We proposed simultaneous imaging of flow and sound by using parallel phase-shifting interferometry and a high-speed polarization camera. The proposed method enables the visualization of flow and sound simultaneously by using the following two factors: (i) injection of the gas, whose density is different from the surrounding air, makes the flow visible to interferometry, and (ii) time-directional processing is applied for extracting the small-amplitude sound wave from the high-speed flow video. An experiment with a frame rate of 42,000 frames per second for visualizing the flow and sound emitted from a whistle was conducted. By applying time-directional processing to the obtained video, both flow emitted from the slit of the whistle and a spherical sound wave of 8.7 kHz were successively captured.

• R. Tanigawa et al., ``Optical visualization of a fluid flow via the temperature controlling method,'' Opt. Lett., vol.43, no.14, pp.3273－3276, 2018. [Paper] 

• K. Yatabe et al., ``Time-directional filtering of wrapped phase for observing transient phenomena with parallel phase-shifting interferometry,'' Opt. Express, vol.26, no.11, pp.13705－13720, 2018. [Paper]