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. 2018 May 10;13(5):e0197380. doi: 10.1371/journal.pone.0197380

Fig 2. Frequency spectrum of the sound signals acquired from the hydrophone.

Fig 2

(a) Frequency spectrum with no boiling occurrence in vivo (T<100°C, n = 3). The inset is the same data shown in the log scale. (b) Frequency spectrum at the onset of boiling (T = 100°C) both in vivo (n = 4) and in tissue-mimicking phantoms (n = 4); +: environmental noise. The figure shows that there are several consistent peaks between 0.4–1 kHz which are associated with boiling. These peaks were selected as boiling signatures and the area under curve (AUC) within 0.4–1 kHz was calculated to represent the sound signal strength. Statistics: mean ± std.