Objective To clarify the characteristics of shock wave sources generated at different medium interfaces. Methods The experiment used an in vitro adjustable impact pressure shock wave generation and signal acquisition system combined with a flexible PVDF sensor. The waveform of the shock wave generated by the applicator at the interface of different media (soft tissue-mimicking phantom, water and air) was explored. The characteristics of the shock wave source in the time and frequency domains were analyzed. Results When the same impact pressure was applied, shock waveforms generated at the interfaces of the phantom and water exhibited similar characteristics from a time-domain perspective. At the same time, both differed significantly from those generated at the air interface, where the absolute values of the positive and negative pressures were noticeably reduced. The characteristics of the shockwave spectra in various media revealed three distinct peak frequencies, with the modulation frequencies varying in the phantom (12.2 kHz), water (8.5 kHz), and air (7.2 kHz). In contrast, the carrier frequency remained relatively constant (between 82 and 83 kHz). When different impact pressures were applied, there was little influence on the waveform at the same medium interface, indicating that the impact pressure affected only the shockwave amplitude and not the peak frequency. As the impact pressure increases, the absolute values of the positive and negative pressures at the medium interface increase linearly. Conclusions Shockwave sources can be effectively measured using a flexible PVDF sensor. Shock waves generated at different medium interfaces exhibit temporal and spectral differences, indicating that the characteristics of shock wave propagation in air or water cannot be substituted for those in biological soft tissues. These findings provide crucial information for evaluating shockwave devices and formulating treatment protocols in the clinic.