iFlyChat JavaScript SDK has a function named 'setSound' which can be used to mute/unmute the chat notification of current user. You may use the function in the following manner:
iflychat.setSound({sound: true /*If sound notification needs to set on or off */​});
This function takes a JS object as parameter which should have following properties:
sound
Possible values of status are :
true - Sound On/ Unmute
false - Sound Off/ Mute