Strange sounds heard worldwide!?

[zenmaster]

they were not aware that this was a widespread phenomenon either.

But is it? AFAIK, these are different sounds, therefore different causes. From just these youtube videos, can we actually say it is a phenomenon? Also, something as seemingly out in the open like this, and relatively long lasting in metro areas, would be recorded by more individuals and have been subjected to scientific scrutiny. Yet that has not happened.
However, there is definitely an attempt to link these together and attribute them to paranormal causes and all manner of conspiracies - why is that? Has a single one of these, lacking an explanation, been independently experienced?