Cylindrical acoustic wavefront generation by means of ionic speakers

We present the use of ionic transducers to generate acoustic waveforms of cylindrical shape. We resorted to “cold discharge” transducers where momentum transfer from ions to neutral molecules is the main sound-generating process. Since the electrodes can be given a fairly arbitrary shape and the airflow is normal to the former, it is possible to obtain, close to the electrodes, a wavefront quite different from those obtained with standard, piston-like, loudspeakers. We present the acoustical characteristics of a cylindrical transducer and the use in the study of a bandpass, sonic-crystal based filter.