Looks like I've found something

Take look at this, it's located in "game.cfg"
<Player_Darkness
MinLightLevel = "0.15"
RadiusAdd = "3"
AmbientLightMinLightLevel = "0.2"
AmbientLightRadius = "6.5"
AmbientLightIntensity = "0.32"
AmbientLightFadeInTime = "2.8"
AmbientLightFadeOutTime = "2.3"
AmbientLightColor = "0.5 0.5 1 0"
LoopSoundFile = "player_darkness.ogg"
LoopSoundVolume = "0.2"
LoopSoundStartupTime = "1.0"
LoopSoundFadeInSpeed = "0.05"
LoopSoundFadeOutSpeed = "0.4"
/>