That acoustics is always insufficiently taken into account in a swimming pool (or in an aquatic center), due to the lack of appropriate soundproofing, and that such a place is ipso facto (too) poorly endowed with the equipment allowing to obtain the sound comfort required for such a place is a fairly widespread opinion.

Thus, the famous author of spy novels John Le Carré wrote [1] in his bestseller “Tinker, Tailor, Soldier, Spy”, about a shout of fury, that it “echoed many times like a shout in a swimming pool ».

It is true that at the date of publication of this novel (1974), the precautions taken with regard to the soundproofing for acoustic quality of swimming pools (and aquatic centers) were probably - in many places - less than what would have been desirable, and/or less than they are nowadays, although there is still (at the beginning of 2020) no specific regulation applicable in France on the subject.

It is therefore not entirely useless to emphasize that the lack of soundproofing and of acoustic comfort in a swimming pool (or in an aquatic center) is not inevitable, but (often) the consequence of the lack of knowledge (that which the acoustical engineer or the soundproofing technician can share, if he is involved in the context of a project), a lack of ambition or a lack of means of the participants in its construction (sometimes: in its renovation).

In France (it is referred to as NF P 90-207) and in Germany (it is referred to as DIN 18041) - to speak only of these 2 countries -, a (different) standard sets - depending on the volume, and considering the octave bands of central frequency between (at least) between 125 Hz and 4000 Hz - reverberation time limits (each: with different formulations) for sports halls (among which: swimming pools and aquatic centers).

With regard to France, despite it is not of compulsory application, it is possible to consider that the normative document mentioned above, whose specifications are - for all or part - included in different publications relating to sound insulation in buildings, entitled "guides", makes sufficient technical sense (being the subject of a broad consensus among acoustics and soundproofing professionals) to be able to usefully base the definition of objectives in terms of acoustics for a swimming pool or for an aquatic center.

There remains the necessary definition of means suitable for meeting the objectives.

Obviously, the floor of a swimming pool or of an aquatic center (and, if applicable: the stands) do(es) not constitute a set of surfaces with regard to which the acoustician can exert its beneficial influence in aid of users (and of the personnel who exercise their professional activity there), the circulations and the beaches surrounding the pools filled with water can not be otherwise than tiled: no one among these surfaces (including: watery) is significantly better than some others in terms of sound absorption since the sound absorption coefficient is always of the order of 0.01 i.e. 1% [2] for the mid and high frequencies [3].

Fortunately, this is not the same for other sets of surfaces, where it is possible to consider the positioning of materials that significantly absorb sound (the sound absorption index [3] can reach values of the order of 0.90 i.e. 90% or even 1 i.e. 100% [3]):

  • for roof

In the case of contemporary swimming pool or aquatic center projects, it is possible to envisage constructive systems for the roof having (with regard to the interior of the building) good sound absorption properties (significant qualitative progress have been observed in recent years for what is available on the market).

If it is not used, or in the context of renovations, it is possible to envisage the use of suspended absorbent elements, in the form of ceiling panels (installed horizontally or inclined depending on roof slop), or baffles (sometimes designated, we do not know why ? by the expression "acoustic receivers") vertical or not.

In all cases, the roof constitutes an important deposit of available surfaces for the implementation of soundproofing devices.

  • for walls

More or less regardless of the initial construction period considered, it is possible to envisage for the walls the use of materials having a good sound absorption.

Of course, it is necessary to exclude the portions of envelope walls dedicated to natural lighting and to vision towards the outside (bay windows), whose influence can be - taking into account some architectural biases - very significant in the context of some projects, and internal partitions that are not opaque, but (as the case may be) glazed or openwork (separations from offices, from an infirmary, from a catering or relaxation area) as well as doors and connections towards adjoining premises.

Whether long sections, transverse walls, partitions, (full) railings of balconies or cantilevered works: the practicality of all surfaces (perfectly vertical or inclined) with respect to the installation of reverberation limitation linings must be thoroughly reviewed.

This is appropriate because the soundproofing (i.e. the acoustic treatment) of the walls is necessary for the homogeneity of distribution of the sound absorbing materials between opposite planes delimiting the space (desirable, this homogeneity is never perfect - except in an anechoic room – due to the impossibility of favorably modifying the acoustic absorption of the ground in general, and in the case of a swimming pool or an aquatic center in particular, as already mentioned).

This is also appropriate because it is there (and rarely elsewhere, except sometimes on the underside of walkways or platforms) that constructive systems can be installed with enhanced acoustic performance at the lowest frequencies of interest, which can then usefully supplement that (in general: mostly at higher frequency) associated with the use of materials at the level of the roofing).

To limit reverberation and associated noise, ITS participated in a soundproofing project to improve acoustics in a swimming pool (aquatic center), in the Auvergne-Rhône-Alpes region (France).

It involved implementing, on the underside of a walkway and on longitudinal walls, linings absorbing sound mainly at low and medium frequency, consisting of perforated plates (openwork blades) installed in front of a mineral fiber filling with an anti-defibration cloth.

The reverberation time measurements conducted before this operation made it possible to highlight the deficit of the pool (aquatic center) in sound absorbing materials, and had triggered the action.

The reverberation time measurements conducted after the soundproofing works made it possible to validate the improvement in the acoustics of the swimming pool (aquatic center), at the end of an engineering process with regard to which the sizing of appropriate constructive systems (perforated plate resonators with slots) was a key step, for which Module 2 of the acoustics simulation software SILDIS® (developed and marketed by ITS) was particularly useful.

[1] in the begining of chapter 27 [2] on a scale from 0 to 1 i.e. from 0 to 100 % [3] where sound emissions relating to human voice (speech, shouts) are maximum