The physical parameter required for the measurement principle is the well known distance among the sensors. The new system described here consists of ultrasonic sensors, changing the natural pressure ,stochastic fluctuations of velocity and density into two signals with a real-time correlator and a delay time T and obtaining the delay time from the signals and calculating the average rate of flow of the fluid. In dissimilarityto established flow methods for measuring, no deceive bodies are essential and electrical conductivity of the fluid is not required. In this paper a detailed theoretical signal model describing the interaction of sound waves in random continuum and turbulent media will be presented. Measurements have been carried out with 27 mm pipe diameters for clamp-on transducers.