Fig. 1: Acoustic wave propagation and sensing.

a Representative frequency ranges of acoustic waves and corresponding sensor detection capabilities: microphones, hydrophones, and acoustic emission (AE) sensors used for monitoring boiling-induced acoustic phenomena. b Acoustic wave propagation at key material interfaces involved in boiling: liquid–solid, liquid–air, and solid–air. Arrows denote wave paths, red for incident (i), green for transmitted (t), and dashed black for reflected (r), with line thickness indicating relative energy transmission and reflection. Schematic illustrations of typical pool boiling setups with various heater configurations and sensor placements: c Type I configuration: plate heater with AE sensor embedded beneath the heating surface, d Type II configuration: rod-type heater (fuel cladding analog) with AE sensor positioned at the remote end, and e Type III configuration: block heater with AE sensor mounted on the chamber wall. In all three configurations (Types I–III), the positions of the hydrophone and microphone remain fixed, with only the AE sensor placement varying.