Vibration signatures of a wall of a bubbling fluidized bed were measured in order to investigate the effect of change in particle size on fluidized bed hydrodynamics. Vibration signatures were analyzed using wavelet transform and decomposed into three scales: micro-, meso- and macro-scales. Principal component analysis (PCA) was employed to gain a deeper insight into the dynamic behaviour of each sub scale. Bubble and emulsion phases were distinguished by the PCA as first and second components. (C) 2016 Elsevier B.V. All rights reserved.