I've heard plenty of sonic booms before as well as military training up close and from afar. I haven't heard any of the mysterious booms myself, so I am only going off second hand accounts, but the witnesses I've talked to say these booms are nothing like the ones they've all grown up hearing. The reports are of localized "booms", sensed by their dogs before anyone else (like seismic activity), and loud enough to rattle bookshelves, windows and picture frames.