Seeing how the volume values are directly linked to percentage and further linked to a mixer using dB values - I would love a general "volume knob". Like:
class Tank: Tank
masterVolumeEnginesExt = 0.5; // 50%=-6dB volume reduction for all EngineExt sounds in this class
masterVolumeEnginesInt = 0.5; // 50%=-6dB volume reduction for all EngineInt sounds in this class
masterVolumeNoise = 0.5; // 50%=-6dB volume reduction for all noise sounds in this class
oneSound = XXX;
You can even refine this more: Add "overallVolume" values for groups such as Engine, EngineInt, Noise, WHeels, Effects (doors) etc.
This would greatly help BI and the community when it comes to setting volume levels for vehicles but it can be extended to set levels for everything. From human characters to environment sounds.
Deep in the engine code you would need to program something like this:
engine - play sample, look for volume1 in config (volume is 1), look for masterVolume in config (volume is 0.5 for example), subtract 50%/6dB from signal volume
This seems complicated but when done it will really make work so much easier, don't you agree?