Latest Vivaldi snapshot for version 1.7 has improved the tab muting feature introduced in version 1.0 by providing commands to control the sound in tabs, here they’re: Mute/Unmute Tab, Mute other Tabs, Mute all Tabs, Unmute other Tabs and Unmute All Tabs. You can find these in Quick Commands, press F2 to bring it up and type mute and select the option via arrow keys.

READ: Vivaldi gets Tab Audio Indicators and Muting Support

You can define keyboard shortcuts for these by visiting settings > Keyboard > Keyboard shortcuts > Tab

You can download Latest Vivaldi snapshot 1.7.735.11 from here.

READ: Vivaldi 1.7: Hide Extension icons and Take Screenshots of Web Pages

Latest Vivaldi Snapshot improves Screenshot feature