Measurements are presented of the acoustic pressure resulting from the periodic absorption and emission of radiative energy by an infrared‐active gas contained in a closed, cylindrical tube. The acoustic waves are generated by means of an external, sinusoidally time‐modulated blackbody source. The pressure measurements are for both resonant and nonresonant conditions at acoustic frequencies from about 60 to 600 Hz. Comparison of the measurements with predictions shows that the response is due primarily to the modified‐classical acoustic wave, but that a small contribution from the so‐called radiation‐induced wave can be measured in certain of the tests. Strong effects of vibrational nonequilibrium, similar to those observed previously in spectrophone studies, were found in some of the tests. Generally, the agreement between theory and experiment is satisfactory and provides verification of the basic physical and mathematical models of the theory.