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
@@ -1,5 +1,7 @@
 /* $Id$ */
 
+/** @file null_s.cpp The sound driver that doesn't produce sound. */
+
 #include "../stdafx.h"
 #include "null_s.h"