Deng Hongxing: Senior Electroacoustic Engineer
Unconsciously, I found that more and more people love to watch movies. Movies have gradually become part of the spiritual and cultural life of Chinese people. There are more time to watch movies, and the time for playing mahjong landlords is naturally less. This is a good thing. Representing the progress of society. With the skyrocketing of the cinema box office, the private custom-made cinemas have flourished. In the past two years, the commercial small-scale cinemas have sprung up everywhere. Nowadays, there are more and more ways to enjoy film and television programs, programs are becoming more and more abundant, and the viewing effect is constantly improving.
Although the commercial operation is relatively successful, it is still difficult to conceal the technical design deficiencies. From the perspective of sound and picture effects, both domestic commercial cinemas and micro cinemas are currently in a preliminary stage, and the design taste and sound quality are uneven. Most of the theaters are in a state of "big dry" but inferior. This article is based on the author's years of private cinema design experience combined with relevant theories, around the acoustic design of the cinema, system commissioning, in accordance with the time sequence of construction as a sequence, step by step design design and installation design and attention elements, hope to the majority Micro-camera practitioners and related hobbyists provide reference.
Micro-camera: including shadow bar, shadow K, from the design point of view is a form of commercialization and popularization of private cinemas. From the design considerations based on cost, all equipment and decoration are more streamlined, functionally speaking Shadow Bar K has more karaoke functions.
The need for acoustic design
Is there any need for acoustic design? The author's work experience in recent years has seen that most of the lithography on the market does not consider the design of acoustics. Some think that this is not important, as long as the screen is large enough, some think that this is too troublesome and costly. I feel sorry for not receiving investment.
First of all, what I want to say is that the effect of not making acoustic design may not be bad, but it is luck, the effect is not too bad, more often the sound is very poor, and the performance of the equipment is not fully utilized. What the audience gets will be a bad experience. Therefore, I think that acoustic design is very necessary. At the very least, the basic principles should be grasped. You can't make low-level mistakes. Otherwise, it is absolutely possible to make a 1000 yuan effect for the equipment you bought for 10,000 yuan.
In addition, is the cost of acoustic design increasing a lot? Not necessarily, I have seen that the cost of many micro-shadows in decoration is not low. If you consider using some of them as acoustic treatment, the cost may not increase, even if there is an increase, it will not be much. The key is to make scientific and rational use of acoustic materials, and the sound effects are much better.
Micro Theater Room Size and Shape
We all know that due to the presence of standing waves, when the sound energy of the room is full, the indoor sound waves are undulating. The consideration of room size in the early stage is mainly to reduce the room standing wave and improve the balance of room sound energy.
Regarding how to choose the size, I read the previous article and provided a lot of detailed reference. Due to objective conditions, I know that most people don't think too much about it. But in the end, do you want to consider it? I think that if the room is free to be separated, of course, it is better to control the size ratio to the recommended ratio range.
The above is the best size recommended by the major institutions, organizations, and experts collected by the author. In addition, the corresponding size can be found within the range of the bolt chart.
Of course, in most cases the size of the room can not be changed, then I have to grasp a principle, that is, the length of the room: width: high can not have a multiple of the proportion, such as 1:2:2, not to appear In the case of squares, when the conditional limit is just the case, I suggest trying to change the parallel faces, such as the following: These shapes are all good for improving the standing wave problem.
Sound insulation considerations
The place where the business is operated may sometimes require multiple rooms to operate at the same time. Therefore, the sound insulation of the micro theater is more important than that of the private theater. If the sound insulation of two adjacent rooms is less than 35 dB, when it is simultaneously displayed, The loss of sound detail caused by mutual interference is very serious. Compared with the K room, the noise interference of the theater is more affected and more viewers cannot accept it.
3.1 Sound insulation of walls
1. When the conditions permit, generally you can directly use the solid brick wall of 18cm or more, and the sound insulation can easily achieve 45dB or more without gaps;
2. When the room area is limited, the double-layer lightweight slab wall with sandwich structure can control the weight while ensuring the sound insulation. The more commonly used plates are wood, gypsum board, calcium silicate board, FC board cement fiber board. , made of composite structure with 9mm plate +80mm air layer +9mm plate, the board with the above four materials can achieve 22dB, 35dB, 45dB, 50dB, respectively, the sound insulation material board and gypsum board is relatively poor, Calcium silicate board and FC cement board are very effective. If the 80mm air layer in the middle is refilled with rock wool or fiberglass, the sound insulation of 5dB or more can be increased.
3. Regarding the cost issue, many people are thinking, will it be so complicated and costly? According to the author's experience, if the cost is controlled to a minimum of 150 yuan per square meter or even lower, the effect of this cost is considered to be very worthwhile.
3.2 Sound insulation of doors and windows
Under normal circumstances, we do not recommend windows in the audio-visual room, because the sound-insulation cost of doors and windows is much higher than the wall, and the sound insulation of the doors and windows is not good, the wall sound insulation is also invalid or greatly discounted, so in terms of sound insulation, The sound insulation of doors and windows should be as close as possible to the level of sound insulation of the wall. According to experience, if the cost of the same sound insulation door and window may go to the wall 10 times or more, the cost of the wall may not be obtained.
The sound insulation of doors and windows is a bottleneck of the sound insulation of the audio-visual room. It is also a difficult problem. I tell you a few basic principles. Try to do thick and heavy, and seal well. Just like the feeling of car door and pressure cooker sealing, grasp these two. The points are generally soundproof. As for the specific amount that can be separated, it is affected by many factors, and it is impossible to elaborate on the space here.
Sound absorption, reverberation time control
Excessive reverberation time directly affects the clarity of the sound, which has a great impact on the performance of film and television programs, so whether it is necessary to absorb sound in the cinema or private theater, the purpose of sound absorption is to reduce the reverberation time. So how long is the reverberation time? Various standards give different suggestions, but for 200m3 volume or below 60m2 area, it is basically between 0.2-0.5s. How to control the reverberation time to the optimal range, will the cost be high? This is a question that everyone cares about.
First, how to control the reverberation time, detailed design and calculation formulas I will not elaborate here, I only talk about experience, I have been to a lot of shadows, found that most of the decoration is relatively simple, most of them are wallpaper, painting For hard walls, there are a few acoustic treatments, that is, the cheapest poly-fiberboard, here I suggest that the room soft sound-absorbing materials should occupy as much as 1/4 or 1/3 of the room, when using thinner soft When the sound-absorbing material is used, the area can be appropriately increased, and the cavity is left behind, even if only 3-5 cm has a good effect. At present, the room space of the cinema is relatively small, and the control of the reverberation time is relatively easy to control to a lower level. Of course, the low frequency sound absorption requires sufficient cavities, so the low frequency sound absorption of the micro theater can be considered if it is required to be high. Low frequency trap. Is the cost of acoustic processing so high? Not necessarily, the simple use of polyester fiber board after the empty 5cm, should be able to achieve a minimum of 60 yuan per square meter, this price may be a good layer of latex paint is not necessarily enough.
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