Gas-solid flow regimes have a significant impact on particle transport and separation in a fluidized bed reactor.In this study,to determine flow regime transitions in gas-solid fluidized beds,an acoustic tech-nique was used to detect and analyze the behavior of gas and solids.Algorithm complexity,fluctuation complexity,and Shannon entropy analyses of acoustic emission signals were performed to examine nonlinear system characteristics,and to determine the flow regime transition velocities uc,uk,and uFD.Moreover,using the standard deviation of pressure signals,pressure measurements and acoustic mea-surements were compared.The relative deviations(RDs)between the experimental and empirical values of uk were 8.8％,13.7％,8.8％,and 30.4％for the algorithm complexity,fluctuation complexity,Shannon entropy,and pressure signal standard deviation,respectively,while the respective RDs for uFD were 15.7％,23.9％,15.7％,and 97.8％.The RDs between the experimental and empirical values of uc were all 6.4％.The experimental values obtained from acoustic signal measurements were therefore closer to the empirical values.In summary,the integration of non-intrusive acoustic measurements,complexity analysis,and Shannon entropy analysis is suitable for identifying flow regime transitions.