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Swimming pool hall acoustics — reverberation, humidity and corrosion
Water, tiles and glass reflect almost everything, so an untreated swimming pool hall has a reverberation time of around 5–10 s. The standard allows 1.8 s. How to calculate that, and what a ceiling needs to survive the humidity and chlorine compounds in the air.
For designers and contractors of swimming pools, water parks and hotel pools.
A swimming pool hall is one of the most acoustically difficult interiors there is. The water surface, the floor and wall tiles, the glazing — all these surfaces reflect sound. An untreated hall has a reverberation time of around 5–10 seconds, and the shouting of children and the announcements of lifeguards blur into a continuous roar.
On top of that comes the environment: constant humidity, condensation and chlorine compounds in the air. An acoustic ceiling in such a hall therefore has to meet three conditions at once: absorb sound, not deform from moisture, and have a grid that will not corrode.
How much reverberation the standard allows
PN-B-02151-4:2015-06 — the Polish standard — sets, for swimming pool halls in baths and water parks: T ≤ 1.8 s at a volume up to 5000 m³ and T ≤ 2.2 s above that. The requirement applies to every octave band from 250 to 4000 Hz, in the finished hall, with no people present.
Do the maths yourself. A hall measuring 34 × 20 × 7 m has V = 4760 m³, so the 1.8 s limit applies. From the Sabine formula, the absorption needed is A = 0.161 × 4760 / 1.8 ≈ 426 m². A material with a coefficient of 0.90 therefore has to cover about 426 / 0.90 ≈ 473 m² — nearly 70% of a 680 m² ceiling. By comparison, a hall with a 7 s reverberation time needs only A ≈ 766 / 7 ≈ 109 m².
Where to place the sound-absorbing material
A sound-absorbing ceiling from wall to wall — that is the foundation. When a full ceiling is not possible, free-hanging elements are added.
Absorption on the walls, on at least two adjacent ones. Without it, a flutter echo forms between bare, parallel walls — one that the ceiling cannot remove.
The low frequencies (125 Hz) are the most difficult. Here, suspended ceilings with an air gap work better than panels glued directly to the soffit.
Humidity and corrosion
Humidity in a swimming pool hall is usually 50–60%, rising to 70% or more at peak occupancy. Glass-wool panels for such interiors are tested for stability at 95% relative humidity and 30 °C. Above the pool basin, the grid and fittings must meet corrosivity category C4 under ISO 12944; C3 is enough in the shower area.
For swimming pool halls, Ecophon specifies, among others, Hygiene Performance Ds on the Connect C4 grid. We explain why “stainless steel” alone is not enough for load-bearing elements above a pool in our article on corrosion protection classes for structures.
Najczęściej zadawane pytania
What reverberation time should a swimming pool hall have?
Under PN-B-02151-4:2015-06, no more than 1.8 s at a volume up to 5000 m³ and 2.2 s above that, across the bands from 250 to 4000 Hz.
Can an ordinary acoustic ceiling be installed above a pool?
No. The panels must be designed for high humidity, and the grid and hangers must be in corrosivity class C4. An ordinary office-grade grid (C1) will corrode.
Is it enough to treat just the ceiling?
Usually not. The ceiling shortens the reverberation time the most, but without absorption on the walls, a flutter echo remains between the parallel surfaces. The amount and layout are best confirmed in an acoustic report.
Źródła
- Ecophon — Polska Norma PN-B-02151-4:2015-06. Objaśnienia i komentarze (requirements for swimming pool halls)(otwiera się w nowej karcie)
- Ecophon — How swimming pool ceilings handle moisture, echo and indoor comfort (humidity, 95% RH, C3/C4, reverberation 5–10 s)(otwiera się w nowej karcie)
- Ecophon — Pool areas: recommendations for swimming pool halls (wall-to-wall ceiling, walls, Connect C4)(otwiera się w nowej karcie)