Background Noise Surfaced and Submerged
 

I'm running TWoS. The background sound is the same either surfaced on diesels or submerged on electric motors. The difference in sounds by diesels or electric motors running on batteries is unmistakable. Would it be difficult to mod a different sound when the command to switch to electric motors is given?

I'm not really sure why would you experience something like you've described but I can confirm that diesel and electric engines sounds in TWoS are clearly distinguishable.