Is the world you see and hear is real?

  We are all walking wave signal receivers. In this world full of electromagnetic and mechanical waves, the eyes perceive electromagnetic waves with a wavelength of 380 to 760 nanometers-that is, “light”, and ears perceive mechanical waves with a frequency of 20 to 20000 Hz-the so-called “sound”. We are also sophisticated waveform signal processors. Those lights, shadows and sounds are processed layer by layer and reflected in the brain, making us form a rich perception of the world. The so-called smart people have clear ears and eyes. However, what you can see and hear is often limited; between seeing and hearing, there is real and virtual. Let us re-examine the virtual and real world between audio and visual from a scientific point of view.
  How do we know the sound of color vision
  acoustic waves corresponding to mechanical vibrations, thousands of times per second just commonplace. Touching the throat or horn, you can feel its vibration, but it is difficult to distinguish the content of the sound. So, how do we hear the sound? First, the auricle collects the sound and transmits it to the tympanic membrane through the external auditory canal to make it vibrate; the vibration is transmitted to the inner ear through the auditory ossicles, etc.; the spirally curled cochlea is sensitive to vibrations from high to low frequencies from the outside to the inside. The hair cells at the location sense vibrations and convert them into electrical signals to be transmitted to the auditory nerve; the signals are finally transmitted to the brain to form hearing.
  The above four steps are like the process of “centralized amplification, impedance matching, spectrum analysis, and data integration” in electronic signal processing. One of the most subtle is the “spectrum analysis” function of the cochlea. For example, hang a row of clothes of different shapes, materials, and weights on a clothesline, swing the rope left and right, and the clothes will follow. Some clothes follow when shaking fast, and some follow when shaking slowly, which realizes frequency discrimination. The cochlea is such an exquisite frequency analyzer. Its sensitive frequencies vary with its local size and stiffness, and correspond to high and low frequencies from the outside to the inside. The sound of a certain frequency is only perceived by the hair cells in a small part of the area.
  For light waves, it is more complicated. The light that the human eye can see has an electromagnetic field that changes 400 to 800 trillion cycles per second. Cells cannot keep up with the mechanical structure based on mechanics. This requires the help of electrons. The eye not only sees a beam of light, but also sees the spatial distribution of the light, which requires an imaging system. So, how do we see objects? The first is that the cornea, lens, etc. form a lens group, which refracts the light and image it on the retina; there are some special molecules in the photoreceptor cells, and the electrons therein undergo transfer and transition under the action of light, causing a series of biochemical reactions. Transform light signals into nerve impulses; several types of nerve cells in the eye initially organize and transmit information layer by layer; the information finally enters the visual center of the brain to form a more detailed and comprehensive perception.
  This is the process of “optical imaging, biochemical sensitization, preliminary synthesis, and comprehensive processing”. Among them, “biochemical sensitivity” is the most critical. Photoreceptor cells include elongated rod cells and pointed cone cells. The former can feel extremely weak light, but cannot distinguish colors. The latter is less sensitive to low light than the former, but has the ability to distinguish colors. The so-called color, in essence, is the subjective feeling of the frequency of light in the human brain. But light sensing is not as easy as detecting sound. We can easily place rows of densely packed hair cells in the cochlea to be responsible for the detection of sounds of different frequencies, but it is difficult to place a prism or spectrometer in the eye with rows of photoreceptor cells, and each of them happens to be sensitive to the corresponding frequency. Light sensitive. However, if there is only one type of photoreceptor cell, the world in your eyes is only light and dark without color. Humans have made some compromises, but they are lucky to have three types of cones, which are responsible for the detection of long, medium and short wavelength light. The sensitive area is about the red, green, and blue wavebands. In this way, the color you see is expressed as a combination of three cone cell responses.
  Physical, visual defects on the physiological
  fact, human perception to the information from the real world there is always a deviation compared. The factors that cause deviations are embodied on multiple levels such as physics, physiology, and psychology.
  On the physical level, in terms of hearing, such as the auricle and ear canal, the transmission channels of sound are different in their passing efficiency of sound waves of different frequencies. The length of the ear canal has naturally given special care to the frequency around 3000 Hz. For example, if you roll paper into a cylinder and put it on your ears to listen to the sound, the length of the cylinder changes and the sound you hear is different. In terms of vision, for example, when light of various frequencies is refracted through the cornea and lens, its refractive index increases with the increase in frequency. This will cause them to focus near the retina, there is a slight difference in front and rear positions, so it looks like a The illusion that red is closer and blue is farther. For another example, due to the wave nature of light, diffraction occurs when passing through a finite size pupil, which is one of the factors that limit the resolution of the human eye.
  Physiologically, in terms of hearing, the resonance of the tympanic membrane, the size and texture of the cochlea, the decay and aging of hair cells, etc., all directly affect its frequency response range to sound, and these are related to the individual characteristics of people, such as age, gender, Physical fitness etc. In terms of vision, the blood vessel layer and the nerve layer are in front of the photosensitive layer of the retina, which will inevitably block some of the light and cause some net-like shadows. For another example, the size of photoreceptor cells will limit the resolution of the human eye, and the number of types and frequency range that can be responded to directly affect our perception of color. The same world has subtle differences in the eyes of different people. In the eyes of people with the characteristics of color blindness, because one or more of the photoreceptor cells are abnormal or even missing, it is very different from what others see. Even if the same person sees the same object, it will vary with age, environment, viewing process and duration, and even life experience.
  Small deviations, such as stars. We all know that the twinkling of stars is caused by the uneven refractive index of the atmosphere. But even if the stars do not “blink”, there will still be faintly visible corners, the so-called “starburst”. This is reflected in many paintings, and the shapes of the stars are also different. In fact, it is related to the unevenness and asymmetry of the eyeball, the irregularity of the pupil edge, and the diffraction effect.
  Severe deviations, such as blind spots. Since the nerve layer is in front of the photosensitive layer, it must pass through the retina to gather information and transmit it to the brain behind. There are no photoreceptor cells at this convergence point, and a “hole” is formed, which is a blind spot of vision. The blind spot is close to the side of the eye and the nose, so if we close the left eye and look straight ahead with the right eye, an area in the front right will be imaged on the blind spot and it will not be perceived at all.
  Desertion nervous system caused by the bizarre illusion
  on the psychological level, the nervous system leading to the illusion produced, the more complex and the bizarre. Common, such as staring at a picture with lighter colors and fuzzy outlines for a period of time, you will find that it gradually disappears! After staring at the red object for a while, and then observe the white wall, you will find a green phantom on it, which is a visual negative afterimage effect. For another example, if two identical objects are placed in different backgrounds, their brightness and color will look very different. What is bizarre, such as “being out of nothing”: you can’t see anything in the blind spot, but why don’t we think there is a hole there? In fact, the image in this part of the area is “brained” by us. When the gap between the two rectangular strips falls on the blind spot, a certain area will be “brained” to connect the two. There is even “seeing movement in stillness”: due to the difference in the visual response time of the human eye to areas of different color contrast, plus the slight eyeballs and the compensation of the brain, it will produce a dynamic illusion of static pictures. The above seem to be flaws, but they are extremely useful features in real life scenes. They can help us ignore less important background information and focus on high contrast, edges and edges, dynamic changes, and more. Value information goes up to better adapt to the environment.

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  The illusion of hearing is equally bizarre. An audio creator recorded the pronunciation of “Laurel”, but many people read “Yanny” after listening. This is because different people have different sensitivity to high and low frequency bands. For example, people who are sensitive to low frequency bands sound like “Laurel”, and people who are sensitive to high frequency bands sound like “Yanny”. On the other hand, this is also related to the recognition process of the brain. When judging the fundamental frequency, harmonics, formants, etc., there will be multiple results. In addition, in the process of language learning, you may notice that when there is no difference in the signals received by the ears, people are more likely to distinguish the details of the sound from the language they are familiar with, but they are less able to distinguish the unfamiliar language. This is also affected by nervous system training.
  There is even an illusion that various sense organs interfere with each other. When you have a cold and stuffy nose, eating is not fragrant; smelling Coke and drinking Sprite, guess what it smells like? The reddish-orange crayfish in the restaurant seemed fresher and more attractive. Vision and hearing are no exception. I took off my glasses and watched TV, and without the actor’s lip-synching reference, it seemed that the lines sounded blurred. The “Megk effect” in psychology describes this kind of phenomenon: visual information interacts with auditory information, causing interference with speech perception.
  What is the real world? What is the relationship between the world itself and our perception? On the one hand, the sense organs transmit external signals to the brain to be perceived by us; on the other hand, the brain’s neural activity and own experience will in turn affect our resolution and processing of information, sometimes even greatly deviating from the real world . The audio-visual system is not just a one-way information transmission system like a camera and a microphone, but has a rich network structure and a large amount of closed-loop feedback. The so-called “authenticity” is only relative, and biology is actually more concerned about “reasonability” and “adaptability.” With the help of modern scientific instruments, we can better collect sound and light physically, cover a wider frequency domain and intensity, and understand the objective world more extensively and accurately, rationally and quantitatively. However, although this aid is powerful, it cannot completely replace the incomparable senses that human beings have evolved over generations, even with some defects.

  Further reading
  Sensory world of animals
  in the process of evolution, animals have senses will be different emphases. Large ones such as whales and elephants are more sensitive to low-frequency sounds. Animals that live in the deep sea or caves for a long time often have visual degradation. In the eyes of some birds with four-color vision, the world may be more colorful. Bees and other insects can see ultraviolet light, and the flowers in their eyes have a different brilliance. In the eyes of some Shrimpidae, such as mantis shrimp, there can be as many as a dozen color receptors, and even the polarization of light can be sensed. However, many mammals belong to different degrees of “color blindness”, and many more animals can only perceive the brightness of light, but they have no color, and they can’t even perceive the shape-their world is really too monotonous.