A strange and disturbing sound is making for some sleepless nights for people who live near the Monterey Bay.
But experts say the puzzling hum is probably just a fish. A toadfish, to be exact.
The droning sound, which sometimes lasts for more than an hour, has led neighbors to come up with many theories, including secret military experiments.
Experts from the Monterey Bay Aquarium told NBC Bay Area on Monday the noise likely comes from "lonesome males" trying to attract a mate.
Toadfish mating season usually starts in May and ends in September.