Stable Parametric Amplification Using Elastic Microcapsules Placed in Silicone Rubber

To realize a stable parametric amplification, elastic polymer microcapsules are applied instead of microscopic gas bubbles. Small quantities of the microcapsules are compounded with the silicone rubber, and the mixture is formed into a cylindrical shape as a sample of a nonlinear device. The device is located on the sound-field where the finite amplitude sounds of two near frequencies are trasmitting. It is experimentally observed that the strong nonlinear vibration of the spatially fixed microcapsules generates a stable difference-frequency sound with high efficiency and wide frequency range.