The build quality- which varies a lot- can determine how much noise a shutter in an old soviet camera makes. My quietest camera is one Zorki-1, but my other Zorki-1 and FED-1 are also among the noisiest as well. My FED-2 also fire with more noise. The laths used in the shutter - early ones used plain metal ones with the cloth wrapped around it, and the latter ones used crimped metal- would determine the firing sound as well. The latter, found in FED-2 and later cameras- tend to create more noise.
Then there is shutter tensioning as well. The more tensioning there is in the shutter, the more noise it would likely produce.
The soviet RF which I found to make the least sound when firing are the Kiev RF, the older ones in particular. They "sigh" rather than "wheeze" as the latter ones would.
If I were to select the soviet camera in my stash which makes the least noise when firing, it would be the Kiev-35A, Smena-8M and Lubitel-1.
Jay