An Experimental and Numerical Investigations of Integrated Passive Noise Control Strategies

Abstract

The usage of passive materials is an effective way to control unwanted sound, and newlineit has been practising widely in all noise control applications. In this work, a novel newlinedesign is proposed that will reduce noise in broad ranges of frequency. The design newlineintegrates the low-mid-high frequency material, namely Helmholtz Resonator (HR), newlineMicro-perforated panel (MPP), and Polyurethane Foam (PuF) respectively. Further, it newlineis necessary to characterize passive materials individually before coupling, and each newlinematerial is tested experimentally in an impedance tube setup as per standard ASTM newlineE-1050 and the same validated theoretically. The proposed material tested in real-time cavity testing, which shows better noise reduction in both experimentally and numerically. The following works have been carried out. For high frequency [1000 6300] Hz - Bio-polyurethane foam is developed by incorporating two different natural fiber in the form of powder and short fiber with a loading percentile of 3, 5, and 10. The prepared sample is tested in an impedance tube, and the results are validated theoretically using acoustic prediction models. However, these acoustic models demands the physical parameters such as porosity, flow resistivity, tortuosity, viscous, and thermal characteristic length. Only the first three parameters are measured using simple experimental setup, and remaining characteristic lengths is predicted using genetic algorithm by inverse characterization technique. The results indicate that addition of fiber leads to average of 10 to 12 % increase of noise reduction coefficient than the raw Pu foamFor mid-frequency [500-1000] Hz - New countersunk perforation proposed in thin MPP, which is made possible using 3D printing technology. An additional porous material is added to the panel to make a multilayer configuration and tested its sound absorption in the impedance tube. Using the transfer matrix method, the theoretical sound absorption of multilayer configuration is calculated and compared to experimental.