Not too realistic, but it's getting there! 20,000 feet not sure you'd hear the jet so loudly, but the boom you'd hear for sure. Remember the F22 that shot down the balloon? It was at like 50-60k feet and in the videos you could clearly hear the sonic boom but not really the jet. Also what the games can't get across is at 20k feet you'd "feel" the boom more than hear it, meaning it'd be like a car hit the side of your house, so it's feel like movement more than sound. Maybe they should add a slight "shake" for a few frames? Either way DCS is the best
Yeah that happens occasionally. The echo is easier in the lower mountain ranges, in the desert you'll hear a longer boom but lighter, from variables of altitude flying characteristics, of a specific aircraft!