MY FIREFOX IS HAVING AUDIO ISSUES. THE VOLUME INCREASES BY ITSELF. ITS A IRRITATING REGULAR OCCURANCE. HOW DO I FIX THIS ?

MY FIREFOX IS HAVING AUDIO ISSUES. THE VOLUME INCREASES BY ITSELF IT HAPPENS USUALLY IF I ENTER OR EXIT FULL SCREEN MODE, OR IF THE VIDEO OR MOVIE STOPS TO BUFFER FOR A MOMENT IT WILL COME BACK ON AT 3 OR 4 TIMES THE VOLUME. ITS A IRRITATING REGULAR OCCURRENCE. IVE TRIED SETTINGS, AND UPDATES BUT NOTHING SEEMS TO FIX IT. IT SEEMS TO HAPPEN ON ANY WEBSITE I USE. (YOUTUBE, SEVERAL MOVIE WEBSITES AND CARTOON WEBSITES. ITS BEEN GOING ON FOR A COUPLE OF YEARS AND ITS VERY FRUSTRATING. I HAVE TO CONSTANTLY READJUST IT IN AND OUT OF ALMOST EVERYTHING I WATCH. HOW DO I FIX THIS ?