A sonar-based flow measurement technology well-suited for the pulp and paper industry is described. Developed and field proven in numerous applications within the oil and gas industry over the last four years, the methodology provides robust, high-accuracy, volumetric flow rate measurement for a broad range of single and multiphase flow applications. The methodology can be implemented with pressure transducers ported to process fluid or with non-contact sensors clamped-on to existing process piping. Sonar-based flow metering technology utilizes an array of sensors to listen to the unsteady pressure field within standard process flow lines. Flow rate is determined using sonar array processing techniques to track the speed at which coherent structures, inherent within the turbulent pipe flow of the process fluid, convect past the sensor array. This convection speed is directly related to volumetric flow rate through a Reynolds number calibration. Results from a single-phase calibration facility are presented demonstrating 0.5% accuracy for pipes ranging from 3 to 16 inches in diameter.