Figure 1

Appearance of the shock-wave generators and characteristics of the shock wave used in the experiments. (a, b) Experimental setup of the shock tube. The stainless steel tubing (inner diameter: 25 mm, outer diameter: 34 mm) was divided by a polyester diaphragm into high- and low-pressure parts (length of low-pressure part: 800 mm, high-pressure part: 400 mm). The mouse was placed 55 mm diagonally beneath the edge of the tube (c, d). Experimental setup for the LISW. Shock waves were generated by irradiating a laser target with a Q-switched Nd:YAG laser. Plasma formation occurred at the interface of the laser target, and its expansion was accompanied by the generation and LISW, which was irradiated onto the inner ear through the skin (e, f). Typical temporal pressure waveforms of the shock wave generated by the shock tube as measured at the tragus (e), and LISW (f). Typical negative pressure followed by positive peak pressure was clearly reproduced by the shock tube (e). LISW can generate intense positive peak pressure with a considerably shorter duration compared to the shock tube (f). (g, h) Pressure frequency spectra were obtained from the pressure waveforms of the shock waves spanning the range of peak pressures using fast Fourier transform. While the respective forms of each spectrum were similar, the frequency range of the shock wave generated by the shock tube (x-axis: frequency) (g) was substantially narrower and lower than that in the LISW (h). LISW, laser-induced shock wave. RMS, root mean squared.