When Boom was testing last year, the sonic boom never reached the ground, as I recall. That can be arranged at higher altitudes, but doesn't work at low ones.
That's only possible under specific climatic conditions where there's separate temperature/pressure layers. Which is why they asked to repeal the ban on supersonic flight over populated areas. If they actually thought it wouldn't make noise they wouldn't be asking for the rule to be changed.
They didn't ask for only a non audible change, because they know that it will not be. It's just marketing and misdirection because the truth is much less rosy.