The aquatic creatures couldn't hear the loud beats of the sound blasters because their brains and internal organs were liquified on contact before boiling without heat. They simply didn't have the brain capacity to process the sound because the sound had processed their brain matter into sludge.
The only enemies who could hear the sound of the sound blasters were the ones who were too far away and didn't die instantly. But this didn't mean that they wouldn't die.
The shockwaves created by the sound blasters can still batter, cripple, smash, and injure obstacles that they encounter. Some powerful creatures could survive these far-traveling shockwaves, but only divine beings could survive being close to the sound blasters.
As Loki watched with pride, he saw the ocean forced to boil, burn, explode, and evaporate against its will and against the natural behavior of water.
