We are making a fairly significant update to our audio engine in this patch (8.5), if you want more details we will be posting an article later this week that will go over it, and some other changes on the horizon. Things to be aware of for this PBE Deploy:
You will be downloading almost every audiobank in the game, be prepared for a large download.
There will be missing sounds, we have been testing this change for a while now, but there will always be bugs that slip through. If you notice any missing sounds/VO while playing on PBE please let me know so we can resolve it asap.
Types of issues that you may see:
* Audio missing on abilities
* Audio playing two times when it used to play once
* Missing VO
* Missing music
* This will not effect LCU sounds.
Thank you for your ear time, and patience.
Link to a more in depth explanation - https://na.leagueoflegends.com/en/news/riot-games/editorial/some-larger-patches-incoming