Solo Sound от babinomec

Solo Sound keeps your browser quiet by ensuring only one tab plays audio at a time. When a tab starts playing sound or gets unmuted, all other audible tabs are automatically muted.

To avoid muting short notification sounds (Gmail, Slack, Discord, etc.), the extension includes a configurable debounce delay and a title whitelist. Tabs matching the whitelist are never muted and never trigger muting of other tabs. Regex patterns are supported.

Additional options include ignoring pinned tabs and auto-unmuting muted tabs when switching to them. All settings are configurable from the options page.

No data is collected or transmitted. Source code: https://github.com/babinomec/firefox-solo-sound