ENHANCEMENT OF THE Q OF A NONLINEAR ACOUSTIC RESONATOR BY ACTIVE SUPPRESSION OF HARMONICS

Finite-amplitude stationary acoustic waves in a closed resonator subje cted to simultaneous excitation at fundamental frequency and its secon d harmonic are analyzed in the frame of the second-order nonlinear the ory. The conditions when the dual-frequency excitation leads to a qual ity factor Q higher than in the case of a single-frequency excitation are derived. The Q enhancement can be explained in terms of active sup pression of cascade processes of the generation of higher harmonics. T he second harmonic generated in the resonator is compensated by the se cond harmonic radiated by the piston. Suppression of higher harmonics also can be explained as being due to effective down conversion of ene rgy from the second harmonic to the fundamental wave in the nonlinear parametric process. (C) 1998 Acoustical Society of America.