The design and construction of an anechoic chamber is aimed at creating an environment that can meet specific acoustic requirements, with the main purpose of providing a free field or semi free field space for precise acoustic testing. The following are some key points in the design and construction of anechoic chambers:

1. Functional positioning
-Free field space: One of the main functions of an anechoic chamber is to provide a free field or semi free field space. Free field refers to the state where sound waves propagate in infinite space without any reflectors or surfaces
-Background noise control: The anechoic chamber should also have the characteristic of low background noise to ensure that the testing environment is as pure as possible. Within the testing frequency range, the sound pressure level of background noise should be at least 6 dB lower than that of the tested sound source, and ideally 12 dB lower

2. Structural design
-Fully anechoic chamber and semi anechoic chamber: Depending on the testing requirements, the anechoic chamber can be designed as a fully anechoic chamber or a semi anechoic chamber. A fully anechoic chamber refers to a room where all six interfaces are covered with sound-absorbing materials; The semi anechoic chamber consists of five surfaces covered with sound-absorbing materials
-Sharp wedges and sound-absorbing materials: In order to achieve the desired sound-absorbing effect, sharp wedges or other types of sound-absorbing materials will be arranged inside the soundproof room. The sound absorption coefficient of these materials should reach 0.99 above the cutoff frequency to ensure compliance with free field conditions

3. Technical indicators
-Acoustic indicators: During design, relevant standards such as ISO3745-2003, GB6882, and ISO7779 must be followed to ensure that various acoustic indicators such as background noise, cutoff frequency, available space, and vibration reduction meet the standards
-Sound insulation and vibration reduction: In order to prevent interference from external noise and vibration, the design of an anechoic chamber must include effective sound insulation and vibration reduction measures

4. Practical considerations
-Convenience of use: In addition to acoustic performance, design also needs to consider convenience of use, such as component installation and handling, ventilation conditions, instrument wiring, and monitoring conditions
-Aesthetics: A well-designed anechoic chamber is not only a functional building, but also emphasizes aesthetics, striving to become an indoor artwork

In summary, the design and construction of an anechoic chamber is a comprehensive project that involves multiple aspects such as the application of acoustic principles, the selection of materials science, and the implementation of engineering technology. A properly designed and constructed anechoic chamber can greatly improve the accuracy and reliability of acoustic testing.