diff -r ed54fb0a10b6 src/newgrf_sound.cpp
--- a/src/newgrf_sound.cpp	Thu Jun 23 21:33:42 2011 +0200
+++ b/src/newgrf_sound.cpp	Thu Jun 23 21:36:33 2011 +0200
@@ -66,7 +66,8 @@
 	if (callback == CALLBACK_FAILED) return false;
 	if (callback >= ORIGINAL_SAMPLE_COUNT) {
 		callback -= ORIGINAL_SAMPLE_COUNT;
-		if (callback > file->num_sounds) return false;
+		/* If the GRF asked to play an invalid sound, play nothing as indicated by the specs */
+		if (callback > file->num_sounds) return true;
 		callback += file->sound_offset;
 	}