attaching opposite sides of an enclosure together will not work in many applications for most active panels or enclosures it is preferable to use piezo patches i e multimorphs in the bending mode the piezoelectric means are controlled by electronic controllers operating as described in u s pat nos 4 878 188 to ziegler 5 105 377 to ziegler and or 5 091 953 to tretter which are hereby incorporated by reference herein a test was performed to demonstrate the utility of the layered piezo patches and the configuration is shown in fig1 the test device was a 1 8 inch thick by 10 inch square aluminum plate 10 with 1 8 by 3 4 inch aluminum welded perpendicular to the edges the plate was simply supported initially a single 0 020 inch thick piezoceramic patch 11 was attached to the plate see fig1 a modal test was then performed to determine the resonant frequency for the 1 1 mode for the plate with the single piezo patch it was determined that the 1 1 mode for the plate was 274 hz a 274 hz 20 0 volts peak signal was then applied to the piezo this resulted in an.