Abstract: A method for determining the flow situation in a transport system where the flow medium occurs in multi-phase and is conducted through a structural detail such as a choke valve, which acts on the flow of the medium and produces turbulence causing acoustic energy signals which are generated in and immediately close to the structural detail. The acoustic energy signals are sensed by one or a plurality of acoustic sensors with an acoustic broad-band connection with the structural detail. The sensor converts the energy signal to transmittable signals to a signal processing unit utilizing known signal analysis principles to provide interpretable information on the actual flow situation and the flowing medium which is influenced by the structural detail. The structural detail to which the acoustic sensor is connected may be incorporated in a subsea production system.