Like many other sports facilities, swimming pools are often places where the acoustic comfort of users requires a reduction of the reverberation, which can be achieved through the implementation of sound absorbing materials.
ITS has completed the design of the construction systems for the reduction of the reverberation of a swimming pool having a volume of 8200 m3 (equipped with bleachers) near Grenoble in the Rhône-Alpes region (France) and has made the commitment of the in-situ acoustic result on the basis of a sizing job 100% based on computer simulations, which is in such cases a practice for the time being not very common elsewhere - at least in the context of such projects - (as far as known by the writer of the present article).
Indeed, predicting the reverberation time (e.g. after soundproofing work) of a premise of this type is usually done by using as input data the absorption coefficients of the considered acoustical materials, as obtained by acoustic measurements in a laboratory.
But the creativity of the management team in charge of the project (architect and acoustics consultance office) led them to envisage construction systems out of the common range (in the opinion of all suppliers of insulation materials requested) given the installation conditions foreseen: no input data in terms of absorption coefficient measured was thus available.
Those construction systems had to meet both the architectural design selected, a target of cutting-edge acoustic performance (i.e. the compliance of the pool with respect to a draft of a regulation for sports facilities: the decree has not been published yet ...) and constraints of an installation in aggressive atmosphere (mainly because of its high humidity).
Were therefore considered:
- on the one hand a wall lining made of a mineral wool and of an appropriate cloth - with a rear plenum - protected (in front) with spaced metal blades, with dimensions, spacing (and thus a perforation rate) as well as whose combination with other components of the acoustic multilayered structure for the installation conditions foreseen had never before led to any characterization of acoustic performance that could be brought to the knowledge of ITS in a useful time
- on the other hand a suspended ceiling below a technical gallery made of a mineral wool and of an appropriate cloth - with a rear plenum - protected (in front) with a microperforated sheet, with dimensions (and with a perforation rate) as well as whose combination with other components of the acoustic multilayered structure for the installation conditions foreseen had never before led to any characterization of acoustic performance that could be brought to the knowledge of ITS in a useful time
Therefore, the simulation of the sound absorption coefficient of the envisaged construction systems in the foreseen installation conditions was performed by the means of the software SILDIS (cf. acoustics simulation software).
The results of this simulation were used as input data for the prediction by ITS (computer calculation) of the characteristics of the pool after acoustical works founding the commitment to results taken by ITS in-situ (reverberation time guaranteed) on the basis of a quantity of materials to implement (area of surfaces treated obviously impacting the cost of the works) to the liability of ITS.
Measurements made after acoustical work in the swimming pool have allowed to verify the compliance of the facility with respect to the commitment made by ITS in terms acoustic performance, the (favorable) discrepancy between calculation and measurement of the reverberation time being less than 7% in the medium and high frequencies (where is located the maximum sensitivity of human hearing), which attests to the almost perfect matching of means implemented under the responsibility of ITS with respect to the objective of the operation.
In addition, the course of this project shows - once again - the possibilities for design and optimization of the software SILDIS, whose computing power and reliability, as well as whose versatility made of it a choice tool for the selection of products and construction systems for many projects of sound insulation.