For example, say the cartridge is 45/70 and the firearm is very strong and modern, maybe a RUGER #1. Given the same weight bullet, let's say 450 grain, and let's say we dialed-in two loads, one going 975 fps using some type of black powder. The other also going 975 fps using 4350 or 4831 or some slow powder. Both are sub-sonic.
Would the sound be less with the black powder load........???