[2.1.19] Big oil refinery groups are unbearable loud

[AntiElitz]

When you look at a group of like 100 running Oil refineries they are really really loud compared to a bunch of furnaces or anything else. When I meassured the volume I meassured -33db for a huge furnaces array. -30db for a huge general factory part and -20db in the oil rig. This is way to loud and not in line with the rest of the game.

[Donion]

Thanks for the report.
For the next release, 2.1.21 we've added a limit on how many oil refinery working sounds can play at the same time, resulting in lower volume.
I don't consider this to really be a bug so no changelog.