Because the creatures don't hear, they're completely unaware of it.

Perhaps the creature heard him, for it stopped those efforts, took more of the drug and tried to squeeze through the barrier.

The creature heard the subtle click and, startled, turned to look.

He had to force himself to speak at all, though he knew the creature couldn't hear them talk.

"All the creatures of the forest have good ears and can hear you coming long before they see you."

"I am sorry," Herald said, though he knew the creature could no longer hear him.

Ian's voice was still pitched low, as though the creature might hear them.

The clear barrier even gave slightly under its weight, and the creature could hear sounds through it.

And the large creatures we hope to ambush hear even better.

He saw nothing, heard nothing except for the faint calls of night creatures near the water.