Acoustical waves have been observed in CO2, at initial pressures between 2 and 25 Torr, caused by sudden heating from incident CO2laser pulses. The effect was observed by monitoring the temperature increase of the window of the absorption cell due to the incident sound wave. Results indicate that the influence of a high‐power laser beam upon the penetrated atmosphere—and the feedback of the disturbed atmosphere on the propagation of the laser beam—may be conveniently studied under simulated laboratory conditions.