diff --git a/src/sound.cc b/src/sound.cc
index 7170986..07fc52b 100644
--- a/src/sound.cc
+++ b/src/sound.cc
@@ -1,7 +1,6 @@
 #include "sound.h"
 
 #include "debug.h"
-#include "memory.h"
 #include "platform_compat.h"
 
 #ifdef _WIN32
@@ -20,26 +19,62 @@
 
 #include <algorithm>
 
+#define SOUND_FLAG_SOUND_IS_PLAYING (0x02)
+#define SOUND_FLAG_SOUND_IS_PAUSED (0x08)
+
+typedef char*(SoundFileNameMangler)(char*);
+
+typedef struct STRUCT_51D478 {
+    Sound* field_0;
+    int field_4;
+    int field_8;
+    int field_C;
+    int field_10;
+    int field_14;
+    struct STRUCT_51D478* prev;
+    struct STRUCT_51D478* next;
+} STRUCT_51D478;
+
+static void* soundMallocProcDefaultImpl(size_t size);
+static void* soundReallocProcDefaultImpl(void* ptr, size_t size);
+static void soundFreeProcDefaultImpl(void* ptr);
+static char* soundFileManglerDefaultImpl(char* fname);
+static void _refreshSoundBuffers(Sound* sound);
+static int _preloadBuffers(Sound* sound);
+static int _soundRewind(Sound* sound);
+static int _addSoundData(Sound* sound, unsigned char* buf, int size);
+static int _soundSetData(Sound* sound, unsigned char* buf, int size);
+static int soundContinue(Sound* sound);
+static int _soundGetVolume(Sound* sound);
+static void soundDeleteInternal(Sound* sound);
+#ifdef HAVE_DSOUND
+static void CALLBACK _doTimerEvent(UINT uTimerID, UINT uMsg, DWORD_PTR dwUser, DWORD_PTR dw1, DWORD_PTR dw2);
+static void _removeTimedEvent(unsigned int* timerId);
+#endif
+static void _removeFadeSound(STRUCT_51D478* a1);
+static void _fadeSounds();
+static int _internalSoundFade(Sound* sound, int a2, int a3, int a4);
+
 // 0x51D478
-STRUCT_51D478* _fadeHead = NULL;
+static STRUCT_51D478* _fadeHead = NULL;
 
 // 0x51D47C
-STRUCT_51D478* _fadeFreeList = NULL;
+static STRUCT_51D478* _fadeFreeList = NULL;
 
 // 0x51D480
-unsigned int _fadeEventHandle = UINT_MAX;
+static unsigned int _fadeEventHandle = UINT_MAX;
 
 // 0x51D488
-MallocProc* gSoundMallocProc = soundMallocProcDefaultImpl;
+static MallocProc* gSoundMallocProc = soundMallocProcDefaultImpl;
 
 // 0x51D48C
-ReallocProc* gSoundReallocProc = soundReallocProcDefaultImpl;
+static ReallocProc* gSoundReallocProc = soundReallocProcDefaultImpl;
 
 // 0x51D490
-FreeProc* gSoundFreeProc = soundFreeProcDefaultImpl;
+static FreeProc* gSoundFreeProc = soundFreeProcDefaultImpl;
 
 // 0x51D494
-SoundFileIO gSoundDefaultFileIO = {
+static SoundFileIO gSoundDefaultFileIO = {
     open,
     close,
     compat_read,
@@ -51,10 +86,10 @@ SoundFileIO gSoundDefaultFileIO = {
 };
 
 // 0x51D4B4
-SoundFileNameMangler* gSoundFileNameMangler = soundFileManglerDefaultImpl;
+static SoundFileNameMangler* gSoundFileNameMangler = soundFileManglerDefaultImpl;
 
 // 0x51D4B8
-const char* gSoundErrorDescriptions[SOUND_ERR_COUNT] = {
+static const char* gSoundErrorDescriptions[SOUND_ERR_COUNT] = {
     "sound.c: No error",
     "sound.c: SOS driver not loaded",
     "sound.c: SOS invalid pointer",
@@ -92,38 +127,38 @@ const char* gSoundErrorDescriptions[SOUND_ERR_COUNT] = {
 };
 
 // 0x668150
-int gSoundLastError;
+static int gSoundLastError;
 
 // 0x668154
-int _masterVol;
+static int _masterVol;
 
 #ifdef HAVE_DSOUND
 // 0x668158
-LPDIRECTSOUNDBUFFER gDirectSoundPrimaryBuffer;
+static LPDIRECTSOUNDBUFFER gDirectSoundPrimaryBuffer;
 #endif
 
 // 0x66815C
-int _sampleRate;
+static int _sampleRate;
 
 // Number of sounds currently playing.
 //
 // 0x668160
-int _numSounds;
+static int _numSounds;
 
 // 0x668164
-int _deviceInit;
+static int _deviceInit;
 
 // 0x668168
-int _dataSize;
+static int _dataSize;
 
 // 0x66816C
-int _numBuffers;
+static int _numBuffers;
 
 // 0x668170
-bool gSoundInitialized;
+static bool gSoundInitialized;
 
 // 0x668174
-Sound* gSoundListHead;
+static Sound* gSoundListHead;
 
 #ifdef HAVE_DSOUND
 // 0x668178
diff --git a/src/sound.h b/src/sound.h
index 34d3aee..3672e7e 100644
--- a/src/sound.h
+++ b/src/sound.h
@@ -4,9 +4,6 @@
 #include "memory_defs.h"
 #include "win32.h"
 
-#define SOUND_FLAG_SOUND_IS_PLAYING (0x02)
-#define SOUND_FLAG_SOUND_IS_PAUSED (0x08)
-
 #define VOLUME_MIN (0)
 #define VOLUME_MAX (0x7FFF)
 
@@ -49,7 +46,6 @@ typedef enum SoundError {
     SOUND_ERR_COUNT,
 } SoundError;
 
-typedef char*(SoundFileNameMangler)(char*);
 typedef int SoundOpenProc(const char* filePath, int flags, ...);
 typedef int SoundCloseProc(int fileHandle);
 typedef int SoundReadProc(int fileHandle, void* buf, unsigned int size);
@@ -110,64 +106,19 @@ typedef struct Sound {
     struct Sound* prev;
 } Sound;
 
-typedef struct STRUCT_51D478 {
-    Sound* field_0;
-    int field_4;
-    int field_8;
-    int field_C;
-    int field_10;
-    int field_14;
-    struct STRUCT_51D478* prev;
-    struct STRUCT_51D478* next;
-} STRUCT_51D478;
-
-extern STRUCT_51D478* _fadeHead;
-extern STRUCT_51D478* _fadeFreeList;
-
-extern unsigned int _fadeEventHandle;
-extern MallocProc* gSoundMallocProc;
-extern ReallocProc* gSoundReallocProc;
-extern FreeProc* gSoundFreeProc;
-extern SoundFileIO gSoundDefaultFileIO;
-extern SoundFileNameMangler* gSoundFileNameMangler;
-extern const char* gSoundErrorDescriptions[SOUND_ERR_COUNT];
-
-extern int gSoundLastError;
-extern int _masterVol;
-#ifdef HAVE_DSOUND
-extern LPDIRECTSOUNDBUFFER gDirectSoundPrimaryBuffer;
-#endif
-extern int _sampleRate;
-extern int _numSounds;
-extern int _deviceInit;
-extern int _dataSize;
-extern int _numBuffers;
-extern bool gSoundInitialized;
-extern Sound* gSoundListHead;
 #ifdef HAVE_DSOUND
 extern LPDIRECTSOUND gDirectSound;
 #endif
 
-void* soundMallocProcDefaultImpl(size_t size);
-void* soundReallocProcDefaultImpl(void* ptr, size_t size);
-void soundFreeProcDefaultImpl(void* ptr);
 void soundSetMemoryProcs(MallocProc* mallocProc, ReallocProc* reallocProc, FreeProc* freeProc);
-
-char* soundFileManglerDefaultImpl(char* fname);
 const char* soundGetErrorDescription(int err);
-void _refreshSoundBuffers(Sound* sound);
 int soundInit(int a1, int a2, int a3, int a4, int rate);
 void soundExit();
 Sound* soundAllocate(int a1, int a2);
-int _preloadBuffers(Sound* sound);
 int soundLoad(Sound* sound, char* filePath);
-int _soundRewind(Sound* sound);
-int _addSoundData(Sound* sound, unsigned char* buf, int size);
-int _soundSetData(Sound* sound, unsigned char* buf, int size);
 int soundPlay(Sound* sound);
 int soundStop(Sound* sound);
 int soundDelete(Sound* sound);
-int soundContinue(Sound* sound);
 bool soundIsPlaying(Sound* sound);
 bool _soundDone(Sound* sound);
 bool soundIsPaused(Sound* sound);
@@ -176,24 +127,15 @@ int soundGetDuration(Sound* sound);
 int soundSetLooping(Sound* sound, int a2);
 int _soundVolumeHMItoDirectSound(int a1);
 int soundSetVolume(Sound* sound, int volume);
-int _soundGetVolume(Sound* sound);
 int soundSetCallback(Sound* sound, SoundCallback* callback, void* userData);
 int soundSetChannels(Sound* sound, int channels);
 int soundSetReadLimit(Sound* sound, int readLimit);
 int soundPause(Sound* sound);
 int soundResume(Sound* sound);
 int soundSetFileIO(Sound* sound, SoundOpenProc* openProc, SoundCloseProc* closeProc, SoundReadProc* readProc, SoundWriteProc* writeProc, SoundSeekProc* seekProc, SoundTellProc* tellProc, SoundFileLengthProc* fileLengthProc);
-void soundDeleteInternal(Sound* sound);
 int _soundSetMasterVolume(int value);
-#ifdef HAVE_DSOUND
-void CALLBACK _doTimerEvent(UINT uTimerID, UINT uMsg, DWORD_PTR dwUser, DWORD_PTR dw1, DWORD_PTR dw2);
-void _removeTimedEvent(unsigned int* timerId);
-#endif
 int _soundGetPosition(Sound* sound);
 int _soundSetPosition(Sound* sound, int a2);
-void _removeFadeSound(STRUCT_51D478* a1);
-void _fadeSounds();
-int _internalSoundFade(Sound* sound, int a2, int a3, int a4);
 int _soundFade(Sound* sound, int a2, int a3);
 void soundDeleteAll();
 void soundContinueAll();