METAPOROUS STRUCTURE DESIGN FOR ELECTRIC TRAIN NOISE CONTROL IN A TUNNEL

• Main Author: Azzahra Nadiva, Kamila
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/73150
• Institution: Institut Teknologi Bandung

<p align="justify"> Railway noise covers low to high frequencies. The train tunnel area has a high noise, so using certain materials is necessary. In general, sound absorption material is used to absorb noise. However, the material must be a quarter wavelength for the thickness to absorb efficiently. The implementation is not easy, especially in limited places. Therefore, an absorbent material is needed to overcome the constraints on the thickness of the material, which has a wide sound absorption range. In this study, the absorption capability of porous materials will be enhanced by designing the shape and configuration of the resonator so that the material can achieve broad bandwidth absorption the sub-wavelength structure. This research conducted modeling and numerical simulation of absorbing sound in porous materials, resonator configuration design, and implementation of the proposed metaporous layer in the tunnel area using the finite element method. These are used with a sound source in the path source form to evaluate the implementation of a metaporous layer in tunnel paths. The simulation results show that porous materials have low sound absorption at frequencies less than 1000 Hz. So, it is necessary to add a resonator to form a metaporous layer. The proposed resonator is a Helmholtz resonator with an extended coil neck. A metaporous with the highest increase in sound absorption was found in the broadest and shortest neck resonators, namely 9 mm and 33.5 mm. Besides, parameter modifications to the resonator were carried out to increase the absorption performance at the desired target frequency. This configuration has a thickness of 0.33 thinner or ????/11 than the longest wavelength in the frequency target. Four test samples from the proposed metaporous design and adjustment of the sound absorption coefficient with an impedance tube according to ISO 10534-2 standard. A comparison of the simulation and experimental results reveals the features of the absorption peaks and overall absorption performance so that the observed metaporous behavior is valid. The use of metaporous can inhibit noise in the tunnel up to 13.26 dB. The metaporous usage as an absorber can reduce reflections due to railway noise sources, especially at frequency 500 Hz.