The Human Interpretation of Sound

As we know, a sound wave consists of vibrating particles. These knock into other particles causing them to vibrate, and so the sound can travel away from the source. You can hear sound because the vibrations in the air cause your ear drums to vibrate. This vibration is converted into signals which travel down a nerve to your brain and similarly, microphones can detect these vibrations and convert them into electrical signals.

The human ear is made up of three parts, the inner, middle, and outer ear. The outer ear collects sounds and directs it to the middle ear. The middle ear translated the sound into internal vibrations of the bone structure which then gets translated into a compressional wave. Lastly, the inner ear takes this compressional wave and translates it into nerve impulses using ear fluid so the impulses can be sent to the brain.

The outer ear is made up of the external cartilage of the earflap and the ear canal which is about 2-cm long. The earflaps’ main purpose is to protect the middle ear and the ear canal to prevent damage to the eardrum. Due to the length of the ear canal, it is capable of amplifying sounds with frequencies of approximately 3000 Hz. As sound travels through the outer ear, the sound is still in the form of a pressure wave, with an alternating pattern of high- and low-pressure regions. This is because the sound waves only become converted into vibrations of inner bone structure when the mechanical waves reach the middle ear.

Then at the middle ear the sound passed through a tiny air-filled cavity home to three interconnected bones, the hammer, anvil, and stirrup. As pressure waves reach is rightly stretched membrane vibrates thus vibrating the eardrum at the same frequency. This membrane is connected to the hammer and causes the hammer, anvil, and stirrup to all vibrate at the same frequency. The stirrup is also connected to the inner ear causing a compression wave in the fluid.

The inner ear is made up of the cochlea, the semicircular canals, and the auditory nerve. Both the cochlea and the semicircular canals are filled with a water-like fluid. These fluid and other nerve cells are only a means of detecting accelerated movements and maintaining balance they actually do nothing in terms of hearing. The cochlea is shaped like a coiled tube and its inside is covered in hair and filled with fluid. As a compressional wave gets passed to the inner ear from the stirrup it interacts with the small hair-like nerve cells. Each hair is sensitive to a individual frequency, and when the compressional wave matches that frequency the hair will resonate with a larger amplitude of that same vibration creating an electrical impulse that gets passed along the auditory nerve towards the brain. Then the brain takes that impulse and interprets them into sound.