ITS will participate in soundproofing work in a public access building (PAB) broadcasting amplified music, to improve acoustic comfort, in the Auvergne Rhône Alpes region (it is said that this is the largest dance hall of the region).

Like concert halls (not only for folk, rock or op music) and other public access buildings (PAB) and premises broadcasting amplified music, a dance hall (in this case: with a volume of nearly 4,500 m3, and welcoming music groups with a sound system) is a space in which, in particular at medium and high frequencies (in particular therefore: in the frequency interval 500-2000 Hz), a certain quality of soundproofing is necessary, without which the acoustic comfort is considered insufficient by too many people.

Too much reverberation in the space under consideration is, then, frequently the cause; recriminations from customers, staff, musicians (and therefore: depreciation of the place and its activities) are then (invariably) the effects, when amplified music is not broadcast under conditions allowing it to be appreciated at its true value (akin to noise more than a successful combination of sounds, rhythms and harmonies - which it should be - and thus failing in its vocation to soften habits [1] a fortiori in the presence of the Larsen effect, which is far from being disadvantaged in such contexts, causing then very unpleasant whistles) and when a hubbub takes the place of a sound environment outside the periods of broadcast of amplified music.

This is what measurements (based on standard NF EN ISO 3382-2 Acoustics - Measurement of room acoustic parameters - Part 2 : Reverberation time in ordinary rooms) have shown for this premise hosting public and diffusing amplified music: the reverberation was too high, with regard to the recommended reverberation time limit values [2] (resulting from specific studies, relating to a large number of such venues receiving public whith amplified music, of which soundproofing grade was correlated with occupants satisfaction with regard to acoustic comfort).

From the comparison of these measurement results, carried out in unoccupied premises, normally furnished (with tables and chairs installed on the outskirts of the dance floor, the place being equipped with a bar and offering fast food) by the experienced human resource from ITS (using a noise generator and a sound level meter) to the target values for this room (taking into account its volume and use), it was possible to propose (as part of an engineering mission combining an on-site diagnosis and subsequent study work, with predictive acoustics calculations) paths to progress for this public access building (PAB) broadcasting amplified music :

  • the installation of curtains (in particular: at the back of the room), allowing - in a premise with a roof height of more than 6 m in places - to limit the volume of the dance room, by extending (in the upper part) existing partitions e.g. delimiting workspaces, storerooms (with a roof, and with a storey height); this will favor, all things being equal, the reduction of the reverberation time (increasing with the volume of the considered space), all the more so as the curtains will have properties in terms of sound absorption, i.e. an ability to not reflect sound waves (without sound absorption property, such separations would reflect sounds that previously propagated to an adjoining space, which could be counterproductive in terms of soundproofing performance)
  • the implementation of sound-absorbing panels, with a sound absorption coefficient close to 100% in 1/1 octave frequency bands of central frequency 500 Hz, 1k Hz and 2 kHz, in quantity and with a distribution (as uniform as possible) suitable for reducing the reverberation of sounds :
    • in the form of wall panels (covering hard surfaces, hitherto reflective (with regard to sound waves)
    • in the form of elements (in this case: rectangular, they could have been considered, in another context, with a different geometry) suspended on the underside of the roof, the installation of which will be possible despite the presence many equipment and accessories (networks, lighting, heating devices) that would oppose the implementation of continuous insulation under sloped roof

Crafted (for the wall panels: tailor-made, for the suspended elements: in a generally unique size, despite dimensional variations could be possible), by a specialized workforce, from large material boards – this latter: factory made -, these sound-absorbing panels will consit of non-combustible mineral fiber, and will be light enough not to cause excessive overload on the supports.

(Sound absorbing) wall panels and suspended elements will be matched, both as regards the infill as for the frameworks, so as to satisfy the needs in terms of aesthetics of this place which must be distinguished by its qualities in terms of habitability: the visual comfort of this soundproofing system will not be left out.

There is no doubt that after such soundproofing works, the acoustic quality of this public access building (PAB) broadcasting amplified music will be greatly improved, and that the subjective appreciation of its users will also increase [3]

Acoustic comfort in buildings

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[1] (ancient)Greek proverb

[2] time required for the average acoustic energy density in an enclosure to decrease by 60 dB after the emission from the source has ceased

[3] for other public access buildings (PAB) and premises : whether it comes to a school, a nursery, a university, a health establishment, a swimming pool, a gymnasium, a hotel, a shop, a shopping mall, a cinema, a theatre, a restaurant … ITS can also intervene to improve acoustical comfort