apps no longer have sound in iOS 9.

hi. I recently upgraded my iPod touch 6g to iOS 9, and found out that some apps make no sound anymore. I encountered this in need for speed most wanted and hot pursuit, and also in call of duty strike team. none of my notifications make sounds either. I understand this is a widespread problem, and I was wondering if there was a fix, or if Apple planned to fix this. I don't know if it's iOS 9 or the apps, so if anyone knows how to help, thanks in advance. (ps: deleting and redownloading did not help). 😟