Sorry for that inconvenience but the developer is not yet expert Ren'Py game developer and just recently add the musics and sounds to this game. You have found a minor bug though, good job!
Flynn974
IMO, there are mistakes while creating the sound channels for the ambients sound, which makes the channels volume not controllable via the mixer in the Preferences. The issues are in chapter_7.rpy file, line 648 to 650, where it is using the wrong mixer "sound" instead of the default "sfx". See fixed codes below:
Python:
647 init python:
648 renpy.music.register_channel("effects", "sfx")
649 renpy.music.register_channel("background_s", "sfx")
650 renpy.music.register_channel("background_s2", "sfx")
However, if you actually want to create a different mixer called "sound", then the volume control should probably be included in the Preferences as well so that players can adjust the volume.
DarkBlade12345, if you know how to edit code, then you can make the same changes above ( in the file game/chapter_7.rpy ), basically just change from "sound" to "sfx" on line 648 to 650. Otherwise, you wait for next release or when
Flynn974 release a patch.
Hope that helps.