Does bạn mean a sort of noise that sounds like 'whatwhatwhatwhatwhat'? I think it is a guinea pig (quite literally) talking to itself "What is this here? Hmmm I need to give this a sniff, and look at it from all angles and what do I think of it (etc etc etc)?" Generally, the thêm curious a guineapig is about something, the faster they say 'whatwhatwhatwhatwhat'.
I discovered a website thats really good it might have your answer type in "Guinea pig noises" into searchbar click on the one that says Guinea pig noises and its a segment on the website JackiesGuineapigs. Hope u can find out y on there.