During the construction of many cinemas, we found that due to the owners, the technicians responsible for the construction and the design and construction personnel, the building acoustics was not fully understood and valued, and the completed cinemas had certain examples of sound defects.
In the "Modern Film Technology" 2007 No. 3 (Construction of Cinema) column, Comrade Chen Jiang of the Star Rating Assessment Group of the State Administration of Radio, Film and Television has also pointed out a lot of questions about the acoustics of cinema architecture in view of the problems existing in the current star rating of cinemas. Some defects, such as low sound insulation in adjacent audience halls, high background noise, and reverberation time are not up to standard. The author also believes that these defects are currently present in the construction of theaters. I would like to talk about some of my own views on specific issues.
I. About the construction of new multi-room cinemas with sound insulation, most of them are mainly small multi-rooms, in order to make full use of the limited area and space to maximize the number of cinemas.
As the number of film shows has increased every year and digital movies have become more and more popular, the scale of multiplex cinemas has also expanded year by year. In large and medium-sized cities in China, the number of auditoriums in general multiplex cinemas is more than 6, 7 or more. The more common scale is a medium-sized cinema with about 300 seats. Then, according to the effective area, there are a number of small cinemas between 100 and 200 seats. Conditionally, a small VIP high-end auditorium can be designed to form different sizes. A multi-room cinema with diverse levels and complete formats.
Since most multiplex cinemas are located in densely populated commercial centers or large commercial buildings, the venue rental costs are relatively high, which requires the owners to make full use of the leased area as much as possible, increase the number of cinemas, and strive for higher The return on investment and the complete business format.
Based on the above situation, the projection process designer is required to make full use of the effective site area and space during the planning and design, as much as possible to arrange the number of cinemas and the completeness of the format, and also meet the relevant specifications. In order to achieve the above objectives, it is inevitable to form a partition wall or a walkway adjacent to the audience hall and the auditorium. In such a close arrangement of the theater, the sound insulation between each other is particularly important.
l. The sound insulation between the hall and the hall shall be in accordance with the requirements of the Digital Stereo Cinema Technical Standard. The sound insulation of the shared partition wall between the audience hall and the auditorium shall have a sound insulation effect of not less than 60dB (C). In order to meet the above standard requirements, there are still some difficulties in general, especially in dealing with low frequency sound.
Firstly, the load of the original structure of the building is generally not allowed to be built according to the mass law of the air noise of a certain decibel value of the component. At the same time, the state also restricts the use of clay components with higher quality. At this time, consideration should be given to the use of other lightweight new materials to build the wall with a certain width of cavity (some also consider the use of a certain lightweight structure to assist the sound insulation). When using this method to separate the auditorium, it is necessary to carefully analyze and calculate, so as not to make the wall of the partition wall too thick (some partition walls are nearly 1mm thick after completion), and the effective site area is lost. It can also achieve the corresponding sound insulation effect; at the same time, it should also consider the economic factors such as the selection of materials.
Another way is to arrange an audience entrance and a walkway between the hall and the hall. In doing so, each hall can be constructed with a new material, lightweight wall or a lightweight structure. In this way, the sound insulation effect is very good, but the site occupancy is relatively large. To adopt this method, it is necessary to control the width of the walkway as much as possible according to the size of the hall and the relevant specifications. Under the premise of meeting the requirements of the specification, the control of the walkway of the audience will not be too wide and waste the area. At the same time, it should also be noted that the size and length-to-width ratio of the auditorium on both sides of the walkway meet the requirements of the standard, as well as the standard requirements for construction, and cannot be ignored. If a wall is not in the position of the structural beam, it is necessary to negotiate with the relevant parties to consider how to solve the load problem of the floor. Therefore, the projection process designer should pay attention to the relevant specifications and requirements of architectural acoustics when designing the process.
2. Sound insulation between the auditorium and the screening room and other layouts According to the requirements of the Architectural Acoustics Design Specification for Theaters, Cinemas and Multi-purpose Halls, the intermediate frequency sound insulation of the partition walls of the auditorium and the projection room should be ≥45dB. However, in the actual design operation, the sound insulation problem of the projection window and the observation window should also be fully considered. Because of the thickness of the optical glass and the sealing of the window, it is easy to cause the sound insulation to fall below the standard. I tend to have a smaller area of ​​the projection window as long as it satisfies the projection light and the viewing angle is unobstructed. At the same time, the sound absorption and noise reduction treatment of the projection room should also be considered, and the partition wall should be rationally designed according to the specific conditions.
If the exterior of the audience hall is a bustling commercial center (such as a pedestrian street) or a busy road, what is the maximum noise of a commercial center or a busy road? What is the relative distance between the location of the cinema and the noise source? According to the above-mentioned situation, the air sound insulation scheme is determined by calculation. Under normal circumstances, the noise of the commercial center and the general road will not exceed 75dB (A). The partition wall of the auditorium can basically be aerated concrete block wall or hollow brick wall with a thickness greater than 200mm and a surface density greater than 160KG/m2. If there are special circumstances (such as the car whistling frequent streets, etc.), in order to increase the sound insulation, it should also be appropriate to thicken the wall, or use a larger weight of materials, or add other lightweight structures to support sound insulation.
The partition wall between the partition wall of the audience hall and the entrance lobby or the entrance and exit walkways is relatively simple. Generally, the noise in the entrance hall is not very large, and it is basically in accordance with the above-mentioned external wall design. If the auditorium is close to other entertainment venues (such as OK Song City, entertainment facilities, etc.), or if there is only one wall, then the necessary sound insulation measures should be taken.
The sound insulation design of the slab and roof should also be fully considered. Since the thickness of the concrete poured in the general slab is only 12-15 cm, it should be treated separately according to the different business formats of the partition. In the case of a lightweight grid roof, measures should be taken to increase the amount of sound insulation in the auditorium based on the material of the lightweight roof and the thickness of the insulation. Attention should also be paid to the handling of impact sounds and solid sounds.
3. When the soundproof door and the sound lock solve the problem of sound insulation of the partition wall, we must also consider the sound insulation problem of the entrance and exit doors of the audience hall.
In terms of safety and fire prevention, each auditorium is a fire compartment. The entrance and exit doors of the auditorium are also part of the fire compartment, and also require certain fire resistance. However, from the perspective of cinema acoustics, each auditorium is also a closed acoustic partition. The auditorium entrance and the field gate are also part of the partition, and should also block the transmission of sound. Individual designers who do not have a good understanding of the acoustics of the theater building do not mention any acoustic requirements for the entrance and exit of the auditorium. They believe that it is sufficient to meet the fire protection specifications and decorative effects of the Class B fire doors. As everyone knows, the sound insulation requirements of the entrance and exit doors are neglected, and the separation wall is not good enough. In addition to the role of fire partitioning and decorative effects, sound insulation performance should also be included in the important content of procurement or production.
Generally, the sound insulation performance of the sound insulation door should be more than 35dB, which is the standard of the class III sound insulation door specified in the national standard "Airway sound insulation performance classification and detection method for building doors". The general fire door is still far from the above standards. In practical applications, not only the designer must propose the fire and sound insulation requirements of the entrance and exit doors, but also the necessary supervision of the installation quality during the construction and installation, especially the sealing of the door joints and the firmness of the components.
Because there is always a certain defect in the sound seal of a door, some design units introduce the voice lock into the design. The sound lock can effectively cut off (or weaken) the sound penetration of the access channel, which is very common in conditional situations. But everything has its positive and negative factors, such as cost issues, space issues, etc. have certain restrictions on this. For the sound gate, the author believes that it is not necessary to do it on the door. Even if the space of the venue permits, there is still a problem of cost. The purchase price of fireproof soundproof door and the cost of sound gate production are relatively high, and it is also the responsibility of the designer to save investment for the owner. As long as the ambient noise does not generate more than the allowed noise value in the corresponding hall when the soundproof door is closed, it is not necessary to install the voice lock.
In short, the planning division of the auditorium, the material and form of the partition wall, the selection of the soundproof door and the sound lock, etc., regardless of the method, must comprehensively consider the overall layout of the theater and related specifications and standards, but also fully consider Meet the relevant needs of cinema building acoustics. Only in this way can we achieve a perfect planning and design layout.
Second, on the construction of multiplex halls for noise reduction, unless the venue conditions are not permitted, it is generally designed and constructed in accordance with the four- and five-star standards in the "Star Rating Requirements for Cinemas" (Trial) of the State Administration of Radio, Film and Television. For the construction of four- and five-star cinemas, the above requirements stipulate that the "dynamic noise floor should meet the NC30 noise evaluation curve". In order to meet the requirements of the NC30 noise assessment curve, in addition to the above sound insulation effects, we should have sufficient knowledge and understanding of the following aspects.
l, air-conditioning room, fan room, etc. should be far away from the auditorium. If the equipment room is required to be installed with the partition wall of the audience hall, the sound insulation measures of the wall should be increased, and noise reduction and noise reduction should be done inside the air-conditioner room and fan room. Handling, as well as good vibration isolation and vibration damping measures for the machine. If some air-conditioning ventilation equipment and facilities with certain noise are to be placed (or hoisted) in the projection room or office, lobby, etc., in addition to good vibration-damping measures, sound-proof enclosures should be made for the above facilities, but absolutely Installation is not allowed within the space of the auditorium.
2. Noise reduction measures for ventilation ducts Air-conditioning ventilation ducts, fire-fighting exhaust ducts, etc. cannot be arranged in the hall; the wind speed of the pipelines and inlets and outlets must not be too high; the main ducts of ventilation should be added with necessary noise-reducing facilities to attenuate The main engine noise of the auditorium is transmitted through the ventilation duct. Inside the auditorium, it is recommended to use air-conditioning ventilation ducts made of polymer materials.
3. Noise control of other pipelines, such as rainwater pipes, downpipes, etc., which often have water flow, should be avoided in the interior space of the auditorium. If rainwater pipes, downpipes, etc. have been installed in the structure of the house and they cannot be moved, it is required to perform the swirling treatment and the necessary sound insulation treatment of the above water pipes (especially the riser part).
4, should pay attention to deal with the floor impact noise If the upper floor of the audience hall is a dance hall, song city and other places that can emit strong impact noise, we must consider adding a certain measure of vibration reduction and sound insulation. In addition to the damping material applied to the floor and the ceiling to increase the sound absorbing material, if necessary, the spring sound insulation ceiling can be added. However, for very strong impact noise, the effect of solid noise transmission on the enclosure wall is also taken into account. 0至20. 20dB/米。 The theoretical value of the impact of the impact of the sound is only 0. 02 ~ 0. 20dB / m. Welcome to China Home Theater Network
5. Pay attention to the sound transmission caused by holes and slits. Due to the diffraction effect of sound waves, the voids and gaps of the envelope structure have a great influence on the sound insulation effect. Some data show that when the hole area accounts for 1% of the entire envelope structure, the structural sound insulation will not exceed 20dB. Moreover, the larger the area of ​​the holes and the slits, the lower the sound transmission frequency. Therefore, special attention should be paid to the sealing of the holes and slits in the partition wall of the audience hall during construction.
Third, on the sound absorption coefficient <br> The new multi-room cinema auditorium, the majority of the sound is also used digital stereo sound reproduction equipment. As we all know, digital stereo theaters require relatively short reverberation time for hall theaters, etc., and digital stereo cinemas are generally 5.1-channel stereo sound-relay mode, and some even reach 7.1-channel reverberation mode, so emphasis is placed on The dialogue is clear and the sound field is positioned so that the audience has a very strong sense of three-dimensionality and immersiveness. However, too short a reverberation time will make the sound dry and there is no heavy feeling. Therefore, the reverberation time must be controlled within the allowable range.
In the industry standard "Technical Standards for Digital Stereo Cinemas", the corresponding relationship diagrams of reverberation time and different audience hall volumes, as well as technical parameters such as upper and lower limit calculation formulas and reverberation time frequency characteristics of reverberation time are clearly defined. To achieve the above indicators, first of all, according to the decorative surface material of the audience hall and the sound absorption factors such as seats and air, combined with the corresponding calculation formula. Specific calculations, etc., many magazines, books and magazines have been introduced, this article is not much to repeat. However, the reverberation time and reverberation frequency characteristics are indeed important indicators of cinema acoustics, and it is easy to take detours with a little carelessness. The author briefly describes the situation regarding the sound absorption performance of the facing engineering, which directly affects the above indicators and is easily overlooked.
1. A shadow hall in a wall section uses a variety of different decorative and sound absorbing materials according to different wall requirements, and various materials have different sound absorption coefficients. General finished sound absorbing materials will provide a set of test data, including different sound absorption coefficient indicators of each series of products. A part of the sound absorbing material needs to be processed on site according to the design requirements. At this time, the sound absorption coefficient index should be judged based on the experience and various aspects of the data. There are also some sound absorption coefficient indicators such as wall skirts, entrance and exit gates, etc. It is necessary to determine the sound absorption coefficient according to the construction method or product structure with reference to relevant indicators.
Wall sound absorption production generally has two forms, one is to select the finished decorative sound absorbing material, the wall surface is directly attached to the wall surface after the foundation is made; the other is to use the plastic keel to absorb the sound material (such as certain bulk density) The centrifugal glass wool, etc.) is applied to the wall and covered with a flame-retardant sound-permeable fabric.
The general finished decorative sound absorbing materials have their own sound absorption coefficient indicators, such as a variety of decorative sound absorbing materials produced by Qingdao Fuyi Factory, each of which has a tested sound absorption coefficient. However, it should be noted that the sound absorption coefficient listed on the product is the data detected under the special environment specified by the inspection. It is very different from the actual situation on the site, and cannot directly fit into the formula for calculating the reverberation time. To carry out the calculation, according to the designer's certain experience, or with reference to the experts' opinions, the formula is put into the formula according to a certain calculation ratio.
When the wall surface sound absorption treatment is performed by another method as described above, it is generally impossible to obtain data through rigorous detection. This requires the designer to find (or refer to) the corresponding sound absorption coefficient index according to the bulk density and thickness of the selected material, or determine the sound absorption coefficient based on experience, and then nest the calculation formula.
The wall surface should also determine the sound absorption coefficient according to the wall parts. For example, the back wall of the screen and the back wall of the audience hall are to absorb sound at full frequency. It is necessary to determine the corresponding sound absorption coefficient according to the specific design of the designer. Both sides of the wall, there are decorative sound absorbing materials with large sound absorption effect on the medium and high frequency, and wall skirt parts with a certain sound absorption effect on the middle and low frequency, as well as decorative light troughs and scattered field doors. Materials are selected according to the different sound absorption coefficients designed according to the decorative effect and the structure of the building. These also need to be carefully calculated.
2. On the ground part, most of the audience seats now use fabric soft seats that are close to the sound absorption performance of the human body. Therefore, the reverberation time of the auditorium allows for empty field detection. The sound absorption coefficient of the audience seat area is calculated by the designer according to the sound absorption coefficient of each seat given by the seat manufacturer; the other is to set the seating area of ​​the audience hall to a higher sound absorption coefficient. To calculate.
Other parts of the ground are generally carpets and plastic floors, etc., which depends on the specific situation to determine the sound absorption coefficient. If you want to consider the thickness and material of the carpet, whether it is lining the rubber; whether the plastic floor in the seat area has calculated the sound absorption coefficient according to the range of the seat area. Welcome to China Home Theater Network
3. The sound absorption coefficient of the suspended ceiling of the ceiling part should be determined according to the sound absorption performance of the decorative material and the environmental space. Some ceilings use general decorative materials, such as paper and plasterboard; some use mineral wool sound absorbing materials; Use a mineral wool board to cross the ceiling with other materials. The sound absorption performance of these materials is different, and the position of the ceiling is also different. Some ceilings are attached to the bottom of the beam because of the height space; some ceilings still have a certain height of space, etc., and these reasons also affect the specific Sound absorption performance. Therefore, this is also to determine the sound absorption coefficient according to the specific situation.
In short, due to the different situation on the spot, the sound absorption coefficient of various materials in the specific use of the site is generally not determined by the quantitative data can be applied. Designers must accumulate experience, familiar with the sound absorption performance of different materials in different environments, and determine the sound absorption coefficient of materials used on each surface according to the site conditions. This will directly affect the quality of the auditorium.
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