"Mid-frequency active sonar sends sound pules through the water to listen for what objects the sound bounces off of ..."

Sound pules? Alas, "pule" is a verb and not the noun pertaining to that verb (to make a thin wail, in some definitions similar to one of the sounds a chicken makes) and so mid-frequency sonar doesn't send chicken-mutterings through the water. Must be a regular ol' typo, then.