You could use ‘do when condition is true’ workflow to play the sound in the User’s browser (the user who you want to hear the sound).
You’d have to have a database field such as a yes/no called ‘play sound’, and set the condition to play the sound whenever the current User’s Play Sound is yes.
Then, when a User is selected in the RG, set that User’s Play Sound Field to yes.
You’d need to reset that field value back to ‘No’ after the sound has been played, so in the Play Sound workflow, just add an action to reset the value for the current User.