The Secret Sound is played Monday to Thursday after 3pm in James' show.  Listen out for the sound, call in and have a guess, if you speak to James and guess correct you could win the cash, which accumulates each day. 
Competition terms and conditions apply.

Wrong guesses so far are: 

BRAND NEW; 7th October

An old car trying to start

A guillotine slicing paper 

The mechanism on a rowing machine 

A soda stream maker