Very fine particles in the Geldart C range, are difficult to fluidize because of interparticle forces. When a bed of fine particles is fluidized in the presence of an acoustic field, the sound waves agitate the bed material, helping to disrupt the large clusters of particles formed by interparticle forces, thus promoting more uniform fluidization and bed expansion. The present paper reports on the combined effects of gas velocity and frequency and intensity of the sound waves on bubbling behavior. Data on minimum bubbling velocity, bubbling frequency and bed expansion were obtained in a shallow batch fluidized bed with fine fly ash particles at room temperature.