One of the unique selling points of their proposed aircraft is that it won't be so loud:
> Boom says Overture will be a lot quieter than Concorde and the supersonic military aircraft that were flying at the time the FAA ban
How have they demonstrated that they know how to cause quieter sonic booms?
Secondly: Although the final proof of it is in the full scale aircraft for sure, a lot can be done with software modelling (1) and wind tunnels these days. And with the scale model that just flew, to be followed by "checking the actual performance that was demonstrated against what our models predicted, and how we expected it to fly." (2)
Thirdly, I point you to other "quieter supersonic" aircraft work in progress, the X-59. Some of their evidence-gathering process is detailed at the Wikipedia link, "development" section. (3)
It will be interesting to see how these work out; but if they do not, then it's a failure of modelling and design, not because they missed the directly obvious. But if you are an aerospace engineer and know more about this subfield, then say so.
1) "Boom has perfected its aircraft’s efficient, aerodynamic design using computational fluid dynamics, which “is basically a digital wind tunnel"."
https://edition.cnn.com/2025/01/28/travel/boom-supersonic-fi...
2) https://www.livescience.com/technology/engineering/boom-supe...
3) https://www.lockheedmartin.com/en-us/products/x-59-quiet-sup...
There's been considerable work on sonic boom mitigation for many decades. Boom's long nose, flat underside, top engine, small wingspan delta wings are all designs expected to mitigate a sonic boom. Let's see if it works in practice.