I’ve experienced a similar issue where FX Sound builds up static and becomes unbearable to listen and just one occasion when it did lost the sound. I used to experience this issue in games such as Battlefield BFBC2/BF3 and most of the time it came down the CPU/RAM resources.
The solution to this for me was to restart the FX Sound application in Task Manager. The sound would return to normal right after. I suspect this releases whatever resources were overflowing and purges whatever buffers have exhausted itself.
For me, in Windows 7/8/9x/10x when the sound suffers from static buildup, I stop and restart the Creative Sound Service and this ends the crackling/humming/reduced volume issues. You should know that in the past Windows 10 would also override the custom drivers with it’s own Windows Update drivers.
I tend to uninstall the default Windows / Windows Update WHQL outdated sound drivers via the Device Manager and favour the one from the manufacturer.
NOTE: If the latest official sound drivers are installed, sometimes uninstalling without driver deletion then allowing Windows to redetect/reassign it after reboot also helps to correct issues. You can reference Google to find out how to stop Windows from Updating and switching drivers to it’s own outdated WHQL defaults.
NOTE: I reboot PC on a regular basis so I wouldn’t experience this sort of issue often due to force of habit and given the need to release a file handle lock for impossible to delete files. I’m aware that terminating Explorer.exe often resolved file locking and such but not all the time. A neat tool to use would be SYSINTERNALS ProcessExplorer tool to find that hidden process thread that’s causing resource spike within the sound driver service or FX Sound application.