ooossshhh
"Ooossshh" is a word made popular by Keith Lemon, but in fact the word has been around since time immemorial. It describes the effect of great excitement and is the sound emitted when pressure is released when opening a can of shaken lager. It can also be the description of other activities.
I was rigourously sucking the nipples of my heavily pregnant girlfriend when she ooossshhhed all over my moustache.