Flame-acoustic interactions are known to lead to localized perturbations in the flame surface. These perturbations are observed to travel as a wave along the flame surface, resulting in a spatially distributed disturbance in the flame heat release rate. The specific characteristics of this interaction are of utmost importance to the physics of thermoacoustic instabilities. The speed of wave propagation is a useful quantity for application to flame dynamic modeling strategies, such as flame sheet models. Additionally, the time delay associated with the motion of the disturbance through the flame is crucial to predicting the frequencies at which instabilities may occur. Measurements of this wave motion were made in a low-swirl burner configuration (that was capable of exhibiting self-excited instabilities) through the use of flame radical chemiluminescence imaging.