NL Enhanced V4 - Engine sounds showcase

Finally I've adressed issues with engine sounds, revisited all of them, to ensure all are on at least 'not so annoying level'. Main changes happend to D08 engines, but all of them got uniform 3D source positions now, so it will make all of them not so varying in loudness.

OMSI 2 MAN NL Enhanced V4 - Engine Sounds Showcase (YouTube)