At air shows with fighter jets I would expect there would be a demonstration of supersonic flight. But in this flight of a Eurofighter Typhoon, no sonic boom was heard.
What is the reason?
Is it that there is no supersonic flight involved due to loudness or needing a bigger distance to accelerate?
Or is the sonic boom inaudible for a reason related to the short time delay of the sound between the noise source and the microphone, or some other physical reason?
Just for a bit of flavour, I recall an article from Air Progress from the late 70s about Darryl Greenamyer setting the low altitude absolute speed record, in his "homebuilt" F-104, of Mach 1.3 (mentioned in this article) in 1977.
For the run he had to cross very low over timing trigger devices at the start and end of the speed course at the dry lake bed at Edwards, which were set up with cars parked beside them.
I remember the description of the event by the writer who witnessed it from somewhere along the middle of the course, a safe distance away with other observers. The F-104 passed over the car at the 1st speed trap at 60 ft AGL and passed the writer in absolute silence, and it wasn't until a second or so had passed that a sound like a dynamite explosion a couple hundred feet away went off. All the glass of the cars at the speed traps blew out and their trunks popped open. The writer was warned in no uncertain terms that if he didn't protect his ears he'd get hearing damage, and not to be fooled by the initially silent passage of the jet itself into taking his fingers out of his ears.
Imagine that happening at an airshow.
In a lot of areas, sonic booms are illegal over land or near residential areas. Yes it's loud, yes it's potentially damaging, especially at low altitudes. I've been to a lot of airshows, I've never seen a supersonic demo.
Sonic booms have a lot of, lot of, lot of throw. There would be no way to confine a sonic boom to just the airfield. People two towns over would have have car alarms set off and houses shaken. It would upset animals, it would upset people! It would trigger PTSD for some and panics for others. It would generate hundreds of phone calls to 911.
Keep in mind the airplane has to accelerate to and through supersonic well before the airfield, and then has to slow down again. It's covering a mile every 5 seconds, so this, combined with the throw, sweeps a whole lot of area.
John K has already provided an example of what a sonic boom feels like from very close, and Harper - Reinstate Monica describes it in general terms. Let me give you a practical example of what a sonic boom did in a radius of 100 km.
On 22 March 2018, Air France flight AF671A from Réunion to Paris Orly was flying over northern Italy when it lost radio contact with Air Traffic Control. Two Eurofighter Typhoons were sent to investigate, and as they rushed there they broke the sound barrier.
The sonic booms were heard from Aosta to Bergamo, which are 180 km apart. And at first they were mistaken for bombs. The result? Among other things, there were hundreds of calls to the police, people ran out of buildings in panic, some schools and offices were evacuated, and some windows got broken.
And at an airshow they'd fly much lower, so it would be louder!
To be fair, it was explained that the wind and weather conditions were unfortunate, as they favoured the propagation of sound, but in any case a sonic boom is way too loud to be done for fun: it's only allowed in case of emergencies.
By the way, in the end it turned out it was a false alarm, so at least there was a happy ending.
[Sources: in English, in Italian]
