After looking at some of the game files, there's a couple of things I'm wondering about in regards to the respective self noise rates. These seem to be in decibels but I have to question some of the settings.
Skipjack = 140 (machinery bolted down as on previous submarines)
Permit = 136 (first class to use raft isolation mounts for machinery)
Sturgeon = 130 (refinement of Permit class)
Narwhal = 105 (natural convection reactor very quiet)
Los Angeles = 115
My specific issue here relates to the relationship between the Skipjack, Permit and Sturgeon class. I don't have a problem with the 140 rating for the Skipjack, but I do think that consideration should be given to possibly slightly lowering it for the 84 campaign. The top speed from 1968 to 1984 has already been lowered, from what I can tell to reflect the new "scimitar" curve blade 7-blade screw, which was required to deal with wake-instability (as far as I can tell vibration of the blades as they passed through the wake from the control surfaces) on the initial 5 bladed screw (basically these vibrations emitted a particular noise which made the sub louder than it should have been at speeds below the cavitation threshold). As far as I know, there isn't anything in CW that could simulate this issue, so making the sub louder/quieter should suffice quite well.
The value used for the Permit class, 136 db. While it did use the same S5W reactor (and probably much of the steam turbine machinery) the Thresher/Permit class was notable as they were the first submarine design to make use of rafted / sound isolated mountings and foundations for much if not all of their machinery. By all reports, they were notably quieter than the Skipjack class and stealth was a big consideration in their design. The only other thing to add here is that initially, the USS Thresher did turn out to be quite loud as built and fitted with a
The Sturgeon class, 130 db was for all intents and purposes an evolution of the Permit design, being enlarged to have more room for things such as electronics spaces. This brings us to the crux of the matter. While I do not think it is particularly far-fetched to imagine that they might be able to further quiet the machinery on the Sturgeon, especially as the technology matured, I'm not seeing why the Sturgeon class should be 6 db quieter than the Permit while the Permit is only 4db quieter than the Skipjack.
TLDR: Think about making the 1984 Skipjack slightly quieter, Permit class should probably be quieter as well (bigger difference between Skipjack & Permit).
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