Abstract: A method is described to register structural features in an acoustic conducting material, such as the sheet material of a pipe, a duct, container or the like, where instrumentation fitted at the surface of the material, is used to emit and receive signals in/through the solid material and also to register changes in the received signals as a consequence of changes in the material structure. The method is characterised in that a sensor, or several sensors mutually spaced apart, is (are) arranged to be in contact with the surface of the material, and the sensor(s) is (are) arranged to emit and receive signals to provide an acoustic network with information about the structure of the material, and that the received acoustic signals are compared to previous acoustic signals to ascertain the existence of structural changes in the solid material, and any occurrences of defects in the solid material, and also the position of such defects. A system to carry out the method is also described.

Abstract: A description is given of a method for operating a measuring instrument (10) fitted onto the surface (16) of a fluid carrying body (18), in particular a hollow body such as a pipe, which transports multiphase fluid flows, especially fluids containing solid particles, wherein acoustic data related to fractions and amounts of the different phases in the fluid flow are registered.