Judging whether an anechoic chamber is qualified usually involves a series of standardized test procedures designed to verify whether the acoustic performance of the anechoic chamber meets the predetermined design standards. The following are some of the main evaluation steps and indicators:

Noise floor measurement:
Use a high-precision sound level meter to measure the A-weighted sound pressure level (dBA) at multiple locations in the anechoic chamber, including the center and corners of the anechoic chamber.
The measurement should be performed when the environment is the quietest to avoid interference from external noise.
The goal is to ensure that the noise floor is lower than the preset standard. Usually, the noise floor of the anechoic chamber is lower than 10 dBA, and some are even lower, with 6 dBA as the standard.

Cutoff frequency verification:
Test the effective frequency range of the sound-absorbing material to ensure that the sound-absorbing material can effectively absorb sound waves above the specified cutoff frequency.
The cutoff frequency refers to the lowest frequency at which the sound-absorbing material begins to work effectively, usually required to be 100 Hz or lower.

Sound absorption coefficient measurement:
The sound wave is emitted through a standard sound source, and the sound pressure level difference before and after the sound-absorbing material is measured to calculate the sound absorption coefficient.
The sound absorption coefficient should be close to 1, indicating that almost all sound energy is absorbed.

Sound insulation test:
Measure the sound insulation of the walls, ceilings, doors and vents of the anechoic chamber to ensure that external noise cannot significantly affect the indoor environment.
The sound insulation should meet the design requirements, generally greater than 45 dB(A).

Vibration test:
Use a vibration sensor to check the vibration level of the anechoic chamber structure to ensure that it remains stable in the expected vibration environment.

Air tightness and environmental condition monitoring:
Check the air tightness of the anechoic chamber to prevent external air flow from affecting the acoustic test.
Monitor temperature and humidity to ensure that they remain stable during the test.

Electromagnetic shielding test:
For some anechoic chambers, it is also necessary to test their electromagnetic shielding performance to ensure that the electromagnetic radiation of electronic equipment does not interfere with the acoustic measurement.

Visual and material inspection:
Check the appearance quality of the anechoic chamber, including the installation and integrity of the sound absorbing material.
Perform chemical analysis of the material to ensure that its composition is safe and meets environmental requirements.

Standard sound source test:
Measure the sound power level using a standard sound source to verify the acoustic performance of the anechoic chamber.
The test results should be compared with international standards (such as ISO 3745, ANSI S12.55 and GB 6882, etc.) to ensure that the performance of the anechoic chamber meets or exceeds the design specifications. If the results are not up to standard, rectification may be required, including replacement of sound absorbing materials, structural improvements or upgrades to the environmental control system.