Hearing Definition

Hearing is the ability of an organism to perceive sounds, mostly direction-sensitive with respect to the sound source. It is one of the five senses. Observing this sense is called "hearing". The ear is the organ of hearing in which sound waves are converted to action potentials in the auditory nerves.

The anatomy and physiology of the ear organ can be read on the topic 'ear'.

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Function

The function of the hearing sense is to locate sound sources, communicating with similar organisms, or recognize the sounds of other types of organisms.

Localization of sound sources is needed for orientation of the organism in the wrapper objects world where such objects make noise or echo sound.

The function of communicating with similar bodies is especially necessary for maintaining social ties with their own group. Hence, the most organisms are specialized in recognizing sounds with a volume corresponding to the normal volume of the mutual communication, such as voice in humans. Also for the sound reproduction is a widely used means of communication between peers of the opposite sex, and compared with rivals of the same sex. The one which best brays or the finest flute gets the most and best females.

In addition, recognizing the sounds of other organisms, a feature that is essential for many animals to locate prey and danger (eg. Predators). It is thus a tool that helps hunt the prey and an agent on the other hand, the prey helps timely notice of the hunter. Of course, be noticed and tracked by the hearing other types of danger: falling boulders, rushing trains etc.

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Types perceived sound stimuli

The sound stimuli are generated by sound vibrations which through the air or through the water to reach the tympanic membrane. And like all the vibrations also have a frequency of sound vibrations, an amplitude and a phase.

Overall it is stated that human hearing is able to take frequencies from 20 Hz to 20 kHz, where (if the noise is louder than the threshold of hearing). However, this can vary from person to person and is influenced by age, health and possible hearing damage from any cause whatsoever. Some people are able to display up to 22 kHz to observe, others do not go beyond 16 kHz. Frequencies which are within the range of human hearing are often referred to by the term audio. Frequencies above them will be called ultrasonic, frequencies that lie underneath called infrasonic. The vibration frequency passed in action potentials is interpreted as sound by the brains. The resonance frequency of the ear canal is about 4 kHz. Sounds are reinforced with that frequency transmitted to the eardrum. That is no coincidence: Around this frequency to detect the most human / animal sounds.

In addition, sound vibrations to man an intensity, with a perceptible sound pressure between the hearing threshold of 0,00002 (2-hundred-thousandths) pascal and the pain threshold of 200 PA. The order converted into action potentials is interpreted by the brain as noise. Because the perceived loudness is not linear but logarithmic expires (for example, a 4 times as high sound pressure is like 2 times as hard heard), one uses frequently the logarithmic decibel, or better, the dB scale. On that scale can hear the man between the-6 dB to 140 dB. Sound of 0 dB is so no absolute silence, but the smallest audible intensity at a tone of 1 kHz, namely 1 pW/m2 which corresponds to a sound pressure of 0.02 mPa.

At sound that is harder than 120 dB also go the pain nerves in the ear pulses firing. For the organism the sign to get out of the painful sound environment to get away. The working conditions Act indicates that exposure of 8 hours per day for 5 days a week at a noise level 80 dB (A) hearing protection must be used.

Because sound waves coming from one side of the head, arriving simultaneously in both ears, it is possible from the time difference (phase difference) can be traced from which direction the sound should come. This is called directional hearing. Stereo sound makes use of this property by providing sound to both ears which contains the same phase differences, so that the illusion that the sound is coming from a certain point in space. People who are profoundly deaf on one side, are not able to determine from which direction the sound is coming.

The phenomenon of echolocation is especially extremely perfected by bats and cetaceans.

Sound can not only through the ear canal and ear bones, but is also available directly through the skull. This is called bone conduction. Hearing underwater done mainly through bone conduction, but it is also easy to detect by tapping the skull.

Deviations from the hearing can be determined with an audiological evaluation.

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