Fig. 3. Audio signals (amplitude vs. time) (A, D), mel spectrograms (B, E), and digital subtraction angiography image (C, F) of 61-year-old males with brachiocephalic fistula and cephalic arch stenosis.

A-F. A, B, and C represent images before PTA (“pre-PTA”), and D, E, and F represent images after PTA (“post-PTA”). Compared to the post-PTA sound, the pre-PTA sound shows a stronger magnitude of the audio signal and higher pixel signal intensities at high-pitch frequencies with systolic accentuation in mel spectrograms. PTA = percutaneous transluminal angioplasty