Index: src/newgrf.cpp
===================================================================
--- src/newgrf.cpp	(revision 27506)
+++ src/newgrf.cpp	(working copy)
@@ -1402,7 +1402,7 @@
 				break;
 
 			case 0x12: // SFX
-				rvi->sfx = buf->ReadByte();
+				rvi->sfx = GetNewGRFSoundId(_cur.grffile, buf->ReadByte());
 				break;
 
 			case PROP_ROADVEH_POWER: // Power in units of 10 HP.
@@ -1590,7 +1590,7 @@
 				break;
 
 			case 0x10: // SFX
-				svi->sfx = buf->ReadByte();
+				svi->sfx = GetNewGRFSoundId(_cur.grffile, buf->ReadByte());
 				break;
 
 			case 0x11: { // Cargoes available for refitting
@@ -1758,7 +1758,7 @@
 				break;
 
 			case 0x12: // SFX
-				avi->sfx = buf->ReadByte();
+				avi->sfx = GetNewGRFSoundId(_cur.grffile, buf->ReadByte());
 				break;
 
 			case 0x13: { // Cargoes available for refitting
Index: src/newgrf_sound.cpp
===================================================================
--- src/newgrf_sound.cpp	(revision 27506)
+++ src/newgrf_sound.cpp	(working copy)
@@ -161,7 +161,23 @@
 	return false;
 }
 
+/**
+ * Resolve NewGRF sounds IDs.
+ * @param file NewGRF to get sound from.
+ * @param sound_id GRF-specific sound ID. (GRF-local for IDs above ORIGINAL_SAMPLE_COUNT)
+ * @return Translated (global) sound ID, or INVALID_SOUND.
+ */
+SoundID GetNewGRFSoundId(const GRFFile *file, SoundID sound_id)
+{
+	/* Global sound? */
+	if (sound_id < ORIGINAL_SAMPLE_COUNT) return sound_id;
 
+	sound_id -= ORIGINAL_SAMPLE_COUNT;
+	if (file == NULL || sound_id >= file->num_sounds) return INVALID_SOUND;
+
+	return file->sound_offset  + sound_id;
+}
+
 /**
  * Checks whether a NewGRF wants to play a different vehicle sound effect.
  * @param v Vehicle to play sound effect for.
@@ -185,15 +201,11 @@
 	/* Play default sound if callback fails */
 	if (callback == CALLBACK_FAILED) return false;
 
-	if (callback >= ORIGINAL_SAMPLE_COUNT) {
-		callback -= ORIGINAL_SAMPLE_COUNT;
+	callback = GetNewGRFSoundId(file, callback);
 
-		/* Play no sound if result is out of range */
-		if (callback > file->num_sounds) return true;
+	/* Play no sound, if result is invalid */
+	if (callback == INVALID_SOUND) return true;
 
-		callback += file->sound_offset;
-	}
-
 	assert(callback < GetNumSounds());
 	SndPlayVehicleFx(callback, v);
 	return true;
@@ -207,11 +219,8 @@
  */
 void PlayTileSound(const GRFFile *file, SoundID sound_id, TileIndex tile)
 {
-	if (sound_id >= ORIGINAL_SAMPLE_COUNT) {
-		sound_id -= ORIGINAL_SAMPLE_COUNT;
-		if (sound_id > file->num_sounds) return;
-		sound_id += file->sound_offset;
-	}
+	sound_id = GetNewGRFSoundId(file, sound_id);
+	if (sound_id == INVALID_SOUND) return;
 
 	assert(sound_id < GetNumSounds());
 	SndPlayTileFx(sound_id, tile);
Index: src/newgrf_sound.h
===================================================================
--- src/newgrf_sound.h	(revision 27506)
+++ src/newgrf_sound.h	(working copy)
@@ -33,6 +33,7 @@
 SoundEntry *AllocateSound(uint num);
 void InitializeSoundPool();
 bool LoadNewGRFSound(SoundEntry *sound);
+SoundID GetNewGRFSoundId(const struct GRFFile *file, SoundID sound_id);
 SoundEntry *GetSound(SoundID sound_id);
 uint GetNumSounds();
 bool PlayVehicleSound(const Vehicle *v, VehicleSoundEvent event);
Index: src/sound_type.h
===================================================================
--- src/sound_type.h	(revision 27506)
+++ src/sound_type.h	(working copy)
@@ -119,4 +119,6 @@
 
 typedef uint16 SoundID;
 
+static const SoundID INVALID_SOUND = 0xFFFF;
+
 #endif /* SOUND_TYPE_H */