Since version 45, Google Chrome automatically shows an audio indicator for music playing tabs, like this:
To mute the tab, you need to right-click the tab and choose Mute tab.
There is also a setting that you can turn on to let you mouse click the sound icon on the tab to mute the sound. Go to chrome://flags page, search for “muting” to find a specific setting named “Enable tab audio muting UI control“, and click Enable link to turn it on. Then click the big blue Relaunch Now button to restart the browser.
With this special flag turned on, not only can you mute the tab by simply clicking on the sound icon using your mouse, you can also use keyboard shortcut Alt + M as well. Surprisingly, the same shortcut key works in Firefox also.
If you have multiple tabs running sounds that drive you crazy, you can also mute them all the same time as well. Hold down the Ctrl key to select the tabs that have sound running, then right-click on any of the tabs you selected and select “Mute tabs“. You will feel the quietness momentarily.
If this happens quite often, it would be nice having a keyboard shortcut set up to mute sounds from all tabs with a single keystroke. Mute Tab Shortcuts extension is the one that you may need to install to get this feature.