Foshan central centre multi-functional conference room is a new project, the project is located in a new district, Foshan city, the total area of 8550 ㎡, with 1200 people large multi-functional conference room, hall, medium-sized conference room 600 250 people meeting rooms, etc. An acoustic analysis of 1200 large multi-functional conference rooms is conducted. The main function of the conference room is to hold the multimedia conference, performance, and film, etc., mainly to hold large meeting functions. It has a large stage with a depth of 15.8m and a width of 39.5m. The audience hall has a platform, which divides the auditorium into two levels. Multi-functional conference room covers an area of about 1780 ㎡, venue effective volume is about 18500 m after, about 20 m high. Aimed at such places sound quality design, both must consider the sound absorption, from the museum reverberation time control within the scope of the design, but also for different metope diffusion and reasonable reflection processing, make more people get up early reflections and the whole acoustic field distribution is more uniform.

Sound field analysis:

1. The multifunctional conference room is large in space, with a volume of 18,500 m3, each volume reaching 15m3/person, long reverberation time, easy to form acoustic defects such as echoes, multiple echoes, acoustic defects causing turbidity in the auditorium, thereby affecting speech intelligibility;

2. Since the field is a large plane, it is easy to produce multiple reflections sounds in a single direction or a small area, that is, there may be a long echo.

3. Due to the low frequency of sound absorption in the entire audience, this is a common commonality of all materials, which has produced a strong masking effect, undermined the clarity of the language, and was prone to roaring and echoing.

4. Because the sound line of the hall is too long, the air absorbs the different efficiency of each frequency point, so the frequency response curve is not good, which is the sound pressure imbalance at each frequency point.

5. The space in the conference room is caused by the large height of the space above and below so that the reverberation in a certain area is too long, and eventually, there may be a phenomenon such as howling.

6. The entrances are provided on three sides, and the entrances are provided with sound gates, that is, sound-absorbing structures are installed on the entrances of the exterior walls and the entrances of the halls, so as to eliminate the influence of the noise at the entrances on the internal meeting rooms.

Standard specifications and design basis:

1. Design Code for Architectural Acoustics of Theaters, Cinemas and Multi-purpose Halls GB/T 50356-2005

2. Cinema Building Design Specification JBJ58-2008

3. Sound Environmental Quality Standard (GB 3096-2008)

4. Design Rules for Hall Sound System” (GB 50371-2006)

5. Reverberation time measurement specification GBJ76-84

6. Building Sound Insulation and Sound Absorption Structure  (National Building Standard Design Atlas 08J931)

7. Civil Construction Project Indoor Environmental Pollution Control Regulations (GB50325-2001)

8. Code for sound insulation design of civil buildings GB 50118-2010

9. Building Interior Design Fire Prevention Code (GB50222-95)

10. Digital Sound Signal Source Code Technical Specifications GB/T 14914-1994

11. Environmental noise emission standards for social life  GB 22337-2008

12. Party A’s requirements and related architectural and decorative drawings

Acoustic design goals:

The aim of architectural acoustics design is to make the multi-functional conference room sound and sound in the process of use, with a certain speech clarity and reverberation. According to the theatre, the cinema and multi-purpose halls architectural acoustics design specification “GB/T 50356-2005, meeting rooms full intermediate frequency (500 Hz) appropriate of reverberation time at about 1.3 s (meeting room recommended and sound absorption performance is close to the human body the cloth soft chair, avoid open stoping with designing a sellout reverberation time value difference too far, influences the effect of design), low frequency reverberation time allows longer, high-frequency reverberation time permits slightly shorter. The frequency characteristics of the reverberation time are shown in table 1:

Acoustic solution:

Because the project requires an acoustic environment that meets the acoustic requirements of the building, it must meet the aesthetics and advancement of the interior decoration. Therefore, it brings great challenges to our acoustic design. The architectural acoustic decoration project proposed by our company is as follows:

1.ceiling

According to the “Code for Architectural Acoustics Design of Theaters, Cinemas and Multi-purpose Halls” GB/T 50356-2005, the capacity of multi-function halls cannot exceed 5.5 seats per square meter, because the ceiling height above the stage is controlled within 8 meters. The ceiling of the audience hall ceiling cannot exceed 11.5m. According to the general control principle of the reverberation time of multi-function halls, soft mattresses are installed on the ground and fibration carpets are laid on walkways to reduce the strong reflection sound energy on the ground. Therefore, sound absorption treatment may not be considered for ceilings. However, the shape of the ceiling directly affects the clarity of the audience and the uniformity of the sound field. At the same time, in order to enhance the early reflections of the front row audience and increase the clarity and enjoyment, smallpox must be treated with reflection and diffusion. Therefore, the ceiling is made to have a certain curvature. The maximum arc span is 4.6m and the minimum is 3.7m. The thickness of the ceiling diffusion material is 30mmGRG.

2. Wall surface

The wall is an important part of the acoustic design of a multi-functional conference building. In order to achieve design requirements such as speech intelligibility, sound field uniformity, reverberation time, and lateral energy factor, different sound absorption and diffusion treatments are used for different wall surfaces:

（1）The front wall of the stage mouth is made of 12 thick flame-retardant splints, and a 3 mm thick veneer is attached outside. The structure can effectively reflect part of the sound energy so that the front row audience can obtain more early reflections.

（2）The wall on both sides of the audience hall is a typical parallel wall surface. Without any acoustic treatment, multiple echoes will be generated, causing the middle and rear rows to listen to listeners as muddy. If only simple sound absorption processing is performed, because the venue also takes into account the performance of performing arts, the sound absorption due to reflection of sound energy from both sides of the wall at the time of use as an auditorium causes the sound of the entire venue to be dry and has no sense of depth. Therefore, the wall must consider sound absorption to control reverberation, and also consider diffusion to make the entire sound field evenly distributed. Therefore, the surface is made of solid wood grille diffuser shape.

（3）The distance between the back wall and the wall at the picking station is far from the sound source, and the attenuation of the sound energy at the middle and high frequencies is obvious. Therefore, the material with sound absorption at a low frequency is used here. The perforated sound-absorbing structure of wood: the perforation structure of perforated wood is 11 %, filled with 50m48K centrifugal glass wool stick sound-absorbing black felt.

（4）The stage area is 600m3 and the stage is relatively large. If no sound absorption treatment is performed, it will have a coupling effect with the audience, which will seriously affect the reverberation time control and sound quality of the audience room. In order to harmonize the tone of the stage and auditorium styles, wooden perforated sound-absorbing structures were installed on the walls around the stage: perforated wood perforated structures with a perforation rate of 11% were filled with 50m 48K centrifugal glass wool and sound-absorbing black felt.  Sound gate In order to reduce the impact of external noise on the auditorium, all auditorium entrances are silenced. The installation material is a wood perforated sound-absorbing structure: the perforation rate of the wooden perforated sound-absorbing structure is 11%, and the sound-absorbing black felt is filled with 50m 48K centrifugal glass wool.

Acoustical effect after decoration

After the acoustic decoration, the on-site acoustic effect test was conducted, and the test results were as follows:

From the test results, it can be concluded that the 500Hz average reverberation time in the multi-function hall is 1.35s, and the average reverberation time at 1000Hz is 1.28s to meet the design requirement, eliminating echo, multiple echoes, and tremor echo. Defects, clear listening, meeting national standards.