The sounds we hate

Scientists have discovered why unpleasant sounds trigger a negative response. When we hear unpleasant sounds such as a fork scraping a plate or nails against a chalk board, the auditory cortex of the brain and an area of the brain called the amygdala interact to produce a negative response.

The auditory cortex processes sound while the amygdale is responsible for processing emotions such as fear, anger, and pleasure. When we hear an unpleasant sound, the amygdala heightens our perception of the sound. This heightened perception is deemed distressing and memories are formed associating the sound with unpleasantness.

How We Hear

Sound is a form of energy that causes air to vibrate, creating sound waves. Hearing involves the conversion of sound energy to electrical impulses. Sound waves from the air travel to our ears and are carried down the auditory canal to the ear drum. Vibrations from the eardrum are transmitted to the ossicles of the middle ear. The ossicle bones amplify the sound vibrations as they are passed along to the inner ear. The sound vibrations are sent to the organ of Corti in the cochlea, which contains nerve fibers that extend to form the auditory nerve.

As the vibrations reach the cochlea, they cause the fluid inside the cochlea to move. Sensory cells in the cochlea called hair cells move along with the fluid resulting in the production of electro chemical signals or nerve impulses. The auditory nerve receives the nerve impulses and sends them to the brainstem. From there the impulses are sent to the midbrain and then to the auditory cortex in the temporal lobes. The temporal lobes organize sensory input and process the auditory information so that the impulses are perceived as sound.

10 Most Hated Sounds

According to a study published in the Journal of Neuroscience, frequency sounds in the range of around 2,000 to 5,000 hertz (Hz) are unpleasant to humans. This frequency range also happens to be where our ears are most sensitive. Healthy humans can hear sound frequencies that range from 20 to 20,000 Hz. In the study, seventy four common noises were tested. The brain activity of participants in the study was monitored as they listened to these sounds. The most unpleasant sounds as indicated by participants in the study are listed below:

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

Listening to these sounds induced more activity in the amygdala and auditory cortex than did other sounds. When we hear an unpleasant noise, we often have an automatic physical reaction. This is due to the fact that the amygdala controls our flight or fight response. This response involves the activation of the sympathetic division of the peripheral nervous system. Activation of the nerves of the sympathetic division may result in accelerated heart rate, dilated pupils, and an increase in blood flow to the muscles. All of these activities allow us to respond appropriately to danger.

Least Unpleasant Sounds

Also revealed in the study were the sounds people found least offensive. The least unpleasant sounds indicated by participants in the study were:

• Applause
• Baby laughing
• Thunder
• Water flowing

Why We Don't Like the Sound of Our Own Voice

Most people don't like to hear the sound of their own voice. When listening to a recording of your voice, you may wonder: Do I really sound like that? Our own voice sounds different to us because when we speak, the sounds vibrate internally and are transmitted directly to our inner ear. As a result, our own voice sounds deeper to us than it does to others. When we hear a recording of our voice, the sound is transmitted through the air and travels down the ear canal before reaching our inner ear. We hear this sound at a higher frequency than the sound we hear when we are speaking.