Hearing ability, ear, hearing, hearing organ, auditory sense, auditory sense, acoustic perception, auditory perception,
Hearing / human hearing is our best developed sense. This means, for example, that we are able to distinguish twice the amount of auditory impressions than we can with visual impressions: From more than 24 images per second we no longer recognize individual images, but a flowing film. Our eyes are overwhelmed, so to speak.
But even with a volume of 50 auditory impressions per second, our ears are still able to make distinctions and transform these auditory impressions into information that can be used by our brain for further processing. We are even able to pitch sounds in their different qualities (up to 7000 different), Volume, distance and directional hearing (accurate to 2 °) to distinguish and divide.
Our hearing is also very important: It serves as a warning and protection system, for communicating and for pleasantly beautifying our everyday life.
Ever since people have existed Listen as much as life insurance. Only those who could hear well could hunt animals, avoid predators or communicate appropriately with neighbors. But even then, as now, there was a decline in hearing. During excavations of ancient Egyptian graves, clay tablets with inscriptions were found in which the deities were asked to restore hearing to the deceased in the afterlife.
The Greek scholars also frequently took up the subject of “hearing”, which is what is probably the oldest writings on the subject sound and vibration originated.
In the centuries later, numerous attempts followed to fathom this marvel of divine creation.
But much of the knowledge from that early period was forgotten again over the centuries.
It was not until the late 19th century that a special medical branch on this topic emerged. The Ear, nose and throat medicine was created!
But ours can ear hear everything physically?
Unfortunately, or luckily no! We only hear acoustic events in a range of 0 dBwhat a sound pressure of about 20 µPa (= 2 · 10-5 Pa), to over 130 dB (~ 10,000 kPa) - still quite a considerable range. The unit D.ezibel (dB) is a quantity that increases slowly and then faster and faster (logarithmic) and which compares all values with the sound pressure at 0dB. So 0 dB represents the hearing threshold, i.e. the softest perceptible noise (e.g. a very slight breeze).
At 130 dB one speaks of the pain threshold, i.e. the sound pressure level at which a noise is perceived as pain. The normal language area is roughly between 40 dB and 80 dB at a pitch of around 2000 Hz. This is where the sensation of our hearing organ is greatest. We hear tones that are higher or lower than this frequency, much quieter and therefore not as good.
Hear in detail
Some mechanical action creates a sound, an oscillation of the air that moves as a sound wave. Different sound waves are generated depending on the noise source. This hits the ear from the outside (auris externa) and is first captured by the auricles and bundled through the external auditory canal to the pea-sized eardrum (membrana tympani, myrinx) directed. On this flexible round membrane, the first adjustments to our hearing can be made in the event of fright or expectation of a loud noise: With the help of a small muscle (tensor tympani muscle) the membrane can be stiffened and thereby the normally occurring vibration can be reduced; we hear quieter.
The eardrum also closes the next cavity, the tympanic cavity in the air-filled middle ear (auris media) against the ear canal. Like a drum, it is supported by a tendon ring (annulus fibrosus) in the bony ear frame (sulcus tympanicus) clamped. So that the eardrum can vibrate optimally, the pressure in front of and behind it must be the same. Eustachian tube (tuba auditiva).
With closed ears and a swallowing process, or with a closed nose and pressure built up inside, pressure compensation can be consciously effected. Anyone who has flown by plane can certainly confirm this.
On the inside is a little bone, the hammer (maleus) with its grip attached to the eardrum. When the eardrum vibrates, it is also set in motion and directs the movement with the aim of mechanical sound amplification (around 22 times) via a chain of ossicles - the anvil (incus) and the stirrup (Stapes) - to the oval window, the wall of the inner ear (auris interna) forwarded. Here too, a "braking muscle" on the stirrup (stapedius muscle) the transmission of sound is attenuated, especially if you have a loud voice.
In the following fluid-filled cochlea (cochlea) the wandering sound waves trigger vibrations in a special membrane at certain locations depending on their pitch. Think of it like a strip of paper that you hold between your index finger and thumb.
If you now blow the paper strip from the direction of the thumb, it begins to make waves. These waves get bigger towards the unattached end of the paper, because there is less holding resistance to overcome. However, in order to make the paper vibrate strongly near the fingers, one has to blow extremely hard, i.e. H. a high sound pressure can be built up. Listening to different sound frequencies works in the same way. High notes have a lot of energy and cause the membrane to vibrate near its anchoring. On the other hand, low tones with low energy only manage to cause a vibration towards the free end of the membrane. This splitting of the different sound frequencies is called dispersion.
Reinforced by easily activated "additional springs" on the membrane (process of fine dispersion), some of the 20,000 or so hair cells are bent over at the point of maximum membrane oscillation, causing them to send out electrical signals.
These signals can then finally pass through a annoy (cochlear nerve) in the brain, are directed to a special hearing center, where they are sent through various filters and evaluated. These filters make up our actual hearing: They select sounds that belong together from strangers, remove unnecessary background noise and only give us the opportunity to listen to a person in a concentrated manner. It is possible that in the middle of a party with a lot of conversation and therefore a high level of noise, our name is suddenly mentioned. Although the volume and pitch may not differ from the other conversations, we are able to filter out this familiar hearing impression and let it become clear to us without background noise.
The information from both ears is offset against each other in further filters. The same hearing impression arrives at both ears with a time delay, as they are located on the right and left side of our head. In this way, our brain can use this time difference to calculate where the noise is coming from. Our sense of direction arises. Some acoustic signals are also assigned to optical sensory impressions, which is what makes it possible for us to name things or to recognize a great speaker as such!
In short: Only through the extensive filter system in our brain can noise become meaningful hearing!
Our hearing cannot rest. It is always active, even if we do not notice it. For example, parents sleep in the adjacent street in spite of the heavy traffic, but the bright sound of the child's voice triggers an alarm and the "Alarm program“The body sets in.
Embryology of hearing
The Inner ear is the first sense organ that develops in us humans. Its development already begins in the 4th week of pregnancy and is with the 24th week of pregnancy completed. Nevertheless, it takes until the 26th week of pregnancy until we can finally hear the parental voices muffled. From the 6th month of pregnancy, a fetus should respond to sound stimuli. If hearing disorders are suspected, this should be checked as early as possible.
Up to the 8th month of pregnancy, that too outer ear and the Middle ear relatively well trained to hear. But that doesn't mean that our hearing system is fully developed and fully functional. To do this, you only have to go through "diligent listening training“The nerve tracts to the brain and the manifold connections that make sorting and filtering possible in the first place. Any links and interconnections that have not yet been formed, however, are irretrievably lost. Listening exercises in these first years of life are an absolute MUST! Because: If you want to become a master, you practice early!
We are therefore able to recognize different tones and noises, to filter certain out of a multitude of others, to make ourselves noticeable in the dark and to link our various senses properly. This miracle machine now - our human hearing / hearing, our most differentiated sense - is very important for human life and at the same time our first opportunity to participate in the outside world. That is why it is important to do our best as early as possible to ensure that our little fellow human beings are well educated and to help our big ones to keep them functioning for as long as possible!