Last year, the discovery of SACER inN2/H2mixtures was reported [J. Acoust. Soc. Am. Suppl. 178, S45 (1985)]. This paper discribes similar measurements inN2/HeandN2/CH4mixtures. Sound amplification has been observed, and its dependence upon gas pressure, sound frequency, foreign gas concentration, and vibrational temperature is that generally expected from a crude relaxation model for the gases and published values of the relaxation times. However, as in the case withN2/H2mixtures, the gain is an order of magnitude bigger and persists longer than expected. An electrical discharge was passed through the gas to initiate the acoustical oscillations and elevate the vibrational temperature. InN2/CH4mixtures, the gain and the nature of the electrical discharge were found to depend on the number of times the discharge was passed through the gas. This result is interpreted as being due to a chemical reaction betweenN2andCH4that produces an impurity that shortened the relaxation time. [Work sponsored by the ONR.]