Brain research reveals what is the most annoying noise in the world

Scientists have used brain imaging to work out what is the most annoying noise in the world (Image: Rex)

The most annoying sound in the world is the scrape of a knife down the side of a glass bottle - with the horrible screech of nails on a blackboard placing in fifth.

The chart is based on magnetic brain images of how sounds provoke a response within the amygdala, the brain's 'emotion centre'.

People also find nails on a blackboard, bicycle brakes, and electric drills highly unpleasant.

The research hints that we evolved this response long before blackboards, bottles and even knives existed.

All the sounds in the top ten are similar in frequency range to human distress signals such as female screams or babies cvrying.

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"It appears there is something very primitive kicking in," says Dr Sukhbinder Kumar, the paper's author from Newcastle University. "It's a possible distress signal from the amygdala to the auditory cortex."

All the sounds come from roughly the same range of high-pitched frequencies, say the Newcastle scientists that made the discovery.

Anything in frequency range of around 2,000 to 5,000 Hz was found to be unpleasant. Dr Kumar explains: "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."

Researchers at the Wellcome Trust Centre for Neuroimaging at UCL and Newcastle University used functional magnetic resonance imaging (fMRI) to examine how the brains of 13 volunteers responded to a range of sounds.

Listening to the noises inside the scanner they rated them from the most unpleasant - the sound of knife on a bottle – to pleasing - bubbling water.

Researchers were then able to study the brain response to each type of sound.

Researchers found that the activity of the amygdala and the auditory cortex varied in direct relation to the ratings of perceived unpleasantness given by the subjects.

The emotional part of the brain, the amygdala, in effect takes charge and modulates the activity of the auditory part of the brain so that our perception of a highly unpleasant sound, such as a knife on a bottle, is heightened as compared to a soothing sound, such as bubbling water.

Scientifically, a better understanding of the brain's reaction to noise could help our understanding of medical conditions where people have a decreased sound tolerance such as hyperacusis, misophonia (literally a "hatred of sound") and autism when there is sensitivity to noise.

Professor Tim Griffiths from Newcastle University, who led the study, says: "This might be a new inroad into emotional disorders and disorders like tinnitus and migraine in which there seems to be heightened perception of the unpleasant aspects of sounds."

The worst sounds in the world

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

6. Female scream

7. Anglegrinder

8. Brakes on a cycle squealing

9. Baby crying

10. Electric drill