It makes a fart sound under max load, in order to appeal to the masses for a more sporty sound....
On a serious note, it's a noise maker, it's sole purpose is to project more engine noise into the drivers cabin for a more sport like sound. I am dead serious and not joking... it can safely be deleted. However you will need to find something to close the hole. Search for forum for "noise maker delete" and you will find more info...