New technology, based on arrays of passive sensors and SONAR processing algorithms, has spawned new capabilities in flow and entrained air monitoring, allowing a higher degree of process efficiency. This new technology, which performs accurate, robust, non-invasive flow measurements, gas volume fraction (entrained air) measurements, and other performance measurements, will be described. Its impact on hydrocyclone flow measurements will be illustrated. Its use in the presence of ferromagnetic ore such as magnetite and pyrrhotite and in flow with entrained air to potentially increase the accuracy of mass balance calculations and enhance hydrocyclone performance will be detailed.