If there are 3 parameters, then from second (volume in dB) is used for maximum distance calculation, max. distance is emitter distance from listener where sound from this emitter is not audible.

When in cfg are four parameters, then 4 parameter is distance in meters, and second parameter (volume in dB) is ignored - is recalculated based on max distance.

0dB == 1000m

is recalculated based on max distance

What max distance is this - related to view distance?

Sample volume is recalculated, volume is derived from distance ( where 0dB = 1000m ), there is no “real” difference between these to entries.

Distance == view distance.

Some more good information - details about new class Sounds of cfgVehicles.

• frequency range is [0.6, inf] but usable range is somewhere about 1 that's [0.8, 1.2]
• randomize = small random number unique for each vehicle, range [0, 1]
• angular velocity - but this controller is not much usable, because values are discrete, not smooth, so in frame N it should be 0 and in frame N+1 it should be 2
• factor - linear interpolation between A and B based on x, value = A + (B - A) *x, trick to get peak is using min{ X factor [A, B], X factor [B, A] }

Here is example helicopter engine / rotor sound config.

		class Sounds
		{
			class Engine
			{
				sound[] = {"pmc\vte_sounds\vehicle\CH47_engine_high_ext.wss", 1, 1, 800};
				frequency = "rotorSpeed";
				volume = "camPos*((rotorSpeed-0.72)*4)";
			};
 
			class RotorLowOut
			{
				sound[] = {"pmc\vte_sounds\vehicle\CH47_rotor_ext.wss", 3.1622777, 1, 1500};
				frequency = "rotorSpeed";
				volume = "camPos*(0 max (rotorSpeed-0.1))";
				cone[] = {1.8,3.14,2.0,0.9};
			};
 
			class RotorHighOut
			{
				sound[] = {"pmc\vte_sounds\vehicle\CH47_rotor_forsage_ext.wss", 3.1622777, 1, 1800};
				frequency = "rotorSpeed";
				volume = "camPos*10*(0 max (rotorThrust-0.95))";
				cone[] = {1.8,3.14,2.0,0.9};
			};
 
			class EngineIn
			{
				sound[] = {"pmc\vte_sounds\vehicle\CH47_engine_high_int.wss", 1.7782794, 1};
				frequency = "rotorSpeed";
				volume = "(1-camPos)*((rotorSpeed-0.75)*4)";
			};

Check out basic Sound config tutorial.