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Control of reflection coefficient of surfaces using piezoelectric materials

The efficiency of conventional passive coatings for the reduction of the reflection coefficients of surfaces in underwater acoustics is limited, especially at low frequencies. Progress in active control makes us consider the possibility of using piezoelectric transducers to control the reflection coefficients of surfaces. The latter depends on the frequency, the physical characteristics of the transducer, the radiation impedance and the control impedance. By considering an analog circuit of the system, expressions of the reflection coefficient, and of the optimum control impedance to reduce it, are given. Numerical examples and the influence of some parameters are also studied.