Acoustic engineer Professor Trevor Cox has developed a far-reaching internet experiment to discover the worst sound in the world.
To make his experiment fair, he developed an easily accessible website and randomised the order in which the sounds were played to counteract "sound fatigue" - which makes the early noises sound worse than later ones.
Trevor's experiment got him news headlines around the world, and also demonstrated a new way of conducting acoustic research over the internet.
So what is the worst sound in the world? Watch the programme to find out!
Watch our range of bonus clips which accompany this programme.
