diff --git a/src/audio/soundcore.c b/src/audio/soundcore.c
index 75acef80..02af095f 100644
--- a/src/audio/soundcore.c
+++ b/src/audio/soundcore.c
@@ -239,7 +239,7 @@ static void _destroy_enumerated_sound_devices(void) {
     }
 }
 
-bool DSInit()
+bool DSInit(void)
 {
     if(audio_isAvailable)
     {
@@ -289,7 +289,7 @@ bool DSInit()
 
 //-----------------------------------------------------------------------------
 
-void DSUninit()
+void DSUninit(void)
 {
     _destroy_enumerated_sound_devices();
 
@@ -319,7 +319,7 @@ void DSUninit()
 static int g_nErrorInc = 20;    // Old: 1
 static int g_nErrorMax = 200;    // Old: 50
 
-int SoundCore_GetErrorInc()
+int SoundCore_GetErrorInc(void)
 {
     return g_nErrorInc;
 }
@@ -330,7 +330,7 @@ void SoundCore_SetErrorInc(const int nErrorInc)
     LOG("Speaker/MB Error Inc = %d\n", g_nErrorInc);
 }
 
-int SoundCore_GetErrorMax()
+int SoundCore_GetErrorMax(void)
 {
     return g_nErrorMax;
 }
diff --git a/src/audio/soundcore.h b/src/audio/soundcore.h
index 4aa50af1..69b683a9 100644
--- a/src/audio/soundcore.h
+++ b/src/audio/soundcore.h
@@ -94,24 +94,25 @@ bool DSZeroVoiceWritableBuffer(PVOICE Voice, char* pszDevName, unsigned long dwB
 typedef enum eFADE {FADE_NONE, FADE_IN, FADE_OUT} eFADE;
 void SoundCore_SetFade(eFADE FadeType);
 
-int SoundCore_GetErrorInc();
+int SoundCore_GetErrorInc(void);
 void SoundCore_SetErrorInc(const int nErrorInc);
-int SoundCore_GetErrorMax();
+int SoundCore_GetErrorMax(void);
 void SoundCore_SetErrorMax(const int nErrorMax);
 
-bool DSInit();
-void DSUninit();
+bool DSInit(void);
+void DSUninit(void);
 
 extern bool audio_isAvailable;
 
 typedef struct audio_backend_s {
 
-    // mandatory audio backend functions
-    long (*init)(const char *sound_device, SoundSystemStruct **sound_struct);
-    long (*shutdown)(SoundSystemStruct **sound_struct);
-    long (*pause)(void);
-    long (*resume)(void);
-    long (*enumerateDevices)(char ***sound_devices, const int maxcount);
+    // basic backend functionality controlled by soundcore
+    PRIVATE long (*init)(const char *sound_device, SoundSystemStruct **sound_struct);
+    PRIVATE long (*shutdown)(SoundSystemStruct **sound_struct);
+    PRIVATE long (*enumerateDevices)(char ***sound_devices, const int maxcount);
+
+    PUBLIC long (*pause)(void);
+    PUBLIC long (*resume)(void);
 
 } audio_backend_s;
 
diff --git a/src/common.h b/src/common.h
index 9cafaca0..57a1e48f 100644
--- a/src/common.h
+++ b/src/common.h
@@ -64,6 +64,8 @@
 #define INPARM
 #define OUTPARM
 #define INOUT
+#define PRIVATE
+#define PUBLIC
 
 #define CTOR_PRIORITY_FIRST  101
 #define CTOR_PRIORITY_EARLY  111