diff --git a/src/music/dmusic.cpp b/src/music/dmusic.cpp
--- a/src/music/dmusic.cpp
+++ b/src/music/dmusic.cpp
@@ -4,7 +4,6 @@
 
 #ifdef WIN32_ENABLE_DIRECTMUSIC_SUPPORT
 
-#include "../openttd.h"
 #include "../debug.h"
 #include "../win32.h"
 #include "dmusic.h"
@@ -218,7 +217,7 @@ static void DMusicMidiSetVolume(byte vol
 }
 
 
-extern "C" const HalMusicDriver _dmusic_midi_driver = {
+const HalMusicDriver _dmusic_midi_driver = {
 	DMusicMidiStart,
 	DMusicMidiStop,
 	DMusicMidiPlaySong,
@@ -227,4 +226,4 @@ extern "C" const HalMusicDriver _dmusic_
 	DMusicMidiSetVolume,
 };
 
-#endif
+#endif /* WIN32_ENABLE_DIRECTMUSIC_SUPPORT */
diff --git a/src/music/dmusic.h b/src/music/dmusic.h
--- a/src/music/dmusic.h
+++ b/src/music/dmusic.h
@@ -7,4 +7,4 @@
 
 extern const HalMusicDriver _dmusic_midi_driver;
 
-#endif
+#endif /* MUSIC_DMUSIC_H */
diff --git a/src/music/null_m.h b/src/music/null_m.h
--- a/src/music/null_m.h
+++ b/src/music/null_m.h
@@ -7,4 +7,4 @@
 
 extern const HalMusicDriver _null_music_driver;
 
-#endif
+#endif /* MUSIC_NULL_H */
diff --git a/src/music/win32_m.h b/src/music/win32_m.h
--- a/src/music/win32_m.h
+++ b/src/music/win32_m.h
@@ -7,4 +7,4 @@
 
 extern const HalMusicDriver _win32_music_driver;
 
-#endif
+#endif /* MUSIC_WIN32_H */
diff --git a/src/sound/null_s.cpp b/src/sound/null_s.cpp
--- a/src/sound/null_s.cpp
+++ b/src/sound/null_s.cpp
@@ -1,7 +1,6 @@
 /* $Id$ */
 
 #include "../stdafx.h"
-#include "../openttd.h"
 #include "null_s.h"
 
 static const char *NullSoundStart(const char * const *parm) { return NULL; }
diff --git a/src/sound/null_s.h b/src/sound/null_s.h
--- a/src/sound/null_s.h
+++ b/src/sound/null_s.h
@@ -7,4 +7,4 @@
 
 extern const HalSoundDriver _null_sound_driver;
 
-#endif
+#endif /* SOUND_NULL_H */
diff --git a/src/sound/sdl_s.cpp b/src/sound/sdl_s.cpp
--- a/src/sound/sdl_s.cpp
+++ b/src/sound/sdl_s.cpp
@@ -44,4 +44,4 @@ const HalSoundDriver _sdl_sound_driver =
 	SdlSoundStop,
 };
 
-#endif
+#endif /* WITH_SDL */
diff --git a/src/sound/sdl_s.h b/src/sound/sdl_s.h
--- a/src/sound/sdl_s.h
+++ b/src/sound/sdl_s.h
@@ -7,4 +7,4 @@
 
 extern const HalSoundDriver _sdl_sound_driver;
 
-#endif
+#endif /* SOUND_SDL_H */
diff --git a/src/sound/win32_s.cpp b/src/sound/win32_s.cpp
--- a/src/sound/win32_s.cpp
+++ b/src/sound/win32_s.cpp
@@ -42,29 +42,27 @@ static void CALLBACK waveOutProc(HWAVEOU
 {
 	switch (uMsg) {
 		case WOM_DONE:
-			if (_waveout) FillHeaders();
+			if (_waveout != NULL) FillHeaders();
 			break;
-
-		default:
-			break;
+		default: break;
 	}
 }
 
 static const char *Win32SoundStart(const char* const* parm)
 {
 	WAVEFORMATEX wfex;
-	int hz;
-
-	_bufsize = GetDriverParamInt(parm, "bufsize", 1024);
-	hz = GetDriverParamInt(parm, "hz", 11025);
 	wfex.wFormatTag = WAVE_FORMAT_PCM;
 	wfex.nChannels = 2;
-	wfex.nSamplesPerSec = hz;
-	wfex.nAvgBytesPerSec = hz * 2 * 2;
-	wfex.nBlockAlign = 4;
 	wfex.wBitsPerSample = 16;
+	wfex.nSamplesPerSec = GetDriverParamInt(parm, "hz", 11025);
+	wfex.nBlockAlign = (wfex.nChannels * wfex.wBitsPerSample) / 8;
+	wfex.nAvgBytesPerSec = wfex.nSamplesPerSec * wfex.nBlockAlign;
+
+	_bufsize = GetDriverParamInt(parm, "bufsize", 1024);
+
 	if (waveOutOpen(&_waveout, WAVE_MAPPER, &wfex, (DWORD_PTR)&waveOutProc, 0, CALLBACK_FUNCTION) != MMSYSERR_NOERROR)
 		return "waveOutOpen failed";
+
 	PrepareHeader(&_wave_hdr[0]);
 	PrepareHeader(&_wave_hdr[1]);
 	FillHeaders();
diff --git a/src/video/dedicated_v.h b/src/video/dedicated_v.h
--- a/src/video/dedicated_v.h
+++ b/src/video/dedicated_v.h
@@ -7,4 +7,4 @@
 
 extern const HalVideoDriver _dedicated_video_driver;
 
-#endif
+#endif /* VIDEO_DEDICATED_H */
diff --git a/src/video/null_v.h b/src/video/null_v.h
--- a/src/video/null_v.h
+++ b/src/video/null_v.h
@@ -7,4 +7,4 @@
 
 extern const HalVideoDriver _null_video_driver;
 
-#endif
+#endif /* VIDEO_NULL_H */
diff --git a/src/video/sdl_v.cpp b/src/video/sdl_v.cpp
--- a/src/video/sdl_v.cpp
+++ b/src/video/sdl_v.cpp
@@ -510,4 +510,4 @@ const HalVideoDriver _sdl_video_driver =
 	SdlVideoFullScreen,
 };
 
-#endif
+#endif /* WITH_SDL */
diff --git a/src/video/sdl_v.h b/src/video/sdl_v.h
--- a/src/video/sdl_v.h
+++ b/src/video/sdl_v.h
@@ -7,4 +7,4 @@
 
 extern const HalVideoDriver _sdl_video_driver;
 
-#endif
+#endif /* VIDEO_SDL_H */
diff --git a/src/video/win32_v.h b/src/video/win32_v.h
--- a/src/video/win32_v.h
+++ b/src/video/win32_v.h
@@ -7,4 +7,4 @@
 
 extern const HalVideoDriver _win32_video_driver;
 
-#endif
+#endif /* VIDEO_WIN32_H */