I am trying to figure it out because I would like to get him/her a friend/mate. I have never heard any calling but he/she is pretty shy, on another note I have a different auratus morph that is 7-9 months old and I heard a noise come from one of the frogs but it wasn't a buzzing noise like I have been told auratus make, and I think it would be to young to call, any info is appreciated.
By the way he's just sitting in your hand I'll assume he's not HORRIBLY mortified by human interaction as some of my auratus are. I dont know what kind of setup youve got for em, but make sure theyre are lots of hiding places, mist a few times a day for long periods and try and keep in tank interference to an all time minimum. Then listen during morning and evenings... I hear mine nearly every dawn and dusk. I bet if you leave em alone a good deal, spray em, etc. you will hear some calling. Listen extra hard during rainy days.