Abstract: The difference between the SPL value calculated by classical formula and the value measured in high intensity sound reverberation chamber is very large. A quasi-empirical formula based on experimental statistics is presented as L_w=L_p+6.67log₁₀（V）-Z,Z=8-8.5 where Lw is the acoustic power level in dB with respect to 10-12W, Lp is the sound pressure level in dB with respect to 2x10^-5Pa, V is the volume of the reverberation chamber in m3. This formula is featured by unity parameter and easy to use. The volume, sound pressure level and sound source power measurements in twenty-seven reverberation chamber are compared.