I have a Samsung Galaxy TAB E That i bought 3 years ago. In the beginning all was good. But lately I've noticed the level of media sound has decreased to an almost whisper when the volume sitting is at about 90%
It could be the sound settings in an app or two rather than the whole device settings. Try starting up the tablet in "Safe Mode". While you will have limited access in that mode, you will be able to check certain sounds. If the volume is louder when in this mode, then you have one or more apps that are the cause.
To get into "Safe Mode" please do the following.
1. First turn off the tablet.
2. Next press and hold "Power" until you see the manufacturers logo on the screen, then release the power button.
3. "Quickly" press "Volume Down" and hold it for few seconds until you see the message "Safe mode: ON" or something similar.
4. If you wanted disable it, simply repeat the steps above, and you should see "Safe Mode: OFF" rather than on.
I followed all your instructions, got in to safe mode and maximized the volumes. There was no change. I noticed that all the apps that I added had been greyed in safe mode. You mentioned that it could be some aps that are causing that. That will take some time if a sound test is done after the deletion of an ap. Is worthwhile bringing my tablet to Best buy Geek Squad for repair.