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With normal hearing, hearing is a matter of course that nature has endowed us with. But it is a complicated process that comes about in a finely built and sensitive sense organ.

Structure & function of hearing & ear

Schematic representation of the anatomy of hearing and hearing. Click to enlarge.

What we call the ear in common usage is only the outer auricle, which has no practical significance for hearing itself, at least in humans, except to collect and bundle sound, tones and noises in a more directed manner, similar to a satellite dish.

It starts at the ear canal, which leads with a slight curve into the inside of the skull and ends at a depth of about 3.5 cm at a thin membrane, the eardrum. Behind the eardrum lies the middle ear, which is normally filled with air and communicates with the nasopharynx through the tubular ear trumpet.

The auditory ossicles, the smallest bones in our body, are located in this 1 ccm large middle ear. According to a finely constructed lever system, they are articulated to one another and form the ossicular chain. The first, the hammer, has its handle attached to the inside of the eardrum. With its head turned inwards, it lies in a trough-shaped depression in the second bone, the anvil. The other end of the stirrup touches the stapes, the third bone in the chain, the shape of which is exactly like a real stirrup.

The sounds of our environment, e.g. Spoken words or music physically represent air vibrations, which hit the eardrum as sound waves from the outside world through the ear canal and make it vibrate. The recorded vibrations are passed on from the hammer grip via the ossicular chain to the footplate of the stapes.

The actual hearing organ, the so-called inner ear, lies deep in the skull and is embedded in the hardest of our bones, in the labyrinth capsule of the temporal bone. The outer wall of this bone is also the inner wall of the middle ear. There are two small windows in it. The stirrup footplate is clamped in the larger oval window so that it can vibrate, while the smaller round window is closed by an elastic membrane.

The inner ear, surrounded by bones, is filled with lymph fluid and consists of two parts, the semicircular canal system as our organ of equilibrium and the cochlea, in which the actual hearing organ is located. Inside, a spiral-shaped duct runs around a bony, spindle-shaped axis, which is divided into three continuous channels by two thin membranes.

Up to this point the whole process is a purely physical one, by means of which the sound waves from the outside world are mechanically guided first through the ossicles and then in the fluid of the inner ear to the sensory cells. This is known as sound conduction, and any damage or disruption in the course of this complicated system means an interruption or weakening of the sound transmission to the nervous receiving apparatus.

The stimulation of the sensory cells caused by the recorded vibrations is transmitted from here via the auditory nerve to the cerebral cortex, and only there does it come to sensory perception as an auditory sensation. The physical vibration processes of the environment then enter our consciousness as tones, sounds or noises.

Hear tones, noises & words

Schematic representation of the anatomy of the auditory pathway, auditory system. Click to enlarge.

The human hearing organ is able to perceive both very low and very high tones. Our so-called hearing field therefore has a very considerable frequency range of around 20 to 20,000 double oscillations per second (Hertz). Only when hearing damage occurs in the range of these speech frequencies is the person concerned hard of hearing in the narrower sense, as he now has difficulty talking to his fellow human beings.

It is different for listening to music. The tones of orchestral instruments are between 64 and 10,000 Hertz, so that damage to the senses in this extended frequency range will impair the full enjoyment of a symphony concert, for example.

However, every single tone is not only perceived, but also perceived according to its volume. You only get a proper idea of ​​this fact when you consider that the sensitivity of our hearing extends over an enormous volume range. For example, we are able to perceive the very faint hum of an insect and also hear the booming thunder of a waterfall.

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Diseases & Disorders of Hearing

With such a complicated process it is natural that even small disturbances can be very sensitive and impair hearing. Since the intact hearing is now the prerequisite for learning and understanding the language, it is the most important factor for the undisturbed relationship between people and their environment.

Disturbed relationships in this regard can have far-reaching, often fate-determining effects on a person's environmental relationships in society, at work, even in the smallest circle of the closest family. It is therefore a high social duty and duty to help the hard of hearing as far as possible so that they can more easily cope with all the difficulties and hardships of their suffering, which life forces them every day anew.

In particular, however, it must be an essential task of the education of children and young people to teach hard-of-hearing children in special schools so well that they, as cheerful and creative people, can take a full place in society that corresponds to their abilities.