The major task of the human ear is to detect and analyse noises by transduction. Another very important function is to maintain the sense of balance.
The best way to describe the functioning of the ear is to describe the path that the sound waves take on their way through the ear. The ear is divided into three different parts:
- The outer ear
- The middle ear
- The inner ear
The outer ear
The only visible part of the ear is the pinna (the auricle), which, with its special helical shape, is the first part of the ear that reacts to sound. The pinna acts as a kind of funnel that assists in directing the sound further into the ear. Without this funnel, the sound waves would take a more direct route into the auditory canal. This would be both difficult and wasteful, as much of the sound would be lost, making it harder to hear and understand the sounds.
The pinna is essential due to the difference in pressure inside and outside the ear. The resistance of the air is higher inside the ear than outside because the air inside the ear is compressed and thus under greater pressure.
In order for the sound waves to enter the ear in the best possible way, the resistance must not be too high. This is where the pinna helps by overcoming the difference in pressure inside and outside the ear. The pinna functions as a kind of intermediate link, which makes the transition smoother and less brutal, allowing more sound to pass into the auditory canal (meatus).
Once the sound waves have passed the pinna, they move two to three centimetres into the auditory canal before hitting the eardrum, also known as the tympanic membrane.
The eardrum (tympanic membrane), which marks the beginning of the middle ear, is extremely sensitive. In order to protect the eardrum, the auditory canal is slightly curved. This makes it more difficult for insects, for example, to reach the eardrum. At the same time, earwax (cerumen) in the auditory canal also helps to keep unwanted materials like dirt, dust and insects out of the ear.
In addition to protecting the eardrum, the auditory canal also functions as a natural hearing aid that automatically amplifies low and less penetrating sounds of the human voice. In this way, the ear compensates for some of the weaknesses of the human voice, and makes it easier to hear and understand ordinary conversation.
(Health24, updated December 2008)