Not sure who to blame for this one.
Since installing Windows 10, sound volume has not been particularly good but not bad enough to revert back to Windows 8.1.
Apart from YouTube videos, I don’t listen to much and some videos have captions anyway, but it is annoying.
So, all obvious volume controls are set to MAX, except for one that is NOT obvious.
If you go into Control Panel > Sound and right click on the device outputting the sound, and then click on the Playback tab, you will notice that volume is set for 67%. I pushed mine to 100% and now I can hear videos better..
It’s not what I would call perfect but it works.. 🙂