The possibility of acoustic amplification in a gas subjected to an external means of overpopulating internal energy levels has been explored theoretically. The basic concept that the temperature variation of the sound wave controls the flow of energy from the source to translation must take into account the internal structure of the gas. When the gas is pumped optically, the strong temperature dependence of the collisional de‐excitation rate constants is included in addition to the temperature and pressure dependence of the optical absorption coefficient considered by others. The resulting attenuation or amplification of sound has been calculated both for a two‐level and a multilevel gas. For illustrative purpose, a 90% CO‐10% H2numerical example has been developed. This example demonstrates that sound amplification should be experimentally observable.