Where is this claim?
From the top of their corporate website, there is a video explaining this:
https://boomsupersonic.com/boomless-cruise
And from the top of their wikipedia page:
"is expected to reach supersonic speeds without causing a sonic boom at ground level by taking advantage of a physics phenomenon known as mach cutoff"
https://en.wikipedia.org/wiki/Boom_Overture
alt Hacker News
From the top of their corporate website, there is a video explaining this:
https://boomsupersonic.com/boomless-cruise
And from the top of their wikipedia page:
"is expected to reach supersonic speeds without causing a sonic boom at ground level by taking advantage of a physics phenomenon known as mach cutoff"
https://en.wikipedia.org/wiki/Boom_Overture