DEVELOPMENT OF BROADBAND SONIC CRYSTAL SILENCER CASE STUDY: FAN COIL UNIT (FCU) NOISE SOURCE

• Main Author: Akmal Putra, Ramadhan
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/36156
• Institution: Institut Teknologi Bandung

The main problem of the implementation of sonic crystal for noise reduction system is the narrow band transmission loss performance that generated from the construction compared with conventional solid noise barrier or resistive duct silencer system, which is just 1-octave band in maximum. In this study, further analysis for sonic crystal system is reviewed in intention to get broader band of transmission loss performance. Investigation of slotted scatter was carried out so that as the same time it can be functioned as a resonator. Subsequently, some configurations of resonator was developed further such as: (1) Multi-layer split ring resonator facing the same direction; (2) spiral multi-layer resonator The results obtained from finite element method numerical simulation and modelling studies, those configurations designed ar implemented as silencer of fan coil unit system within 60 m2 occupied room with 500 – 2000 Hz dominant noise frequency range and maximum 2000 cmh volume air flow. The result shows that sonic crystal with spiral-shaped multi-layer sesonator has the broadest band of the evaluated frequency. It is suspected that such configuration could produce more resonance frequency while maintaining bandgap due to the existance of multi-resonant system. Thus, the overall attenuation per frequency range has broadband characteristics. The results were validated with laboratory measurement of physical models on a scale of 1: 4. The variation of split ring resonator configuration in sonic crystal system are affecting bandwidth frequency and level of amplutide of transmission loss performance. The more layer of resonator in result of broader bandwidth frequency, the longer the wavepath the higher the transmission loss amplitude value of non-resonance frequency range. Developed sonic crystal duct attenuator has 690 mm x 528 mm x 300 mm dimension and 31% opening area with dominant resonance occured at 500 – 2000 Hz frequency range and 9 dB in average of minimum transmission loss amplitude. Those parameters have the same agreement with the characteristic of porous duct attenuator, or in the other words, the developed sonic crystal system in this study could be an alternative solution for conventional porous duct attenuator for FCU system.