Knife on a bottle the most unpleasant sound in the world: study

Researchers scanned brain activity while people listened to 74 different sounds

If you thought nails scraping on a chalkboard was the most unpleasant sound in the world, you'd be wrong. It's number five.

The "most annoying sound in the world" as screamed by Lloyd Christmas in the film Dumb and Dumber didn't make the list.

But scientists at the Wellcome Trust Centre for Neuroimaging at UCL and Newcastle University in the U.K. have found the screeching of a knife on a glass bottle is the worst sound to the human ear. The most pleasant sound is bubbling water.

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These scientists had people listen to 74 different recordings while their brain activity was measured by an MRI scanner.

The results are published in the latest issue of the Journal of Neuroscience. Anything with a frequency between 2,000 and 5,000 Hz was found to be unpleasant.

"This is the frequency range where our ears are most sensitive," said paper author Dr. Sukbinder Kuman in a statement. "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 scientists studied people's reactions to 74 different noises. After a knife on a glass, the most unpleasant sounds are a fork on a glass, chalk on a blackboard, a ruler on a bottle and nails on a chalkboard.

Listen to the sounds

1. Knife on bottle

2. Fork on glass

3. Chalk on blackboard

4. Ruler on bottle

5. Nails on chalkboard

The reason we find these sounds unpleasant is because the amygdala, which are neurons in the brain that play a role in processing emotions such as fear and pleasure, provokes a negative reaction.

"It appears there is something very primitive kicking in," said Kuman. "It's a possible distress signal from the amygdala to the auditory cortex."

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The authors conducted the tests to better understand how the brain reacts to sounds to hopefully one day better understand conditions, such as migraines or autism, where noise plays a part.

The sounds are supposed to be ones we encounter in our everyday lives, but luckily it's be a while since I've heard any of these sounds.

(Getty Images)

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