The process and way of hearing sound

Animals can search for food according to sound signals, avoid enemies, mate and feed their offspring. Human beings can communicate with each other, exchange ideas and live together through language and sound. It is very important to listen to the sound for both animals and human beings, and the ear is the auditory organ that receives the sound stimulation

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How do we hear? With our ears!

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The structure of the ear

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The human ear is mainly divided into three parts: the outer ear, the middle ear and the inner ear.

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The outer ear – including the pinna and the external auditory canal that we see every day; many people think that these are the whole part of the ear, but this is not true.

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Middle ear – tympanic membrane is a part of the middle ear. We can see it through otoscope, and separate the outer ear from the middle ear. Behind the tympanic membrane, there is a ossicular chain composed of malleus, incus and stapes; Eustachian tube, tympanum, etc. these parts are normally invisible to otoscope.

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Inner ear – includes cochlea, vestibule and semicircular canal. The inner hair and outer hair cells of the auditory nerve and cochlea are connected.

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Sound wave transmission in normal ears

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Sound – collected by the auricle – through the external auditory canal – to the tympanic membrane – causes the mechanical movement of the ossicular chain – the vibration of the stapes floor causes the movement of the vestibular window – energy is introduced into the inner and outer lymph in the cochlea, and becomes liquid vibration – the movement of hair cells on the basement membrane produces bioelectricity – nerve impulse, which passes through the auditory nerve, extends the nerve pathway – to the center of the auditory cortex – auditory cortex Produce.

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Transmission of sound waves during tympanum perforation

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When the tympanic membrane is perforated, the ossicular chain is interrupted or fixed and other diseases, people can’t hear clearly, the normal sound transmission path is disconnected, forming conductive deafness; it needs a louder voice to be heard.

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At this time, the sound transmission path is: sound – auricle – external auditory canal – tympanum – cochlear circular window membrane vibration – causes the inner and outer lymph fluid vibration – the later transmission path is consistent with that in the normal ear. Both tympanic membrane and ossicular chain are not involved in the process of acoustic transmission.

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The above sound wave transmission belongs to the air conduction mechanism; however, the sound wave transmission is not only one path, it can also be conducted through bone.

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Bone conduction

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When we cover our ears or wear sound isolating earplugs, we can still hear our own voice and part of the external voice. How can we hear the voice?

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At this time, the sound is transmitted through the second method – skull, the path is: sound wave – Skull vibration – cochlear lymph vibration – the subsequent transmission path is consistent with air transmission. It does not need the outer and middle ear to transmit sound.

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Summary:

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The human ear is not only sensitive to weak sound, but also can feel strong sound. They are not only a very sensitive microphone, but also play the role of acoustic analyzer.

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The production of hearing is a very complex physiological process. The inner ear (cochlea) is a very important part of the sound perception and energy exchange. The function of sound perception and preliminary analysis mainly depends on the function of inner ear auditory receptor; the central nervous system plays an important role in the process of sound resolution.

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