The thermodynamic solid-gas theory of Kerr and Atwood is combined with an expression for electret microphone sensitivity to predict the dependence of photoacoustic signal strength for a nonresonant cell on heat capacity and sample pressure of a pure gas. We measure the photoacoustic signal dependence on sample pressure for four hydrocarbon gases and find that the signal increases with pressure but reaches a plateau whose height varies inversely with C-v, The results are in accord with our simple theoretical analysis. We measure the photoacoustic signal dependence on added krypton pressure for propane, isobutane, and naphthalene. After an initial increase with increasing krypton pressure, the photoacoustic signal eventually falls off at higher krypton pressures. We discuss the results on the basis of our analysis of a pure gas.