Sonic responses of an electrorheological layer with one side of grating electrodes

Transmission of sound through a flexible electrorheological (ER) layer, in which ER fluids are sandwiched between two plastic sheets and a single face of grating electrodes is employed, is investigated experimentally. The periodic grating electrodes provide an electric field that is approximately parallel to the surface plane of the ER layer, so the sound propagation direction is treated as vertical to the electric field. It is found that the transmitted sound pressure level (SPL) can be modulated (debased or/and augmented) by the electric field. For one kind of ER material, the intrinsic resonant frequency of the ER layer is determined by the face size of the ER layer, the resonant state can be tuned via the electric field. For a face size of 90 × 90 mm² the transmitted SPL tends to increase with increasing electric field, but for a face size of 20 × 20 mm² it tends to decrease with increasing electric field, while for a face size of 40 × 40 mm² it both increases at higher frequencies and decreases at lower frequencies. The viscoelasticity in ER fluids and the complex vibration modes on the ER layer may be responsible for the experimental results. It is thought that the investigated thin ER layer is usable for tunable acoustic devices.