These two sounds have disappeared and as subtle as it may seem, after a few days away from this program, it was a shock to me. I noticed I felt substantially less motivates and wish I could have them back 
Readlang has never had these sounds. Maybe you’re getting mixed up with Duolingo or another language learning app? 
I agree that they would be a nice addition! (probably should be optional though)
Just added some basic sounds for:
- correct answer
- incorrect answer
- session complete
Refresh any open Readlang tab to ensure you are running the latest version. You can enable/disable these sounds from the Settings page