The inherent ability of ultrasonic wave to propagate in dense and opaque suspensions makes it a desirable method for online measurement of particle size distribution in industrial operations. The ability of ultrasonic attenuation spectroscopy to determine particle size distribution has been extended to dense suspensions of particles lying predominantly in the intermediate wave propagation regime at the measurement frequencies. This was achieved by accounting for the effect of detector size and shift in the frequency spectrum under dense conditions in the theoretical model and deconvolution algorithm, respectively. The proposed modifications enable the application of this technique in various industrial processes requiring in situ and real-time measurement of particle size distribution such as crystallization, mineral processing and food processing. (C) 2010 American Institute of Chemical Engineers AIChE J, 56: 2825-2837, 2010