Resonator Source

This is underneath my apartment and the stairs which lead up to my apartment. It just so happens to be that the manager has a storage room right under my apartment. One night I went outside to discard some trash in the dump and while coming back up I heard this sound which is consistent with the same sounds I hear in my apartment. And here as well as in the other videos Ive uploaded you can hear when it is turned off and it even seems to jolt and give off a slightly harder vibration right before turning off.