Improving the acoustics of a restaurant for noise limitation is often a necessity in view of the disadvantages that (if not) presents the situation resulting from the absence of particular precautions regarding sound comfort.
This did not escape the fine observer of everyday life in Western Europe in the 20th century (but how different is the beginning of the 21th from this point of view?) that Georges Simenon was, who so well transcribed in his many novels.
"The rumor that filled the grill, the noise of crockery, knives, forks, the murmur of conversation, the laughter and the music that came from the great hall, prevented him from hearing. "
This extract from the book “Maigret's revolver”, written at Shadow Rock Farm, Lakeville (Connecticut), in June 1952, describes a place that the story situates in London (and of course, infinitely better than the author of this article could do this: the latter will therefore abstain from any additions concerning the description of the symptoms of an acoustic quality that is insufficient for a space such as a restaurant), which can commonly be observed when what is necessary for acoustical comfort has not be done.
Why should we consider improving the acoustics of a restaurant to reduce noise?
Because for such a space - this is also true for cafeterias, fast food places, dining rooms in hotels, and collective dining rooms (canteens, university restaurants, business restaurants), the challenge is to create an environment calm enough to allow the occupants to restore (this is what it comes to indeed, when you are in a restaurant !), i.e. according to the definition of the Larousse dictionary, "to regain strength in eating”.
Needless to say that some ambience conditions are required to allow the relaxation of which it is desirable that it can be associated with this particular moment which punctuates our days, and so that when they take place (it is not forbidden to eat his meal in silence, especially if one is, intentionally or not, alone at the table, to savor a particularly successful dish), conversations in normal voice can be held.
For these purposes, the control of reverberation phenomena - illustrated by a sufficiently low value of the performance indicator that is the reverberation time - is essential, in the context of an improvement in the acoustics of a restaurant for noise limitation, because without it:
- there is no moderation of the ambient sound levels - because they are (too much) amplified by the presence of a reverberant acoustic field (due to the existence of a ground, of walls, of a ceiling or of a roof reflecting sound waves) which is superimposed on the direct acoustic field related to the sound sources mentioned above –
- there is no sufficient intelligibility of speech (nor of music, when there is any)
- there is no limit to the verbal escalation leading everyone to try (but this is often counterproductive) to be better heard - to be complete, it must be said that the Lombard effect, also commonly called "cocktail effect" is a phenomenon involving a modification of human pronunciation (fundamental frequency, sound volume, articulation, lengthening of vowels) to compensate for the presence of surrounding noises –
To do well (regarding the problems relating to reverberation), it is necessary that are installed materials:
- in appropriate quality (i.e. with a sound absorption coefficient as close as possible to 100%, especially in the frequency range corresponding to octave bands with a central frequency 500 Hz, 1000 Hz and 2000 Hz or even – this is even better – for lower and higher frequency e.g. in central frequency octave bands 250 Hz and 4000 Hz)
- in sufficient quantity: it depends on the volume of the room, and its geometry (e.g. height under ceiling, total surface of the walls)
- with a sufficiently homogeneous distribution: in a high-rise dining room, the best acoustic suspended ceiling (despite can be useful or even necessary) will not always be sufficient if no wall absorbing lining is installed otherwise, while it is often required
Moreover, in terms of improving acoustics, limiting noise propagation (e.g. from a table towards neighboring tables) is often an important issue, and it should therefore not be neglected: the use of dividers (vertical screens, allowing to create separations in the space that constitutes a restaurant e.g. between groups of tables) is often appropriate in the context of sound insulation in buildings.
The best is, of course, that such soundproofing devices are made of materials capable of contributing (because of their ability to absorb sound) to the limitation of the reverberation in the restaurant.
ITS contributed in improved restaurant acoustics for noise limitation in the area of Paris (France). It was a canteen, for which ITS has marketed high acoustic absorption dividers.