For clientsFor designers
Sound absorption and sound insulation — two different numbers
The αw coefficient shows how much sound a ceiling absorbs inside the room. Sound insulation, measured in decibels, shows how much sound it lets through to the neighbour. A board with the top absorption class can still have poor sound insulation — and the other way round.
For investors and designers who want quiet behind the wall but receive a quote for an acoustic ceiling — or the other way round.
Building acoustics involves two entirely different tasks. The first: keeping the room from booming, keeping speech intelligible, and stopping noise from building up. That is what absorption does. The second: stopping sound from one room reaching another. That is what insulation does.
Both subjects are often lumped together under “soundproofing”. Yet materials that absorb well are usually light and porous, while materials that insulate well are heavy and airtight. Hence the confusion: an acoustic ceiling will not stop conversations from behind a wall, and a thick wall will not shorten reverberation in a hall.
Two numbers, two scales
Przewiń w poziomie, aby zobaczyć wszystkie kolumny
Do the maths yourself: the same board, two ratings
Ecophon Master E carries the top absorption class A, αw = 1.00. In an insulation test between two rooms connected through the space above the ceiling, the same board (1200 × 1200 mm format) achieves Dn,f,w = 29 dB. The manufacturer notes that the on-site result will be 5–8 dB lower, so realistically 29 − 8 = 21 to 29 − 5 = 24 dB.
For ordinary offices, Ecophon recommends R′w = 35 dB between neighbouring rooms, which requires a ceiling with Dn,f,w above 40 dB. Boards with an additional insulating layer reach 39–43 dB in the same test. The 43 − 29 = 14 dB difference means roughly 25 times less sound energy passing over the partition wall, because every 10 dB is a tenfold change.
What this means when ordering
You want shorter reverberation and less noise in the room — look at αw and the absorption class. More on reading this symbol in the article about the αw absorption class.
You want conversations not to be heard in the next room — look at the ceiling’s Dn,f,w and the insulation of the walls. A partition wall that stops below a suspended ceiling lets sound pass over the top, through the void above the boards.
No acoustic or stretch ceiling will solve a noise problem coming from the neighbour above or through a wall. That is a job for a heavy, airtight partition — and for an acoustic report that pinpoints the sound-transmission path.
Najczęściej zadawane pytania
Will an acoustic ceiling quiet noise from the neighbours?
No. It will shorten the reverberation in your room, making it more pleasant, but sound passing through a floor slab or wall is stopped by the mass and airtightness of the partition, not by absorption.
Why is the on-site result worse than the laboratory one?
Because sound seeks flanking paths: through external walls, ventilation ducts, and leaks around installations. Ecophon estimates this difference at 5–8 dB relative to the laboratory value.
Can αw and Dn,f,w be compared with each other?
No. These are different quantities on different scales: αw is a fraction from 0 to 1, while Dn,f,w is a number of decibels. A high αw says nothing about insulation, and vice versa — which is why a specification states both when both are needed.