- Sound insulation from the inside: the mass-spring-mass principle
- Airborne noise and contact noise: watch out for doors, windows and floors!
Almost all French people are worried about noise pollution. The acoustic or acoustic insulation of dwellings is a major challenge. Noise is not only the primary reason for moving, but it is also an important factor of stress and fatigue. Sound insulation reduces the impact of noise on a daily basis and improves comfort and peace of mind. For effective insulation, it is important to choose the materials adapted to the sources of the noise, but especially to the structural and material specificities of the house.
In terms of soundproofing, both in renovation and construction, the choice of suitable materials is firstly done with a good knowledge of the immediate environment of the building site.
- airborne noise, those whose propagation is in the atmosphere and in the air (such as the sound of a conversation in the street or a passing vehicle;
- impact noises (sometimes called "solidiens") which spread by contact or shock with a solid (the sound of neighbors on their floor or the fall of an object on the ground, for example).
It is therefore necessary at first pinpoint the main sources of noise pollution in the environment, since noises are transmitted directly (or indirectly) through the walls or floors of the building. An acoustic diagnosis made by a professional is valuable at this stage of the project.
Once the noise sources identified, we can act at different levels. A change of windows and a choice of glazing can help protect against outside airborne noise and work on the walls, walls or doors will effectively fight against interior airborne noise. Finally, work on the intermediate floors will help to combat the impact noise inside.
Sound insulation from the inside: the mass-spring-mass principle
In theory, the best way to isolate yourself from noise is to use the principle of "mass" using the heaviest and densest construction materials possible (a concrete slab on the ground or a stone wall by example). Fortunately, there is an alternative to the mass-spring-mass principle, which consists of trapping a flexible insulator between two walls to create a still air cushion in order to "block" the noise. This principle works as well in the case of partitions as suspended ceilings.
The insulation used must of course be the most acoustically efficient possible to provide the expected performance. There are two indices (expressed in dB) that identify the appropriate material;
- the sound reduction index Rw is relevant for airborne noise (the higher it is, the better the performance of the material);
- the ΔLw index indicate the performance of the material with respect to shock and impact noises.
In isolation from the inside, three types of interventions are possible on the walls;
- the pose of ready-to-use panels composed of a plasterboard, a central insulation and a face to be glued to the wall;
- the pose of panels on metal frame or wood frame (the insulation is then inserted between the panels and the wall);
- laying a bulkhead in plaster or brick tiles on wooden or metal frame (again, the insulation is inserted between the new partition and the wall).
Whatever the technique chosen, the most common materials for sound insulation are natural wools and mineral wools.
Among the performance mineral wools, we count:
- glass wool which, despite thin fibers, has a good sound absorption capacity;
- rockwool, whose insulating performance is excellent for the reduction of impact noises.
Natural wools such as wood wool, sprayed cellulose (faster to lay than projected cellulose), cork or wood fiber can be just as effective as mineral wool, provided that panels of one significant density.
Experts advise against the use of polyurethane or polystyrene (expanded or extruded): if these foams excellent for thermal insulation, their phonic performance is not sufficient when used alone. Similarly, natural insulation such as linen, sheep's wool, cork or hemp will need to be supplemented with additional coating to provide an attractive noise attenuation.
Airborne noise and contact noise: watch out for doors, windows and floors!
If the installation of partition or false ceiling remains a solution of choice to mitigate the consequences of the noisy nature of the neighborhood, we must not forget that the sound insulation is also played on windows, doors and floors.
When opting for a window change, a double glazing phonic (its outer glazed surface is slightly thicker than the inner pane) will make a major difference in isolating airborne noise from the street or garden. A thick glass is also a good solution, but it has the disadvantage of not offering any thermal insulation. The mention "AR" offers a classification on six levels (from AR1 to AR6) and it allows you to identify a reinforced acoustic insulation (AR6 being the best performing class).
Inside a dwelling, unless the separation walls of the dwelling are sufficiently thick, noises necessarily circulate from one room to another. To minimize the transmission of noise between rooms, soundproof door units (or "acoustic door units") consist, depending on the model, of a core made of insulating material, a sound seal at the periphery, etc..
On a light floor, carpet-type upholstery solutions with underlayment will not be sufficient to isolate contact noises. It will again be necessary to implement a mass-spring-mass solution in order to obtain a significant acoustic efficiency.
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