Fine particles are difficult to fluidize due to strong interparticle attraction. An attempt has been made to study the bed expansion of silica gel (d(p) = 25 mu m) powder in presence of an acoustic field. A 135 mm diameter fluidized bed activated by an acoustic field with sound intensity up to 145 dB and frequency from 90 Hz to 170 Hz was studied. The effects of sound pressure level, sound frequency and particle loading on the bed expansion were investigated. Experimental results showed that, bed expansion was good in presence of acoustic field of particular frequency. In addition, it was observed that in presence of acoustic field the bed collapses slowly.