Desing of a novel sound insulation structure incorporating quasi-zero stiffness and vacuum cavity

This thesis focuses on a novel sound insulation structure design. Existing sound insulation methodsin the literature have been examined, their strengths and weaknesses have been identified. For the especially challenging low frequency sound insulation problem, a sound insulation structure incorporating quasi – zero stiffness and vacuum (impedance mismatch) has been designed. The potential improvements of low stiffness and vacuum have been studied. Analytical solutions for sound insulation barriers have been studied. The effects of lowered stiffness and impedance mismatch on sound transmission loss performance have been investigated. Finite element analyses were carried out to obtain the potential of the proposed design. Literature research has determined the improvement rates achieved with these methods in the present day. Exceptional improvement potential in low-frequency sound insulation have been observed and the objectives of the study have been defined. Designs incorporating low stiffness and vacuum have been developed. Finite element analyses and optimization studies have been carried out to achieve high sound transmission loss at low frequencies. Transmission loss measurements of prototypes with different vacuum ratios and stiffnesses have been carried out. The experimental results of the designed structures have been compared with finite element analyses. The potential improvements and limitations have been discussed.