"This is another smoking gun for me," Balcomb says of the necropsy results.
Marine mammal expert Anna Hall agrees.
"What that tells us is that there was enough energy in that sound to actually rupture membranes and cause internal bleeding and perhaps death," Hall says.
Hall says it is impossible to be absolutely sure that the piercing sound of the sonar testing caused the porpoises' deaths, but in her opinion there is "a high probability."
The U.S. government is investigating the deaths, but the final results of the inquiry aren't expected for another couple of months.
A decision is expected from Congress next month on whether to exempt the U.S. Navy from the Marine Mammal Protection Act.
"I'm concerned that the design of the way this whole investigation has gone on is intended to slow things down," Balcomb says.
The U.S. Navy says they are concerned about the health of marine mammals, but it says the sonar tests will go on because the training saves soldiers' lives in combat.