Fine particles are typically difficult to fluidize with gas, due to interparticle forces that cause the bed material to be cohesive. The use of acoustic waves, generated by a loudspeaker positioned above the bed, to agitate the bed material and enhance fluidization, has been investigated. The bed was fluidized with air at conditions near minimum bubbling. Sound-pressure measurements within the bed showed the presence of acoustic standing waves throughout the bed. Acoustic standing-wave theory, which assumes that the bed behaves as a 1-D, quasi fluid with constant speed of sound, was used to model the sound-pressure-level data. It was found that the parameter kh, where k is the wave number and h is the bed depth, determines the sound-pressure amplitude throughout the bed. The system reaches its highest sound pressure at resonance conditions for kh = (2n - 1)pi/2. A comparison indicates good agreement between the theory and the experimental data.