In an office we can face two distinct acoustic problems that require completely different solutions. The first is an excessively long reverberation time: sound bounces off hard surfaces and does not decay, which makes the space sound like a sports hall. The second is sound transmission between rooms or zones: a phone call heard across the whole floor, a meeting in a conference room audible through the wall.
Confusing these two problems is one of the most common mistakes when planning an office.
RT60 is the time after which the sound level drops by 60 dB once the sound source is switched off. In practice it is measured with an app or a dedicated device: a short impulse is generated and its decay is recorded. For open-plan offices, the PN-B-02151 standard recommends an RT60 in the range of 0.4–0.6 s. In conference rooms the target value is 0.3–0.5 s. A typical unfurnished office with hard floors and ceilings reaches an RT60 of around 0.9–1.4 s.
Upholstered partitions, carpets, acoustic ceilings and upholstered furniture reduce RT60 by absorbing the energy of the sound wave.
Absorption is measured by the absorption coefficient α (alpha) on a scale of 0–1. A material with α = 1 absorbs 100% of the incident sound energy. Upholstery fabrics used in office partitions reach α ≈ 0.6–0.85 in the speech bands (500–2000 Hz). Glass has α ≈ 0.03–0.05, meaning it absorbs almost nothing.
- High-density fabric — α ≈ 0.80–0.85 for 52 mm panels
- Tempered glass — α ≈ 0.03
- Acoustic glass with a PVB interlayer — α ≈ 0.06–0.10
- Perforated sheet metal with an acoustic insert — α ≈ 0.50–0.70
Insulation (denoted Rw or DnTw) measures by how many decibels a partition attenuates sound passing from one room to another. Here what matters most is the mass and the airtightness of the structure: gaskets, infill, profile thickness.
System 32 with an upholstered infill reaches Rw ≈ 38–42 dB. With laminated glass the values are similar. This is comparable to a masonry or plasterboard partition wall.
System 20 and desktop screens are not intended for insulation: their job is absorption and the visual separation of a zone.
If the problem is general noise and a long reverberation time in an open space: absorption (fabric, acoustic ceilings, carpets). If the problem is conversations carrying between zones or rooms: insulation (System 32, a full wall up to the ceiling, gaskets). If both: start with absorption, which is cheaper and more flexible, and apply insulation selectively.