Noise reduction is necessary in many premises, when it is desired, given their function, that they have one or more of the following qualities :

  • a good intelligibility of speech, to make possible in a normal voice [1] (i.e. without sound overbidding - often: counterproductive - which is the result of situations where one cannot hear oneself speaking) conversations between occupants of the the space considered (e.g. in catering rooms: for the guests of the same table)
  • sufficient discretion, so that the content of a conversation is not understood beyond a perimeter (variable depending on the context), thus guaranteeing the confidentiality of the words exchanged in many places frequented for daily life:
    • brasseries, canteens, tea rooms, pubs and other catering premises: for the guests seated at neighboring tables
    • spaces intended for public acces (e.g. counters of banks, social or medical establishments, credit areas of supermarkets)
    • open-plan offices, places in which it is - moreover - undesirable for conversations to be a source of distraction which could be harmful (due to the inherent loss of attention) to a good execution tasks assigned to everyone, even in the context of a job that does not require special concentration

The satisfaction of such acoustic quality objectives of premises in which there are particular challenges in terms of hearing comfort requires the implementation of specific soundproofing actions:

  • for a control of the reverberation (due to the reflection of sound waves on the walls delimiting the space considered), generally characterized by the time needed for the decrease in a ratio of 106 to 1 of the sound pressure level after stopping of a noise generator (this duration, usually expressed in seconds, must be sufficiently short) [2] [3]
  • for a control of the spatial sound decay (combining the effects of the geometric divergence occurring during the propagation of sound waves and the presence of obstacles, where the diffraction phenomenon occurs), generally characterized by the reduction of the sound pressure level when the distance from a noise source doubles (this rate of spatial sound decay, usually expressed in dB(A) must be sufficiently high) [2] [4]

When the necessary steps are not taken to obtain hearing comfort appropriate to such premises requiring soundproofing, and when the sound environment leaves much to be desired, various drawbacks may appear, which vary depending on the context.

When it comes to places for which the question "to be or not to be (there) ?" makes sense, the user can sometimes adopt the "policy of the empty chair" made famous in his time by a French leader (in relation, it is true, to other matters than the acoustical quality of interior spaces).

Thus, the journalist Eugénie Bastié reports, in her book "The war of ideas - Investigation in the heart of the French intelligentsia" [5], that an intellectual whom she wished to meet for a conversation "likes better to welcome at home than to have lunch in noisy restaurants in the city center ” (that the domicile in question is located in the region of Paris - in France - is secondary, that this anecdote is very recent is significant because much remains to be done - in 2021 - in terms of sound comfort in catering establishments).

To come back to the project which motivated this post, ITS marketed acoustic screens for noise reduction in premises requiring soundproofing: this was the space intended for the reception of customers of an medical test laboratory, near Nantes, in the Pays de la Loire region (in France).

This is indeed a type of room requiring soundproofing, except accepting the idea that everyone is satisfied that their health problems are brought to the attention of other customers because of the need to speak loudly (without necessarily being  well understood, if everyone does as much): this does not always lead to laughter, unlike the song "I’m not in good health" [6].

In such a context, high sound absorption screens are a good way to create an appropriate sound environment, on condition that different acoustic quality criteria are met, as regards their filling:

  • they must have a sufficient surface mass (at least 5 kg/m2 in case of a compressed mineral wool) to oppose sound transmission (one speaks of sound reduction index, expressed in dB) through the wall they constitute; they thus are an obstacle to acoustic propagation, by creating sound comfort zones with variable influence depending on the context (e.g. depending on the dimensions of the screen, the relative distances of the noise emission point and the reception point, the presence of objects and surfaces reflecting sounds nearby, the characteristics of the room in terms of reverberation)
  • they must have a sound absorption coefficient (sometimes referred to as a practical sound absorption index) as close as possible to 100% [2], which is generally associated with a sound absorption class A (corresponding to a weighted sound absorption index, i.e. multi-frequency αw = 1.00) [7] [8] [9] ; they thus participate (in proportion to their sound-absorbing surface) in the limitation of their reverberation (one speaks of acoustic correction of the room)

Concomitantly, it should be borne in mind that the positioning of sound-absorbing surfaces near a noise source (i.e. a speaker) makes it possible to avoid sound wave reflections on hard surfaces, the consequence of which is would be - all other things being equal - an increase in the sound pressure level (in one or more directions), for a given sound power level (the following being valid for a free sound field):

  • if there is 1 reflective wall (infinite): 3 dB increase in sound level
  • if there are 2 perpendicular reflecting walls (infinite): 6 dB increase in sound level
  • if there are 3 perpendicular reflecting walls (infinite): 9 dB increase in sound level

The high sound absorption screens marketed by ITS (see brochure here) fully meet these specifications in terms of acoustics, their quality also extending to other aspects of their design and manufacture - in France - (fire behavior, cleanability, modularity, mobility - a fortiori when on wheels -).

In addition, offered in different formats (with or without glazing), and with no less than 13 possible colors, they can be suitable for all arrangements, and match all visual atmospheres, actively participating - which is not nothing - to the decoration of the premises in which they are installed.

This is why the implementation of acoustic screens for noise reduction in these premises requiring soundproofing has emerged within the context of this project as a solution to improve the sound environment being qualitative, effective and, what is more, easy to implement.

There is no doubt that the quality of reception in this Public Acces Building (PAB) will thus be significantly improved.

Acoustic comfort in buildings end faq

[1] a sound pressure level of 60 dB (A) to 65 dB (A) at 1 m, facing the speaker, is often associated with a normal voice

[2] in particular at frequencies corresponding to the human voice: in the 1/1 octave bands centered on 500 Hz, 1kHz, 2 kHz or even 4kHz

[3] the target values - in general: variable from a fraction of a second to a little over a second - depend on the use and the volume of the considered room

[4] target values - in general: variables from 2 dB (A) to 4 dB (A) - depend on the use and the volume of the considered room

[5] Robert Laffont (2021) p. 161

[6] by the French comic Gaston Ouvrard (1934)

[7] the behavior of each of the layers constituting the lining is important: the surface layer (i.e. visible, generally thin - also with decorative functionality -) and also the layer located at the back (often: thicker)

[8] translucent parts are possible (without noise reduction alteration, however to the detriment of sound absorption - thus : to be considered sparingly -)

[9] of course, such a property on 2 sides is preferable, even if the corresponding screens are in the upper part of the price range of acoustic claustras