Out of 74 sounds, volunteers rated the five most unpleasant as:

1. Knife on a bottle

2. Fork on a glass

3. Chalk on a blackboard

4. Ruler on a bottle

5. Nails on a blackboard

I'm suprised this didn't make the list...

Why do nails on a chalkboard drive us crazy?

Scientists say our reaction to the
sound of scraping nails – which is in the same frequency range as screams and
babies' cries – could be an ancient survival instinct.

The study scanned the brains of 13
volunteers while they listened to a range of sounds before rating how much they
liked them.

The more unpleasant a sound, the
greater an almond-shaped
brain region known as the 'amygdala' lit up.

It then activated the auditory cortex,
which processes sound, leading the volunteers to perceive the noise more keenly.