This plugin was originally for a paid request. Author allowed me to release it publicly, as there was no plugins doing such a thing (wtf, honestly...).
Features :
Play a random sound to clients that connect
Since it uses this, it is easy to add a sound to play; just add a sound to the folder (defined by cvar 'sm_join_sound') and wait for map change.
Allows client to disable the welcome sound via client prefs.