An alternative temporary solution is to download an equalizer app. Drop all the controls down to zero and then bring them back up one by one. I had a sound issue with just one app on my Samsung galaxy ace II so this might work on your note 3. Ran the equalizer, ran the app, no more screeching or buzzing. When equalizer off, app on its own reproduces sound problems. Several equalizer apps I tried seemed to do the trick. DSP allows you to disable and enable when required. This is my first post and as a noobie I read the terms and conditions first; but I apologize if I have still not followed protocol. Hope this is still relevant.