(https://extensions.gnome.org/extension/1271/sound-settings/)
or
$ git clone https://github.com/yomun/sound-settings.git
$ cd sound-settings
$ mv yomun@yahoo.com ~/.local/share/gnome-shell/extensions
Copyright © 2017 Jason Mun (jasonmun@yahoo.com)
Released under the terms of the GNU General Public License, version 3