Anechoic (fully reflection-free) and semi-anechoic test rooms are specialised laboratories with all six (or five — floor reflective) interior surfaces lined with high-absorption wedges, an Rw 50-70 dB sealed outer shell and structural-vibration isolation. They provide a reflection-free environment in the 100-100k Hz band for sound-power measurement, acoustic R&D, microphone calibration and EMC antenna testing.
What is an anechoic / semi-anechoic room?
An anechoic room is a space whose six interior surfaces are entirely covered with high-absorption acoustic wedges so that sound waves do not reflect back. In a semi-anechoic room the floor is left hard (reflective) because some standard tests (ISO 3744, automotive sound power) include one floor reflection. Both types are isolated from outside sound and vibration.
System architecture
- Interior absorber: glass-wool wedges (30-100 cm deep)
- Walkable inner surface: steel wire grid or mesh
- Outer shell: double wall with cavity, Rw 50-70 dB
- Structural isolation: spring-based floating floor
- Door: Rw 45-55 dB certified acoustic door
- Ventilation: ultra-quiet silenced ducts
Performance values
- Cut-off frequency: 80-200 Hz (depending on wedge depth)
- Free-field accuracy: ±10-25% (above cut-off)
- Background noise: NR 0-10 (5-15 dBA)
- Outer isolation (Rw): 50-70 dB
- Standards: ISO 3745 (anechoic), ISO 3744 (semi)
Where they are used
- Sound-power measurement
- Microphone and loudspeaker calibration
- Automotive NVH testing (semi-anechoic)
- Appliance emission measurement
- Telecommunications device testing
- EMC / RF antenna characterisation (with Faraday lining)
- Acoustic R&D and patent testing
Sizing criteria
- Cut-off frequency: wedge depth = λ/4 (lowest frequency)
- Net interior volume: free space after wedges
- Minimum 1 λ distance: measurement point to surface
- Typical outer dimensions: 6-10 m sides, 4-6 m height
Engineering process
1) Test standard chosen (ISO 3744 / 3745). 2) Lowest measurement frequency set, wedge depth calculated. 3) Target background NR designed. 4) Floating-floor spring frequency selected for structural vibration. 5) Ventilation silencer sized. 6) Manufacturing, installation and certification measurement performed.
Related
For industrial applications see industrial acoustic enclosures; modular systems: modular acoustic panel systems.
Features
Internationally fire-retardant certified (BS476 Class 0, UNI 9175 M1)
Custom-size and custom-color production options
High acoustic performance and long service life
Easy installation and application-friendly
Durability in industrial and residential projects
Usage Process
Site Measurement
On-site acoustic and dimensional measurement.
Product Selection
The right specification for the performance target.
Cutting & Supply
Custom-size preparation and packaging.
Installation
DIY application or expert installation.
Technical Specifications
| Standard | BS476 Class 0, UNI 9175 M1 |
|---|---|
| Typical Thickness | 20-100 mm (project-dependent) |
| Custom Cutting | Available (2-5 business days) |
| Warranty | Manufacturer warranty + Dedatek quality assurance |