The One Pound Sound

Can you work out the mystery sound to WIN cash with the One Pound Sound on Stu Haycock at Breakfast? It's small change... mind.

We play at 8:15am each weekday morning - and Stu adds a quid a day to the prize total until it goes!

Here's the wrong guesses so far:
A wardrobe door.
A car door.
A washing machine door.
A tumble dryer door.
A book being dropped on a table.
Car door central locking.
Closing the lid on a tupperware box.