Significant activity in areas of the brain associated with emotion and hearing could explain why the sound of fingernails on a chalkboard or a knife on a glass bottle is so uncomfortable.

In a study published in the Journal of Neuroscience, funded by the UK’s Wellcome Trust, scientists at Newcastle University in the UK found that when noise is heard, the brain is responsible for The auditory cortex, which processes sound, interacts with the amygdala, which is active in response to negative emotions.

Brain imaging  has shown that when we hear uncomfortable noises, the amygdala modulates the activity of the auditory cortex and triggers us to react negatively.

Dr Sukhbinder Kumar, an author of the paper from Newcastle University, said: “It seems to be a primitive natural response. The amygdala may send a pain signal to the auditory cortex.”

Using functional magnetic resonance imaging (fMRI), researchers at the Wellcome Trust Center for Neuroimaging at University College London (UCL) and the University of Newcastle examined 13 How the brains of volunteer subjects respond to a series of audio-variant sounds. After listening to the sounds made by the instruments, the subjects rated the sounds from the most unpleasant (for example, a glass bottle being scratched by a knife) to the most pleasant (for example, the sound of running water). This allows researchers to study how the brain responds to different types of sounds.

The researchers found that activity in the amygdala and auditory cortex correlated directly with the subjects’ perceived noise ratings. In fact, the amygdala, which is associated with emotions in the brain, controls and regulates the activity of areas related to hearing, and when we perceive a very annoying sound (for example: cutting a glass bottle with a knife), it is associated with reassuring Sounds (for example: the sound of running water) are relatively strong.

An analysis of sound by acoustic features found that audio frequencies between 2,000 and 5,000 hertz (Hz) sounded the most unpleasant. Dr. Kumar explained: “This happens to be the most sensitive range of our ears. While there is still a lot of debate as to why this is the range, it does contain screams that we inherently consider to be uncomfortable.”

Scientifically speaking, understanding the brain’s response to noise can help us clarify the situation of patients with low noise tolerance (hyperacusis) and misophonia (literally, “extreme dislike of sound”).

Study leader Dr Tim Griffiths, from Newcastle University, said: “This research sheds new light on the interaction between the amygdala and the auditory cortex. Chance of migraine—they all seem to have an overly intense perception of noise.”