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 The miracle of hearing
The purpose of the human ear is to perceive pressure vibrations in the air as a sound or noise. Such vibrations are called sound. |
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If the ear drum is impacted by sound waves, it transmits its movement via the auditory ossicles of the hammer, anvil and stirrup, to the coiled, spiral pea-sized cochlea of the inner ear.
Here there are about 25,000 tiny sensory hairs in fluid. The mere bending of these hairs by the size of a hydrogen atom is sufficient to convert the energy to an electromechanical signal and transmit it via the auditory nerves to the brain.
1 Hammer, 2 Anvil, 3 Stirrup, 4 Semicircular canals of the organ of equilibrium,
5 Auditory canal, 6 Ear drum, 7 Cochlea, 8 Eustachian tube
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Frequency and decibels
The shorter the intervals between waves, the higher the pitch heard. The unit of measurement of wave frequency (waves per second) is hertz (Hz). A human’s audible range is between 16 Hz and 16,000 Hz, whilst some animals can hear levels of up to 100,000 Hz.
In addition to frequency, sound pressure also plays a decisive role. Its level is measured in decibels (dB). The higher the number of decibels, the louder the sound heard. If a sound measurement is in dB(A), it follows the A-scale and attempts to aurally compensate the volume. It thus takes into account the sensitivity of the human ear.
Decibel is a logarithmic quantity. 3 dB difference is scarcely perceivable, but is physically twice the sound intensity. 10 dB already corresponds to ten times the sound intensity, but humans only experience this as twice as loud. |
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Hearing problems due to noise
The stronger the impacting sound, the greater the damage to the sensory hairs. It starts with conglutination and the loss of elasticity and ends with the fine structures breaking off – like blades of grass in the wind. Based on the latest findings, free radicals also contribute to the damage process.
The tiny hairs in the front are responsible for higher frequencies. As they are the first to die, hearing problems generally begin in this frequency range. The falling out of half of the tiny hairs does not yet lead to any noticeable hearing loss. The start of a hearing problem is often recognised when it is already too late. Hearing problems cannot be healed, but can be only be compensated with a hearing aid.
In addition to the sound intensity, the impact time also contributes to the duration of the hearing damage. Up to a certain stress level, the tiny hairs are mostly able to recover provided they are subsequently given sufficient rest. As a rule of thumb: after going through a stress phase, the hairs usually require at least twice as much rest. |
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How much noise can the ear bear?
The industrial health and safety associations have determined how long workers can be exposed to noise in one working day without jeopardising their hearing. In leisure time, too, you should also be guided by these values!
85 decibels (A) – harmless for up to 8 hours
88 decibels (A) – harmless for up to 4 hours
100 decibels (A) – harmless for up to 15 minutes
119 decibels (A) – harmless for up to 1 minute
Extreme noise such as gunshots, bangers, etc., can cause instant damage.
Caution! We usually don’t notice when the ear is exposed to too much noise. The first warning signs, such as a sensation of deafness, ringing in the ears and headaches, are not reliable, and are often ignored. Many people refuse to believe it, but you cannot get used to noise! |
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