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Wyszukujesz frazę "Meissner, M." wg kryterium: Autor

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    Wyświetlanie 1-11 z 11
    Tytuł:
    The response of a Helmholtz resonator to external excitation. Part II: Flow-induced resonance
    Autorzy:
    Meissner, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/177560.pdf
    Data publikacji:
    2005
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    sound generation
    flow-induced resonance
    acoustic resonators
    Opis:
    In the paper a phenomenon of sound production in a resonator driven by an air jet has been investigated. Measurements of sound spectra at the closed end of the resonator cavity were performed to determine the influence of the jet velocity on the frequency and amplitude of excited acoustic oscillations. It was found that in the sound generation process two ranges of the jet velocity could be distinguished where different variations of the oscillation frequency with the growing jet velocity were observed. After the onset of oscillation the frequency increased fast with growing jet velocity and the frequency increment was directly proportional to a value of jet velocity. At higher flow velocities an increase in the frequency was still observed, but the frequency growth was much smaller. The experiment has shown also that due to an excitation of mechanical vibrations of the resonator elements a rapid change in the oscillation frequency occurred. Finally, the experimental data were compared to calculation results to examine the accuracy of the theoretical model, in which a force driving the resonator was predicted from the vortex sound theory and the resonator was modelled by an equivalent impedance circuit.
    Źródło:
    Archives of Acoustics; 2005, 30, 1; 57-71
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Sound Energy Field in a System of Coupled Rooms
    Autorzy:
    Meissner, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1196695.pdf
    Data publikacji:
    2014-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    43.55.Br
    43.55.Ka
    43.20.Ks
    Opis:
    The paper presents a theoretical basis of calculations of the sound intensity in enclosed spaces and shows results of numerical visualization of the active intensity in a room with absorptive walls formed by two coupled rectangular subrooms. The study was focused on the low-frequency range, therefore to describe the active and reactive intensities, the modal theory of room acoustics was applied. Space distribution of eigenfunctions, modal frequencies and modal damping coefficients were calculated numerically using the forced oscillator method (FOM) and the finite difference time-domain (FDTD) method. Based on theoretical and numerical results, the computer program has been developed to simulate the active intensity vector field when the room is excited by a harmonic point source. Calculation data have shown that the active intensity was extremely sensitive to position of the source since at a fixed source frequency, different source locations always generate different distributions of characteristic objects of the active sound field such as energy vortices and stagnation points. Because of complex room shape, the vortex centers are in most cases positioned irregularly inside the room. Almost regular arrangement of vortices was found only in the case when the source frequency was tuned to the frequencies of modes which were strongly localized in one of the subrooms.
    Źródło:
    Acta Physica Polonica A; 2014, 125, 4A; A-103-A-107
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Simulation of Acoustical Properties of Coupled Rooms Using Numerical Technique Based on Modal Expansion
    Autorzy:
    Meissner, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1537509.pdf
    Data publikacji:
    2010-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    43.55.Br
    43.55.Ka
    43.20.Ks
    Opis:
    In the present study, the acoustic characteristics of coupled rooms were investigated using the computer modelling application based on the modal expansion method. A numerical procedure enables the computation of shape and frequency of eigenmodes, and allows one to predict sound decay times at any point of a room space. Results of numerical simulation have shown that along with a change in a coupling area the effect of a mode degeneration appeared and there are two main reasons for this. First, a mode degeneration is associated with a convergence of frequencies of neighbouring modes with a decrease of coupling area. Another reason for the mode degeneration are variations in a sequence of modes with a change in the coupling area. It was demonstrated that in the coupled rooms several modes exhibit a considerable localization. A degree of mode localization was described theoretically by the "existence surface" of mode and it was found that the localization phenomenon has a great effect on the reverberation process because for some absorbing material distributions it caused the double-slope decay characterized by steep initial and slow late sound decays.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 1; 123-127
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Accuracy Issues of Discrete Hilbert Transform in Identification of Instantaneous Parameters of Vibration Signals
    Autorzy:
    Meissner, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1490326.pdf
    Data publikacji:
    2012-01
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    02.30.Uu
    46.40.Ff
    43.20.Ks
    Opis:
    In the paper, an accuracy of the discrete Hilbert transform method in a detection of amplitude and frequency of vibration signals has been examined. This issue was studied for sinusoidal damped vibrations often encountered in practical applications. It has been shown that an inexactness of the Hilbert transform generates fictitious oscillations of amplitude and frequency. For small damping of vibrations these oscillations were significant only at both ends of a discrete signal. An error induced by a numerical algorithm was especially severe for strongly damped vibrations because it manifested itself by a large overestimation of amplitude and erroneous jumps of frequency. To reduce the error generated by the Hilbert transform method, the appropriate modification of discrete signal was proposed.
    Źródło:
    Acta Physica Polonica A; 2012, 121, 1A; A-164-A-167
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical Modelling of Coupled Rooms: Evaluation of Decay Times via Method Employing Hilbert Transform
    Autorzy:
    Meissner, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1504422.pdf
    Data publikacji:
    2011-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    43.55.Br
    43.55.Ka
    43.20.Ks
    43.60.Ac
    Opis:
    In the paper, a usefulness of the Hilbert transform in a computer modelling of reverberant behaviour of rooms is demonstrated for the enclosure consisting of two coupled subrooms. In numerical simulations a decay of the sound pressure is computed and the Hilbert transform methodology is used to determine an envelope of this decay. Calculation results have shown that, because of the mode localization, a distribution of absorbing material has a great influence on decay times evaluated from changes in the pressure envelope. For example, when a difference between the sound damping in subrooms is large, the localization effect is responsible for a creation of a nonlinear decay of the sound pressure level characterized by rapid early and slow late sound decays.
    Źródło:
    Acta Physica Polonica A; 2011, 119, 6A; 1031-1034
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Examination of the Effect of a Sound Source Location on the Steady-State Response of a Two-Room Coupled System
    Autorzy:
    Meissner, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/177058.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    coupled room system
    steady-state room response
    potential and kinetic energy densities
    localization of modes
    Opis:
    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.
    Źródło:
    Archives of Acoustics; 2011, 36, 4; 761-775
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Evaluation of Decay Times from Noisy Room Responses with Pure-Tone Excitation
    Autorzy:
    Meissner, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/177891.pdf
    Data publikacji:
    2013
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    room acoustics
    reverberation
    decay times
    room response
    background noise
    coupled rooms
    Opis:
    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.
    Źródło:
    Archives of Acoustics; 2013, 38, 1; 47-54
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A Novel Method for Determining Optimum Dimension Ratios for Small Rectangular Rooms
    Autorzy:
    Meissner, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/177897.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    room acoustics
    small room
    optimum dimension ratios
    room impulse response
    frequency room response
    Opis:
    A new method for determining optimum dimension ratios for small rectangular rooms has been presented. In a theoretical model, an exact description of the room impulse response was used. Based on the impulse response, a frequency response of a room was calculated to find changes in the sound pressure level over the frequency range 20-200 Hz. These changes depend on the source and receiver positions, thus, a new metric equivalent to an average frequency response was introduced to quantify the overall sound pressure variation within the room for a selected source position. A numerical procedure was employed to seek a minimum value of the deviation of the sound pressure level response from a smooth fitted response determined by the quadratic polynomial regression. The most smooth frequency responses were obtained when the source was located at one of the eight corners of a room. Thus, to find the best possible dimension ratios, in the numerical procedure the optimal source position was assumed. Calculation results have shown that optimum dimension ratios depend on the room volume and the sound damping inside a room, and for small and medium volumes these ratios are roughly 1 : 1.48 : 2.12, 1 : 1.4 : 1.89 and 1 : 1.2 : 1.45. When the room volume was suitably large, the ratio 1 : 1.2 : 1.44 was found to be the best one.
    Źródło:
    Archives of Acoustics; 2018, 43, 2; 217-225
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of Cross-Sectional Area Discontinuities in Closed Hard-Walled Ducts on Frequency of Longitudinal Modes
    Autorzy:
    Meissner, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/177934.pdf
    Data publikacji:
    2010
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    longitudinal duct modes
    discontinuity in duct cross-section
    contraction ratio
    Opis:
    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.
    Źródło:
    Archives of Acoustics; 2010, 35, 3; 421-435
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Prediction of Reverberant Properties of Enclosures via a Method Employing a Modal Representation of the Room Impulse Response
    Autorzy:
    Meissner, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/177946.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    room acoustics
    indoor reverberation
    room impulse response
    modal expansion method
    decay times
    Opis:
    A theoretical method has been presented to describe sound decay in enclosures and simulate the room impulse response (RIR) employed for prediction of the indoor reverberation characteristics. The method was based on a solution of wave equation with the form of a series whose time-decaying components represent responses of acoustic modes to an impulse sound source. For small sound absorption on room walls this solution was found by means of the method of variation of parameters. A decay function was computed via the time-reverse integration of the squared RIR. Computer simulations carried out for a rectangular enclosure have proved that the RIR function reproduces the structure of a sound field in the initial stage of sound decay sufficiently well. They have also shown that band-limitedness of the RIR has evident influence on the shape of the decay function and predicted decay times.
    Źródło:
    Archives of Acoustics; 2016, 41, 1; 27-41
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Active vibroacoustic control of plate structures with arbitrary boundary conditions
    Autorzy:
    Nowak, Ł.
    Zieliński, T. G.
    Meissner, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/31343106.pdf
    Data publikacji:
    2013
    Wydawca:
    Instytut Podstawowych Problemów Techniki PAN
    Tematy:
    vibroacoustics
    active control
    plate vibrations
    aktywne sterowanie
    wibroakustyka
    Opis:
    The paper describes briefly some main aspects of the active feedback control system that has been developed and constructed for reduction of vibroacoustic emission of vibrating plate structures with arbitrary boundary conditions. Relations between the forms and frequency of the vibrations induced by an external harmonic excitation and the distribution of the generated acoustic pressure field are investigated using the developed numerical model based on indirect variational boundary element method. The aim of the control system is to minimize the sound pressure level in a given point of the ambient space. The system uses small, rectangle-shaped piezoelectric transducers as both sensors and actuators. The transducers are connected in a number of independent feedback loops, and the feedback gains are the control parameters which are optimized using the developed optimal control algorithm. The constructed active system has been tested for the stability and control performance during experimental research performed in an anechoic chamber. Results of experiments are presented in the paper, proving a high level of noise reduction and a good agreement with numerical predictions.
    Źródło:
    IPPT Reports on Fundamental Technological Research; 2013, 4; 5-9
    2299-3657
    Pojawia się w:
    IPPT Reports on Fundamental Technological Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-11 z 11

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