If there is an actuator sending a wave package, assume at 100 Hz, without dispersion, it arrives at the sensor after time of Dt. If 500 Hz data is collected, by plotting input and output over the at the actuator and sensor, it is possible to show the time spent between two maxima. Distance between actuator and sensor divided by Dt gives then the wave speed (velocity). But of course, the sent and captured have to be the same mode (normal or shear strain, but the same one).

Thank you so much for your answer, B. Emek Abali . However, it does not seem to work in my case. In my experiment, the 2 mm thcikness Aluminum plate was conducted, the used frequency is 250 kHz and I am working with dispersion wave, as you said, I can get the wave speed not phase velocity. I want to calculate the group and phase velocity of this plate. If you have time or any idea, you can send me via email: [email protected]. Thank you so much. B. Emek Abali