Reverberation Room

A reverberation room is the complement to an anechoic chamber. Where an anechoic room eliminates all reflections, a reverberation room maximises them — creating a dense, diffuse sound field where sound energy is uniformly distributed throughout the room volume. This diffuse field is the required measurement condition for ISO 3741 (sound power), ISO 354 (absorption coefficient), and the ISO 140/717 series (sound insulation ratings).

HEMU Acoustics reverberation rooms are designed to ISO 3741 Annex A criteria. The key performance requirements are: minimum room volume (typically ≥ 80 m³ for high-frequency measurements, ≥ 200 m³ for low-frequency), reverberation time RT60 > 1 s across the measurement range (typically 100 Hz–10 kHz), background noise ≤ NC-20 (often NC-15 for precision facilities), and spatial standard deviation of sound pressure level ≤ 1.5 dB across a grid of measurement positions.

Diffuse field conditions are achieved through a combination of room geometry (non-parallel walls at 5–10° angles), volume-distributed acoustic diffusers (fixed fiberglass panels and rotating paddle diffusers), and the hard reflective finish on all room surfaces (polished concrete, epoxy-painted concrete, or glazed ceramic tile).

Background noise control is achieved through composite construction: floating floor on spring isolators, wall and ceiling panels on resilient mounts, and acoustically sealed penetrations. Background noise levels of NC-15 to NC-20 are standard. For rooms adjacent to high-noise environments (e.g., near production floors), additional isolation shells can be incorporated.

Rotating diffuser motor drives are provided in speed-controlled packages (typically 1–5 rpm) to ensure adequate spatial and temporal averaging during measurements. Drive motors are isolated from the room shell to prevent structure-borne noise contribution.