If a big proportion of business-travel-miles are flown over oceans (which seems reasonable between the most common routes like New York-London, SF-Tokyo, SF-HK...), would it not be cost and time efficient to use low-drag but noisy planes and just hit the speed of sound over the ocean? Flying .9 Mach over the land and 1.5 (or whatever was reasonable) would still save a lot of time and wouldn't disturb anyone.