Electrorheological fluids (ERF) show a large variation of their viscoelastic properties in a strong electric field. Applications suggested so far aim at electrically controllable clutches and hydraulic shock dampers. A new field of ERF applications is underwater sound where the construction of absorbers with electrically adjustable properties appears possible. These two fields of applications differ in the frequency and strain ranges: The mechanical (macroscopic) applications exhibit large strains at low frequencies, the acoustical systems small strain at higher frequencies. This is not a trivial difference due to the nonlinear behavior of the ERF. Experimental results will be presented on sound velocity and absorption of selected ERFs in a wide range of frequency, temperature, and electric-field strength for sound propagation parallel and perpendicular to the electric field. It turns out that, e.g., a temperature-induced shift of the absorption coefficient can be compensated, within certain limits, by an enhanced electric field. Preliminary results obtained with a laboratory setup of an absorber with transformed ERF particle velocity will also be presented.