The Chambers

Reverberation Rooms 1 and 2

Two rooms of 204 m³ each, coupled by a 10 m² test aperture, built as independent concrete boxes on separate foundations with no rigid connection between them. That structural separation is what makes transmission measurement possible: without it, sound would travel through the building rather than through your specimen.

Neither room has a pair of parallel surfaces. The walls are splayed and hanging diffusers are suspended at irregular angles, because a diffuse field — sound arriving equally from all directions — is the assumption the whole method rests on. Diffusivity is verified annually against ISO 354 Annex A.

Property	Room 1	Room 2
Volume	204 m³	204 m³
Empty reverberation time, 500 Hz	8.4 s	8.1 s
Lowest qualified third octave	100 Hz	100 Hz
Test aperture	10 m² shared, 3.6 × 2.8 m
Background level	below 18 dB(A)

Semi-Anechoic Chamber

A 340 m³ chamber with glass-fibre wedges on all walls and the ceiling and a hard reflecting floor, giving free-field conditions above a reflecting plane — the geometry ISO 3744 assumes for machinery. Qualified to 100 Hz. The floor is rated to 1,200 kg and there is a 2.4 m door, so most floor-standing equipment gets in.

Working inside it is a strange experience for about ten minutes. Your own voice sounds close and dead, and people instinctively speak more quietly.

Impact Test Floor

A 140 mm reinforced concrete slab of 20 m² between the two vertically stacked rooms, forming the standard reference floor for ISO 10140-3. Coverings are laid directly on it, tapped, measured and lifted.

Instruments and Traceability

• Class 1 measurement microphones, calibrated annually against a traceable reference
• Field calibration check before and after every measurement session — if the two disagree by more than 0.3 dB, the session is repeated
• Rotating microphone booms in both reverberation rooms for spatial averaging
• Reference sound source, recalibrated every two years
• Environmental logging of temperature and humidity throughout every test; both change absorption in air at high frequency

The traceability chart — which instrument is calibrated against what, and by whom — is published on the accreditation page.

What The Chambers Cannot Do

• Below 100 Hz the rooms are not qualified. Low-frequency questions need a different approach, and we will say so rather than extrapolate.
• Very large façade assemblies beyond 10 m² do not fit the aperture. Those go to a laboratory with a larger opening; we will name one.
• In-situ building acoustics — measuring a finished building rather than an element — is a field service, not a laboratory one. We do it, but the standard and the report are different (ISO 16283).