Why can sound be recorded?

Sound can be recorded because it is continuous air vibration, belonging to longitudinal wave in mechanical vibration, with magnitude and direction. We can record this mechanical vibration through certain technical means, so the sound can be recorded.

There are two common recording methods, one is analog and the other is digital.

The way of simulation is to change the air vibration of sound into a continuous electrical signal corresponding to its intensity, and then into a continuous magnetic signal, which can be recorded on magnetized media, such as steel wire recorders (very early equipment) and tape recorders. When the magnetized medium passes through the coil (magnetic head) at a certain speed, the changing magnetic field induces a changing electric field to form a corresponding changing current, and then the current is amplified in a certain way to restore the recorded sound ~

Another simulation method that does not use magnetic media is vinyl records. Its recording principle is the same as that of using magnetic media before, but the latter converts the air vibration signal into mechanical vibration, drives the recording needle, and records the vibration law on the vinyl master, that is, engraving a circle of grooves on the master to make the master of vinyl records, and then copying the practical vinyl records through certain technical means. When the sound is restored, it is just the reverse process of the above recording process. When the stylus is placed in the groove and the record rotates, the stylus will generate corresponding mechanical vibration according to the depth and bending degree of the groove, and then this mechanical vibration will be converted into an electrical signal, and the recorded sound will be restored through detection and amplification.

In the digital mode, firstly, the air vibration of sound is converted into a continuously changing electrical signal, and then this continuously changing signal is sampled (the value of an electrical signal is obtained every other time period, and the shorter the interval, the closer the obtained electrical signal value sequence is to the continuous waveform value), and a series of data obtained by sampling are converted and compressed through a certain algorithm, and finally a series of data of sound signals are obtained, and then recorded in the form of files. Playback is the reverse of the above process. Finally, we get a changing electrical signal, drive the speaker, and convert this changing electrical signal into air vibration to form the sound we hear.

Numbers can be converted into images,

First of all, talk about digital images, and draw up an algorithm to specify how many points a picture is decomposed into horizontally and vertically, and each point is called a pixel. The color of each pixel is decomposed into three colors: red, yellow and blue. In order to form the specified color, the depths of the three colors of each pixel are different, such as deep red, bright red and light red, and so on. The depth of this color is expressed by levels, such as pure red (bright red), which is defined as level 0, and finally the transition from red to light white is level 255 (this level is generally 8 and 6545). The finer the division, the more accurate the color, and the closer the mixed color of the three colors is to reality. This level is generally called color depth. So with an A-level, such as a pixel x[i], it can be expressed as red is A-level, yellow is B-level, blue is C-level, and mathematically it is x[i]=[a, B, c], so all pixels of the whole picture,

The process of converting these digital signals into images is the reverse of the above process. The digital signal is converted into the expression value of pixel color, and then the mathematical expression value is converted into electrical signals corresponding to three colors through machine language translation to drive related circuits.

If it is a cathode ray tube display, the three-color electric signals respectively drive the three-color electron guns in the display to bombard the fluorescent screen, thus obtaining the corresponding pixel points.

If it is a liquid crystal display, the electrical signals of the three colors respectively drive the twisting angles of the crystals in the three-color pixels in a pixel, so as to change the light transmittance of the three colors and present the required pixel color value macroscopically.

Convert many pixels in this way, and then arrange them in a certain order, and finally get the image we see.

The digital signal is finally converted into the image we see, and the process is quite complicated ~ Let's talk about it ~ ~