AcouS STIFF® Software

AcouS STIFF® is software used for predicting the sound reduction index. Our program complies with ISO 717-1, NFS 31-051 and ASTM-E413 standards. In addition to our tutorials, our team teaches you how to use the AcouS STIFF® software.

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Presentation of AcouS STIFF®

Presentation of AcouS STIFF® acoustic software (Acoustic Software Sound Transmission Index Full Forecast)

The sound reduction index of a wall can be measured in a laboratory specially designed for this purpose (decoupling of sending and receiving cells, shapes and sizes of cells, ....).

However the sound reduction index of a wall depends on a very large number of parameters. One naturally thinks of the thickness, or density of constituent materials, but particularly variable settings from one application to another, such as length and width of the panels are also of great importance, as evidenced by the following figure :

R as a function of embedding dimensions of the glazing

R as a function of embedding dimensions of the glazing

Under these conditions, the number of walls to be tested is infinite and a uniquely experimental approach, by the time and cost it represents, can not suffice.

Predicting then appears as an essential complementary approach.

Both approaches, laboratory measurement and calculation of estimates, far from being exclusive are complementary and necessary to one and the other : the experimental approach can be considered only as the number of cases to be tested, but the models simulation to be validated should be on individual cases properly chosen, of a comparison with experimental values.

AcouS STIFF® acoustic software is a simulation tool for calculations of sound reduction index.

Areas of application of the software

Acous STIFF® acoustic software is a simple and adapted tool that allows you to :

  • Determiner the sound reduction index of a simple or complex wall,
  • Assist in new product development,
  • Optimize measurement campaigns in a laboratory,
  • Appreciate the performance of a doubling in function of its support,
  • Extrapolate the performance conventional structures,
  • Forecast unconventional structures and their optimization,
  • Understand the acoustic behaviour of a wall.

The results are presented as graphs and /or tables showing the overall values in accordance with ISO717-1, NF S 31-051 and ASTM E 413.

Complex wall structure simulation

Complex wall structure simulation

Calculation model

Defining the types of walls calculable using AcouS STIFF®

AcouS STIFF® acoustic software can perform calculations of forecast reduction index of the following types of walls :
  • single wall (consisting of a single plate)
  • laminated or multilayer wall,
  • orthotropic wall,
  • wall composed of a porous material,
  • wall lined with a porous material,
  • detached double wall,
  • rigid double wall,
  • triple wall.

In addition, one can perform the following operations on the sound reduction indexes :

  • arithmetic sum of up to ten sound reduction indices,
  • difference (Delta) between two indices of acoustic attenuation,
  • heterogeneous walls composed of more than ten different wall elements.
AcouS STIFF : wall types

AcouS STIFF : wall types

The different types of bonds

On distingue les différentes liaisons mécaniques suivantes :

  • ponctuelle : une distribution régulière de points de liaison, exprimée en nombre de points par mètre carré,
  • linéique : des lignes de liaison parallèles, type poutre, cette répartition est exprimée par l'entraxe de ligne à ligne en mètres,
  • surfacique : toute la surface du matériau intermédiaire constitue la liaison mécanique entre les parements externes. Seul le facteur de désolidarisation FD doit être renseigné,
  • périphérique : c'est seulement l'assise de la paroi qui constitue la liaison mécanique entre les parements externes. L'utilisateur a le choix de sélectionner de 1 à 4 côtés de la paroi avec un facteur de désolidarisation FD différents pour chacun des côtés s'il le souhaite. Pour chaque côté, la liaison périphérique est exprimée en mètre. Seuls les côtés dont la longueur et le facteur de désolidarisation FD sont renseignés seront pris en compte dans le calcul.

Pour une même paroi, il peut exister plusieurs types de liaison entre les parements externes.

Calculation model

There are two types of basic components in AcouS STIFF®:

First basic component : the plate

This element is solid, homogeneous, isotropic, rectangular is shape, its thickness is small compared to its lengths and widths and also before the wavelengths of play, especially in solids. Subsequently, this only works in Plate bending : no shear wave, surface taken into account.

It also represents a barrier which is supposed to be completely airtight; the speed of a particle of air on the Plate is equal to the speed of the plate at the point. Which distinguishes it fundamentally from the other basic component, the Porous.

Important parameters :

  • length, width (m)
  • thickness (mm)
  • density (kg/m3)
  • Young's modulus (in N/m2) : is the stiffness in tension or compression of the material forming the plate. This is the dynamic Module of Young, which may differ slightly from the static module.
  • internal loss factor (dimensionless) : combining the magnitude of the intrinsic material losses and those due to mounting. The material database provides such value, which can only be approximate and has been developed through practice.

Second basic component : the porous

It consists of a solid element or an aggregate of solid elements with blank spaces that could be saturated by a fluid. It presents itself as the assembly of two phases :

  • a solid phase representing the skeleton or structure of the environment consists of :
    • fiber in the case of mineral wool (rock, glass) or of textile fabrics,
    • a matrix in the case of foam,
    • grains in the case of sand, stacking logs...
  • a fluid phase, for example a gas saturating the voids of the skeleton, in this case it will be air.

All porous materials characterized by such behavior in the acoustic software AcouS STIFF® are permeable to air, for example, foams are open pores. Indeed, the acoustic behavior of closed-cell foam (e.g. polystyrene) is of the type Plate. This is the fundamental difference between the two basic components.

Important parameters :

  • thickness (mm)
  • resistivity to the flow of air (or in Pascal s/m2 or rayls/m): measurable physical parameters, intrinsic characteristic of a porous material. It is to some related to the density which it incorporates among other information. It calculates the coefficient of grain flow (currently informative parameters) from the density of porous material, in order to provide feedback to users accustomed to using this coefficient.
  • Young's modulus (in N/m2): comparable to the compressibility of air saturating the structure; isothermal compressibility at low frequencies because there is heat exchange between air and the structure during adiabatic acoustic vribrations, from a certain frequency located sufficiently high in the audible range not to be taken into account.


Double skin :

  • Double skin cladding with a double skin steel tray 75/100 + VN30 + VN70 + steel cladding of 75/100
  • Calculation : RW = 46
  • Measure : RW = 45
Double skin

Double skin

Steel deck 75/100 :

  • Steel 0.75 mm
  • Calculation : RW = 23
  • Measure : RW = 22
Steel deck 75/100

Steel deck 75/100

Steel deck 63/100 :

  • Steel 0.63 mm
  • Calculation : RW = 16
  • Measure : RW = 15
Steel deck 63/100

Steel deck 63/100


Reinforced concrete 8 cm :

  • Reinforced concrete 8 cm
  • Calculation : RW = 46
  • Measure : RW = 47
Reinforced concrete 8 cm

Reinforced concrete 8 cm

Reinforced concrete 10 cm :

  • Reinforced concrete 10 cm
  • Calculation : RW = 49
  • Measure : RW = 48 à 51
Reinforced concrete 10 cm

Reinforced concrete 10 cm


Cellular concrete 14 cm :

  • Cellular concrete 14 cm
  • Calculation : RW = 41
  • Measure : RW = 40
Cellular concrete 14 cm

Cellular concrete 14 cm

Cellular concrete 20 cm :

  • 20 cm aerated front coated concrete
  • Calculation : RW = 46
  • Mesaure : RW = 46
20 cm aerated front coated concrete

20 cm aerated front coated concrete


Doubling on gypsum :

  • Gypsum 7 cm + glass wool rigid than 5 cm + 1 BA10
  • Calculation : RW = 56
  • Measure : RW = 55
Doubling on gypsum

Doubling on gypsum

Reinforced concrete 20 cm :

  • Doubling on concrete 20 cm : reinforced concrete 20 cm + 8 cm glass wool rigid + 1 BA10
  • Calculation : RW = 71
  • Measure : RW = 73
Reinforced concrete 20 cm

Reinforced concrete 20 cm

Brick :

Doublage sur brique :

  • Brick hollow 5 cm with an air gap of 1 cm + 3 cm of glass wool rigid + 1 BA10
  • Calculation : RW = 54
  • Measure : RW = 54


Frame :

Doubling on frame :

  • Reinforced concrete 16 cm + 3,5 cm air gap + 7,5 cm of glass wool a semi rigid +1 BA13
  • Calculation : RW = 74
  • Measure : RW = 74



Wood floor :

  • 1 wood panel (CTBH) de 22 mm + 165 mm air and 200 mm IBR + 1BA13
  • Calculation : RW = 61
  • Measure : RW = 62
Wood floor

Wood floor

Floating floor :

  • Reinforced concrete 14 cm with Rocksol 15 mm mortar and a cap of 4 cm
  • Calculation : RW = 58
  • Measure : RW = 58
Floating floor

Floating floor


Single glass :

  • Glass 6 mm
  • Calculation : RW = 29
  • Measure : RW = 30
Single glass 6mm

Single glass 6mm

Laminated glass :

  • Laminated glass consists of a 5 mm glass + viscoelastic + 5 mm glass
  • Calculation : RW = 38
  • Measure : RW = 39
Laminated glass

Laminated glass

Double glazing 44.2/20/55.2

  • 2 laminated glass 4 mm, air gap of 20 mm and 2, 5 mm laminated panes of glass
  • Calculation : RW = 48
  • Measure : RW = 47 à 49
Double glazing 44.2/20/55.2

Double glazing 44.2/20/55.2


  • 21mm de Pin/sapin +32 mm lame d’air +2 LV de (145mm+45mm) +BA13
  • Essai laboratoire: Rw = 55dB
  • Calcul AcouS STIFF: Rw = 54dB
Façade avec isolation rapporté par l'intérieur

Façade avec isolation rapporté par l'intérieur


Parois à simple ossature:

  • 2 BA 13 de 12.5 mm+36mm lame d’air+100mm LV+36mm lame d’air+2BA13 de 12.5mm
  • Essai laboratoire: Rw = 61dB
  • Calcul AcouS STIFF: Rw = 61dB
Parois séparatives à simple ossature

Parois séparatives à simple ossature

Parois séparatives en panneaux massifs contrecollés:

  • Panneau de 94mm d’épaisseur
  • Essai laboratoire: Rw = 34dB
  • Calcul AcouS STIFF: Rw = 34dB
Parois séparatives en panneaux massifs contrecollés

Parois séparatives en panneaux massifs contrecollés


Cloison plâtre:

  • BA13+45mm LV+BA13
  • Essai laboratoire: Rw = 46dB
  • Calcul AcouS STIFF: Rw = 46dB
Cloison plâtre

Cloison plâtre


  • Enduit 15mm+326 mm de paille+ enduit 15mm
  • Essai laboratoire: Rw = 45dB
  • Calcul AcouS STIFF: Rw = 45dB



Parpaing creux 100 enduit 1 face:

  • 3 parements de 115 mm d’épaisseur
  • Essai laboratoire: Rw = 43dB
  • Calcul AcouS STIFF: Rw = 42dB
Parpaing creux 100 enduit 1 face

Parpaing creux 100 enduit 1 face

Parpaing creux 200 enduit 1 face:

  • 3 parements de 215 mm d’épaisseur
  • Essai laboratoire: Rw = 55dB
  • Calcul AcouS STIFF: Rw = 55dB
​Parpaing creux 200 enduit 1 face

​Parpaing creux 200 enduit 1 face


Porte isophone-portaphone
  • 40 mm portaphone+80mm d’air+40mm isophone
  • Essai laboratoire: Rw = 57dB
  • Calcul AcouS STIFF: Rw = 58dB
Porte isophone-portaphone

Porte isophone-portaphone

Porte sans joint au sol:

  • Essai laboratoire: Rw = 24dB
  • Calcul AcouS STIFF: Rw = 24dB
Porte sans joint au sol

Porte sans joint au sol


Toiture acier:
  • 5mm de bitume (étancheité)+100mm LV+0.75mm d’acier+80mm d’air+100mm LV+80mm LR+0.75mm d’acier
  • Essai laboratoire: Rw = 55dB
  • Calcul AcouS STIFF: Rw = 53dB
Toiture acier

Toiture acier

Toiture tuile:
  • 10mm de toiture tuile plate+57mm d’air+280mm de LV+BA13
  • Essai laboratoire: Rw = 54dB
  • Calcul AcouS STIFF: Rw = 53dB
Toiture tuile

Toiture tuile


1. Overview

The AcouS STIFF® software, developed by GAMBA Group, simulates the sound reduction index of complex walls.

This tutorial is an overview of this software.

2. AcouS STIFF® Software: Sound Reduction Index Simulation of partitions

How to simulate the sound reduction index of partitions with plasterboard and insulation with AcouS STIFF® software ? Tutorial by GAMBA Group

AcouS STIFF® Training

Training objectives :

  • Provide participants with the basic knowledge to understand the acoustic behavior of a wall and to highlught the influence of parameters which can be used to optimize a piece of work.
  • Mastering the use of AcouS STIFF® software.

People concerned :

The course is valuable for engineers who design or prescribe the walls, including :

  • the engineers of studies who propose solutions for constructive systems,
  • technical sales people responsible for prescribing a work derived from a system catalog,
  • the engineers of R&D department responsible for the development of a wall or a mounting system, or manufacturing technology.

Similar sessions

Maintenance & Updates

Related services

For all our software, a complete range of products and services is at your disposal :

Maintenance contract

This maintenance contract provides among other things : the maintenance of the software and the dongle, the delivery of software updates for free for holders of the maintenance contract, phone support, special discounts on other software


Each year a new version containing additions or changes in the software is available.

Training and seminars

We regularly organize inter-company and intra-company training courses on the use of the software.

Day of information and exchange

Each year and each software program, at least one day of information and discussion is held with the users of such software.

Calculations on demand service

We can do calculations of acoustic simulations on request with the use of our software.

You can avail of these services free or at very favorable terms for an annual fee.

For more information, please contact us


You will find below answers to some questions you ask and which we hope will give you the information you seek.

  • Can we create our own software database ?

    Yes, just create simple or porous siding in a file from the database, give the name of the component that you want and enter its physical characteristics (density, Young's modulus and factor loss for material type "plate" and resistivity to air flow for porous materials with open pores).

  • Can attenuation indices already measured in the laboratory be added to the software?

    Yes, it is possible to integrate acoustic test reports into AcouS STIFF. On the other hand, if the RE of a roof is added to an R of a suspended ceiling, the interaction between the two (mass/spring/mass, cavity reverb, connection, etc.) will not be taken into account, the result will therefore be false from a physical point of view. I therefore advise to do the simulation of the roof (calibration calculation measurement from the test report) and then to integrate a suspended ceiling below in simulation. Example: If the steel roof is a bitumen waterproof roof + insulation + steel: simulated with double wall Then simulated with triple wall by taking the elements of the double wall and integrating the suspended ceiling. Additions of experimental and simulation values are dangerous and can only be done when no interaction between the two elements exists.

  • Currently determining the composition of a wooden floor and how can we model a weighting with gravel. My goal is to determine the difference between gravel and concrete. Can we do this?

    We can take gravel into account, but the method depends on whether we make impact noise or airborne.

    In the air, you can do multilayer, so you put the CLT on one layer and the gravel on another. For gravel, you can put the right density and thickness. Must indicate a low Young's modulus so as not to have a critical frequency in the observation spectrum and put a fairly large loss factor, but in any case will have no impact given the position of the critical frequency that you will choose.

    For the shock, we cannot make a multilayer, we must therefore create an equivalent floor, which has the total thickness CLT + gravel, the surface mass which is also the sum of the two. You have to keep the Young's modulus and the loss factor of the starting CLT, or readjust the surface Young's modulus so that the EQ floor is the same critical frequency as the starting CLT if it has really moved a lot.

  • Does the software provide flanking transmission ?

    AcouS STIFF® allows to take into account that direct transmissions on the other hand we have another calculation module called AcouS STICS 21® who is in the test phase which allows lateral transmission calculations to be made.

user manual and tutorials

user manual and tutorials

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