We have all experienced sounds that make us cringe. Whether it is nails against a chalkboard or a crying baby, we all have that one noise we hate to hear. But why do these certain sounds bother us so much? What makes them special compared to other neutral or pleasant sounds? Recent research suggests that it may be your brain’s response making the difference.

A 2002 study found evidence that the amygdala becomes activated when people are exposed to unpleasant sounds. The amygdala is responsible for processing emotional responses. In the study participants’ cerebral blood flow was monitored while they listened to white noise to act as a control condition and then to a series of unpleasant sounds. These sounds included nails scratching, metal scraping, Styrofoam squeaking, a dentist drill, and a scratchy violin. Compared to the white noise, the participants’ lateral amygdala/claustrum regions saw significant increases in cerebral blood flow when hearing the aversive sounds.

Newcastle University extended on this work in 2012 by testing a larger range of unpleasant and pleasant sounds while using functional magnetic resonance imaging (fMRI) to observe a neural response. Participants rated how pleasant/unpleasant each sound was to them. Activity of the amygdala and the auditory cortex directly related to the unpleasantness of a sound. The more negatively a sound was rated, the higher activity that was observed. The results were interpreted to suggest that the amygdala modulates the activity of the auditory cortex so that the perception of an unpleasant sound is heightened. The study complied a list of the top ten most unpleasant noises from the stimuli they used. It was found that unpleasant sounds were in the frequency range of 2,000 to 5,000 Hz.

The resulting list can be seen below this post. I just hope the participants of the study were well compensated, because having to listen to all these horrid sounds must have been quite uncomfortable!

Most Unpleasant Sounds:

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

References:

Newcastle University. (2012, October 12). The worst noises in the world: Why we recoil at unpleasant sounds. ScienceDaily. Retrieved April 17, 2015 from www.sciencedaily.com/releases/2012/10/121012112424.htm

Zald, D. H. & Pardo, J. V. (2002). The neural correlates of aversive auditory stimulation. NeuroImage, 16, 746-753.