Air absorption factor is applied to the dB value, not linear gain

2 files changed, 16 insertions, 13 deletions

diff --git a/Alc/ALu.c b/Alc/ALu.c
index f2ffb739..9baf6cee 100644
--- a/Alc/ALu.c
+++ b/Alc/ALu.c
@@ -383,34 +383,36 @@ static ALvoid CalcSourceParams(ALCcontext *ALContext, ALsource *ALSource,
                 break;
 
             case AL_NONE:
-            default:
                 flAttenuation = 1.0f;
                 RoomAttenuation = 1.0f;
                 break;
         }
 
-        // Source Gain + Attenuation and clamp to Min/Max Gain
-        DryMix = SourceVolume * flAttenuation;
-        DryMix = __min(DryMix,MaxVolume);
-        DryMix = __max(DryMix,MinVolume);
-
-        WetMix = SourceVolume * RoomAttenuation;
-        WetMix = __min(WetMix,MaxVolume);
-        WetMix = __max(WetMix,MinVolume);
-
         // Distance-based air absorption
-        if(ALSource->AirAbsorptionFactor > 0.0f)
+        if(ALSource->AirAbsorptionFactor > 0.0f && ALContext->DistanceModel != AL_NONE)
         {
             ALfloat dist = Distance-MinDist;
             ALfloat absorb;
 
             if(dist < 0.0f) dist = 0.0f;
-            absorb = pow(ALSource->AirAbsorptionFactor * AIRABSORBGAINHF,
-                         Distance * MetersPerUnit);
+            // Absorption calculation is done in dB
+            absorb = (ALSource->AirAbsorptionFactor*AIRABSORBGAINDBHF) *
+                     (Distance*MetersPerUnit);
+            // Convert dB to linear gain before applying
+            absorb = pow(0.5, absorb/-6.0);
             DryGainHF *= absorb;
             WetGainHF *= absorb;
         }
 
+        // Source Gain + Attenuation and clamp to Min/Max Gain
+        DryMix = SourceVolume * flAttenuation;
+        DryMix = __min(DryMix,MaxVolume);
+        DryMix = __max(DryMix,MinVolume);
+
+        WetMix = SourceVolume * RoomAttenuation;
+        WetMix = __min(WetMix,MaxVolume);
+        WetMix = __max(WetMix,MinVolume);
+
         //3. Apply directional soundcones
         Angle = aluAcos(aluDotproduct(Direction,SourceToListener)) * 180.0f /
                 3.141592654f;
diff --git a/OpenAL32/Include/alMain.h b/OpenAL32/Include/alMain.h
index fb9cfb5e..f378a72f 100644
--- a/OpenAL32/Include/alMain.h
+++ b/OpenAL32/Include/alMain.h
@@ -126,6 +126,7 @@ extern char _alDebug[256];
 
 #define SPEEDOFSOUNDMETRESPERSEC   (343.3f)
 #define AIRABSORBGAINHF            (0.994f)
+#define AIRABSORBGAINDBHF          (-0.05f)
 
 #define LOWPASSFREQCUTOFF          (5000)