Sonic vibrations at frequencies of 600 c. p. s. and 1700 c. p. s. have been applied to the gas stream of a system in which post-aerated town gas burns with a diffusion flame in a 5-foot vertical water cooled tube. The main effects were to increase the heat transfer by factors of 2 to 3 in the lower parts of the tube and to lower the positions of maximum heat transfer and radiation heat transfer. Flame temperature was generally reduced but in the lower part of the tube emissivity was increased. The flame was shortened. The variables studied were sound pressure, sound frequency, gas momentum flux and gas flow rate. Their effects were examined in a factorial group of experiments and equations were derived enabling a, number of properties of the system to be related to the variables. The properties included total thermal efficiency and radiation efficiency for the whole tube, excess air and flame length. For the lowest 16" of the tube equations were derived relating total thermal efficiency, radiation efficiency, total heat transfer rate and radiation heat transfer rate to the variables.