Method and system of deducing sound velocity using time-of-flight of surface wave

An ultrasonic measurement system for measuring ultrasonic velocity, the system comprising:

• an emitting probe operable with an emitting wedge and a receiving probe operable with a receiving wedge, wherein the receiving probe is an array probe having a number N of receiving elements, the receiving elements designated element (n) for n=1 to N, and wherein the wedges are configured to be in contact with a test surface of a test object;
• a known parameter unit for storing known parameters for the probes and the wedges;
• an acquisition unit configured to fire at least one emitting element of the emitting probe, thereby causing the at least one emitting element to emit beams of ultrasonic energy into the emitting wedge, including a critical beam at a critical angle which generates a surface wave propagating near the test surface in the test object towards the receiving wedge, the acquisition unit further configured to receive corresponding A-scans from each element (n) of the receiving probe, the A-scans comprising amplitudes of received echo signals as function of arrival times at each element (n);
• and,
• at least one velocity unit configured to determine at least one surface wave velocity of the surface wave, and,
• wherein the known parameters comprise the number N of the receiving elements, a pitch p, wherein p is the distance between adjacent receiving elements, an emitting wedge angle θw′ of the emitting wedge, a receiving wedge angle θw of the receiving wedge, and a wedge velocity Vw, wherein Vw is the velocity of longitudinal waves in the receiving wedge.