Wave Transmission Damping using Wall Controlled by Switched Piezoelements Lionel Petit, Claude Richard, Daniel Guyomar, Adil Faiz Laboratoire de Génie Electrique et Ferroélectricité, INSA Lyon 8 rue de la physique, 69621 Villeurbanne Cedex France. Daniel.guyomar@insa-lyon.fr Abstract This papers describes the implementation of a semi passive piezoactive damping technique for transmission damping. Based on a non linear treatment of the piezoelements voltage, this control causes a degradation of the energy absorbed by the piezoelement when it is driven by an incident acoustic wave. The ultimate aim of such work is to produce a “piezoactive panel” which is light and stiff but with high transmission damping for acoustic wave. 1. Introduction The wave transmission damping through a partition wall separating two domains allows to reduce the noise level in the receiving domain when a disturbing acoustic source is radiating in the source domain. The use of passive absorbing viscoelastic material is a very common way to reduce the transmission coefficient of a partition wall but have some limitations: • Low damping in the low frequency area • Bulky and heavy device • temperature dependence of the transmission coefficient Source domain receiving domain E i E r E t M C K u(t) p t p i p r E a x Figure 1 : Energy balance and lumped model of the wall. p i , p r and p t are respectively the incident pressure, the reflected one and the transmitted one. u(t) is the wall displacement. Active or semi passive absorbing walls using bonded or embedded piezoelements permit to bypass these limitations [1,2]. The recent switched semi passive control [3,4,5] called SSDI (Synchronized Switch Damping on Inductor) based on a non linear processing of the piezoelement voltage reduces the wall vibration amplitude and then limits its sound radiation. This control is inherently broadband and is not sensitive to environmental changes. The energy absorption mechanism of the SSDI technique is described. Then an experimental set-up illustrating the validity of this technique to achieve plane wave transmission control through walls is detailed. This set-up consists of a tube splitted in two volumes separated by a wall consisting of the piezoelement itself. An acoustic source generates a plane wave excitation in the first zone, and the pressure of the wave transmitted in the receiving zone is monitored. When the SSDI control is on, it is shown that this pressure level is decreased for the structural resonance frequencies of the electro-active wall. 2. Energy absorption mechanism 2.1 Energy balance Figure 1 summarizes the energy balance of the system. When a disturbance radiation arrives in the source domain, the sound incident energy E i is divided in several components at the partition wall : A part is directly reflected (E r ) and depends on the reflection coefficient ℜ . The residual energy is transmitted in the partition wall which can be simply modeled as a spring K /mass M/damping C system. The transmitted energy in the receiving domain is : t i r a i a E E E E (1 )E E = − − = −ℜ − (1) Figure 2 : the SSDI device: schematic. switch control piezoelement R s L s min/max detector V(t) V sw (t) wall SSDI Mo.P2.16 I - 763