Muzzle Blast: More Powder or More Pressure

[Bull45cal.]

Ok a ? for all you arm chair ballisticians (and real ballisticians). I have developed a reduced load for the purpose of reducing muzzle blast with the added benefit of highly reduced recoil. I am currently loading 155gr. A-Max over 28gr. of SR-4759 in a .30-06 (MV @ 2300 fps + or – as few). I have been contemplating the development of another purpose built gun that would be chambered in something considerably smaller than .30-06 (maybe 30BR or 30 Remington AR). If I were to use a smaller cartridge to achieve the same velocity with the same bullet and powder type, then the charge weight should be less. Correct? For this to happen the pressure would increase. Correct? Now my true question! Where audible muzzle blast is concerned, would I be better to stick with the larger case using more powder @ lower pressure or should I use a smaller case with higher pressure. Which one would have less audible noise?

Thanks,
Shane