Yes, that's correct, I worded that improperly. It reduces noise by some 20db, as explained here in the article accompanying the picture:
Der Schallschutz-tunnel ist technisch einfach, ortsbild-und landschaftsverträglich, verhältnis-mässig kostengünstig und sehr wirk-sam (
bis 20 dB[A] Reduktion).
Swiss Shooting Tunnel My German is a bit rostig, although in my defense the article was written with a heavy Swiss accent.
