Calculations have been made which predict sound amplification under certain conditions when propagated through a gas with an overpopulation of vibrationally excited states. Three metastable states have been analyzed, where the vibrational temperature is varying slowly on the scale of the sound period. The first is that of a long‐lived vibrational mode in a diatomic gas. Calculations were made for N2, CO, O2, and Cl2. The second is that of a fast v–v exchange followed by a slow v–t. Calculations were made for CD4as an example of this situation. And the third is that of a slow v–v followed by a fast v–t. Calculations were made for a mixture of N2/CO2/He as an example of this situation. Some of the difficulties in experimentally observing the gain are discussed.