Heterogeneous (HG) blanket design strategies for passive control of aircraft interior noise

This paper is concerned with the design of heterogeneous (HG) blankets, which are used in this investigation to reduce the sound transmission through double panel systems. HG blankets consist of poro-elastic media with small embedded masses, which act similarly to a distributed mass-spring-damper-system. Previous work has shown that proper tuning of the HG blankets can result in noise and vibration reduction at low frequencies without compromising the inherent high frequency performance of the poro-elastic media. The masses can be tuned to certain frequencies by varying their weight, shape, and position within the poro-elastic media. In this paper, a theoretical and experimental comparison of different design techniques for choosing the location and tuning of embedded masses is presented. These design techniques are the random placement of the mass inclusions, the mass placement using a modal design, and an optimized design technique using a numerical design tool.