Would like an option to disable Factorio sounds when the game is not in focus (in background).

I like the sounds when actively playing, but not when I have Factorio in the background while doing other computery things. Hearing the drone of the machinery while on Skype or YouTube can be annoying.

I ...

I was unable to to complete the third tutorial due to mods (Train schedules and train stops).

I traced the problem to the 'Skip first hour' mod from Aidan647, though other train mods also affected previous tutorials.

Replication steps:

Install Skip first hour mod
Create new game (default ...