Scientists from Newcastle University have drawn up a league table of the least pleasant sounds we may encounter as part of everyday life – albeit a slightly old-fashioned life as the top five include the rasp of chalk on a blackboard.
Working with 13 volunteers, they tested reactions to 74 different noises both in outward response and more closely via small changes in the brain.
The results are published in the latest issue of the Journal of Neuroscience and show, among other things, 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, is not surprised. He says:
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, funded by the Wellcome Trust, took place at the trust's Centre for Neuroimaging at University College, London, using 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. The paper shows how in reaction to these, the amygdala modulates the response of the auditory cortex heightening activity and provoking our negative reaction.
Dr Kumar says:
It appears there is something very primitive kicking in.IIt's a possible distress signal from the amygdala to the auditory cortex.
The leader of the study, Professor Tim Griffiths from NewcastleUniversity, says that better understanding of the brain's reaction to sound could help in the study of medical conditions where sensitivity to noise plays a part. He says:
Shedding new light on the interaction of the amygdala and the auditory cortex 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.
Would you like to test your own reactions? Here you go, with the five least pleasant sounds from the study.
First, here's the knife on a bottle
Next, a fork on a glass
Now for us older ones, chalk on a blackboard
A ruler on a bottle, which most be the most unusual of the Worst Five
And finally nails on a blackboard
And that's it. As they say nowadays, Enjoy, although that isn't the right word.
