The energy reflection coefficient of electrorheological fluid with continuously changing acoustic impedance

The electrorheological fluid (ERF), among the complex fluids, is a kind of smart or intelligent material. At the presence of an external electric field, the dispersed particles in ERF suspensions can form orderly microstructures to a certain extent, resulting in the drastic changes of many physical properties of the materials, such as acoustic impedance. This paper analyzes acoustic attenuation and velocity of acoustic wave in ERF, as a theoretical model the Biot theory has been applied. Then impedance-matching properties of ERF, whose specific acoustic impedance varies smoothly across the ERF, from the effective value of the transducer specific acoustic impedance to the value of the output medium specific acoustic impedance, is analyzed with the transmission matrix method and get the reflection coefficient of ERF. At last, calculate the reflection coefficient of ERF with three impedance profiles. The results show that This impedance matching technology (IMT) is the most effective for active noise control.