Merely an Ear

Behold, the ear!

(source 21)

The Hills Are Alive With the Sounds of Physics (Or, rather, physics of sound)

Definitions: 

Frequency: The number of sound waves that pass within a certain time, typically a second (18).

Pitch: How high or low a sound is as qualified by its frequency (19).

Amplitude: The length between either consecutive crests or troughs of a wave, defining loudness in sound waves (20).

Which Ear is Here?

The ear, being a complex structure, is divided into multiple sections, including “inner” and “middle”. The middle ear contains the eardrum, the tympanic cavity, and three small bones called the hammer, the anvil, and the stirrup (16). The inner ear contains the cochlea, the semicircular ducts (which are attached to the cochlea), and the auditory tube (this drains excess fluid). It also contains the cochlear and vestibular nerves, which connect the inner ear to the brain (17).

Hear Ye, Hear Ye

How does this all come together to allow us to hear? How do sound waves become auditory signals in the brain?

The pinna (the outermost part of the ear) reflects sound waves into the ear canal, which then reach the ear drum and cause it to vibrate. The hammer, anvil, and stirrup- collectively known as the ossicles- transmit vibrations to the cochlea. The vibrations cause the fluid within the cochlea to move, which causes the cilia to move. The movement of these hairs create neural signals where it is transmitted to the brain via the auditory nerve. The brain then processes these impulses and converts it into recognizable sound (15).

At a Loss for Hearing Loss?

There are two types of hearing loss:

Conductive Hearing Loss- Any damage or obstruction that prevents sound waves from traveling from the outer ear to the inner ear. This can happen as a result of any damage to the outer ear, ear canal, or middle ear. Hearing loss caused by age or exposure to loud sounds is typically conductive hearing loss (14).

Sensorineural Hearing Loss- Any damage to the cilia within the cochlea or the auditory nerve. This nerve damage is often congenital or as a result of disease. It is possible that significant exposure to loud sounds or aging can cause sensorineural hearing loss, but it is less likely (14).