Pokročilá akustická přepážka

Abstract

The scope of this thesis project is to design advanced acoustic barriers and to test the acoustic transmissibility. To this goal CAD was used and 3D printing to create innovative structures, subsequently these structures were tested for acoustic performance (absorption and reflectivity) in a 2-microphone impedance tube setup. The designs were 3D printed using an FDM 3D printer. The design of test samples was inspired by existing studies about acoustic metamaterials. The advanced options in the PrusaSlicer software allowed to determine the impact of different infill structures. The designs varied from basic to advanced geometry. All these structures are of interest to be implemented in future soundproofing applications. Their applications vary from dashboards that reduce the interior sound level to noise-canceling covers for headphones. To test the various designs, an impedance tube/Kundt tube was used. This test setup worked well to compare different design features and evaluate which design/geometry is better at absorbing or reflecting acoustic energy. This impedance tube was constructed by the university and the input signal is controlled by a MATLAB script that can be customized by the user. The measured results are analysed using another MATLAB script. This script calculates the reflection factor and the absorption coefficient of the tested samples. The calculation is performed by doing a FFT (Fast Fourier Transformation) on the measured microphone signals. The obtained transfer functions and acoustic parameters are then plotted to verify and compare the measurements. After performing all the measurements, it can be concluded that all the samples are good at reflecting the sound energy. The reflection factor is always high. The 3D printed samples are stiff and are great acoustic reflectors. By comparing the transfer functions determined using the four-microphone method, it can be concluded that the 3D printed acoustic barriers that contain lots of thin and curved features are better at blocking the acoustic energy.

The scope of this thesis project is to design advanced acoustic barriers and to test the acoustic transmissibility. To this goal CAD was used and 3D printing to create innovative structures, subsequently these structures were tested for acoustic performance (absorption and reflectivity) in a 2-microphone impedance tube setup. The designs were 3D printed using an FDM 3D printer. The design of test samples was inspired by existing studies about acoustic metamaterials. The advanced options in the PrusaSlicer software allowed to determine the impact of different infill structures. The designs varied from basic to advanced geometry. All these structures are of interest to be implemented in future soundproofing applications. Their applications vary from dashboards that reduce the interior sound level to noise-canceling covers for headphones. To test the various designs, an impedance tube/Kundt tube was used. This test setup worked well to compare different design features and evaluate which design/geometry is better at absorbing or reflecting acoustic energy. This impedance tube was constructed by the university and the input signal is controlled by a MATLAB script that can be customized by the user. The measured results are analysed using another MATLAB script. This script calculates the reflection factor and the absorption coefficient of the tested samples. The calculation is performed by doing a FFT (Fast Fourier Transformation) on the measured microphone signals. The obtained transfer functions and acoustic parameters are then plotted to verify and compare the measurements. After performing all the measurements, it can be concluded that all the samples are good at reflecting the sound energy. The reflection factor is always high. The 3D printed samples are stiff and are great acoustic reflectors. By comparing the transfer functions determined using the four-microphone method, it can be concluded that the 3D printed acoustic barriers that contain lots of thin and curved features are better at blocking the acoustic energy.