Plasma Loudspeaker

Introduction

A plasma loudspeaker converts electrical signals into acoustic pressure waves using a gaseous discharge[1] as the transducer. Common types of plasma loudspeakers include RF corona, DC corona and DC glow. Using a glow discharge has advantages rather than other types of discharges. [2]

Model

The acoustic field in a plasma loudspeaker can be described as an ordinary pressure wave in a neutral ideal gas driven by discharge-induced source terms. Bastien’s formulation emphasizes the general source structure: a heat term and a force term. Mazzola and Molen show that, for the DC glow loudspeaker, the dominant mechanism is thermal: current modulation changes the plasma temperature, temperature modulation causes pressure modulation through the ideal-gas relation, and efficient sound radiation occurs only when the plasma becomes sufficiently adiabatic relative to the modulation frequency. [2,3]