Sound Insulation?

Hello,

when I go to the detailed stats tab on any of my cars, I get a -12.8% on sound insulation.
Yet I see no way of improving the sound insulation it seems…

Is that feature still missing or am I missing it?

sound insulation is part of the interior choice, which starts from basic (least) to hand-made (most) that also depends on your car segmentation & budget. You don’t want to give an econobox a state-of-the-art interior, vice versa to luxury & exotic cars.

Ok, I somewhat figured it out I think.
There is one more thing which confuses me: Passenger Volume
It depends on the body used, but even on some large estates or Suvs I get a passenger volume penalty…

check on your car’s market segment, be sure to give at least minimum seating
about volume? try not to cramp up with too much seating