Design of Acoustic Metamaterials for Cabin Noise Reduction and Pressure Sensing in Propfan Aircrafts

Abstract

This research is about to address the main challenge related to newly emerging airplane engines, namely open rotor (propfan). Though these engines show high efficiency, yet the noise generated is very high. This research focuses on designing a new class of ‘Acoustic Metamaterial’ to overcome the noise reaching the passenger cabin. An acoustic metamaterial is a complex composite structured material that exhibits negative density and negative bulk modulus either individually or simultaneously. The objective of this research is to design an acoustic fuselage using a combination of Negative density acoustic material (NDAM) and Negative bulk modulus acoustic material (NBAM) to reduce the noise transmission into the passenger cabin. Furthermore, the developed acoustic metamaterial structure can be used for pressure sensing application. Based on the literature reviews, experiments pertaining to the combination of NBAM and NDAM are limited. Hence, an integration of both structures is very appealing to be developed. Accordingly, the research will design a combination of two types of Helmholtz resonators (Conventional with one inner membrane and two inner membranes) of negative bulk modulus acoustic metamaterial. This filter can be embedded in a sandwich structure to obtain a new type of cabin wall. Hence the design and development of such acoustic metamaterial are expected to reduce the noise inside the cabin to a minimum. Also, the designed structure will be able to sense pressure at selected locations inside the cabin.