diff --git a/Sounds/cfm56-sound.xml b/Sounds/cfm56-sound.xml
index 75f4d669..e49487ee 100644
--- a/Sounds/cfm56-sound.xml
+++ b/Sounds/cfm56-sound.xml
@@ -544,9 +544,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>-1</x>
@@ -575,9 +574,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>-1</x>
@@ -606,9 +604,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>-1</x>
@@ -637,9 +634,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>-1</x>
@@ -668,9 +664,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>1</x>
@@ -699,9 +694,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>1</x>
@@ -730,9 +724,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<reference-dist>30</reference-dist>
 		<position>
@@ -753,9 +746,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<reference-dist>30</reference-dist>
 		<position>
diff --git a/Sounds/leapx-sound.xml b/Sounds/leapx-sound.xml
index d7ff4875..8156494f 100644
--- a/Sounds/leapx-sound.xml
+++ b/Sounds/leapx-sound.xml
@@ -458,9 +458,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>-1</x>
@@ -489,9 +488,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>-1</x>
@@ -520,9 +518,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>-1</x>
@@ -551,9 +548,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>-1</x>
@@ -582,9 +578,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>1</x>
@@ -613,9 +608,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>1</x>
diff --git a/Sounds/v2500-sound.xml b/Sounds/v2500-sound.xml
index 3fcf70ba..9654322c 100644
--- a/Sounds/v2500-sound.xml
+++ b/Sounds/v2500-sound.xml
@@ -361,9 +361,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>-1</x>
@@ -392,9 +391,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>-1</x>
@@ -423,9 +421,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>-1</x>
@@ -454,9 +451,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>-1</x>
@@ -485,9 +481,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<reference-dist>30</reference-dist>
 		<position>
@@ -508,9 +503,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<reference-dist>30</reference-dist>
 		<position>
@@ -531,9 +525,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>1</x>
@@ -562,9 +555,8 @@
 			</equals>
 		</condition>
 		<volume>
-			<property>/sim/sound/internal-custom</property>
-			<factor>-1</factor>
-			<offset>1</offset>
+			<property>/sim/sound/external-custom</property>
+			<factor>1</factor>
 		</volume>
 		<orientation>
 			<x>1</x>
diff --git a/Systems/sound-common.xml b/Systems/sound-common.xml
index 2f8985b0..eabc0903 100644
--- a/Systems/sound-common.xml
+++ b/Systems/sound-common.xml
@@ -55,6 +55,18 @@
 		<output>/sim/sound/internal-custom</output>
 	</logic>
 	
+	<logic>
+		<input>
+			<not>
+				<equals>
+					<property>/sim/sound/internal-custom</property>
+					<value>1</value>
+				</equals>
+			</not>
+		</input>
+		<output>/sim/sound/external-custom</output>
+	</logic>
+	
 	<!-- Misc -->
 	<filter>
 		<type>gain</type>