The characteristic scale (G1) of acoustic emission (AE) signals that represent the interactions between bubbles and liquid phase in a stirred tank was obtained by using AE measurement based on wavelet transform and R/S analysis.Since the energy fraction of AE signals in G1 scale change regularly with the impeller speed

a criterion to determine the flooding-loading flow regime transition is presented.When the AE energy fraction in the characteristic frequency scales increased rapidly and began to remain constant

the corresponding impeller speed was the minimum speed to prevent flooding(Nf).Furthermore

the influences of aeration rate and total liquid depth on the criterion were investigated by air-water experiments.It was found that Nf increased with increasing aeration rate but decreased with increasing total liquid depth.By comparing experimental results from AE measurement with those from visual observation

the average relative errors of AE method were no more than 2.62%

better than the power consumption method.Finally

it is concluded that multi-scale analysis of acoustic signals is feasible for determining the flooding-loading flow regime transition and is sensitive

non-intrusive and accurate.