The coupling between magnetohydrodynamic waves and acoustic and electromagnetic waves is considered at a sharp boundary between a plasma and a neutral gas, and the coupling between magnetohydrodynamic and plasma waves and acoustic waves is considered at a diffuse boundary. In the sharp boundary problem, the incident wave vector is arbitrary in direction and the magnetic field vector is considered either in the plane of incidence or perpendicular to it. The ratios of the amplitudes and energy in the transmitted waves (electromagnetic or acoustic) to the corresponding amplitudes and energy in the incident waves (fast and slow magnetoacoustic, pure Alfven mode) are determined. In the diffuse boundary problem, the coupled wave equations are presented for a partially ionized plasma of spatially varying composition, with collision terms, in the presence of a magnetic field. The coupling of longitudinal plasma waves to sound waves is considered in the absence of a magnetic field. (Author).