstrate the acoustical quality in an office space to architects and future users. In the example of this paper a U-shaped open plan office is analyzed. Measured and simulated results are compared and the influence of several architectural set-ups is expressed in acoustical quantities and is made audible. The result is an interactive demon-stration set-up ...

This paper presents proposal of the methodology for the multidisciplinary assessment of urban pub... more This paper presents proposal of the methodology for the multidisciplinary assessment of urban public places which can be understood as an initial steps in territorial development policies on the scale of design and renovation of urban public space towards sustainable cities. Proposed method is based on transversal actions between different research fields, such a urban density, mobility, microclimate and pollution, vegetation and biodiversity, artificial lighting, water, acoustics and users, summarized and evaluated in a "transversality matrix". Our network deals with the problematic of public space on a national scale as it includes four interdisciplinary teams from all three regions of Belgium. This research is financed by the Belgian Federal Government (SPP-Politique Scientifique Fédérale) through the project "Development of the Urban Public Spaces Towards Sustainable Cities" (DRUPSSuC).

The scattering coefficient is one of the most important input parameters in room acoustics simula... more The scattering coefficient is one of the most important input parameters in room acoustics simulations. Together with the absorption coefficient they belong to the main descriptors of interior surface properties in a calculation process based on ray or radiosity method algorithms. This contribution deals with the comparison of three predicting software and objective assessment of scattered sound in the example of a virtual concert hall. The influence of scattered sound on the objective room acoustical parameters like T30, EDT, C80, D50 and G, is investigated. Six different alternatives were simulated, where scattering coefficient values s = 10, 30, 50, 60, 70 and 90% respectively, were applied to the interior surfaces of the ceiling, side and rear walls. Analysis has been performed by studying the results of objective room acoustical parameters predicted by simulations done with the software Odeon® 10.1, Catt-Acoustic® v 8.0. and Raven.

This contribution deals with the comparison of three prediction software, and objective and subje... more This contribution deals with the comparison of three prediction software, and objective and subjective assessment of scattered sound in the example of a virtual concert hall. The influence of scattered sound on the objective room acoustical parameters, like T30, EDT, C80, D50 and G, is investigated. Six different alternatives were simulated, where scattering coefficients values s = 10, 30, 50, 60, 70 and 90 % respectively were applied to the interior surfaces of the ceiling, side and rear walls. Analysis has been performed by comparing the results of objective room acoustical parameters predicted by simulations done in the software Odeon® 10.1, Catt-Acoustic® v 8.0. and Raven on one hand, and by investigation of subjective perception of scattered sound on the other hand. Listening tests applying the 3AFC method were performed, with stimuli presented to subjects via headphones by using signals auralized in one of the software (Odeon® 10.1).

Known in the past for its spectacular acoustic characteristics, the ancient theatre keeps today a... more Known in the past for its spectacular acoustic characteristics, the ancient theatre keeps today an important role as a modern stage: during the summer season many important theatrical events are organized in the frame of its ancient ruins, keeping alive a tradition that attracts people all around the world. But, without doubts, the actual conditions for the audience are deeply changed, affected by “modern” noises and damaged situation of the theatre itself. The insertion of the scenery elements has also to be considered as a variable that can modify the sound propagation in the theatre, with better or maybe worst results. In this article a research conducted on the acoustic perception of the audience of the Greek theatre of Syracuse is presented. A parametric study realized through a technical software (Odeon ® version 12.1) has been performed considering different scenery conditions, from the empty theatre and by adding different scenic elements to evaluate their influence on passi...

The complex sound field in performance spaces, characterized by multiple sound reflections from v... more The complex sound field in performance spaces, characterized by multiple sound reflections from various surfaces with different absorptive and diffusive characteristics, makes it difficult to deduce the effect of the single interior surface on the room impulse response. In order to obtain more knowledge on this topic, laboratory experiments were performed in a semi-anechoic room. Three different conditions were studied by monaural and binaural room impulse response measurements. Three types of surfaces with different absorptive and diffusive characteristics (flat surface and two differently absorbing concrete blocks with the same geometrical pattern) were placed on the floor during the experiments. The measurements were performed at the same distance from the surface sample at three different distances from the source position. Moreover, for each microphone position eight different orientations of the artificial head were considered. The monaural and binaural impulse responses have ...

Inclusive design is increasingly receiving attention from researchers and educators in architectu... more Inclusive design is increasingly receiving attention from researchers and educators in architecture and urban planning. Often, however, it is associated with improvement of living environments for people with reduced mobility. The rapidly growing number of older persons who suffer from reduced visual abilities, together with people who are visually impaired represent a considerable percentage of the population. This group raises new questions not only for the medical sector, but also for architectural design and acoustics, where the currently used normative values are optimized for people with “normal” visual abilities. This article discusses questions related to perception of sound and soundscape by people with a visual impairment by combining (1) findings about their superior ability in auditory perception from objective listening test experiments, magnetic resonance imaging and positron emission tomography with (2) insights gained through indepth interviews with and testimonies w...

This paper reports on the application of a recently developed deterministic prediction technique ... more This paper reports on the application of a recently developed deterministic prediction technique called the Wave Based Method (WBM) for the analysis of an interior room acoustics problem. The WBM has been developed as an alternative simulation technique for steady-state dynamic problems. It is based on a Trefftz approach in that exact solution functions of the governing differential equation are used as underlaying shape functions. Its superior convergence rate and lower computational load as compared to other deterministic methods such as the finite element method and the boundary element method, make it applicable also for mid-frequency analysis as has been reported already for various mechanical applications. In this paper, the WBM is applied for the acoustic analysis of an L-shaped room, and prediction results are compared with Fast Multipole BEM predictions, ray tracing results and measurements.

Journal of Sound and Vibration, 2015

ABSTRACT Structural details and workmanship can cause considerable differences in sound insulatio... more ABSTRACT Structural details and workmanship can cause considerable differences in sound insulation properties of timber frame partitions. In this study, the influence of panel fastening is investigated experimentally by means of standardized sound reduction index measurements, supported by detailed scanning laser Doppler vibrometry. In particular the effect of the number of screws used to fasten the panels to the studs, and the tightness of the screws, is studied using seven different configurations of lightweight timber frame building elements. In the frequency range from 300 to 4000 Hz, differences in the weighted sound reduction index RW as large as 10 dB were measured, suggesting that the method of fastening can have a large impact on the acoustic performance of building elements. Using the measured vibrational responses of the element, its acoustic radiation efficiency was computed numerically by means of a Rayleigh integral. The increased radiation efficiency partly explains the reduced sound reduction index. Loosening the screws, or reducing the number of screws, lowers the radiation efficiency, and significantly increases the sound reduction index of the partition.

Journal of Sound and Vibration, 2015

ABSTRACT This paper introduces a methodology that makes use of laser Doppler vibrometry to assess... more ABSTRACT This paper introduces a methodology that makes use of laser Doppler vibrometry to assess the acoustic insulation performance of a building element. The sound power radiated by the surface of the element is numerically determined from the vibrational pattern, offering an alternative for classical microphone measurements. Compared to the latter the proposed analysis is not sensitive to room acoustical effects. This allows the proposed methodology to be used at low frequencies, where the standardized microphone based approach suffers from a high uncertainty due to a low acoustic modal density.

Applied Acoustics, 2015

ABSTRACT A global estimator of the uncertainty of the average frequency response function in mult... more ABSTRACT A global estimator of the uncertainty of the average frequency response function in multi-channel spectral analysis measurements is proposed. The proposed global estimator is a generalization of the random error estimator of the frequency response function magnitude of a single-input–single-output system. In principle, the signal-to-noise ratio (and thus the quality of the frequency response function estimation) is increasing with increasing number of averages M , according to M. However, in the situation that, for practical reasons, there is a maximum imposed upon the total measurement time TmaxTmax, it is clear that there is a trade-off between the number of averages M and the record length T (s) that is used to obtain an estimate of a single-average-frequency-response-function. There is a choice between a few long records or many short records, with the requirement that, assuming zero overlap, the number of averages M times the record length T may not exceed the total available measurement time, i.e. M×T⩽TmaxM×T⩽Tmax. In addition to the existence of such an optimum, a minimum record length is required as well which is related to the reverberation time of the system. The newly proposed global estimator is used to determine the optimal record length of a multi-channel system, such that a minimum error of the average frequency response function is obtained. It is also shown by experimental results that indeed the minimum allowable record length is related to the reverberation time of the system being measured.

Building Acoustics, 2014

ABSTRACT Acoustic scattering has become an important input parameter in geometric models, and in ... more ABSTRACT Acoustic scattering has become an important input parameter in geometric models, and in research concerning the enhancement of auralized sound. This contribution deals with a comparison of four scaled prediction models of the same concert hall and a study of scattering coefficient prominence in simulations, while the size of the concert hall doubled. The hall has is fan shaped with an aspect ratios of about 4.5:2.8:1 and has typical auditorium features, such as a stage and a raked audience area. The influence of a volume scale-factor on the scattered sound effects on the prediction of the objective room acoustic parameters, that is, EDT, C80, D50, LF80 and G, has been investigated. Five different alternatives, in which scattering coefficient percentage values of 10, 30, 50, 70, and 90%, respectively, were applied separately and combined to the interior surfaces of the ceiling, side and rear walls, have been simulated. An analysis has been performed studying the results of the objective room acoustical parameters predicted, through simulations carried out with two kinds of software: Odeon 11.00 and CATT-Acoustic v 8.0.

Applied Acoustics, 2015

ABSTRACT The front-back sound localization performance of human subjects was investigated in 3 vi... more ABSTRACT The front-back sound localization performance of human subjects was investigated in 3 virtual rooms with different acoustic characteristics, and in an anechoic chamber. The three chosen rectangular rooms had the same width-length-height ratio. Their size and reverberation time were systematically varied in order to disentangle the respective effects on the localization cues, perceived during listening tests. The sound absorption was distributed equally over all surfaces. The head related transfer function (HRTF) used in simulation of the receiver was based on measurements on an artificial head. Four stimuli, with different spectra and time domain structure, were presented to the listeners: broadband noise, orchestra legato sound, orchestra staccato sound, and noise containing two one-third octave band components around 0.5 and 3.15 kHz. Significant differences in localization performance were found between sounds presented in the smallest room and the large rooms, and between the anechoic room and the two large rooms. People's localization performance was significantly different between staccato and legato sound stimuli, and it was significantly worse for the noise containing two one-third octave band components compared to the other stimuli. Also learning effects were observed.