An anechoic chamber is a special acoustic testing environment used to simulate free field conditions for accurate acoustic measurements. Its design and construction need to follow strict acoustic standards to ensure the accuracy and reliability of measurement results. The following are the main acoustic standards and core requirements for anechoic chambers:
 

1. International standards
- ISO 3745:2012  
-Standard name: "Determination of sound power level of acoustic noise sources - Precision method for anechoic and semi anechoic chambers"
-Scope of application: It specifies the design, performance evaluation, and sound power level measurement methods for anechoic chambers and semi anechoic chambers.
-Core requirements:
-The background noise should be at least 10 dB lower than the noise of the measured sound source.
-The uniformity deviation of the sound field should be controlled within ± 1.5 dB.
-The frequency range is usually from 100 Hz to 10 kHz, and can be extended to lower or higher frequencies in special circumstances.
 
- ANSI S12.55/ISO 3745  
-The American national standard is basically consistent with ISO 3745 and is applicable to North America.
 
 
2. National standards
- GB/T 6882-2016  
-Standard name: "Determination of sound power level of acoustic noise sources - Precision method for anechoic and semi anechoic chambers"
-The Chinese national standard, equivalent to ISO 3745, is applicable for the design and acceptance of domestic anechoic chambers.
-Core requirements:
-The background noise limit is determined according to testing requirements and is usually below 25 dB (A).
-The uniformity of the sound field is required to be within ± 1.5 dB.
-The frequency range is usually from 100 Hz to 10 kHz.
 
- GB/T 20247-2006  
-Standard name: "Performance testing methods for acoustic anechoic chambers and semi anechoic chambers"
-Specific methods for testing the performance of anechoic chambers have been specified, including background noise, acoustic field uniformity, etc.
 
 
3. Design and performance requirements
-Background noise
-The background noise of the anechoic chamber should be as low as possible, usually requiring less than 20 dB (A) or lower, depending on the testing requirements.
-Uniformity of sound field
-The change in sound pressure level within the testing area should be controlled within ± 1.5 dB to ensure the accuracy of the measurement results.
-Cut off frequency
-The effective frequency range of the anechoic chamber usually starts from 100 Hz, and the sound absorption performance in the low frequency range needs to be considered during design.
-Sound absorbing structure
-Efficient sound-absorbing wedges or materials should be installed on walls, ceilings, and floors, with a sound absorption coefficient close to 1 within the target frequency range.
-Size requirements
-The size of the anechoic chamber should meet the testing requirements, usually requiring the testing area to be at least 1 meter away from the sound-absorbing structure.
 
 
4. Acceptance and testing
-Background noise test
-Measure the background noise in the anechoic chamber using a precision sound level meter to ensure compliance with standard requirements.
-Sound field uniformity test
-Arrange multiple measuring points within the testing area to measure changes in sound pressure levels and evaluate uniformity.
-Sound absorption performance test
-Measure the performance of sound absorbing structures using pulse response method or standing wave ratio method to ensure that they meet design requirements.
 
 
5. Special application standards
-Automotive industry
-As per ISO 362-1, anechoic chambers used for vehicle noise testing must meet specific requirements.
-Electronic products
-As per IEC 60268-16, it is applicable for acoustic testing of electronic products such as speakers.
 
 
summarize
The acoustic standards for anechoic chambers mainly revolve around core indicators such as background noise, acoustic field uniformity, sound absorption performance, and frequency range. During design and construction, it is necessary to strictly follow international and national standards such as ISO 3745 and GB/T 6882, and ensure their performance meets the standards through professional testing.