Impedance matching properties of electrorheological fluids with continuously changing acoustic impedance

Electrorheological fluids (ERF) can, under the influence of an electric field, be reversibly transformed from a fluid-like to a solid-like state, the acoustic characteristic of ERF is electrical controllable. As a theoretical model, the Biot theory has been applied. Then we analyzes the impedance-matching properties of ERF whose specific acoustic impedance varies smoothly across the ER, from the effective value of the transducer specific acoustic impedance to the value of the output medium specific acoustic impedance, the acoustic wave transmission matrix is got, further we calculate the reflection coefficient for different impedance profiles. This impedance matching technology (IMT) is the most effective for active noise control.