• ■ Sound Absorber Material – CPA (Composite Panel Absorber)

The CPA sound absorption structure adopts a modular assembly design. Each module measures approximately 1 m × 1.5 m with an overall thickness of 10 cm. By adjusting the thickness of different vibrating panels inside, its minimum effective absorption frequency can be tuned within the range of 40 Hz to 100 Hz. Therefore, the thickness of the absorber will not increase as the cut-off frequency decreases, maintaining a slim 10 cm profile at all times (see Figure 3).The surface of each CPA module is a 1.5 mm-thick impact-resistant panel treated with double-sided dry powder coating, achieving corrosion resistance compliant with C4 grade specified in ISO 12944.

The first CPA installation was in a BMW anechoic chamber 20 years ago; the absorbers remain free of deformation to this day. The permeable surface withstands mechanical knocks and can be easily wiped clean with cloth to remove oil stains. The interior is filled with Basotec foam, a fiberglass-free and formaldehyde-free porous material with fire resistance rated B1 per Germany DIN 4102 and corresponding Chinese standards. This material has been applied in CPA structures for over two decades. It releases no hazardous gas under normal operating temperatures (0–45 °C). Completed chambers pass testing per GB/T 18883-2002 Indoor Air Quality Standard, meeting environmental requirements for ordinary residential spaces. A third-party environmental test report will be provided upon final acceptance. Customers may select custom exterior colors from standard color charts.

Unlike conventional panel resonant absorbers, CPA features multiple resonant frequencies, vastly expanding its low-frequency absorption bandwidth. Traditional panel resonators only cover a narrow frequency range and cannot deliver broadband low-frequency absorption, making them unsuitable for anechoic chamber construction. This marks a revolutionary improvement of CPA over conventional resonant absorbers. The attached figure shows a laser scanning vibration surface graph of a CPA panel with a specific thickness.

■ BCA – Broadband Compact Absorber

The BCA realizes low, mid and high frequency sound absorption via combined mechanisms: panel resonance, mass-spring resonance system and impedance matching of porous materials.

For mid and high frequencies: impedance matching is adopted with gradient-density porous media to guide sound waves into the material and convert acoustic energy into heat.

For low frequencies: integrated CPA composite panel resonators, which are mass-spring resonators with free boundaries formed by thin steel sheets and elastic/damping open-cell melamine foam frameworks. The damping layer bonded to the thin steel plate acts simultaneously as vibration damper and elastic layer of the mass-spring system, with a total thickness of only 10 cm.

Two absorption mechanisms work synergistically within the system: mass-spring resonance, plus flexural vibration of the panel determined by its stiffness, dimension and thickness — this is the key distinction from ordinary panel resonators. The thin plate generates abundant flexural natural frequencies; combined with the damping layer, it delivers an extremely wide absorption bandwidth. This patented technology creates a resonance peak every 1.8 Hz in the low-frequency range, and damping treatment forms continuous broadband absorption. As an internationally patented product, BCA has gained wide recognition among automotive, engine and related industry clients.

■ ASA – Asymmetric Composite Resonant Absorber

ASA is designed based on the natural modal frequencies of standing waves inside rooms. Reasonable layout of ASA absorbers significantly improves overall absorption efficiency. When constructing anechoic chambers with ASA, acoustic design optimizes both absorber performance and room geometry to achieve optimal sound field performance, with special focus on low-frequency room modes. The attached figure illustrates modal sound field distribution in a typical 3 m × 4 m × 5 m chamber.

■ W100

W100 is a modular absorber filled with 100 mm eco-friendly fiberglass-free polyester cotton, widely deployed in high & low temperature environmental test chambers.

Performance indicators: sound absorption coefficient ≥ 0.9 above 630 Hz, and ≥ 0.95 above 315 Hz.

Installation details: U-shaped keels for floor and ceiling mounting, H-shaped cross keels for intermediate supports. Vertical keels are installed between wall-mounted panels to facilitate equipment attachment.

■ All Types of Acoustic Test Environments