THE SOUND RECEIVING APPARATUS
10.2.1 The Pinna
The auricle, also known as the pinna, constitutes the visible part of the outer ear, serving as the initial collector of sound waves. Its primary function is to channel these sound waves into the ear canal, officially called the external auditory meatus, where the incoming sound is amplified.
As the waves progress along the ear canal, they approach the eardrum, or tympanic membrane, a flexible oval membrane situated at the canal’s termination.The outer part of the ear, referred to as the pinna, has distinctive characteristics despite its limited mobility and relatively weak muscles. Unlike certain animals capable of orienting their ears for improved sound perception, our pinna doesn’t contribute significantly to enhancing our hearing or determining the source of a sound. However, the pinna does have a purpose. Even though it may seem less functional, blocking the hollow parts of the ear or altering its size can affect hearing. For instance, making the pinna larger with your hand can improve the perception of certain sounds, as larger, cup-shaped ears that project at an angle are more effective for hearing than smaller, flatter ears close to the head. Additionally, the pinna has the capability to conduct sound through specific bone structures in a unique manner.
10.2.2 The External Auditory Meatus
The external acoustic meatus, alternatively known as the external auditory canal or ear canal (Latin: meatus acusticus externus), is an air-filled tubular space that extends from the auricle of the external ear into the temporal bone, ultimately leading to the tympanic membrane. Despite its curviness, the size and length of the external auditory meatus are generally inconsequential, except for very high-pitched sounds where it may contribute to amplification. This curvy structure prevents sound waves from directly reaching any part of the eardrum. The meatus is equipped with hair and wax, providing protective functions by preventing dust and bugs from penetrating deep into the ear. Moreover, its sensitivity to touch, governed by nerves, prompts defensive or evasive reactions even to slight touches, enhancing the overall defensive mechanisms associated with this crucial part of the outer ear (Figure 10.1).
10.3