Described is a device for generating an acoustic signal in an electrically conductive medium such as salt water. The device of the present invention has a broadband frequency response and supports high bandwidth data transmission. Reliability is improved in comparison to conventional underwater acoustic transmitters as the device includes no moving components. In one embodiment, the device includes a parallel and alternating arrangement of electrodes and magnets. Neighboring electrodes have different voltages and neighboring magnets have opposite pole configurations such that the magnetic fields overlap the currents between the electrodes in the medium. The currents or the magnetic fields are modulated according to a data signal to generate an acoustic signal in the medium.