James Locascio, a senior scientist with the Mote Marine Laboratory and Aquarium, said the sound could be coming from black drum fish in the bay. He said the fish produce throbbing sounds during their mating season when muscles vibrate against their swim bladders.

He said the sound could reach as far as a mile away from the water.

"It's a low frequency sound, and so they travel much better and go further distances, and they go through dissimilar media more efficiently," Locascio told WTVT-TV.