Infrasound can cause internal hemorrhaging when different organs or tissues vibrate at different resonant frequencies. These structures are ripped apart by certain frequencies not unlike the 'Galloping Girtie' Tacoma Narrows Bridge.
Animals like elephants and whales use infrasound for various reasons. They must already have organs which are particularly resonant at infrasound frequencies. Exposing them to high volume infrasound undoubtably damages those and surrounding tissues. But it's probably more severe than just popping an ear drum. Their whole 'inner ear' is likely damaged which would account for their disorientation ?
http://www.cnn.com/2002/TECH/science/11/18/
navy.sonar.reut/index.html
