The mystery hum which has kept some West Seattle residents up at night may not be man-made after all.
A number of tips led us to the University of Washington's Marine Biology program. Yes, the Midshipman fish, an ugly creature with an odd mating call, could indeed be the sound.
Nearby buildings or the hulls of ships could be acting as giant sub-woofers carrying the low frequency sound for miles.
You can compare the drone to a recording of the midshipman fish made by Cornell University. Listen here