I've started a career last night and playing in a Balao class sub in June , '44. I played through this 1st patrol a couple of times. Main reason being I again hit a place where the game became unplayable (not running smootly, TC was jerky). I decided to load the campaign folder (from v2.0) into v1.3 and see what happened. This area where things became very jerky was around Tokyo Bay and tried playing again after loading the Camapign layers starting up in northern Japan. This time around Tokyo Bay things played very smoothly. So that looks promising. One of the major reasons I gave up playing FOTRS v1.3 awhile back was because in certain area the game became unplayable and it always seems to be in the later years of the game. Anyway, I will keep testing this and see what happens.
While playing in this first patrol of the career on one of the times I heard that tinging sound that Billie was mentioning. It played through the whole patrol when I was submerged. It stopped when I either on the surface or using TC.
I'm just getting ready to go in and start the second patrol with the v2.0 zones loaded. Will report back.