Help avoiding detection

[Theraven]

Hi, I've been playing SH4 on and off for a few months now, experimenting with different ships and years and what not. Ever since I installed the 1.3 patch I've found it impossible to attack any convoys because I ALWAYS get detected by the destroyers that are guarding the convoy. Now when I played with patch 1.2 as long as I wasn't surfaced they wouldn't see me. I even had a couple literally run into me and damage my sub because I was only about 20 feet below the surface and I was still not detected, they just kept on going. Now, under version 1.3, even if I am at periscope depth with my periscope still down even if I'm completely stopped and just sitting there they will detect me and I'll either die or barely make it out of there with my sub intact. At first I thought maybe it was because they heard me approaching even when I was pretty far out but today I was sitting in the spot I wanted to be in for a good 10 hours completely stopped waiting on the convoy to come and they still detected me and came after me. I was at periscope depth with the periscope down, completely stopped and it was at night.

It's really quite frustrating since I basically have to completely avoid convoys now. Am I doing something wrong? Or maybe this is just a bug with 1.3? Is there any way to fix it? Any advice you guys can offer is appreciated.