1、 Overview of Acoustic Design in Cinema Buildings

A cinema is a place where movies are screened for the audience. It is composed of the audience hall, public areas, projection room, and other rooms (including VIP reception room, building equipment room, intelligent system room, etc.). Eliminating the focus of audience hall sound, trembling echoes, and multiple echoes, reducing the sound interference of noise on the sound reinforcement system, and creating a good audio-visual effect, the architectural acoustic design of cinemas is an essential part. The acoustic design of cinemas mainly includes aspects and requirements such as reverberation control, sound insulation design, and noise control.

Cinemas can be divided into three categories based on sound channels: regular channel, stereo channel, four channel, and six channel.

The scale of cinemas can be divided into super large, large, medium, and small according to capacity.

Classification of cinemas by seating capacity

According to JBJ 58-2008 "Code for Design of Cinema Buildings", the quality standards of cinemas are divided into four levels: special, A, B, and C.

2、 Relevant standards and regulations for acoustic design of cinema buildings

1. "Code for acoustic design of theaters, cinemas, and multi-purpose halls" (GB/T 50356-2005)

2. Code for Design of Cinema Buildings JBJ58-2008

3. Technical Requirements for Audiovisual Environment of Cinemas GB/T 3557-94

4. Environmental Quality Standards for Noise (GB 3096-2008)

5. Design Specification for Hall Sound Reinforcement System (GB 50371-2006)

6. GBJ76-84 "Measurement Specification for Hall Reverberation Time";

7. "Building Sound Insulation and Absorption Structures" (National Building Standard Design Atlas 08J931)

8. Code for Indoor Environmental Pollution Control in Civil Building Engineering (GB50325-2001)

9. Code for Fire Protection Design of Buildings GBJ16-1987 (2001 Edition)

10. "Code for Fire Protection Design of Interior Decoration of Buildings" (GB50222-95)

11. Code for Design of Sound Insulation in Civil Buildings (GB 50118-2010)

12. Technical Specification for Digital Stereo Cinema GY/T 183-2002

13. Star rating requirements for cinemas - Document of the State Administration of Radio, Film and Television

14. Green Building Evaluation Standards GB/T 50378-2006

3、 Reverberation time in acoustic design of cinema buildings

《Technical Requirements for Audiovisual Environment in Cinemas》GB/T 3557-94

The ratio of reverberation time at each frequency to 500Hz

《Code for acoustic design of theater, cinema, and multi-purpose hall buildings》(GB-T50356-2005)

500-1000Hz reverberation time in cinema auditorium

The ratio of reverberation time at different frequencies in the cinema audience hall to 500-1000Hz

《Technical specifications for digital stereo cinemas》GY/T 183-2002

各频率混响时间相对500Hz的比值

(1) Solution

1. The architectural design of cinemas should include acoustic design, which should run through the entire process of cinema design.

2. The back wall of the audience hall should adopt a full frequency band strong sound-absorbing structure to prevent echo. The average coefficient should not be less than 0.6s in the range of 125-4000 Hz, and the sound absorption coefficient at 125 Hz should not be less than 0.4.

3. The wall behind the silver screen should be treated with sound absorption

4. Reasonably arrange sound-absorbing materials according to the shape of other walls

5. The ceiling should be arranged reasonably based on the area and type of sound-absorbing materials according to the level of the cinema.

6. Reasonable selection of seats (fully considering the material of the seats and the noise pollution generated)

7. A seat with good stereo effect covers more than two-thirds of all seats.

(2) Solution

1. When the roof engineering of the audience hall adopts a lightweight roof, sound insulation and vibration reduction measures should be taken

2. The setting of elevators or escalators in cinemas should not be close to the audience hall. When setting up close proximity, measures such as sound insulation and vibration reduction should be taken

3. Various types of buildings should be arranged in zones according to their noise levels. Noisy rooms should not be placed adjacent to the audience hall. When setting up in close proximity, measures such as noise reduction, sound insulation, and vibration reduction should be taken. For example, boiler rooms or cooling towers should not be set up in close proximity to the audience hall; When setting up close proximity, measures such as noise reduction, sound insulation, and vibration reduction should be taken.

4. The audience hall should use public spaces such as rest halls, foyers, and corridors as sound insulation and noise reduction measures, and sound barriers should be installed at the entrance and exit of the audience hall.

5. Choose low-noise air conditioning and ventilation systems. Take corresponding measures to prevent interconnection between halls. Air conditioning or ventilation systems should be equipped with noise reduction and vibration isolation measures. The noise transmitted through the air vent to the audience hall is 5dB lower than the allowable noise inside the hall

6. The wall of the audience hall cannot be perforated, and all pipes that need to pass through the wall must be sealed properly. The power sockets on both sides of the wall should be installed in a staggered manner to achieve the best sound insulation measures.

7. The partition wall between the audience hall and the projection room should be treated with sound insulation, and the intermediate frequency (500-1000Hz) sound insulation should not be less than 45dB.

8. The sound insulation between adjacent auditoriums should not be less than 50dB for low frequencies and 60dB for medium to high frequencies.

9. The sound insulation of the soundproof door in the audience hall should not be less than 35dB. Spaces with sound barriers should undergo sound absorption and noise reduction treatment.

10. All air conditioning rooms, ventilation rooms, refrigeration rooms, water pump rooms, transformer and distribution rooms, lighting control rooms, etc. must be treated with sound absorption and noise reduction, sound insulation and vibration reduction. Its sound insulation and vibration reduction capabilities should ensure that the noise transmitted to the audience hall is 5dB lower than the allowable noise inside the hall

5、 Material preparation for acoustic design of cinema buildings

1. The selection of materials for interior decoration in the audience hall should prevent interference with light and use non reflective decorative materials

2. The screen frame, back wall of the screen, nearby side walls, and ceiling in front of the screen should be decorated with matte black or dark materials. The entrance, main screen, and edge screen should be decorated with matte black or dark materials

3. The floor of the projection room should be made of anti-static, dust-proof, wear-resistant, and easy to clean materials

4. The seating step structure in the audience hall should be made of non combustible materials

5. The ceiling materials in the audience hall, sound barriers, and evacuation routes should be A-grade decoration materials, and the wall and floor materials should not be lower than B1 grade

6. Audience hall ceiling should use A-grade materials for sound absorption, insulation, insulation, and maintenance tracks

7. The projection room should be separated from other parts by partition walls with a fire resistance limit of no less than 2.0 hours and floor slabs with a fire resistance limit of no less than 1.5 hours. The ceiling decoration materials should not be lower than grade A, and the wall and floor materials should not be lower than grade Bl.

8. The keel materials used for the ceiling and wall decoration of the cinema should be A-grade materials

9. The indoor decoration ceiling of smoking rooms in cinemas should be made of A-grade materials, and the floor and walls should be made of materials not less than B1 grade

10. The number of evacuation doors in the audience hall should be determined through calculation and should not be less than 2. And it should not be less than 0.90m. Grade A fire doors should be used.