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1
Content available Testing the airborne sound insulation of reduced size baffles with different dimensions
Mleczko Dominik
Vibrations in Physical Systems
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2023
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Vol. 34, nr 2
art. no. 2023206
EN
The article discusses the requirements for determining airborne sound insulation according to ISO 10140-2, which involves measuring sound pressure levels in the source (L1) and receiving (L2) rooms, as well as reverberation time measurements in the receiving room. The size of the free test opening and the equivalent sound absorption area in the receiving room affect the value of L2. While ISO 10140-5 specifies the dimensions of a full-size test opening, reduced-size openings can also be used. However, testing reduced-size baffles with specific dimensions may be necessary, and measurements on rectangular-shaped baffles may yield higher sound reduction indices than square-shaped ones. The article presents a comparative analysis of the spectral characteristics of different types of single homogeneous baffles with various dimensions using experimental methods. It examines the measurement methodology's influence on determining sound insulation spectra and the weighted sound reduction index Rw. The article also calculates the combined uncertainty in determining the sound insulation properties and partial uncertainties in determining L1 and L2.
2
Content available Determination of sound insulation properties of homogeneous baffles using Finite Element Method
Majkut Leszek, Kosała Krzysztof
Vibrations in Physical Systems
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2023
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Vol. 34, nr 2
art. no. 2023222
EN
The basic parameter of materials used in constructional solutions of anti-noise protection, is sound insulation, which can be determined in laboratory conditions and also using theoretical models. The use of numerical methods in the form of the Finite Element Method to calculate the mechanical impedance of a baffle and then the sound insulation of homogeneous baffles was presented in the article. A 1 mm thick steel plate with a square, rectangular and round shape was analyzed. The boundary conditions for simply supported and clamped plate were taken into account in the numerical calculations. The results of the calculations were compared to both the commonly used the mass law and to the experimental tests. These analyzes will be the starting point for analyzes of multi-layer baffles, for which it is no longer possible to apply the mass law.
3
Content available Sound transmission loss calculation for metamaterial plate using combined analytical and numerical approach
Chojnacka Klara, Kras Aleksander, Kamisiński Tadeusz
Vibrations in Physical Systems
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2022
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Vol. 33, nr 3
art. no. 2022314
EN
In recent years acoustic metamaterials are broadly investigated in many different fields of acoustics and one of them is noise and vibration mitigation. The solution with highest potential are locally resonant metamaterials (LRS), which by creation of band gap effect in flexural wave propagation in structure improve its Sound Transmission Loss (STL). Standard STL simulation procedures can be fully analytical or numerical. Analytical solution, when it comes to metamaterial modelling, is fast but it does not take into consideration metamaterial geometry. On the other hand numerical solution even when considering small part of periodic structure, is time consuming and can generate numerical errors related for example to the mesh. In this work combined analytical - numerical method is analysed as the alternative for STL calculation. This method can be a substitute for basic simulation procedures concerning vibro-acoustic metamaterials, since the simulations results are comparable and it is less time consuming method. Formulas and simulation procedure for the presented method are described and compared with analytical and numerical simulation results as well as with STL measurement results.
4
Content available Comparative analysis of the acoustic properties of granular materials determined with the use of impedance tube
Kosała Krzysztof
Vibrations in Physical Systems
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2022
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Vol. 33, nr 3
art. no. 2022321
EN
The results of acoustic property tests for six types of granular materials: perlite, vermiculite, active coconut carbon, rubber granulates, pumice and wood chips, which can be used in noise protection structures, are shown in the article. The characteristics of the normal incidence sound absorption coefficient and the normal incidence sound transmission loss for material specimens with seven thicknesses in the range of 10-100 mm were determined based on the results of experimental tests carried out with the use of an impedance tube. The relationships between the first resonant absorption frequencies and the thicknesses of material specimens were determined. Single-number indices for the tested materials, in the form of the weighted sound absorption coefficients, were determined. Subsequently, dependencies of these indices on the surface mass of the tested materials were determined. The research showed that three materials, perlite, vermiculite and active coconut carbon, were distinguished among the examined granules with the best sound-absorbing and sound-insulating properties. Active coconut carbon had the best sound-insulating properties among the granular materials tested.
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