Thanks for the Sudoku app, I spend way too much time playing on the train (best easy score 1:00, best hard score 2:37).
Your ad network has begun serving autoplay audio ads where you only had banner ads previously.
I'm not stomping off and uninstalling your app (harrumph harrumph). I assume this is a change in someone else's code and you'll fix it in good faith soon enough
It is a deal breaker for me long term though - if you're A/B testing this or something, please take this post as a strong Do Not Want.
This is something we've been trying to figure out for a while. How to identify the offending ad and the network serving it. Meanwhile, if you switch to Full Screen ads (Settings - Ads, requires restart) this should fix it for you.