Yes; we know for a fact that we can make much quieter supersonic aircraft, even for large transport aircraft (existing smaller aircraft of the same period as Co

Yes; we know for a fact that we can make much quieter supersonic aircraft, even for large transport aircraft (existing smaller aircraft of the same period as Concorde were already much quieter, and we've improved on that since). Note however no current proposal for a SST is anywhere near as big as Concorde, which already gives them an inherent advantage.