This work describes the behaviour of the standard deviation of pressure fluctuations, sigma, in fluidized beds for group B particles in the bubbling regime. An empirical-theoretical function, which depends on the gas velocity, is proposed for predicting the pressure signal fluctuations, and the corresponding values of sigma are calculated. The differences in the standard deviation of pressure fluctuations obtained for absolute or differential sensors are analyzed and compared to experimental values corresponding to different bed dimensions, pressure probe positions and particle properties. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.