Speed and quiet - 1/3 vs 2/3 vs full stop
 

I usually try to crawl around at 1/3rd (5 knots) but it is often too slow to maneuver into attack position. Just how loud are the U.S. subs when traveling at 10 knots (2/3rds)?

For example, say a Sturgeon skipper knows there is an enemy sub in the area. Will he slow down to 5 knots or will he feel safe continuing to cruise at 10 knots?

Also, if I am comfortable where I am is it better to go full stop or would it be better to stay at 5 knots? Just wonder if full stop overs any advantages?

It really depends on what the enemies are doing, what sensors they have, if you're in a duct, if there's a layer in between, etc. It is quite possible to stalk enemies up to 20kts if the variables are in your favor. Use the signature analysis to determine this. If engaging surface ships, observe their sprint and drift behavior, then use that to your advantage. Being stealthy does not necessarily mean being slow.

Thanks!. I was about to ask you to talk further about signature analysis but I did some searching and found this nice video from JiveTurkey that covers it. Nice explanation JiveTurkey!

https://www.youtube.com/watch?v=7CqCRNxIjbk

Here's a nice tutorial from my buddy ramjb on why being stealthy doesn't mean you have to be slow.

https://www.youtube.com/watch?v=clhxFImfH9I

This is a lesson I am forced to re-learn, time, after time, after time.

Basically, you've to use the Signature Analysis panel to gauge just how detectable you are versus a specific contact. As long as you're not over 10 dB on any enemy sensor at a given speed, you should be safe.

However, it's a gamble to run above 2/3 speed unless you're more or less certain the enemy won't be detecting you (i.e. you're in their baffles), considering the faster you go, the deafer you are. That can make you lose contacts and prevent you from noticing (and adapting to) changing circumstances. Which can very well happen given escorts and submarines occasionally change course and/or slow down to listen in where they couldn't earlier.

Another thing to consider is that you can't measure yourself against what you haven't detected, so again, caution is advised unless you're fairly sure every enemy is accounted for.

Aren't Narwhal and the 688's the only boats that have natural convection reactors that don't need to actively pump their coolant when running slowly? Is it modelled that they make a big step in quieting when going 1/3rd?

Also Rickover was a dick lol.

AFAIK, there's only one "kink" in the system right now, and that's an jump when you cavitate. Beyond that it is linear with speed.

Perhaps it'll be a good idea to change the text file format to allow for aknot by knot noise value which the game just looks-up. Then we can program in however many kinks we feel is realistic. Pumps on/off, pumps switching to high speed, another pump being brought into the game, the raft being locked on some subs at high speed ... etc.

The 688s use an S6G reactor which isn't natural convection, you're probably thinking of the Ohio's S8G.

I've been told the S6G can also nat-circ, but you have to be STOPPED (hotel load only).

Well in theory if sound is that important just about any boat could be SCRAM'd and run off the battery for some time, as long as enough power is reserved to do a reactor start up again. Screw that up and you're back in the 1950s and its time to raise the snorkel.

Would also be pretty cool if you could put the boat into turbo-electric mode or use the EPM. My understanding is that the EPM is pretty loud though.

EPM and SPM both. Does the term, "Screaming Banshee" mean anything to you? :)

I'm curious from an implementation standpoint - more a developer question - is noise level based more on reactor setting or knots?

So let's say we've got a Skipjack and a Sturgeon. Sturgeon is, by the game files, a quieter noise level boat. But is that at equivalent speed, or equivalent reactor setting?

For example, both boats going 20 knots. Skipjack may only have to be at Standard to achieve this, Sturgeon at Full (just guessing, without verifying in game). Will the Sturgeon be quieter at equivalent speed? Or is that nullified by the fact that it's running at a higher reactor setting?

Not to nitpick but it's more of a throttle setting than a reactor setting.

I don't believe relative plant noise is factored into the game. You have your ownship noise level as specified in the .txt file for the ship, which is then modified by whatever speed the ship is running at. So for something like a Skipjack or a November, that noise is going to be through the roof no matter what it is doing. Ditto for stuff like the Los Angeles or Narwhal being quiet.
The trouble is, this makes certain things (like the claims that the Alfa was actually a quiet boat until it was cranked up, or the "blade-rate" related noise suffered by the early Skipjacks and Permit class with 5 blade screws at certian speeds) impossible to replicate.

What I'm not sure about is whether or not Silent Running will bring you below the base noise-level or just down to it, but other than that you'd have ownship noise + speed modifier.