How many acoustic panels do I need?

Step 1, the current state: the existing equivalent absorption area follows from Sabine, A_current = 0.163 · V / T_current. An office of 120 m³ with measured or estimated 0.9 s has A_current = 0.163 · 120 / 0.9 = 21.7 m². Without a measurement, the calculator derives the current value from dimensions, floor, walls, ceiling and furniture.

Step 2, the target: with the target value of the use, A_target = 0.163 · V / T_target. For 0.55 s that is 0.163 · 120 / 0.55 = 35.6 m². The difference ΔA = 35.6 − 21.7 ≈ 14 m² is the missing equivalent absorption area. It already contains the absorption coefficient; the physical panel area is larger.

Step 3, the panels: n ≈ ΔA / (αw · panel area). Wall panels of 1.2 × 0.6 m (0.72 m²) with αw 0.9 contribute 0.65 m² each; for 14 m² that is 22 panels. Ceiling rafts of 2.4 × 1.2 m with αw 0.95 contribute 2.7 m² each; then five to six rafts are enough. Same area, different count: the number depends on the product, not on the room alone.

The rule of thumb “20 to 30 percent of the wall area” knows neither ceiling height nor use nor the current state. Two rooms with the same wall area but 2.5 and 4 m ceiling height need different amounts of absorption because the volume sets the reverberation time. A classroom with a target of 0.6 s needs much more than a living room where 0.6 s is already pleasant.

Coverage also says nothing about frequency. Thin panels absorb almost everything at 2,000 Hz and almost nothing at 125 Hz; a room can be on target at high frequencies and still boom at low ones. That is why the calculator works per octave band and shows which bands are still open.

Coverage is useful as a final check: if the required area exceeds 60 to 80 percent of the ceiling, a product with a higher αw or more mounting depth is the better choice than even more panels.

Living room, 80 m³, furnished (sofa, carpet, curtain): current state usually 0.7 to 0.8 s, target 0.5 to 0.6 s, ΔA 5 to 10 m². An acoustic picture of 1.2 × 0.8 m with αw 0.8 contributes around 0.8 m², a ceiling raft of 2.4 × 1.2 m with αw 0.9 around 2.6 m². Realistic: one raft above the dining table plus three to five pictures, or eight to twelve pictures.

Office, 120 m³, carpet and plasterboard ceiling: current 0.8 to 0.9 s, target under ASR A3.7 at most 0.6 s, ΔA 12 to 16 m². That is 20 to 25 wall panels of 0.72 m² with αw 0.9 or around 15 m² of ceiling rafts; under DIN 18041 room group B (A/V ≥ 0.25 m⁻¹ in open-plan offices) the room needs around 30 m² of absorption in total.

Meeting room, 100 m³: target under DIN 18041 around 0.5 s, ΔA 15 to 25 m², i.e. a ceiling raft over half the ceiling or an end wall plus a smaller raft.

Classroom, 200 m³, empty 1.5 s: target under DIN 18041 around 0.6 s, ΔA around 35 m². A class A acoustic ceiling over the whole floor area (around 63 m² × 0.9) covers that; with class B the rear wall is needed in addition.

Restaurant, 500 m³: DIN 18041 requires at least 0.20 m² of absorption per cubic metre, i.e. 100 m² in the room. Tiles, glass and a concrete ceiling contribute almost nothing; the ceiling has to be largely covered, for example with acoustic plaster or rafts, plus acoustic pictures on the walls.

All values depend on the current state. A room with carpet and curtains needs half, a room with glass and concrete twice as much. That is why the calculator works with your surfaces and the measured product instead of rules of thumb.

Absorption coefficient: αw 0.9 instead of 0.7 saves around a quarter of the panels. The single number αw underrates the low frequencies; for rooms with booming bass the values at 125 and 250 Hz from the measured curve count, not the class.

Mounting: wall panels with an air gap absorb lower frequencies than directly glued ones, ceiling rafts with air behind them work on both sides. The same board can reach 0.55 or 0.95 depending on the build-up; the test report names the build-up, the calculator shows the variants.

Distribution: distributed absorbers work better than one area in a corner because they meet more reflection paths. Absorbers opposite hard surfaces and at ear height do the most for speech.

Target value: 0.55 instead of 0.50 s saves two to three panels in the example office. Offices follow ASR A3.7, teaching rooms DIN 18041 with its tolerance band; the calculator sets the target from the use.

The count is only as good as the absorption coefficient it was calculated with. Brochure values and class labels without a test report are an estimate; specifications and proofs need values from a reverberation room measurement to ISO 354 with the build-up that is later installed.

In the room acoustics calculator you choose use, dimensions and surfaces, then a product from the database. The quantity suggestion names square metres or units, checks all octave bands against the target and shows whether the free ceiling or wall area is enough. The search filters products by αw, frequency band, installation and mounting.