Time-of-flight analysis
The program relies on the multiple frequency method to obtain the couplant-corrected wave travel times (Pantea et al. Rev. Sci. Instr. 2005, Sturtevant et al. Rev. Sci. Instr. 2020).
A cross-correlation procedure measures the optimal interference between a waveform and its copy with a varying phase shift. This process is used to calculate the time delay between any 2 pulses.
The difference between R1 & R2 reflection = double travel time
\(R2 - R1 = 2 τ\)