The development team focused on overall engine noise characteristics and single component optimization. (greencarcongress.com)
It is more powerful (85 kW, 5 kW more), has further reduced emissions, complies with EU 6d temp including the new requirements relating to Real Driving Emissions — RDE, and has optimized noise characteristics. (greencarcongress.com)
Now you could have done this differently by focussing on the ratio of trends — and I think you could work that out from their paper, but ratios have tricky noise characteristics if the denominator gets small (as here). (realclimate.org)