Purple goggles and no ear muffs. Think of it as a fee trip to the twilight zone.
I think we are due in a year or two. The first time I heard them, I was picking up mulch by Otis Airforce Base. I thought a squadron of jets was at the end of the runway getting ready to take off. After a half hour I asked the loader why the jets had not taken off. He explained what it was. I lived and worked about 15 miles away and never saw or heard them.