Mute Sites By Default

This add-on protects you from sites that automatically play loud or annoying sounds by muting all sites that aren't specified in the whitelist. Muting or un-muting a site will update the whitelist accordingly. This behavior can be disabled on the preferences page if you often want to mute/un-mute sites temporarily.

When manually adding sites to the whitelist, you can use * as a wildcard character.