KING - The mystery hum that has kept some Seattle, Washington residents up at night may not be man-made after all.

A number of tips led to the University of Washington's Marine Biology program.

They say the Midshipman fish, an ugly creature with an odd mating call, could indeed be behind the sound.

Nearby buildings or the hulls of ships could be acting as giant sub-woofers carrying the low frequency sound of the fish's call for miles.

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