A speaker (10) comprises an enclosure (8) defining an internal volume (11); and at least one sound generator (7), the sound generator (7) comprising one or more surfaces defining an air-path conduit (15) through which air operably passes in and out of the internal volume. The sound generator (7) further comprises a plurality of electrodes comprising at least one air-exposed electrode (1, 4) and at least one insulated electrode (2, 3). A voltage source (6) is configured to generate an electrical field between the at least one air-exposed electrode (1, 4) and the at least one insulated electrode (2, 3, 70) to operatively generate a plasma proximal (100) to the plurality of electrodes and within the air-path conduit (15).