"(Do) there have to (be) motor noises at 11:00 PM at night like last night?" wrote a resident of the city of Sunnyvale, according to AppleInsider. "Even with the windows closed I could still hear it." The facility from which the so-called "motor noises" are coming from is widely thought to be the location where Apple engineers are working on Project Titan. We don't know exactly what it is, but rumors indicate it has something to do with cars, and more than just infotainment technology like the award-winning Apple Carplay system.
Granted, "motor sounds" could come from pretty much anything from a power drill to a garage door opener. But, such sounds could also come from the testing of automobiles. And since we don't really know much of anything solid about Project Titan, well... let's just say that the speculation shall run rampant.
So there you have it. "Motor noises" are being reported late at night from an Apple location guarded behind high walls and tight security where an "auto work area" and "repair garage" is thought to exist. What does it mean? We have no idea, but it sure is fun to hypothesize. So feel free to ruminate and hazard your own guesses in the Comments.