I am kind of late to this conversation, but I have some experience with most of the discussed calibers so here goes. The first handgun I ever shot was my Father's 32-20 Colt Police Positive Special. He let me shoot it when I bought the ammunition. Once, I bought some "rifle-only" loads (long story). It bent the crane (yoke) of the gun in the first cylinderfull. I had it repaired and only shot standard loads out of it after that. I inherited it and still have it. A few years later I found a kid with access to his fathers 32-20 Colt SAA. We fired the rest of the "rifle-only" loads in it. The blast was impressive. It was more of a loud CRACK than a loud boom. I would say that it was the loudest handgun cartridge I have ever heard, although I have not heard any handgun more powerful than a .44 Magnum. I attribute at least some of my present hearing loss to those cartridges. We fired some at dusk and there was a 2' or 3' fireball out the end of the barrel. It did not appear to hurt the SAA.
A few years later I got a Thompson Contender barrel in 32-20 and shortly after that, a Marlin 1894 in 32-20. I loaded up some cartridges with 10gr, 12gr and finally 12.5gr of 2400 with 100gr to 115gr bullets of various types. There was no noise problem with shooting that in the Marlin, but it was considerably louder in the Contender. I do NOT believe that it was as loud as the "rifle-only" loads, but who knows for sure. I have loaded hot loads in the 32-20 with SR4756, Unique, and HS-6. None of them were as loud as the 2400 loads.
I have fired 30Carbine cartridges in a friends Ruger revolver. We used my ammunition that was loaded the same as the rifle 32-20 load, 12.5gr of 2400 with a 110gr FMJ or soft-point. I had been shooting it in my M1 Carbine and a Marlin Model 62. Nothing unusually loud with that. The same load in the Ruger was much louder, but again, I don't think it was as loud as the "rifle-only" loads. I have not loaded the 30Carbine with other powders, so I cannot compare their relative loudness.
I have loaded 32 S&W Long for a lot of years, but never at a hot enough load to make it unusually loud. In fact, it could be considered mild. My first 32 H&R Magnum was acquired in the late 1980's or early 1990's. It was a S&W J-frame Super-KitGun, so I did not load it heavier than factory loads. Louder than the .32 S&W Long, but not nearly as loud as the 32-20 or 30Carbine. Later I got a .32 Mag Ruger Super-SingleSix and just recently a Ruger SP-101. I did up the loads in those. I went up to 8.5gr of 2400 in the single-action, but because of sticky ejection, I polished the chambers and reduced the load to 7.5gr. They are loud, but cannot compare with the heavily loaded 32-20 or 30Carbine.
I have no experience with the .327 Magnum (yet), but would expect that it would match the heavily loaded 32-20 and 30Carbine as to noise. It might even match the "rifle-only" loads. If so, I would suggest wearing ear plugs and muffs. You could also experiment with faster powders. It seems that there is a big difference in noise between 2400 or slower powders compared with Unique or faster powders.