Why can the ears hear sounds? Why do ears hear sounds?

The pinna is shaped like a trumpet, which helps to collect various sounds into the ear.

Sound is actually a kind of air fluctuation that is produced by the vibration of an object and can travel around. Like water waves, when a pebble is thrown into a calm lake, the surface of the water will create layers of ripples that spread in all directions. And the substance of the sound wave fluctuations is not water, but.

Invisible and untouchable air. Sound waves are energetic, and they can cause objects they come into contact to vibrate, just as water waves can cause objects on the surface of water to sway. The faster an object vibrates, the higher the pitch it produces; The slower the vibration, the lower the pitch.

The number of times an object vibrates per second is called frequency. For the sake of convenience, scientists call one vibration per second one hertz. Hertz is the unit of frequency.

Not everything is heard by the human ear, only sounds with vibrational frequencies in the range of 20 20,000 hertz can cause hearing.

There are two stages of auditory production, the first stage is called the process of sound conduction. The structures involved in sound conduction are the cochlea of the outer, middle, and inner ears. And there are two paths for sound to reach the inner ear:

The first is air conduction, its process is as follows: the sound is collected through the pinna of the ear to the external auditory canal, which causes the tympanic membrane to vibrate, and then drives the malleus movement, transmitted to the incus and stapes, and the stapes floor vibrates and transmits the energy to the perilymph of the inner ear through the vestibular window, and the peripheral lymph flows like water in a bottle, driving the fluctuation of the basement membrane in it. In this process, the role of the pinna is to collect sound and identify the direction of sound.

The pinna of the human ear has degenerated, and it is not as large and flexible as other animals and can move around, so sometimes listening to sounds requires the help of placing your hands on the pinna or turning your head. However, the external auditory canal pressurizes sound and protects the deep structures of the ear from damage. During the air conduction of sound, the ossicular chain composed of the tympanic membrane and the three ossicles plays the greatest role.

Because the eardrum is a thin membrane, its vibration frequency is generally the same as that of sound waves, which can best sense the vibration of sound waves and can expand the energy of sound waves by 17 times. The ossicles are connected into a chain of ossicles in the form of the most ingenious levers, which multiplies the sound energy. The second is bone conduction, which can cause the vibration of the skull, and transmit the sound wave energy directly to the perilymph to produce hearing.

It seems a little strange to see that the sound waves that can't be grasped can vibrate the hard and heavy skull? But this is true, and there are two ways: mobile bone conduction and compression bone conduction! It's just that bone conduction is not the main way in the process of sound conduction.

The second stage of auditory production is the sensory process of sound, which is mainly done by the cochlea of the inner ear. When the sound of air conduction and bone conduction vibrates the perilymph, it also fluctuates the basement membrane that grows within it. The basement membrane is like a row of toothbrushes that go from long to short side by side.

The energy of the sound waves causes the "toothbrush bristles" (i.e., the ciliated cells on the basement membrane) to bend or deflect, and this bending and deflection generates electrical energy, which travels along the "toothbrush handle" to the nerve center to produce hearing. Sounds of different frequencies can always find a suitable "toothbrush" to pair with the best resonance.

To put it simply, the ear uses the eardrum to collect the vibrations generated by sound waves in the air, which are converted into nerve signals and transmitted to the brain.

Those who can't hear are deaf!

Buzzing.

This is due to the fact that there are always various kinds of voices around us. These sounds resonate with the air in the bottle, and the "buzzing" sound can be heard when the ear is close to the mouth of the bottle, and the air between the mouth and the deep part of the ear can create a vortex, which also produces a sound.

If you put the mouth of an empty hot water bottle, empty bottle, or empty water cup close to your ear, you will hear a buzzing sound. What is the reason for this? There is no sound source in these empty containers! It turns out that this is an acoustic phenomenon of "resonance". Banquet silver.

We know that just as water waves are waves of water:

Sound waves are fluctuations in the air or; More specifically, it is a change in the air that spreads from the sound source in all directions at a certain speed.

The number of density changes per second is called "frequency", and the distance between two adjacent dense parts or parts is called "wavelength". The higher the frequency of the sound, or the shorter the wavelength, the higher the pitch it sounds at.

Generally speaking, sound is caused by the vibration of an object, such as when playing a drum, the drum skin vibrates up and down, thus causing sound in the air.

Different objects, when vibrating at the feast, produce different frequencies of sound. For example, the sound of the big drum and the snare drum have different frequencies.

We can hear sound because the sound is transmitted to our ears, which can cause the vibration of the eardrum, and then the vibration of the object produces sound waves, and the sound waves are transmitted to our ears to cause the vibration of the eardrum, which is transmitted by the auditory nerve to different vocal bodies in the brain to produce sound timbre Different people's perception of sound is to vibrate the eardrum through sound waves, through a complex system, and then to the auditory nerve, so we hear sound.

The ear is a very important hearing organ, including the outer ear, the middle ear and the inner ear. We can only see the pinna and the external auditory canal, the rest is hidden in the skull. Both the pinna and the external auditory canal are parts of the outer ear that are responsible for collecting sounds and identifying the direction of sounds**.

The collected sound waves pass through the ear canal, vibrating the eardrum. The eardrum is an oval, translucent piece. Leather sheets.

Three ossicles are attached to the inward depression in the middle of the eardrum. When the sound waves shake the eardrum, it is like striking with a drumstick, creating a vibration that is transmitted to the three ossicles at the same time. The vibrations are then transmitted to the cochlea, which is connected to the ossicles.

The cochlea looks like a small snail, filled with fluid and receptors, which collect vibrations and transmit them through the auditory nerve to the auditory center of the brain, so that we can hear sounds, and the human ear can feel 16,000-20,000 sound waves per second. And it can distinguish 400,000 different sounds.

The ear is an important organ for us to hear sounds, and the auditory central nervous system is needed to understand sounds and direct the meaning of sounds.

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

Outer ear – Collected by the pinna, sound is transmitted through the ear canal to the middle ear.

Middle ear - The sound collected by the outer ear is transmitted to the eardrum to produce vibrations, which then drive the three ossicles to transmit the sound to the inner ear.

The inner ear is mainly a biological signal transmitted by the cochlea to the auditory central nervous system that converts sound at various frequencies.

The auditory central nervous system receives information from the inner ear and performs various analyses to recognize and understand the content of sounds.

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

The external ear --- includes the pinna as we see it every day, and the external auditory canal; Many people think that these are all the points of the ear, but this is not true.

The middle ear --- tympanic membrane is the part of the middle ear that we can see through an electric otoscope, separating the outer ear from the middle ear. Behind the tympanic membrane there is also a chain of ossicles consisting of the malleus, incus and stapes; Eustachian tubes, tympanum, etc.; These parts are normally not visible with an electric otoscope.

The inner ear --- includes the cochlea, vestibule, and semicircular canals. The auditory nerve connects with the inner and outer hair cells of the cochlea.

Sound wave transmission in the normal ear.

The sound --- is collected by the pinna --- reaches the tympanic membrane through the external auditory canal ------ causing the mechanical movement of the ossicular chain--- the vibration of the stapes floor plate causes the movement of the vestibular window--- the energy is transmitted to the internal and external lymph fluid in the cochlea, and becomes a liquid vibrating --- the movement of hair cells on the basement membrane to produce bioelectrical activity--- nerve impulses through the auditory nerve, extending to the nerve pathway--- reaching the center of the auditory cortex--- auditory production.

Perforation of the tympanic membrane, the transmission of sound waves.

When the tympanic membrane is perforated, the ossicular chain is interrupted or fixed, and others cannot be heard clearly, the normal sound wave transmission path is disconnected, forming conductive hearing loss; You need a louder sound to be heard.

At this time, the sound wave transmission path is as follows: the sound vibrates --- the circumferential membrane of the pinna--- external auditory canal--- tympanic cavity--- cochlea--- causing internal and external lymph to vibrate--- and the subsequent transmission path is consistent with the transmission in the normal ear. Neither the tympanic membrane nor the ossicular chain are involved in the transmission of sound waves.

The above sound wave transmission belongs to the air conduction mechanism; However, there is not only one path for the conduction of sound waves, it can also be conducted through the bones.

When bone conduction covers both ears or wears soundproof earplugs, you can still hear your own voice and some external sounds; At this time, how do we hear the sound?

At this time, the sound is transmitted --- the skull through a second method, and the path is: sound waves --- cranial vibrations--- lymphatic fluid vibrations of the cochlea--- and the subsequent transmission path is consistent with air conduction. It transmits sound without the involvement of the outer and middle ears.

Summary: The human ear is not only sensitive to weak sounds, but also can feel strong sounds; They are both very sensitive microphones and also function as acoustic analyzers.

The production of hearing is a very complex physiological process, and the inner ear (cochlea) is a very important part of the perception and transposition of sound. The function of sound perception and preliminary analysis mainly depends on the role of the inner ear auditory sensory device. The central nervous system plays an important role in the process of sound discrimination.