1、 Equipment name: Semi anechoic chamber

2、 Number of devices: one set.

3、 Equipment function

This product is a semi anechoic chamber, designed in accordance with GB/T 6882-2016 "Acoustics - Determination of Sound Power Levels and Sound Energy Levels of Noise Sources - Precision Method for Anechoic and Semi anechoic Chambers" ISO 3745 Acoustics -- Determination of sound power levels of noise sources using sound pressure -- Precision methods for anechoic and hemi-anechoic rooms  According to the requirements of relevant standards, accurately measure and analyze the noise characteristics of the product to determine its noise level, and take corresponding measures to reduce product noise and improve product quality.

4、 The design basis for the semi anechoic chamber is mainly based on the following standards:

ISO 3745 "Acoustics - Determination of Sound Power Levels of Noise Sources - Precision Method for Fully and Semi anechoic Chambers" GB 6882-2016 "Precision Method for Determining Sound Power Levels and Sound Energy Levels of Noise Sources by Acoustic Pressure Method for Silencing Chambers and Semi anechoic Chambers" JJF 1147-7.2006 "Calibration Specification for Acoustic Characteristics of Silencing Chambers and Semi anechoic Chambers"

5、 Identification method for anechoic chamber:

According to the international standard ISO 3745 "Acoustics Determination of sound power levels of noise sources - Precision methods for anechoic and semi anechoic rooms" and the national standard GB6882-2016 "Determination of sound power levels and sound energy levels of noise sources by acoustic pressure method - Precision methods for anechoic and semi anechoic rooms", the anechoic chamber free field identification method is used for testing. Using a single frequency signal with a center frequency interval of 1/3 octave below 125Hz and above 4KHz, and a single frequency signal with a center frequency interval of 1/1 octave between 125Hz and 4KHz, the difference between the measured sound pressure level and the theoretical sound pressure level is measured. Based on this, according to the maximum allowable difference specified in ISO 3745, GB6882-2016, and JJF 1147, the allowable measurement radius and the free sound field space area that meets the standard can be determined.

The maximum allowable difference between measured sound level and theoretical sound level specified in ISO3745 and GB6882

Test room type

1/3 octave band center frequency Hz

Allowable difference dB

Anechoic chamber

≤630 800～5000

≥6300

±1.5

±1.0

±1.5

Semi anechoic chamber

≤630

±2.5

800~5000

≥6300

±2.0

±3.0

6、 Main technical requirements for anechoic chamber

Our company is a High-tech enterprise that has passed ISO9001 and ISO14001 quality system certifications. The anechoic chamber product is also a high-tech product, ensuring that the product is at a high level of technology.

1. Using imported environmentally friendly sound-absorbing materials, it is required that the raw materials are formaldehyde free environmentally friendly sound-absorbing materials made of non glass wool fibers, and an import customs declaration form should be provided.

2. The laboratory sound-absorbing body adopts a detachable structure, 100% detachable, which is convenient for future relocation

3. The acoustic absorption structure is a flat plate type sound body, ensuring the customer's ground load-bearing capacity and acoustic indicators.

4. The main structure of the soundproof chamber is a customized civil engineering structure.

5. All materials are environmentally friendly and pollution-free, and all materials are flame-retardant.

The acoustic technical indicators are as follows:

Half anechoic chamber footprint size: around 8900L x 7500W x 5000H (mm) (including top civil engineering ring beam)

After the completion of the semi anechoic chamber, the internal net volume is about 7600L × 6200W × 4500H (mm).

Cut off frequency: ≤ 100Hz

Free field radius: length direction radius ≥ 3.2 meters, width direction radius greater than 2.4 meters

Background noise: Under normal working conditions in the laboratory, with no other abnormal noise or vibration interference around, the background noise is below 30dB (A) (with air conditioning and ventilation turned off).

7、 Design principles

The design process is advanced, reliable, and mature. After the completion of the anechoic chamber, various technical indicators such as background noise and cutoff frequency meet the design requirements.

Flexible design processing system, simple equipment operation, and easy maintenance;

The engineering cost is reasonable.

8、 Design conditions

The semi anechoic chamber is placed in the workshop. According to the customer's description, the environmental noise frequency characteristics are low and medium frequency, with a size of 60dB (A) -70dB (A), and its peak range is mainly concentrated in 100-1000Hz, with some noise frequency characteristics distributed at 10KHz;

The environmental noise around and near the semi anechoic chamber should be considered as follows:

Considering the relatively quiet surrounding environment and cost considerations, our company suggests using civil structure soundproof walls.

9、 Design points:

The semi anechoic chamber has been awarded as a high-tech product, and our company has applied it in multiple fields such as automotive, communication, home appliances, aerospace, etc., providing acoustic solutions for many Fortune 500 companies.

Sound insulation index of anechoic chamber:

To ensure that the background noise Lp of the anechoic chamber is ≤ 30dB (A), it is required that the sound insulation enclosure structure of the anechoic chamber has a sound insulation capacity △ Lp ≥ 40dB. It is recommended to use a 250mm mixed brick soundproof wall with a flat sound-absorbing body installed inside, with a designed theoretical sound insulation capacity greater than 51dB.

External power lines and other circuits are introduced into the soundproof chamber through wire holes, and sealing materials with good sealing performance are used to seal the wire holes to ensure that the sound insulation of the wall will not be reduced due to pores and other reasons.

Based on the above on-site conditions and handling situation, ensure that the technical specifications are met.

1. The required dimensions for the soundproof room are:

The anechoic chamber adopts civil structural walls, and our company provides design drawings and on-site guidance; All sound absorbers are modular structures that can be installed on site with screws, and their cutoff frequency is designed to be 100Hz.

2. The door of the soundproof room is a double-layer sealed sound gate, which has superior performance, easy opening, and beautiful appearance.

3. Lighting and distribution system

Install energy-saving lamps for lighting in soundproof rooms to ensure indoor illumination; Energy saving lamps do not produce electromagnetic noise;

Power distribution system: Provide indoor power distribution installation according to the power distribution requirements of the soundproof room, and introduce external power lines and other circuits into the soundproof room through conduit holes.

10、 Design proposal:

The overall plan is as follows:

1. The overall structure adopts civil engineering, and the outer room adopts 240mm solid mixed brick walls; The top adopts a 200mm reinforced concrete civil structure soundproof wall, which has the technical characteristics of low degree and high sound insulation, meeting the technical requirements of external noisy office environments The overall theoretical sound insulation is 51dB. Install 350mm flat sound-absorbing panels on the walls to ensure a reasonable distribution of sound insulation in each frequency range of the overall structure, approaching the standard curve of sound insulation index evaluation, and appropriately increasing in the low frequency range to ensure that the background noise in the anechoic chamber meets technical requirements.

Internally, flat sound-absorbing panels are installed to meet the cutoff frequency requirements, which can meet the performance requirements.

Internally, a 350mm flat sound-absorbing material with a thin plate resonance structure is used. The internal sound-absorbing cotton is imported (not made of glass wool material) and has a flame retardant grade of B1; The outer surface of the sound-absorbing structure is equipped with metal perforated steel plates, with a flame retardant grade of A1, a perforated steel plate thickness of not less than 1.5mm, and a perforation rate of over 42%. Can prevent mechanical collisions, ensure sound transmission, and ensure no deformation within 20 years of use.

Due to the use of non glass wool material for the flat sound-absorbing body and the metal perforated surface, it has a protective function against oil mist, dust, etc. If cleaning is needed, simply wipe the surface with a cloth.

Our flat sound-absorbing body has the following advantages:

A. Environmental Protection:

The overall design adopts our patented technology, which can be installed on site with only screws. It is easy to disassemble, has a beautiful appearance, and has high sound insulation; A staggered combination of steel plates, sound-absorbing damping, soundproof panels, and different density soundproof cotton; All materials are made of environmentally friendly and formaldehyde free materials, meeting and providing the environmental protection requirements of GB18883 in China.

B. Efficient:

The thickness of the sound-absorbing structure is only 350mm, which saves a lot of space compared to the height of 800mm of the sharp edge

C. 100% detachable:

All structures are modular, easy to install and disassemble, and 100% reusable. It can be disassembled and assembled multiple times to prepare for customers' future relocation.

D. Long lifespan:

The flat structure is protected by steel plates, which are resistant to mechanical impact; Acoustic materials shall not detach or remain unchanged for 20 years after system acceptance

The shape and service life can be as long as 10-20 years or more.

E. Light:

The internal light reflects well, greatly improving the working environment.

2. Suspension damping structure

Due to the low requirement for background noise, considering the cost-effectiveness of the customer, we do not adopt a suspended damping structure. The condition is excellent.

3. Soundproof door

The doors of the soundproof room and control room are both made of external pull and internal push sound insulation and absorption composite double doors, with one pair of external pull doors; The sound insulation effect is superior to similar products and easy to use; The size is 2000 * 3000mm, divided into left and right doors. The left door is usually closed, and personnel can enter and exit from the right side; When large-sized products enter, open both doors; For the sound gate, the door frame is made of bent steel plate, and the panel of the door leaf is also made of steel plate. The comprehensive sound insulation capacity △ Lp of the door is ≥ 50dB. It is designed as a two-way, two-level sealed, special soundproof rotary leaf door, introducing new foreign technology, with a three-layer magnetic suction structure, making opening and closing effortless.

To ensure maximum utilization of the interior space of the soundproof room, an external opening method is adopted, and the doors have superior performance, easy opening, and beautiful appearance.

The main way for sound waves to pass through doors is through the door frame and door seams, not the door panel. Therefore, the design of high sound insulation doors starts from these two aspects: the door frame is welded with rectangular steel pipes, and the inner cavity of the door frame is filled with 60kg/m3 multi-layer composite cotton felt;

The sound-absorbing door adopts a unique single axis design, which minimizes reflection when the door is closed (traditional sound-absorbing doors have larger frames). Installing flat sound-absorbing panels on sound-absorbing doors does not affect indoor acoustic performance; When the door is opened, both the inside and outside of the sound-absorbing door are equipped with handles, which can be opened horizontally along the door axis to achieve the maximum passing size.

4. Total Reflection Ground

The floor of the soundproof room is made of the original workshop floor, with an epoxy surface and a sound absorption rate of less than 6%. Meet the technical requirements for a semi anechoic chamber with a free sound field.

5. Lighting

Indoor configuration of dedicated LED lighting system, low-noise and environmentally friendly (background noise less than 15dBA) lighting fixtures should not affect the sound field characteristics of the anechoic chamber. The lighting adopts a curved surface lighting design, with a surface volume less than 3/1000 of the indoor surface area of the anechoic chamber, and the free sound field range is not affected.

In the soundproof room, there is sufficient wiring space between acoustic materials and civil structures, and lighting fixtures can be flexibly arranged in appropriate positions.

Indoor illumination: The indoor environment should meet the requirements of GB/T 13379-1992 for "operations with moderate visual requirements", and the illumination range of the test area should not be less than 500lux (1m above the ground).

Indoor light sources require small size, low energy consumption, high brightness, and low heat. The light source should be sturdy and durable, with a working life of over 50000 hours under normal use conditions. In harsh environments (high temperature and high humidity), the working life should be over 5000 hours;

Emergency lighting is installed in the soundproof room for personnel evacuation. The illuminance value at the entrance should not be lower than 0.5lx.

6. Semi anechoic chamber ventilation system, final muffler, and anechoic duct

Design ventilation system and air conditioning system for semi anechoic rooms; Indoor air ducts are constructed using acoustic materials, utilizing our patented technology and high-efficiency energy-saving mufflers. The unique vortex design improves ventilation efficiency by over 30% and reduces noise by over 15dB compared to similar products.

The air conditioner adopts a silent duct air conditioner, which is connected to the top muffler inlet and outlet through a hose.

One exhaust fan can be optionally configured to suction and exhaust exhaust exhaust or other gases inside the room. It is equipped with pipes, soundproof plugs, and a motor with overheating protection function; The total air volume shall not be less than 15000 cubic meters per hour.

7. Semi anechoic indoor strong and weak electrical interfaces and acoustic treatment

7.1. The semi anechoic chamber shall be equipped with a strong electrical interface box, with at least 2 220V power sockets and 2 380V power sockets.

7.2. The semi anechoic chamber is equipped with a signal interface box and other wiring pipelines. All wiring pipelines are treated with vibration isolation and noise reduction to avoid the formation of sound bridges indoors and outdoors, which may affect indoor acoustic technical indicators. Reserved holes on the wall, loading holes, hydraulic pipeline holes, and testing holes, all of which are designed with our patented technology. The special wiring shielding box suppresses external noise leakage.

8. Distribution system

Provide indoor power distribution installation according to the power distribution requirements of the soundproof room, and introduce external power lines and other circuits into the soundproof room through wire holes. Seal the wire holes with sealing materials with good sealing performance to ensure that the sound insulation of the wall will not decrease due to pores and other reasons.