Effect of exposure duration on lung hemorrhage from low‐frequency underwater sound

Previous research from our lab has shown that low-frequency (∼100–1000 Hz) underwater sound exposure can produce lung hemorrhage in laboratory mammals. The threshold for damage is lowest for exposure at the resonance frequency of lung. In adult mice, the threshold for lung damage is ∼2 kPa using a 3-min continuous wave (cw) exposure at the resonance frequency (∼300 Hz). The objective of this study was to determine the effect of exposure duration on lung damage produced by low-frequency sound. Experiments were performed with anesthetized adult mice. The resonance frequency of each mouse lung was determined using an acoustic scattering technique. Mice were exposed cw at the resonance frequency for durations of 1, 5, 10, 30 s, 1 and 3 min. The threshold for lung hemorrhage was relatively independent of duration for exposures greater than or equal to 1 min. For short exposure durations, the threshold increased and the mean extent of lung damage decreased. In some instances, extensive damage to the lung was observed to occur even for the 5-s exposure duration. However, the likelihood of extensive lung hemorrhage increased with increasing exposure duration.