So what is sound really? And how can just a mash up of vibrations create such lovely and horrible noises in our ears? To understand what sound is, we have to delve deep into physics, biology, and neuroscience. Let's first focus on the physics by imagining sound as it travels. Sound travels as vibrations emitted from a source; these vibrations look like waves because they make air molecules bump into each other, and the size and speed of the wave creates a different sound. For example, a long and slow wave generates a low sound (think foghorn), while a short and fast wave makes a high sound (tinkling bells).
But how do we hear sound? The vibrations from that foghorn or tinkling bell will first reach the folds of you ear, called your pinna, which catch the vibrations and channel them through your ear canal to your eardrum. And just as an actual drum produces sound through vibrations, when the waves in the air hit your eardrum, they make the surface of your eardrum membrane vibrate, which is turn move three tiny bones in your inner ear. These bones then pass the vibrations onto another membrane called the oval window, which leads to the cochlea, in which there is perilymphatic fluid that receive the vibrations. But it doesn't stop there. Deep in the cochlea is the organ of corti, on which there are neurons called hair cells, and these are what conveys the sound waves to your brain. From there, it's up to the primary auditory cortex and several other parts of your brain to recognize the sound in a way that make sense to you!