First, the reason why the home theater needs to spread Before understanding the spread of sound waves, we must first understand what is standing wave. The reason why the standing wave of the audio-visual room is generated is that the sound is reflected back and forth between the two walls (spindle) or the four-sided (tangent) and six-sided (ellipsoidal) walls, and it collides with its own reflected wave to produce an effect of strengthening or weakening. The last wave becomes a wave that vibrates in place and does not move, so it is called a standing wave. Some points (or lines, or faces) will become very loud after forming a standing wave, and the place without sound is called a node (node ​​line or face). If the reflected wave can be diffused in all directions, it will not interfere with itself, even if there are few, so that the sound wave can fill the whole room, not only at a few points. The diffusion of sound waves is the most effective way to deal with standing waves. This uniform sound field generated by diffusion is the dream of all audio fans. So what is the acoustic spread? The definition of academic diffusion sound refers to the sound with the same energy intensity and the same probability of energy flow in all directions in a certain area. The popular saying is that the sound is irregularly reflected, refracted and diffracted in many directions. We can give a diffuse image metaphor: the disco ball of the disco is a good example of light diffusion. Because many lenses placed on the sphere reflect light in all directions, the spot spreads around. By the same token, the sound encounters indoor seats, uneven wall decoration, cylinders, façades, railings, etc. The surface of the object will spread in all directions. At this time, the sound has no direction, and the edges and corners are removed. The sense of hearing becomes stable and relaxed. In other words, the spread is to smooth the sound of the rock that has been undulating and rugged like a bumpy rock into a beach-like feeling. If the audio-visual room is not a good diffuse sound field, the sound in different places or different frequencies in the room will be uneven. Some frequencies or some positions are especially strong, while others are very weak, which will cause it to be restored from the speakers. The flat frequency response is smeared, so the studio must be arranged to have a diffuse sound field.
2. Diffusion Material Selection We know that any convex surface has the ability to diffuse sound waves, including bevels, curved surfaces, and convex arc surfaces. Therefore, in order to make diffuse materials before home theater diffusion measures, what materials should be used for sound diffusion. What? What issues should be noted when choosing. In order to achieve a certain sound diffusion effect in the space, sound diffusers of different geometric shapes such as a cylindrical shape, a triangular shape, a hemispherical shape, a polyhedron shape, a pyramid shape, etc. may be set on the surface of the ceiling, the side wall and the back wall of the video room. It is a three-dimensional relief pattern with artistic decoration effect. In general, triangles and semi-cylinders are widely used in acoustic engineering practice due to their simple construction and good diffusion effects. From the perspective of sound diffusion, the cylinder is slightly better than the triangular body. Of course, the diffusion effect of the two diffusers is related to its size and configuration.
Therefore, when designing and configuring the sound diffuser in the audio-visual room, the following points should be noted:
1 The material of the diffuser should be as large as possible and have certain rigidity, such as concrete, plastered masonry, marble, granite;
2 If wood is used, solid hardwood should be used. For example, teak, oak, rosewood or hardwood surface is affixed with multi-layer composite panels. It is forbidden to use hollow sheets such as plywood or plywood to form a hollow body, which will form a strong absorption of low frequency.
3 Avoid casting the diffuser with gypsum as much as possible. Although the production cost is very low, it will produce metallic sounding, which is not good for the sound.
4 The geometry of each diffusing surface of the diffuser must be sufficient to have a good diffusion effect compared to the wavelength of the acoustic wave. According to the reflection principle, once the size of the diffuser is constant, the degree of diffusion of the indoor sound wave increases as the frequency increases. Therefore, when designing the sound diffusion, attention should be paid to the use of a large-sized diffuser to increase the diffusion ability to the bass. China Home Theater Network
Third, the theater diffusion processing method can be said that the more diffused materials used in the wall of the audio-visual room, the more you can feel the scale and the spaciousness of the recording space in the CD record or movie, extending the natural and loose The elegant high-frequency performance, the details of the music can also be greatly increased, and it is difficult to find some of the weak dynamic changes that are now as if they are vivid. Therefore, in addition to the use of diffusing materials in the ceiling, it can also be used on both sides of the wall, the back wall of the speaker, and the back wall of the listening position. The specific treatment methods are mainly divided into the following types:
1. The cylindrical wall-shaped cylindrical wall surface is made up of many columns close to semi-circles on the wall surface. When the sound waves hit these columns, they will spread out in the vertical direction of the cylinder, but its effective diffusion frequency range It has something to do with its radius. Therefore, to diffuse low frequencies, a large column is required. If you want to buy this kind of diffusion cylindrical building materials in the market, you need to spend a lot of money. In order to save money, we can do this kind of cylindrical wall surface by ourselves. First, we will nail the corner wood according to the width of the column to be done on the wall, and then use a two- or one-minute splint to form a cylinder between the corner woods. Strong wall, which can be stuffed with fiberglass wool, and finally can be decorated with crepe or lacquer on the outside.
2, diffusion box / board This diffusion box / board is mobile, very active, so it is very popular with audio companies, if you have participated in the audio exhibition, you will definitely see these products. Their principle is that if the phase of the wave can be random if the sound wave is reflected back, the direction of the whole wave will spread like in all directions. But how to make the reflected waves random, this is to let each reflected wave go different paths, so it is divided into multiple wireless paths to truly produce a so-called random phase. However, it is good to find that the random path can be simulated by some methods, which is called the quadratic residue method. It is a lattice with different depths separated by thin plates. When the sound waves are reflected back at the bottom of the lattice, because the depth of each lattice is different, the phase of the sound waves reflected by each is different, and is calculated by the second remainder method. Depth, which simulates a random reflection phase. Therefore, the reflected wave will spread in all directions, and the chance of standing the standing wave will be small. As shown in the figure, the Shule RH1516 second-degree space diffuser uses computer calculations to arrange 241 square columns with different lengths to control the reverberation and standing wave reflection sounds that are easily generated in the audio listening space. The two-channel front hemispherical sound field and the multi-channel overall spatial reverberation are effectively processed by different placement locations, thereby obtaining a more accurate sound field image positioning.
3, ceiling diffusion treatment In general, the ceiling is also best to absorb sound and diffusion, so that the sound will be the best. If there is only a hard tone spread, the high frequency reflections from the ceiling will be too strong. 1 Mini diffuser Mini diffuser is an acoustic diffuser which is cheap and convenient to use in the existing diffuser in the world. The compact shape of the mini diffuser can be adapted to many different wall shapes. Moreover, its hollow cavity can also be added with an acoustic sponge or other acoustic material to achieve a good sound diffusion effect and reduce low frequency standing waves.
2 Foam diffusing plate Foam diffusing plate is a kind of economical diffusing plate which is very common. The foam diffusing plate with the size of 60×60cm is generally thicker and the quality is 70 yuan/block, and the common type is 40 yuan/block. Moreover, the use of such a diffuser plate is generally not too much, in addition to its unattractive appearance, it is also a troublesome event that the foam diffuser is attached to the ceiling, if a good and efficient construction method is not mastered. Not only does it post troubles, it doesn't look good, but once it's stuck, it affects the sound quality.
3 Triangles, small arc diffuser triangles, and curved diffusers are most often found in KTV rooms. Generally, they are all covered with small ceilings, which play a good role in diffusing sound. However, this pyramidal diffusion block is used for The home audio-visual room is easy to cause a sense of depression, so ordinary people do not like to use it.
4 Ceiling flower stand This method is a friend who is doing decoration design. He said that if the floor of the room is marble and the ceiling is gypsum board, then the whole room is a “cavity†structure, which not only appears to be turbid when broadcasting the sound. Even speaking is hard to hear clearly. In the case of such a house renovation, the way to solve the sound field is to hang a flower shelf on the ceiling, and then buy some fake vines or other climbing plants, which are covered with the entire flower shelf and turn the room into a green plant. In the flower house, the sound field improved the singing effect significantly improved.
5 The algae well and the central area absorb sound. The so-called algae well is a grid, one layer of the ceiling, which is a beautiful decoration. The ceiling of Chinese old buildings can often see this treatment. The effect of algae diffusion is one layer. The step of retraction, and its absorption is placed in the middle of the piece. If it is a ten-square-meter audio-visual room, divide the ceiling into four to five grids to do the algae well. The disadvantage of algae wells is that they are expensive and troublesome to work.
6 Light steel frame plus mineral fiber board light steel frame plus mineral fiber board is the simplest ceiling treatment, and it is also the most cost-effective treatment. Although this ceiling only absorbs high frequencies without any diffusion function, it is effective for suppressing excessively high frequencies and excessive indoor echo.
4, furniture placed in the industry popular such a saying: the more indoor debris, the better the sound. When you use a diffuser to arrange an audio-visual room without any furniture, you will still feel the sound of the air, but once you move the furniture into the empty room, the empty phenomenon slowly slows down. It even disappears, because the furniture plays a role in dealing with the spread of sound. Furniture and sundries absorb, diffuse, and reflect energy in the high, medium, and low frequency bands. They are the most natural absorption and diffusion bodies. In order to make the sound effect closer to living and listening to music, the placement of furniture must not be lacking. If you lack the natural absorption and diffusion of these furniture and debris, the effect of the whole room sound will be greatly reduced. As for the type of furniture to be placed, there are not many restrictions on it. Generally speaking, leather sofas, wooden tables, wooden cabinets, wooden bookshelves, audio racks, etc. can be used, provided that these cabinets do not have glass doors. And it is best to be solid wood. Of course, the absorption, diffusion and reflection of sounds by furniture debris are not deliberately controlled, so it is often difficult to achieve the best results and additional compensation is needed. This is why we have to do other diffusion measures. China Home Theater Network
5, decorations placed in the audio-visual room can not see the role of the ornament, because these irregular (relative) avoid the same frequency and phase cancel each other, which can effectively improve the clarity and loudness of the sound. Put a plush toy on the sofa in the audio-visual room, decorate the wall with a tapestry ornament, or place a plant pot on the coffee table. These can improve the sound field effect of the room. In addition, there are decorative lights, in addition to downlights and wall lights, if you can buy a unique and unique chandelier, not only can play a decorative role, but also a good diffusion of sound.
4. How to judge whether the diffusion is good When all the sound diffusion measures are done well, it is necessary to judge whether the diffusion state is good, and there are two main methods for judging the diffusion state. First, it is judged whether the attenuation process after the sound stops is uniform, because The decay process time is very short, the general instrument is not competent, and it needs a professional person to measure before, but now it can be done by computer. Second, observe the frequency response of the speaker, compare the frequency response curve measured in the room with the frequency response curve measured in the muffler room, and see the unevenness of the bumps in those frequency segments, so as to judge the diffusion of the room to different frequencies. . If the speaker frequency response curve in the muffler room is not available, and you don't trust the curve given by the factory, you can also use the frequency curve of the near distance in front of the speaker and the frequency response curve of a point at a long distance in the room. Comparison. V. Summary Although the current home video market has developed, the situation is far less than the prosperity of previous years. I think that the focus and enthusiasm of the fans of the year is not enough for many people today. It can be said that many of the knowledge and measures of acoustic diffusion are the result of the research of the older generation of audio-visual hobbyists. Most of the younger generations today are “pre-population trees, and later generations enjoy the coolâ€, and there are few more innovative ideas. Moreover, with the restrictions on housing conditions, many audio-visual people can only move the audio-visual room to the living room. As a result, the diffusion measures are impossible to achieve the professionalization of the separate audio-visual room. The diffusion effect is far from being achieved, and the diffusion has lost its originality. The meaning of the current situation, only a small number of people have diffused measures to fill the audio-visual room, so the diffusion material market gradually abandoned the personal market, and more biased towards professional audio-visual rooms, KTV rooms, theaters, which is why it is not easy to find proliferation now The reason for the material. However, one thing is fortunate. That is, as modern people's aesthetic vision is getting better and better, and the home beautification requirements are getting higher and higher, the diffusion materials are gradually abandoning the rigid design and layout, and the diffusion material shape becomes beautiful. changeable. The above is only recommended as a reference to the specific program to be professional practitioners!
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