Sound Absorption Class

Sound absorption class is a letter rating (A through E) assigned to acoustic products based on their weighted absorption coefficient (αw), as defined in ISO 11654:1997. Class A (αw ≥ 0.90) represents the highest absorption, suitable for specialist acoustic panels and thick mineral wool products. Class B (0.80–0.85) covers high-performance ceiling tiles. Class C (0.60–0.75) includes standard ceiling tiles and moderate absorbers. Class D (0.30–0.55) covers light absorbers and perforated surfaces. Class E (0.15–0.25) includes minimally absorptive surfaces. Products with αw below 0.15 are not classified. The sound absorption class provides a simple, standardized way to compare products and specify performance in building regulations and tender documents. European product standards (EN 13964 for ceiling tiles, EN 14240 for chilled beams) reference ISO 11654 absorption classes. While convenient for specification, the class system should be supplemented with octave-band data for critical acoustic design decisions.