WoW-Mania

I'm not sure how to fix this, I've tried all the options in game but all the sound effects have a crackling noise or a constant stutter.
I'm using on board Realtek and no other games or apps are affected.

Sounds like an issue with the game's audio processing. Since other apps are fine, it might be worth updating your Realtek drivers or tweaking the sample rate in Windows sound settings. Also, try disabling audio enhancements in the sound properties. If the game has different audio settings (like switching between DirectSound or WASAPI), testing those could help.

Are you using any enhancements in sound settings? Disabling them helped me once when I had a similar crackling issue.

Or

May be latency issue. Open LatencyMon and see if anything is spiking.