diff --git a/AV.cc b/AV.cc
index e57d061..0936425 100644
--- a/AV.cc
+++ b/AV.cc
@@ -60,10 +60,14 @@ AV::AV()
         cerr << "SDL_OpenAudio() error." << endl;
         exit(3);
     }
+
+    m_active_sounds_mutex = SDL_CreateMutex();
 }
 
 AV::~AV()
 {
+    SDL_PauseAudio(1);
+    SDL_DestroyMutex(m_active_sounds_mutex);
     SDL_CloseAudio();
     Sound_Quit();
     SDL_Quit();
@@ -134,13 +138,16 @@ refptr<AV::Sound> AV::createSound()
 
 void AV::playSound(AV::Sound * s)
 {
+    SDL_mutexP(m_active_sounds_mutex);
     m_active_sounds.insert(s);
+    SDL_mutexV(m_active_sounds_mutex);
     SDL_PauseAudio(0);
 }
 
 void AV::playCallback(Uint8 * stream, int len)
 {
     memset(stream, 0, len);
+    SDL_mutexP(m_active_sounds_mutex);
     for (std::set<Sound *>::iterator it = m_active_sounds.begin();
          it != m_active_sounds.end();
          it++)
@@ -154,6 +161,7 @@ void AV::playCallback(Uint8 * stream, int len)
     {
         SDL_PauseAudio(1);
     }
+    SDL_mutexV(m_active_sounds_mutex);
 }
 
 AV::Sound::Sound(AV & av)
diff --git a/AV.h b/AV.h
index 149543c..b420bfb 100644
--- a/AV.h
+++ b/AV.h
@@ -77,6 +77,7 @@ class AV
         std::set< refptr<Sound> > m_sounds;
 #endif
         std::set< Sound * > m_active_sounds;
+        SDL_mutex * m_active_sounds_mutex;
 };
 
 #endif