A plane wave study for improving acoustical performance of double wall systems using an active-passive method

Finite multilayer structures are widely used in many engineering applications for increasing the sound absorption and for reducing the sound transmission. These so-called 'double wall system' is made up of two elastic plates and a core such as an air gap or highly-dissipative media like poroelastic materials. Such passive panels are efficient enough at medium and high frequencies but exhibit a lack of performance at low frequency, where resonance inherent to the layer distribution occurs. This paper presents a double wall system combined passive and active means. Passive panels with absorbent materials located in the emission side are used to increase absorption for a wide frequency range. Piezoelectric patches are added to the active panel and behave as a secondary vibrational source, ensuring high performance at low and/or resonance frequencies. The analytical and numerical simulations in Matlab are completed. At last, the result of experiment carried out in the Matisse set-up proposed by LMFA is in good agreement with the simulation. (C) 2009 Institute of Noise Control Engineering.