Hi,
I previously got HIGH CPU usage (>15%) by 'Windows Audio Device Graph Isolation' @ Task Manager when playing anything with audio, eg playing HEVC/x265 movies via MPC-BE. When fix, this process use <5% of my CPU when playing any audio.
This fix WORKS for me: Dell Inspiron 15 Gaming 7567 purchased new in Aug-18.
I downloaded & installed 'Realtek High Definition Audio Driver': Version 6.0.1.8142, A04->
https://www.dell.com/support/home/au/en/aubsd1/drivers/driversdetails?driverId=8WWJK
Must follow the installation process, being,
1. UN-install the existing version & reboot,
2. install the 8142 version & reboot.
If your computer is different make (eg Acer), try downloading 3 versions of the audio drivers approved for your particular model: from current version to the PREVIOUS 2 older versions. Test each version & see which one does NOT create HIGH CPU usage. Then mark that working version for later RE-use.
If the above fix the problem but then the problem RE-ocur down the track, try updating/refreshing the drivers for your audio-hardware @ Device Manager.
In my case, I updated the 'Realtek Audio' hardware with 'Realtek Audio' software (version 8142) previously installed on my laptop.
If you have 'sound cracking' problem, try this method also.
Welcome to IT: lots of trial & error, and frustration.
Good luck.