How to stop Facebook from making a Notification soundNow a days Facebook Develops a new thing called sound for notification. when you got a message at the time of the chating then its makes a sound if you want to turn of that sound then just follow some steps and the turn of the notification sound
1) Click on gear present at upper right hand corner Account setting > Notification (Notification are present left hand side see below picture).
click here to go there directly
2) then click on "How You Get Notification" > "on Facebook" > view
3) Uncheck the box that says "Play a Sound When Each New Notification Is Received." Then click "Save Changes."
4) To start notification sound again checked the box and click on the