To evaluate the effect of positive end‐expiratory pressure (PEEP) on sound propagation through injured lungs, we injected a multifrequency broad‐band sound signal into the airway of eight anesthetized, intubated and mechanically ventilated pigs, while recording transmitted sound at three locations bilaterally on the chest wall. Oleic acid injections effected a severe pulmonary oedema predominately in the dependent lung regions, with an average increase in venous admixture from 19 ± 15 to 59 ± 14% (P<0·001), and a reduction in dynamic respiratory system compliance from 34 ± 7 to 14 ± 4 ml cmH2O−1 (P<0·001). A concomitant decrease in sound transit time was seen in the dependent lung regions (P<0·05); no statistically significant change occurred in the lateral or non‐dependent areas. The application of PEEP resulted in a decrease in venous admixture, increase in respiratory system compliance and return of the sound transit time to pre‐injury levels in the dependent lung regions. Our results indicate that sound transmission velocity increases in lung tissue affected by permeability‐type pulmonary oedema in a manner reversible during alveolar recruitment with PEEP.