The Hobbets hear their voices repeated back to them from within the chest: "EARS!!! Hahahaha! Haw haw haw! Tha's a good one!" It is a disorienting experience, to hear what your own voices sound like!
Then the female voice proclaims: "If you are satisfied with your recording, please release the pull chain."
Assuming that Dougal complies with the instructions, when he releases his grip, the chain retracts into the chest with a tick tick tick sound, like a ratchet and gear. Soon the chest has reverted to the condition our heroes found it, with the 'pull me' tag hanging just outside where the lock would be.
The friendly female voice calmly declares, "Thank you. Have a nice day. Beware the spidergoat."