 The study found that the Mach wave, a type of acoustic wave generated when a pile expands radially during impact, can be detected using hydrophones placed at various distances from the pile. This wave is characterized by a delay time or the amount of time it takes for the wave to reach the hydrophone after the pile has expanded, which is equal to the distance traveled multiplied by the speed of sound. Additionally, the Mach wave is also characterized by a peak frequency, which is determined by the speed of sound divided by the distance traveled. These characteristics allow researchers to estimate the speed of sound and the distance traveled by the pile. This article was authored by Peter H. Dahl, Alexander McGillivray and Roberto Raqqa.