In humans, hearing structures are also commonly known as the ear. The human ear is divided into three functional areas: the outer, middle and inner ear.

The outer ear includes the visible portion of the ear. This portion of the ear acts to collect and focus sound. Without the dish shaped portion of the ear, low intensity sound might escape detection. The visible portion of the ear also includes a structure known as the pinna (or auricle). This is visible as a hole. It leads to a passageway, typically about 0.98 in. (2.5 cm) in length that leads deeper into the ear. The passageway is commonly called the ear canal (or auditory canal). The ear canal is typically not a uniform diameter all down its length. Rather, it narrows about three-quarters of the way inward toward the eardrum to a diameter of...