Re: Not invented here syndrome
When Concorde flew overhead you knew it was Concorde - certainly by the 1990s it was much, much louder than anything else in the sky as it descended over SE London on its way to Heathrow. It was a regular sight when I lived there and sounded like a real monster. Nothing else came close.
Now I live in rural France. Occasionally French air force jets have flown over at supersonic speeds. You know they're supersonic because the impact on the house, while it's never broken windows, feels like an oil tanker must have crashed into the living room at speed. It's truly terrifying.