Mirosław Meissner

Polish Academy of Sciences, Warszawa, Masovian Voivodeship, Poland

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Publications (13)16.11 Total impact

  • Mirosław Meissner
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    ABSTRACT: The paper focuses on a theoretical description and numerical evaluation of active and reactive components of sound intensity in enclosed spaces. As the study was dedicated to low-frequency room responses, a modal expansion of the sound pressure was used. Numerical simulations have shown that the presence of energy vortices whose size and distribution depend on the character of the room response is a distinctive feature of the active intensity field. When several modes with frequencies close to a source frequency are excited, the vortices within the room are positioned irregularly. However, if the response is determined by one or two dominant modes, a regular distribution of vortices in the room can be observed. The irrotational component of the active intensity was found using the Helmholtz decomposition theorem. As was evidenced by numerical simulations, the suppression of the vortical flow of sound energy in the nearfield permits obtaining a clear image of the sound source.
    No preview · Article · Mar 2015 · Journal of Sound and Vibration
  • Mirosław Meissner
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    ABSTRACT: The analytical method has been developed to determine the acoustic behaviour of a lightly damped room excited by a sound source. Using the classical modal analysis, a solution of the wave equation was found as a sum of an infinite number of components representing individual responses of acoustic modes to the sound source. For weak sound absorption a general form of this solution was determined by means of the method of variation of parameters. From this solution the equations for the Green's function and the room impulse response were found. By employing the Green's function, the expressions describing a sound build-up and a sound decay for a harmonic excitation were derived.
    No preview · Article · Sep 2013 · Acta Acustica united with Acustica
  • Mirosław Meissner
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    ABSTRACT: The modal expansion method has been used to formulate expressions for real and imaginary parts of the complex sound intensity inside enclosures. Based on theoretical results, the computer program has been developed to simulate the acoustic intensity vector field inside the irregular room whose shape resembles the capital letter L. Calculation results have shown that a low-frequency distribution of the acoustic intensity is strongly influenced by the modal localization and the characteristic objects in the active intensity field are energy vortices and saddle points positioned irregularly inside the room. It was found that for small sound damping the vortex centers lie exactly on the lines corresponding to zeros of the eigenfunction for a dominant mode. An increase in a sound attenuation results in the change of vortex positions and can cause the formation of new vortices. Finally, an influence of the wall impedance on the quantitative relation between the acoustic and reactive intensities was studied and it was concluded that for very small sound damping the behavior of the sound intensity is basically only oscillatory.
    No preview · Article · May 2013 · Applied Acoustics
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    Mirosław Meissner
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    ABSTRACT: Reverberant responses are widely used to characterize acoustic properties of rooms, such as the early decay time (EDT) and the reverberation times T20 and T30. However, in real conditions a sound decay is often deformed by background noise, thus a precise evaluation of decay times from noisy room responses is the main problem. In this paper this issue is examined by means of numerical method where the decay times are estimated from the decay function that has been determined by nonlinear polynomial regression from a pressure envelope obtained via the discrete Hilbert transform. In numerical experiment the room responses were obtained from simulations of a sound decay for two-room coupled system. Calculation results have shown that background noise slightly affects the evaluation of reverberation times T20 and T30 as long as the signal-to-noise ratio (SNR) is not smaller than about 25 and 35 dB, respectively. However, when the SNR is close to about 20 and 30 dB, high overestimation of these times may occur as a result of bending up of the decay curve during the late decay.
    Preview · Article · Mar 2013 · Archives of Acoustics
  • M Meissner
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    ABSTRACT: The Hilbert transform is an important tool for a signal analysis, and it has been widely used in many areas of science and technology. An application of this method to an analysis of reverberant decay of modal vibrations in enclosures enables a detection of a pressure envelope resulting in a more accurate prediction of a reverberation time. It is shown that the discrete Hilbert transform is not accurate in an envelope detection even for the moderately damped harmonic signals, and a generated error strongly depends on the ratio of a modal damping coefficient to a mode frequency. This inexactness is due to the fact that for exponentially decaying harmonic signals the Bedrosian identity is not satisfied. In order to increase the accuracy of the envelope prediction, appropriate modifications of discrete signals corresponding to different kinds of modes are proposed. This method is successfully tested in the multi-mode case using discrete signals simulating a reverberant response of two coupled rooms.
    No preview · Article · Oct 2012 · Journal of Vibration and Control
  • Mirosław Meissner
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    ABSTRACT: In this paper, the modal expansion method supported by a computer implementation has been used to predict steady-state distributions of the potential and kinetic energy densities, and the active and reactive sound intensities inside two coupled enclosures. The numerical study was dedicated to low-frequency room responses. Calculation results have shown that the distribution of energetic quantities in coupled spaces is strongly influenced by the modal localization. Appropriate descriptors of the localization effect were introduced to identify localized modes. As was evidenced by numerical data, the characteristic objects in the active intensity field are vortices positioned irregularly inside the room. It was found that vortex centers lie exactly on the lines corresponding to zeros of the eigenfunction for a dominant mode. Finally, an impact of the wall impedance on the quantitative relationship between the active and reactive intensities was analyzed and it was concluded that for very small sound damping the behavior of the sound intensity inside the room space is essentially only oscillatory.
    No preview · Article · Jul 2012 · The Journal of the Acoustical Society of America
  • Mirosław Meissner
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    ABSTRACT: In this paper, the computer modelling application based on the modal expansion method is developed to study the influence of a sound source location on a steady-state response of coupled rooms. In the research, an eigenvalue problem is solved numerically for a room system consisting of two rectangular spaces connected to one another. A numerical procedure enables the computation of shape and frequency of eigenmodes, and allows one to predict the potential and kinetic energy densities in a steady-state. In the first stage, a frequency room response for several source positions is investigated, demonstrating large deformations of this response for strong and weak modal excitations. Next, a particular attention is given to studying how the changes in a source position influence the room response when a source frequency is tuned to a resonant frequency of a strongly localized mode.
    No preview · Article · Jan 2011 · Archives of Acoustics
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    Mirosław Meissner
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    ABSTRACT: A simple analytical method is developed to estimate frequencies of longitudinal modes in closed hard-walled ducts with discontinuities in a cross-sectional area. The approach adopted is based on a general expression for the acoustic impedance for a plane wave motion in a duct and conditions of impedance continuity at duct discontinuities. Formulae for mode frequencies in a form of transcendental equations were found for one, two and three discontinuities in a duct cross-section. An accuracy of the method was checked by a comparison of analytic predictions with calculation data obtained by use of numerical implementation based on the forced oscillator method with a finite difference algorithm.
    Preview · Article · Jan 2010 · Archives of Acoustics
  • R. Janczur · E. Walerian · M. Meissner · M. Czechowicz
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    ABSTRACT: In the paper, the simulation program predicting the sound level has been applied to one of buildings neighbouring a road. In the simulation are considered: geometry of road surroundings, the shape of the investigated building façade including, road geometry (number of lanes and their positions) and traffic structure (vehicle flow rates and their average speeds). Adjustable accuracy in an urban system modelling allows finding the model which is adequate to the real system. For the model of the accuracy limited by the simulation error due to vehicle speed estimation, by comparison with the field measurement, the model validation range has been established. Based on the simulation adjustable accuracy, possibilities of the validation range extension have been analysed.
    No preview · Article · Jul 2009 · Applied Acoustics
  • Mirosław Meissner
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    ABSTRACT: In this paper spectral characteristics and a mode localization in acoustically coupled enclosures were studied numerically. In a theoretical model a low-frequency limit was considered where eigenmodes are weakly damped, thus they were approximated by normal acoustic modes for rigid room walls. The effect of acoustic coupling on the mode frequency, the integrated density of states (IDOS) and the “existence surface” of modes were investigated for several coupling areas. Numerical results indicate that a decrease in coupling area causes a decrease of IDOS and results in a stronger localization of modes.
    No preview · Article · Feb 2009 · Acta Acustica united with Acustica
  • Mirosław Meissner
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    ABSTRACT: In this paper, a modal analysis was used to describe a reverberation phenomenon in a room of complex shape. A theoretical model was limited to low sound frequencies, when eigenmodes are lightly damped, thus they may be approximated by uncoupled normal acoustic modes of a hard-walled room. A utility of this method was demonstrated in a numerical example where the enclosure in a form of two coupled rooms was considered. A reverberation time was evaluated from a time decay of spatial root mean square pressure, the overall measure of room pressure. The results of calculations, performed for three different distributions of absorbing materials on room walls, showed how various location of the material can effect a dependence of the reverberation time on a frequency of sound source.
    No preview · Article · Jul 2008 · Applied Acoustics
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    Mirosław Meissner
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    ABSTRACT: The acoustical properties of an irregularly shaped room consisting of two connected rectangular subrooms were studied. An eigenmode method supported by a numerical implementation has been used to predict acoustic characteristics of the coupled system, such as the distribution of the sound pressure in steady-state and the reverberation time. In the theoretical model a low-frequency limit was considered. In this case the eigenmodes are lightly damped, thusthey were approximated by normal acoustic modes of a hard-walled room. The eigenfunctions and eigenfrequencies were computed numerically via application of a forced oscillator method with a finite difference algorithm. The influence of coupling between subrooms on acoustic parameters of the enclosure was demonstrated in numerical simulations where different distributions of absorbing materials on the walls of the subrooms and various positions of the sound source were assumed. Calculation results have shown that for large differences in the absorption coefficient in the subrooms the effect of modal localization contributes to peaks of RMS pressure in steady-state and a large increase in the reverberation time.
    Preview · Article · Jan 2007 · Central European Journal of Physics
  • R. Janczur · E. Walerian · M. Meissner · M. Czechowicz
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    ABSTRACT: In the paper, predictions of relative sound level distribution on building façades in city-centres obtained by using the simulation PROP11 program are compared with measurements. The simulation involves the geometry of surrounding buildings, road geometry (number of lanes and their positions) and traffic structure (vehicle flow rates and their average speeds). The agreement between measurement and simulation results is tested for different directivity characteristics of an equivalent point source representing the vehicles.
    No preview · Article · Jul 2006 · Applied Acoustics

Publication Stats

72 Citations
16.11 Total Impact Points

Institutions

  • 2006-2015
    • Polish Academy of Sciences
      • Institute of Fundamental Technological Research
      Warszawa, Masovian Voivodeship, Poland
  • 2007-2013
    • Institute of Fundamental Technological Research
      Warszawa, Masovian Voivodeship, Poland