Experimental sound restart code:
* snd_restart without changing the driver works. some static sounds
  (such as the fire sound of a nearby torch) get lost.
* Driver switching is not stable enough: ALSA <-> OSS switching
  seems to work at first. But if you switch between them a lot of
  times, then the sound is muted for a very long time and further
  switchings are not stable. If you do a lot of snd_restart in OSS
  mode, and then try changing into ALSA, it crashes. With SDL as
  the previous driver, switching to another driver always crashes.
  These issues aren't properly traced, yet.
* Format switching (such as sample rate) isn't implemented.

If a sound driver is allocating dma memory for itself, make sure that
it does not allocate on the hunk. At present, only the windows wave-
sound driver and the alternative sdl audio driver (which is available
as an extra patch) does that. Therefore, if you try this patch:
* Edit your snd_sdl2.c and make sure that the USE_HUNK_ALLOC definition
  is 0
* If you compile for windows, edit your snd_win.c and make sure that
  the USE_HUNK_ALLOC definition is 0


diff -urNp uhexen2-20070915/hexen2/snd_dma.c uhexen2-20070915x/hexen2/snd_dma.c
--- uhexen2-20070915/hexen2/snd_dma.c	2007-09-15 14:10:03.000000000 +0300
+++ uhexen2-20070915x/hexen2/snd_dma.c	2007-09-15 16:36:46.000000000 +0300
@@ -113,6 +113,67 @@ static void S_SoundInfo_f (void)
 }
 
 
+static void S_ListDrivers_f (void)
+{
+	unsigned int	i = 0;
+
+	while (i < S_SYS_MAX)
+	{
+		if (snd_drivers[i].available)
+			Con_Printf ("%u : %s\n", i, snd_drivers[i].name);
+		++i;
+	}
+}
+
+
+static void S_Restart_f (void)
+{
+	int		c;
+
+	c = Cmd_Argc();
+
+	if (c > 2 || (c > 1 && !strcmp(Cmd_Argv(1),"help")))
+	{
+		Con_Printf ("snd_restart : restart sound system\n"
+			    "snd_restart <enum> : restart sound system with new driver\n");
+invalid:
+		Con_Printf ("(type \"sounddrivers\" to have a list of available drivers)\n");
+		return;
+	}
+
+	if (c == 2)
+	{
+		c = atoi (Cmd_Argv(1));
+		if (c < 0 || c >= S_SYS_MAX || !snd_drivers[c].available)
+		{
+			Con_Printf ("invalid driver number %d\n", c);
+			goto invalid;
+		}
+		snd_system = c;
+		S_InitDrivers();
+	}
+
+	Con_Printf("Restarting sound system in %s mode\n", snd_drivers[snd_system].name);
+	Cache_Flush();
+	S_StopAllSounds (true);
+
+	S_Shutdown();
+	Con_Printf("Sound Shutdown: OK.\n");
+
+	S_Startup();
+	if (sound_started == 0)
+		return;
+
+	ambient_sfx[AMBIENT_WATER] = S_PrecacheSound ("ambience/water1.wav");
+	ambient_sfx[AMBIENT_SKY] = S_PrecacheSound ("ambience/wind2.wav");
+
+	S_StopAllSounds (true);
+
+	if (developer.integer)
+		S_SoundInfo_f();
+}
+
+
 /*
 ================
 S_Startup
@@ -203,6 +264,8 @@ void S_Init (void)
 	Cmd_AddCommand("mute", S_ToggleMute);
 	Cmd_AddCommand("volumeup", S_VolumeUp);
 	Cmd_AddCommand("volumedown", S_VolumeDown);
+	Cmd_AddCommand("sounddrivers", S_ListDrivers_f);
+	Cmd_AddCommand("snd_restart", S_Restart_f);
 
 	Cvar_RegisterVariable(&nosound);
 	Cvar_RegisterVariable(&sfxvolume);