The effects of the combustion tube length and diameter are investigated on oscillation combustion of the tubular flame burner. The flame oscillation and the axial mode of acoustic oscillation are observed by FFT of OH* and sound pressure. The flame oscillation is composed of the primary frequency and its harmonic frequencies that is the integer multiple of the primary frequency. The frequency of flame oscillation indicates the maximum spectral intensity of SPL (Sound Pressure Level). The increase in combustion tube diameter and the short length of the combustion tube are effective to reduce the flame oscillation, so that the SPL is reduced.
