Translation of "mumljati" into English

Vidim ga kaojednog od onih glumaca koji se češu i mumljaju, predodredjenih za manje i karakterne uloge.

I see him as one of those mumbling scratching actors destined only for minor roles and character parts.

Isto tako, pretpostavljam da nemaju nikakvih dobrih ideja, jer ne bi još uvijek mumljao sebi u bradu.

Also assume they didn't have any brilliant ideas or you wouldn't still be muttering to yourself.