Gtk.Settings:gtk-enable-input-feedback-sounds

"gtk-enable-input-feedback-sounds"             Boolean                : Read / Write

Whether to play event sounds as feedback to user input.

See the <ulink url="http://www.freedesktop.org/wiki/Specifications/sound-theme-spec">Sound Theme spec</ulink> for more information on event sounds and sound themes.

GTK+ itself does not support event sounds, you have to use a loadable module like the one that comes with libcanberra.

Since 2.14