The throbbing of the engines...or not!

[Vacillator]

I searched for this and see that it's been asked before but couldn't find a defintive answer, so...

Running either electric or diesel I have no engine noise inside my Type VIIB, all the way up to ahead flank. Now I know I'm not stood next to Johann in the engine room but surely I should get something? Going external gives me some noise close to the camera.

Going external also showed me an odd thing. Was running diesels at ahead flank (and getting 18kts) to test noise. I saw that only one screw was turning, starboard was stationary! I thought 'that can't be right' so I went to 20m and then re-surfaced. This time on ahead flank I got both screws turning! Anyone know what gives? Surely one screw (ooh err missus) wouldn't give me 18kts?

Minor problems anyway but curious.

Oh I should say it's GWX 1.03 but I don't think I've ever heard engine noise in the boat.