I remember that chart, too. If I'm not mistaken, it was later discovered by someone far more knowledgeable of the workings of SC than me that the Seawolf sub did not have significant noise change up to 10 knots, but the Akulas and the 688i began to make more noise after 6 to 8 knots. I believe the amount of noise an object generates is directly related to it's maxium speed. I've learned this from adding new "biologic" contacts to my database. When adding new sounds, I decided that biologics should show up in some way on the narrowband display, so I created a new type of biologic "object", and gave each one a very unique narrowband signature. When I changed the objects maximum speed, it generated more noise depending on how close it was travelling in relation to it's maxium speed.
Sorry if this is like reading Arabic for some, but I like to yap. Anyway, the Seawolf has a pretty high maximum speed, and a very low "noise" level in the database, so you can get her up to 10 knots without seeing much of a change. The 688i and Akula have fairly high maximum speeds, but they also have a higher "noise" level. After reading this thread, I decided to test the theory out, I created a test scenario, tracking several types of boats from close range using USS Seawolf. Sure enough, the Ohio's, Virginia's, and Seawolf's don't have a significant change in noise output until they get up to about 11 knots. The Ohio was about 10. For Trafalgar, Los Angeles and Akula class boats, the noise began to increase around 7 knots. For diesel boats, it was a much lower speed, usually around 6 knots or so, but the real quiet diesel boats, like the Collins, Upholder, and the Swedish subs, the noise didn't begin to rise until around 7 knots, much like the SSN's.
From these tests, I believe the noise level output are pretty darn accurate.
Hope this helps.
Cheers.
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