Sound: Filters – Arma 3

Filters

Distance Frequency Attenuation

Every sound in the game is attenuated by a frequency Low Pass Filter, the frequency cutoff changes with distance.

Default filter is configured in CfgSoundGlobals, however it is possible to define a custom distance attenuation filter for each SoundSet using parameter distanceFilter.

All Distance Frequency Attenuation Filters must be configured in the base class CfgDistanceFilters.

parameter	unit/values	default	descriptions
type	Fitler Type name	"lowPassFilter"	type of filter (note: currently, there only Low Pass Filter is possible)
minCutoffFrequency	[Hz]	300	minimal cutoff frequency (see: Cutoff Frequency on Wikipedia))
qFactor	float (0..1)	1	slope of attenuation curve in frequency spectrum (see Q factor on Wikipedia
innerRange	[m]	100	radius of sphere with sound source in its' center within innerRange distance, no filter is applied
range	[m]	1500	radius of sphere with sound source in its' center outside the range distance, cutoff frequency of filtering stops at minCutoffFrequency
powerFactor	(0..100)	2	relationship between cutoff frequency and distance higher value means faster attanuation

class CfgDistanceFilters
{
	class defaultDistanceFreqAttenuationFilter
	{
		type = "lowPassFilter";
		minCutoffFrequency = 150;
		qFactor = 1;
		innerRange = 10;
		range = 1000;
		powerFactor = 32;
	};
};

Sound Effects

Sound Effects is an older ArmA 3 audio feature which handles sound filtering of a specific group of sounds, like radio protocol, underwater, or interior attenuation.

Attenuation Effects

All attenuation effects have to be configured within class AttenuationsEffects (base class CfgSoundEffects).

It is represented by class containing predefined filter chain (2x4 band equalizer + echo), which is applied on specific groups of sounds witch are considered to come "from outside" of a vehicle or building.

Configuration for vehicles is handled by parameter attenuationEffectType within the vehicle configuration class. It links the vehicle to a specific attenuation class ( e.g.: attenuationEffectType = "CarAttenuation"; A special case is attenuation of sounds related to building interiors, there is no parameter that defines which attenuation class should be used, the expected class name is hard-coded instead: HouseAttenuation

class CfgSoundEffects
{
	class AttenuationsEffects
	{
		class HouseAttenuation
		{
			class Equalizer0
			{
				center[] = { 50, 600, 2000, 6000 };  // 20 - 20000Hz
				bandwidth[] = {1, 2, 2, 2 };         // 0.1 and 2.0
				gain[] = { db-3, db-1, db-5, db-8 }; // 0.126 - 7.94; +/- 18dB
			};
			class Equalizer1
			{
				center[] = { 60, 500, 3000, 15000 }; // 20 - 20000Hz
				bandwidth[] = {2, 2, 2, 2 };		 // 0.1 and 2.0
				gain[] = { db0, db0, db0, db0 };	 // 0.126 - 7.94; +/- 18dB
			};
			class Echo
			{
				WetDryMix = 0.1;   // 0 - 1
				Feedback = 0.01;   // 0 - 1
				Delay = 50;        // 1 - 2000
			};
		};
	};
};

Special Filters

Special Filters are used to filter sounds within specific gameplay conditions like underwater or in an unconscious state.

There are three hard-coded classes that are expected by the audio engine (with different, predefined filter chains): UnderWaterEffects, UnconsciousStateEffect, RadioFilterEffects

All of following have to be configured in base class CfgSoundEffects.

Underwater Filters

class CfgSoundEffects
{
	class UnderWaterEffects
	{
		class Mono
		{
			// 0m - unchanged sound
			// 1m - below surface level all sounds are mixed into mono
			distance = 1;
		};
		class Equalizer
		{
			// in range [0 - 3] equalizer pars are linearly interpolated from neutral values to set
			distance = 3;
			// Equalizer
			center[] = { 100, 800, 2000, 10000 };	// frequencies
			bandwidth[] = { 2.0, 2.0, 2.0, 2.0 };	// must be between 0.1 and 2.0
			gain[] = { db3, db0, db-15, db-18 };	// +/- 18dB
		};
	};
};

Unconscious State Effect

class CfgSoundEffects
{
	class UnconsciousStateEffect
	{
		// linear interpolation ... Echo0 * t + (Echo1 - Echo0), t = [0 - 1]
		class Echo0
		{
			WetDryMix = 0.25;   // 0 - 1
			Feedback = 0.15;     // 0 - 1
			Delay = 50;        // 1 - 2000
		};
		class Echo1
		{
			WetDryMix = 0.5;    // 0 - 1
			Feedback = 0.2;     // 0 - 1
			Delay = 100;      // 1 - 2000
		};
		class Equalizer0
		{
			center[] = { 100, 800, 2000, 10000 }; // frequencies
			bandwidth[] = { 1.0, 1.0, 1.0, 1.0 }; // must be between 0.1 and 2.0
			gain[] = { db0, db-5, db-10, db-10 }; // +/- 18dB
		};
		class Equalizer1
		{
			center[] = { 100, 800, 2000, 10000 };	// frequencies
			bandwidth[] = { 2.0, 2.0, 2.0, 2.0 }; // must be between 0.1 and 2.0
			gain[] = { db0, db-10, db-18, db-18 }; // +/- 18dB
		};
	};
};

Radio Protocol Filters

class CfgSoundEffects
{
	class RadioFilterEffects
	{
		class Part0 
		{
			// Equalizer
			center[] = { 370, 900, 6000, 10000 };	// frequencies
			bandwidth[] = { 1, 2, 1, 1.2 };			// must be between 0.1 and 2.0
			gain[] = { db0, db4, db4, db5 };		// +/- 18dB
			// Limiter
			lim_limit = 1;
			lim_attack = 5;
			lim_release = 50;
			enabled[] = { true, false, true };	// equalizer, limiter, convert to 8bit
		};
		class Part1
		{
			// low pass filter
			filter_cut_off = 650;
			/* Filter radian frequency calculated as (2 * sin(pi * (desired filter cutoff frequency) / sampleRate)).
			The frequency must be greater than or equal to 0 and less than or equal to XAUDIO2_MAX_FILTER_FREQUENCY
			frequency == 11025, cuttoff > 1837 = 1 */
			filter_one_over_Q = 0.5;
			/* 0 - 1, Reciprocal of Q factor. Controls how quickly frequencies beyond Frequency are dampened.
			Larger values result in quicker dampening while smaller values cause dampening to occur more gradually */
			filter_enabled = true;
		};
		class Part2
		{			
			// Equalizer
			center[] = { 100, 250, 900, 5000 };		// 20 - 2000Hz
			bandwidth[] = {2, 1.9, 2, 2 };			// 0.1 and 2.0
			gain[] = { db-18, db-18, db4, db-3 };	// 0.126 - 7.94; +/- 18dB
			// Compressor
			comp_threshold = db0;
			comp_ratio = 0.27;	  	// 1:1
			comp_attack = 1;		// milliseconds			 
			comp_relase = 100;		// milliseconds
			// Limiter
			lim_limit = db-18;
			lim_attack = 1;
			lim_release = 500;
			enabled[] = { true, false, false };   // equalizer, compressor, limiter
		};
	};
};