An anechoic chamber is a specially designed room whose purpose is to minimize sound reflections to provide a free field or near-free field sound environment. This environment is very suitable for acoustic testing, noise evaluation, and electromagnetic interference testing of sensitive electronic equipment. The design and construction of anechoic chambers usually follow the following principles:

Main structure design:

1. Soundproof shell: The anechoic chamber needs to be isolated from the outside world, so thick concrete or metal plates are used as shells to prevent external sound from entering the room.

2. Double door system: To further enhance the sound insulation effect, the anechoic chamber is usually equipped with specially designed soundproof doors, sometimes double doors, to ensure that sound does not leak from the door gap.

3. Suspended structure: In order to reduce vibration transmission, the entire anechoic chamber may be designed to be suspended above the ground and supported by springs or other vibration-damping materials.

Internal sound absorption treatment:

1. Sound-absorbing materials: The inner walls of the anechoic chamber are covered with special sound-absorbing materials that can absorb sound energy and prevent sound reflection. Common sound-absorbing materials include foam plastics, fiberglass, porous materials, etc.
2. Conical sound absorbers: The most typical sound-absorbing structure is the conical sound absorber, which is usually made of foam or hard plastic and can effectively absorb sound waves of various frequencies.
3. Low-frequency sound-absorbing structure: In order to effectively absorb low-frequency sounds, it is also necessary to design a special low-frequency sound-absorbing structure, such as using a resonant cavity or a sound absorber of a special shape. ·

Other details:
1. Electrical shielding: If the anechoic chamber is used for electromagnetic compatibility testing, electromagnetic shielding measures must also be considered to prevent interference from external electromagnetic signals.
2. Ventilation system: In order to maintain indoor air circulation, the anechoic chamber is usually equipped with a special ventilation system, which also needs to have good sound insulation performance.
3. Internal facilities: Depending on the specific application, some necessary test equipment may also need to be installed in the anechoic chamber, such as microphone arrays, speaker systems, etc., and these equipment must also be specially designed to avoid generating additional noise.

The construction of an anechoic chamber is a complex technical task that requires comprehensive consideration of knowledge in multiple fields such as acoustics, architecture, and physics. In the actual design process, computer simulation is usually used to optimize the performance of the anechoic chamber.