Thresholds for sound‐induced lung hemorrhage for frequencies from 100 Hz to 1 MHz

Edwin L. Carstensen has made outstanding and wide‐ranging contributions to the field of biomedical ultrasound. His many achievements span the areas of bioeffects of ultrasound, acoustic cavitation, lithotripsy, thermal and mechanical mechanisms, and nonlinear acoustics. In 1990, Carstensen first reported that pulsed ultrasound at diagnostic exposure conditions could produce mammalian lung hemorrhage [Child et al., Ultrasound Med. and Biol. 16, 817–825 (1990)]. Recent work from our lab has quantified the thresholds for murine lung hemorrhage over a range of acoustic frequencies from approximately 100 Hz to 1 MHz. Various exposure systems were used to generate acoustic fields over this broad frequency range in the laboratory. Through several different investigations, we have shown that murine lung responds to low‐frequency underwater sound as a resonant structure. The resonance frequency of adult murine lung is approximately 325 Hz, and the pressure threshold for lung hemorrhage is lowest at the resonance frequency. The threshold increases for frequencies above lung resonance. The equation P_th=0.01f^0.64, where P_th is the threshold pressure in MPa and f is the acoustic exposure frequency in kHz, approximates our experimental lung threshold data, for long pulse durations, over the 2.5–1000‐kHz range.