The transmission of sound through glow discharge plasma was studied both experimentally and computationally. The main thrust of the investigation was to determine the effectiveness of using glow discharge plasma as a sound barrier in aerospace applications. Experiments were conducted in an anechoic chamber where the attenuation of single-tone sound propagating through a sheet of plasma was measured. These measurements were carried out for a range of air pressures, plasma parameters and sound frequencies. In the computational study the propagation of planar sound waves through regions of hot gas, simulating the plasma, was investigated by solving the unsteady one-dimensional Euler's equations using a second-order accurate finite difference scheme. The shape and extent of the high-temperature region representing the plasma was varied in order to investigate the thermal effects brought on by the plasma heating of the gas. Both the experimental and the computational results show that there is considerable attenuation of the sound pressure amplitude by the plasma.