The difference between image and sound from a neurological point of view

Images and sounds exist through our perception. The eye and ear transform light and pressure into electrical signals, interpreted by the brain. This internal porosity between image and sound enriches our experience and inspires audiovisual creation.

When we talk about images and sound, we usually think of external objects like photos, films on a screen, speakers, headphones, audio players, etc. This is what I call the external perception of images and sound. I propose to approach the subject from the internal side, because images and sounds only exist because we perceive them. Of course, our perceptions come from external phenomena. I’m not saying everything is imaginary, but that we access it solely through our perceptions.

What is an image within us?

How does an image form in our consciousness? Our eye is an optical system, a biological mechanism with lenses that project an image of reality onto our retina, much like inside the dark chamber of a camera. Just as a camera sensor has photosensitive pixels, the back of our eye has photosensitive cells: cones and rods. Cones are for color vision, and rods are for light intensity. The area where the image is sharp is extremely small, called the fovea. The rest is blurry. So why do we see sharp images? It’s due to eye movement. Our eyes constantly move without us realizing it, and our brain reconstructs a perfectly sharp overall image. This is not the real image that exists at the back of our eye. These photosensitive cells send electrical signals to our brain, which interprets them and gives us the impression that we are seeing.

How do we hear?

We live in a gas, air, which has a certain pressure and gives us life because we breathe it. What is sound, externally? It’s a variation in air pressure. For example, if I clap my hands, it’s similar to throwing a stone into water: you see ripples forming, spreading, and fading over distance and time. The same happens in the air when I clap: it creates a pressure change that spreads spherically. Our ear has an eardrum, a thin membrane in contact with the air. If there’s a pressure change, this membrane vibrates. These vibrations activate the mechanisms of the inner ear, producing electrical signals that our brain processes, giving us the sensation of hearing.

A close relationship between image and sound

Whether images or sounds, they are information perceived by our sensory organs, transformed into electrical signals, and processed by our brain to reach our consciousness. This is why, internally, the distinction between images and sounds is much more porous than externally. It’s important to be aware of this to better understand our relationship to images and sounds.

When someone tells me a story, I can see images in my head, like places they describe. I’m not looking at an image, yet it activates my visual perception. Similarly, if I see a silent image of a ringing bell, it activates my auditory perception. And our brain creates images and sounds from scratch in our dreams, for example.

I’m shedding light on the reality of our perception of images and sound to offer food for thought and open perspectives for audiovisual creation. In audiovisual creation, our goal is to evoke images and sounds in the viewer’s mind using technical tools. This process is far more nuanced and complex than simply showing images or playing sounds for them to perceive in a simplistic way.