How Exactly Do We Hear Sounds?

By Antonia Čirjak on June 5 2020 in Answer

Sounds are nothing more than vibrations that your ears detect.
Sounds are nothing more than vibrations that your ears detect.
  • Although most people can not hear frequencies below 30 or 40 Hz, that does not mean that those types of vibrations do not exist in nature.
  • Everyone that wears headphones to listen to music will benefit from a large frequency spectrum covered by those devices. However, long-term exposure that is too loud can permanently damage the hair cells in your ear.
  • Humans can detect sounds that are between 20 Hz and 20 kHz. Dogs and cats can detect more than double that amount, and their range goes all the way up to 55 kHz. That is how they hear that recall whistle!

Sounds are nothing more than vibrations that your ears detect. However, things we hear in our surroundings create an enormous range of sounds, because all of those things vibrate at different frequencies. How are we able to hear those vibrations, and what are our limitations when it comes to hearing? 

Needs More 30 kHz!

If you ever saw an internet-meme of a cat, who is portrayed as a sound engineer, the text must have caught your attention. The cat from the meme says: the sound is kind of dull above 20 kHz (kilohertz). Why is this funny, and how does an internet meme help us here? There is a limit to our hearing, even if your hearing is in perfect condition.

Humans can not hear anything that is above 20 kHz, which is why the cat is making fun of us, as its hearing is far superior to ours when it comes to the spectrum of frequencies they can detect. Now, what are frequencies exactly, and how do they help us describe different sounds?

Sound Vibrates Through Air

Simply put, what we hear when we notice a sound is a vibration that is traveling through the air because the object that is vibrating (within a specific frequency range) is moving the molecules of the air. 

Well, a frequency, in this case, is the number of vibrations a particular sound source is making. If something is vibrating with 100 vibrations in one second, the frequency we can hear from that object is 100 Hz. If an object is vibrating ten times faster, it reaches the frequency of a 1000 Hz, also noted as 1 kHz. The range of a perfectly healthy human ear can detect is between 20 and 20,000 Hz (20 kHz). The higher the frequency - the higher the pitch

Hearing: Cochlea And Brain Working Together 

First, the sound enters our ear canal. As it reaches it, it immediately keeps on traveling to our eardrum. When a sound reaches the eardrum, it makes it vibrate. There are three small bones inside our middle ear that enable the vibration of our eardrums. 

The eardrum is connected with the cochlea, another tiny structure made of bone inside our inner ear. Our cochlea is filled with liquid, which helps the vibrations caused by sounds to reach our hair cells. From there, those nerves are the ones responsible for transferring the message to our brain. As the sound finally reaches our brain, the message, meaning the sound, can finally be perceived.  

Our brain is the one that then ‘’explains’’ the quality of a particular sound: is it too loud, is it too quiet, is it abrasive and hurtful to our ears, or is it pleasant and soothing?

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