In accordance with research and measurement requirements, the core technical parameters of an anechoic chamber include cut-off frequency, free-field range and background noise level. The cut-off frequency refers to the minimum usable frequency that can be accurately measured in the chamber; the free-field range represents the maximum acoustic space available for precise measurement; the background noise is related to the minimum measurable sound level. For acoustic measurements without correction, the background noise of the anechoic chamber shall be at least 10 dB lower than that of the sound source under test.

Conventionally, wedges are adopted as the basic sound-absorbing structures to construct a free sound field indoors. According to classic acoustic principles, the length of wedges shall correspond to one quarter of the wavelength at the cut-off frequency. For instance, a cut-off frequency of 100 Hz requires wedge length of 850 mm, while a cut-off frequency of 50 Hz demands wedges as long as 1,700 mm. Although certain technical measures can moderately shorten wedge length, the reduction margin is limited. Taking the 100 Hz cut-off frequency as an example, wedges still need to be around 750 mm even after applying various optimization technologies. Long sound-absorbing structures occupy substantial space. Therefore, drastically reducing the thickness of absorbers and developing subwavelength structures to meet sound absorption demands have long been key directions of technological advancement, and research on acoustic metamaterials and metastructures is continuously advancing toward this goal.

During the design and construction of anechoic chambers, we adopt proprietary patented fiber-free sound-absorbing structures ASA and BCA independently developed by our team. BCA is a planar composite resonant sound-absorbing structure with an overall thickness of 350 mm; ASA is an asymmetric sound absorber with a total thickness of 650 mm. Both structures can satisfy the sound absorption requirements of anechoic chambers with a low cut-off frequency down to 50 Hz.

Fundamental principles of room acoustics demonstrate that the geometric dimensions of a room exert a critical impact on its internal sound field. In our anechoic chamber design, the room’s geometric dimensions are optimized based on room acoustic theories, endowing the chamber with inherent superior acoustic performance.

For every anechoic chamber design, verified simulation software is deployed to conduct sound field simulation and calculation, so as to check the deviation between the sound field attenuation characteristics inside the chamber and the ideal free field. This practice greatly mitigates engineering risks and ensures the constructed anechoic chamber meets the designed acoustic performance indicators.

Full Anechoic Chamber of Zhijiang Laboratory

 Full Vehicle Full Anechoic Chamber of Guangzhou CVTE

■ Audio Acoustic Testing

■ Acoustic performance testing of electroacoustic components and products, including frequency response and directivity characteristics of loudspeakers & sound boxes, as well as those of microphones

■ Research on stereo sound and spatial sound field

■ Measurement of sound source radiation characteristics, such as sound power

■ Acoustic Metrology Testing