Volume reduction (fade-out) controlled by distance (fraction of audible distance).

Volume reduction (fade-out) or increase (fade-in) controlled by zoom level.

Default: 0

Has to be in the range [-1.0, 1.0].

Positive values are used for night sounds, the volume of the sound is 1.0 when darkness = threshold, 0.0 when darkness = 0.0 and linearly interpolated in between.

Negative values are used for day sounds, the sound of the sound is 0.0 when darkness = -threshold, 1.0 when darkness = 1.0 and linearly interpolated in between.