Mute toggles audioOutput->setMuted(true), but this only works when there is a sound playing.
Reproduce:\ Start yapan, click mute, find update -> Sound plays\ Click mute while the sound plays -> Yapan is muted
Same for unmuting.
My suggestion would be to use a variable "mute" and put "if(!mute)" around the whole sound-part. On the other hand, I don't know anything about Qt and C++ ^^