This week we are starting the new Crastina theme: Science and Sound.

As a neuroscientist, the first thing that came to my mind was: how is a sound understood by the brain? When you are listening to a podcast… or your favourite science rapper song… how is this translated into electrical information for your brain? Touch, taste and smell are quite concrete to understand, it’s mechanic and chemical… but a sound?!

Let me walk you through this wonder.

How are we hearing then?

A sound is like the ripples on the water after a rock pierces its surface. A sound is a vibration, propagating in the form of an acoustic wave. Each sound will have its distinct frequency signature and strength. But what takes place when the acoustic wave, the sound, reaches our ears?

Like the brain, the ear is a fantastic and complex organ.

The ear consists of three parts:

  • The outer ear, with all its curves and places to accessorize, is a literal cone for the sound to bounce in the direction of the middle ear.
  • The middle ear starts with the tympanic membrane or eardrum (it’s what hurts if your go too deep with the cotton swab). The acoustic wave is going to vibrate the eardrum which is connected to the tiniest bone mechanism: the ossicles. They are going to transfer the acoustic vibration to the inner ear.
  • The inner ear contains the cochlea which looks like a snail shell. The inside of the cochlea is covered with cells with a filament-like extremity called hair cells. When the acoustic wave reaches the cochlea, it induces a vibration in the liquid the cochlea is filled with. These vibrations activate the hair cells which send an electrical signal to your brain, which in turn can collect the information from both ears so you can understand it as: it’s my alarm clock… Damn it’s time to wake up and go to work!

When the brain is tricked

Unfortunately, as clever as the brain is… it can be tricked! You may remember the auditory illusion that blew up the internet… was it “Laurel” or was it “Yanny”?

Thanks to this internet buzz, people actually wanted to understand the science behind it (mostly to know who was right). Some sounds like the ones for the L and Y are made of several frequencies at once and share similar frequencies. However, “Yanny” plays on a higher frequency than “Laurel” and because we start losing the hair cell recognizing high frequency, the more mature you are, the more likely you are to hear “Laurel” while younger people would tend to hear “Yanny”! Protect your ears if you want to keep them young!

Now that you understand how we are able to hear and that there is no point in fighting over internet auditory illusions, you are ready to dive into what we have prepared for this theme. The crew will give recommendations of our favorite podcast episodes, we will listen to the sound of the universe and we will interview fantastic scientists who use music to study and communicate science, as this is what we love at Crastina!

About Lauriane Nallet Khosrofian

I am a Neuroscientist passioned by all science. I think the world is a better place with curious people and science communication help fulfilling curiosity. Otherwise, I love, cats and books!