Muggles' Guide to Harry Potter/Magic/Ghoul

Overview
The ghoul, while not exactly the best looking of all magical creatures, isn't all that dangerous. It occupies attics or barns owned by wizards, and resembles a buck-toothed ogre. The most harm it can cause is to growl at someone who unluckily comes across it. It often groans and throws things around.

Extended Description
In Harry Potter and the Chamber of Secrets, it is mentioned that there is a Ghoul living in the attic of The Burrow, the Weasley home; Ron is rather dismissive of it, saying that it is nowhere near as good as having a house-elf. There is mention of a "murderous old ghoul" elsewhere in the books, which would imply that ghouls can also become dangerous as they get old; possibly, like many animals, they get senile.

Analysis
In the case of the Weasleys' attic, the ghoul is used as part of the ongoing illustration of the Weasley family's relative poverty; the idea, one supposes, is that rich families have house-elves to take care of them. Ron does find out that having a house-elf can be a double-edged sword, though, when he has to deal with Kreacher.

Ghouls are also mentioned in Harry Potter and the Deathly Hallows. Ron, with the help of his father, changes his ghoul into a replica of himself with "Spattergroit", so that he can search for the Horcruxes with Harry and Hermione.

Questions

 * 1) What do ghouls eat? Boggarts feed off our fears and so act to inspire fear; what would Ghouls feed off that would cause them to prefer noise? Could it be irritation?