In 2012, researchers at Newcastle University tested 13 people to determine the most unpleasant sounds. The study tested the subjects' reactions to 74 different noises, both in outward response and more closely via small changes in the brain.
The results, reported in the Evening Standard, showed that acoustically anything in the frequency range of around 2,000 to 5,000 Hz was found to be unpleasant.
The author of the paper, Dr Sukhbinder Kumar, said: "This is the frequency range where our ears are most sensitive. Although there's still much debate as to why our ears are most sensitive in this range, it does include sounds of screams which we find intrinsically unpleasant."
The study used functional magnetic resonance imaging to watch how the volunteers' brains responded to the noises. These varied from the sound of a knife on a bottle - which emerged as the most unpleasant - to babbling water, which went down best.
The imaging showed a pattern in the connections between the region of the brain that processes sound, the auditory cortex, and the amygdala, which is active in the processing of negative emotions when we hear unpleasant sounds.
A primitive response
The paper showed how in reaction to these, the amygdala modulates the response of the auditory cortex heightening activity and provoking our negative reaction.
Dr Kumar added: "It appears there is something very primitive kicking in. It's a possible distress signal from the amygdala to the auditory cortex."
Based on the results, the worst sounds from ten to one were as follows: electric drill, baby crying, bike brakes, angle grinder, female scream, nails on a blackboard, ruler on a bottle, chalk on a blackboard, fork on glass, and, finally, a knife being scraped across a bottle.