What is the Most Annoying Sound in the World?

"Hey, want to hear the most annoying sound in the world?"

What makes Lloyd Christmas's shriek so infuriatingly annoying?

Sound is one of our main cues for distress. Consider how in the jungle, when you suddenly hear the distress call of a monkey you may guess something dangerous is near. Now, we don't associate that unpleasant distress call with physical danger so much in a city but it may still illicit an unpleasant response. Aversive noises will create an emotional response.

In a recently published study, how this emotional response is triggered was investigated (Kumar 2012). They found that evoked emotional responses to aversive sounds (like the scream of a woman) were channeled through the amygdala. Variations in the acoustic characteristics of the sound change the connection patterns from auditory cortex to the amygdala, the perceived unpleasantness alters the relay of information from the amygdala back to the auditory cortex. Essentially, Kumar et al found that as the auditory cortex relays raw acoustic data to the amygdala, translation of that data (especially unpleasantness), and the elicited emotional response change how the auditory cortex interprets the acoustic data.

Now consider this, in Minneapolis, Orfield laboratories has a room that is so quiet it rates at -9.4 decibels, an anechoic chamber. The fiberglass walls are so absorbant it actually reduces noise to a perceived zero. Anecdotal stories of the room state that it is so quiet, that spending too long in the room makes it impossible to keep your balance. The absolute lack of noise causes people to seek auditory cues so desperately that they begin to hear the opening of their heart valves, muscles of their digestive tract, and expanding of their lungs. This utter lack of noise is said to be so distressing and unpleasant that the longest anyone has stayed in the room is 30 minutes.

So with the understanding that the amygdala requires acoustic signals to elicit an emotional response, I wonder what it is in an chamber void of sound waves that is signaling the amygdala to create feelings of distress. I would theorize that the auditory neurons, in the complete lack of stimuli, begin to depolarize and signal on their own. This random, uncoordinated signals are interpreted by the amygdala as acoustic information and produces feelings of distress. I would be very interested to see as study that looks at how the auditory cortex and amygdala behave without any form of sound input.



Thornill, T. (2012) "We all crave it, but can you stand the silence? The longest anyone can bear Earth's quietest place is 45 minutes." Daily Mail. Retrieved from: http://www.dailymail.co.uk/sciencetech/article-2124581/The-worlds-quietest-place-chamber-Orfield-Laboratories.html

Kumar, S., von Kriegstein, K., Friston, K., Griffiths, T.D. (2012). Features versus Feelings: Dissociable Representations of the Acoustic Features and Valence of Aversive Sounds. Journal of Neuroscience. 32(41) 14184-14192. doi: 10.1523/jneurosci.1759-12.2012