An acoustic flame detector (AFD) is described. It is based on the measurment of the frequency of an acoustic transients generated at the burner. In this reasearch the oscillating flame of a liquid gas mixture (propane-butane) and air in an open ended stainless steel tube was exploited. O2 gas was selected as a representative sample for the analysis. The changes in generated oscillaing flame were recorded by a CCD camera. The image and sound of the flame were separately examined. The change in different parameters of the generated pulses were exploited as analytical criteria for relating to the presence of analye in the gas minture