Airborne ultrasound based sensor systems have been applied to a variety of problems in robotics and advanced manufacturing. These include slot and hole inspection, and systems suitable for workspace imaging and autonomous guided vehicle (AGV) navigation. The transmission line matrix (TLM) method of modelling wave propagation has been used in the evaluation of these systems. The model gives both graphical and numerical outputs, and allows an improved understanding of the interaction of ultrasonic waves and targets to be obtained.