A kind of Bwowwowow noise if you believe my son.
We read a lot of Hairy Macleary books at casa de huntington-smythe and our particular favourite is Caterwaul Caper
Quite particularly the pages in which all the dogs are underneath the tree that Scarface Claw is trapped in and they all make a noise
'Yip Yip" said Schnitzel von Krum
'Bow Wow Wow Wow' said Bitzer Malony
and so forth
From the repeated readings of this page (and I do mean repeated) Torby has started making the Bwowowow noise a lot.
Mostly at pictures in books and as he thrusts the book at you to read one more time.
This morning, he saw our cat and Bwowowow-ed at her.
We nearly wet ourselves.