A novel quantity, based on the concept of symmetry of the sampled pressure fluctuating signal, is developed and incorporated into our extended fluctuation model of fluidized gas-solid suspensions. The new measure of the signal symmetry makes it possible to define the transition from the final bubbling regime to the onset of turbulence in the bed. Experimental measurements were performed in a transparent glass, 6-m-tall column with an inner diameter (i.d.) of 0.08 m. Three different kinds of solids were employed in the experiments: ceramsite (particle size 1.0-1.25 mm; group D particles; spoutable particles), glass beads (particle size 0.8-1.00 mm; group D particles), and high-calcium, coarse-grained limestone (particle size 0.50-0.65 mm; group B powder; sandlike particles). It was discovered that also the different bubbling regimes and the starting point of dilute (entrainment) regimes call be identified with the aid of the proposed method, The development of the diluted beds is considerably influenced by the architecture and configuration of the top of the fluidization column.