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Wyświetlanie 1-4 z 4
Tytuł:
Prediction of low-frequency sound field in rooms with complex-valued boundary conditions on walls
Autorzy:
Meissner, Mirosław
Powiązania:
https://bibliotekanauki.pl/articles/128275.pdf
Data publikacji:
2019
Wydawca:
Politechnika Poznańska. Instytut Mechaniki Stosowanej
Tematy:
room acoustics
modal vibrations
room impulse response
complex wall impedance
akustyka pomieszczeń
drgania modalne
metoda wymuszeń impulsowych
Opis:
A modal representation of a room impulse response has been used to formulate expressions for low-frequency sound field in rooms of arbitrary shape. Based on theoretical results, a simulation program has been developed to predict a sound pressure distribution and a room transfer function for rectangular enclosure having walls covered by a material of complex impedance. Calculation results have shown that changes in the wall reactance entail a substantial modification of a sound pressure distribution. Furthermore, an influence of wall reactance on the room transfer function was investigated and it was discovered that a change in a reactance sign causes a shift in frequencies of modal vibrations excited in the room.
Źródło:
Vibrations in Physical Systems; 2019, 30, 1; 1-8
0860-6897
Pojawia się w:
Vibrations in Physical Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of high-density sound absorbing materials for improving low-frequency spectral flatness in room response
Autorzy:
Meissner, Mirosław
Powiązania:
https://bibliotekanauki.pl/articles/2146639.pdf
Data publikacji:
2021
Wydawca:
Politechnika Poznańska. Instytut Mechaniki Stosowanej
Tematy:
frequency response of room
spectral flatness
room impulse response
wall impedance
pasmo przenoszenia w pomieszczeniu
płaskość widmowa
odpowiedź impulsowa pomieszczeń
impedancja ściany
Opis:
A room impulse response obtained for complex-valued boundary conditions on wall surfaces was used to determine the frequency response of arbitrary shaped room. Based on theoretical findings, a numerical procedure was developed to test the effectiveness of a high-density sound absorbing material in improving low-frequency spectral flatness. The impedance of absorbing material was determined using the two-parameter Komatsu model. The simulation results have shown that the smoothing effect of the frequency response becomes apparent when the thickness of absorbing material is large enough. This is because as the material thickness increases, the sound absorption tends to increase at lower frequencies.
Źródło:
Vibrations in Physical Systems; 2021, 32, 1; art. no. 2021111
0860-6897
Pojawia się w:
Vibrations in Physical Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Impact of Wall Impedance Phase Angle on Indoor Sound Field and Reverberation Parameters Derived from Room Impulse Response
Autorzy:
Meissner, Mirosław
Zieliński, Tomasz
Powiązania:
https://bibliotekanauki.pl/articles/31340118.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
room acoustics
complex wall impedance
indoor sound field
room impulse response
reverberation parameters
Opis:
Accurate definition of boundary conditions is of crucial importance for room acoustic predictions because the wall impedance phase angle can affect the sound field in rooms and acoustic parameters applied to assess a room reverberation. In this paper, the issue was investigated theoretically using the convolution integral and a modal representation of the room impulse response for complex-valued boundary conditions. Theoretical considerations have been accompanied with numerical simulations carried out for a rectangular room. The case of zero phase angle, which is often assumed in room acoustic simulations, was taken as a reference, and differences in the sound pressure level and decay times were determined in relation to this case. Calculation results have shown that a slight deviation of the phase angle with respect to the phase equal to zero can cause a perceptual difference in the sound pressure level. This effect was found to be due to a change in modal frequencies as a result of an increase or decrease in the phase angle. Simulations have demonstrated that surface distributions of decay times are highly irregular, while a much greater range of the early decay time compared to the reverberation time range indicates that a decay curve is nonlinear. It was also found that a difference between the decay times predicted for the complex impedance and real impedance is especially clearly audible for the largest impedance phase angles because it corresponds approximately to 4 just noticeable differences for the reverberation metrics.
Źródło:
Archives of Acoustics; 2022, 47, 3; 343-353
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of sound absorption performance of acoustic absorbers made of fibrous materials
Autorzy:
Meissner, Mirosław
Zieliński, Tomasz G.
Powiązania:
https://bibliotekanauki.pl/articles/2202433.pdf
Data publikacji:
2022
Wydawca:
Politechnika Poznańska. Instytut Mechaniki Stosowanej
Tematy:
sound absorption
multi-layer absorber
surface impedance
fibrous materials
air gap
chłonność akustyczna
wielowarstwowy pochłaniacz dźwięku
materiały włókniste
szczelina powietrzna
Opis:
Absorbing properties of multi-layer acoustic absorbers were modeled using the impedance translation theorem and the Garai and Pompoli empirical model, which enables a determination of the characteristic impedance and propagation constant of fibrous sound-absorbing materials. The theoretical model was applied to the computational study of performance of single-layer acoustic absorber backed by a hard wall and the absorber consisting of one layer of absorbing material and an air gap between the rear of the material and a hard back wall. Simulation results have shown that a high thickness of absorbing material may cause wavy changes in the frequency relationship of the normal and random incidence absorption coefficients. It was also found that this effect is particularly noticeable for acoustic absorbers with a large thickness of air gap between the absorbing material and a hard back wall.
Źródło:
Vibrations in Physical Systems; 2022, 33, 2; art. no. 2022205
0860-6897
Pojawia się w:
Vibrations in Physical Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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