FAQ.

General topics.

Soundproofing a building is the limitation of noise that can disturb people living in the rooms of the building. Differently from the thermal insulation, which has the main purpose of energy saving, acoustic insulation does not bring direct economic advantages to the operating costs of the buildings, but concurs to a better confort of life and work experience. Today life is often stressful and noise inside buildings is often one of the main reasons of fights and complaints between neighbours and disputes between individuals. That’s why a soundproofed building can have a higher value on the market, compared to a building without insulation.

The acoustic insulation of a building is generally evaluated with the following parameters:

  • Airborne sound insulation: evaluation of the sound reduction given by horizontal and vertical partitions separating two different dwellings, relative to noises generated and propagated through air.
  • Facade acoustic insulation: evaluation of the noise coming from outside the building (traffic, airplanes, outside activities in general, building sites, …).
  • Impact noise: evaluation of the structural noise generated for example by footsteps or furniture movement, transferred to the adjacent rooms vertically and horizontally.
  • Noise from equipment: noise generated due to the use of toilets, showers, but also lifts, air treatment, …

Maximum or minimum performance are required by local laws, specific in every country.

The transmission loss R is a parameter that defines the airborne sound insulation for a partition, generally a wall or a floor separating two dwellings. It is a noise measured in deciBels on a wide frequency range spectrum (100 Hz – 3150 Hz), according to the formula:

R = L1 – L2 + 10Log S/A [dB]

(L1 is the noise level in the room where the noise is generated, L2 is the noise level in the room where the noise is received, S is the surface of the partition, A is the equivalent absorption surface of the receiving room). Since it is obtained from the difference of two noise levels, R has the meaning of “”insulation””, that means the higher is the R value and the better will be the insulation.
From the analysis in the whole spectrum a single rating index can be calculated and identified with the letter “”w””. When evaluated in laboratory, without flanking transmission, the rating index is called Rw, while when evaluated in site it is indicated with a single quote (for example R’w, …), because the flanking transmissions have an influence on the value. The reference standards for the measurement of the impact noise level in laboratory are the series ISO 10140, while the evaluation with the single rating index is done according to the ISO 717-1.

The normalized impact noise insulation is a parameter that defines the sound insulation of horizontal partitions separating dwellings (floors in general, but also including terraces, balconies, …). It is a noise measured in deciBels on a wide frequency range spectrum (100 Hz – 3150 Hz), according to the formula:

Ln = Li + 10Log A/Ao [dB]

(Li is sound pressure level in the receiving room, A is the equivalent absorption surface in the receiving room and Ao = 10 m² is the reference equivalente absorption surface). The structural noise source is called tapping machine and is made of five hammers that impact on the floor surface at a fixed rate. Since the perfromance is measured from a direct measurement of noise, the Ln value must be read inversely, that means the higher is the number and the worse will be the insulation; on the contrary, the lower the value of Ln, the better will be the insulation (the floor emits a lower noise).
From the analysis of noise in the whole spectrum a single rating index can be calculated and identified with the letter “”w””. When evaluated in laboratory, without flanking transmission, the rating index is called Lnw, while when evaluated in site it is indicated with a single quote (for example L’nw, L’nTw, …), because the flanking transmissions have an influence on the value. The reference standards for the measurement of the impact noise level in laboratory are the series ISO 10140, while the evaluation with the single rating index is done according to the ISO 717-2.

An acoustic bridge is a sound leakage wich makes the acoustic performance of a product or partition worse than it could be following a certain installation rule. For example, on an insulated floating floor, a rigid connection between screed and wall is an acoustic bridge, because the screed is not free to move when excited, but transfers the vibration to the adjacent structures, generating noise in the connected rooms. Another example of acoustic bridge is a hole in a wall, that increases the transferred energy and limits the airborne sound insulation strongly.

The acoustic classification scheme is a rating system for the acoustic insulation of buildings. At European level there is not yet a unique standard, but every country has developed its own criteria for the definition of classes. A recent shared document has been built though, during the work of the COST ACTION TU0901, to compare and analyze the global situation in Europe regarding building technology, classification and requirements.

The acoustic insulation in buildings is evaluated through the determination in site of some requirements that depend exclusively on the characteristics of the structures and not on the outside environment. The major requirements are airborne sound insulation, impact sound insulation, facade insulation and equipments. Each country has adopted its own parameters to evaluate the requirements, depending on local building traditions and techniques and the values can be different depending also on the function of the building (residential dwellings, commercial buildings, offices, hotels, hospitals, educational spaces, entertainment, …).

The dynamic stiffness id the parameter that gives information about the elastic characteristics of a material in dynamic conditions. It is measured according to the standard EN 29052-1 through the determiantion of the resonance frequency of a mass-spring system, in wich the “spring” is the material under test. The value of the dynamic stiffness depends on the load applied to the material (the mass per m²), for this reason the standard prescribes a reference load of 200 kg/m². The dynamic stiffness gives a value to the capability of the different materials in attenuationg the vibrations. the lower is the value, lower is the frequency that can be insulated and the better is the global acoustic insulation.

The thickness of a product for impact noise insulation under a floating screed is not a simple dimensional evaluation of the mat or panel “”as is””, but it requires the use of a more complex procedure. A mat for impact noise insulation under load (a sand and cement screed 5 cm thick can have a weight of 90-100 kg/m²) has a thickness wich depends on the applied load itself. The standard EN 12431 provides a method to assess the thickness under load for such products and simulates the long time behaviour through the application of a very high load in a limited time.

The values resulting from this methodology are:
dL = thickness of the mat, measured at the load of 250 Pa for 120 seconds;
dF = thickness of the mat, measured at the load of 2000 Pa for 120 seconds;
dB = thickness of the mat, measured at the load of 2000 Pa, after an additional load of 48000 Pa for 120 s.

The comprimibilty is calculated from the difference between the dB and dF values.

The oscillatory motion generated by moving mechanical components is called vibration and can produce undesired damage to the structures and disturbance to the people. The disturbance to people can be perceived as an oscillatory movement (for example the feeling during the passing of a metro train), but the vibration can be also transformed in noise, through the radiation of building structures (for example inside a building for those noises that arise from the movement of furniture and glazings, during a train passing in the proximity).

The major problems regarding vibration in buildings refer to the disturbance from service equipments (generators, HVACs, …) or disturbance from the proximity of transport infrastructures (railways, metros, roads, …).

In the case of machinery, the vibration is cause by the rotation and movement of mechanical components that generat forces, due to the intrinsic unbalancing, that can be transmitted to the machine first, and then to the connected structures.

In the case of the transport infrastructures, the vibration are generated by the passage of the vehicle itself. In particular the contact between the wheel and rail (or tyre and road) is the cause of the generation and propagation of forces and vibration in the surrounding environment.

HIC is an index about the safety characteristics of floor coverings in playgrounds, according to the suitability of the materials to absorb an accidental impact (a kid in free fall). HIC stands for Head Injury Criterion and it is connected to the Critic Fall Height (the critical fall height is the height in meters wich gives an HIC value during test of 1000).

The prediction of sound insulation in site takes into account the flanking transmission of the structures because of the rigid junctions and connections among the different structural elements, but it does not consider all the particular conditions that can be found during the construction. The installation of electric equipment, for example, can be the cause of a loss in the acoustic insulation, that will be different depending on the base structure, the accuracy of installation and the equipment itself. For example on a light wall made of gypsumboards, the losses from the electrical equipment can be up to 2-4 dB (on the single rating index); the water storage for toilets installed in the wall can reduce locally the thickness of the wall; the pipes can propagate noise between two different dwellings, in the case that they are connected rigidly to the structures in which they are applied.

Technical topics.

The acoustic enhancement of a building has to be planned at the beginning of the design phase. The compliance with the local regulations can be much more difficult and expensive, if acoustic design is done at the end of the building process. From a general point of view, a good design of the rooms position inside a building can help to avoid disturbance and fights between neighbors. For example rooms with the same function should be placed next to each other (a kitchen next to or below another kitchen, bedrooms next to bedrooms, livingrooms with livingrooms, toilets placed in the same column). The entrance doors of two adjacent dwellings should not be placed too close, to avoid direct noise transmission through them. It’s also good to include an impact sound insulation mat at the ground level, especially in those buildings with a multiple function with commercial units at the ground level and residential dwellings at the higher levels, to avoid flanking transmission of vibration and noise (for example from shopping carts, lifts in supermarkets, …).

Isolgomma has a wide range of products for impact noise insulation of floors. Roll, Grei and Upgrei Lines are suitable for the most used floor types (concrete slab, beam and hollow block floors, predalles, CLTs, …). Depending on the acoustic performance of the base floor, products with a higher DLw should be used and for particular or difficult layouts, a specific design for the insulation layer can be developed..

An excellent insulation can be achieved even without demolishing the existing screeds, in the case of renovation. The Sylwood and Sylcer systems have been developed to be applied directly under wood or ceramic finishing. The products have to be installed according to the installation manual, using the suggested glues, where needed.

To reduce effectively the impact noise it is very important to improve the floors from top, with a floating floor, because the noise and vibration energy can be blocked directly at the source. An additional ceiling gives a great improvement in the ariborne sound insulation of the floor, increasing the apparent transmission loss, but there is less influence on the impact noise attenuation (approximately 5 dB of improvement in the impact sound reduction). The use of an additional hanged ceiling and a floating floor together gives very high values of insulation, for both impact and airborne sound insulation. An inclusive solution is based on the simultaneous insulation of the floor, walls and ceiling and this gives a remarkable sound insulation by realizing a “box in a box”, in which all the insulation elements are installed according to the correct instructions and methods (wall claddings separated from the base wall, ceiling installed with damped hangers, …).

When a room has to be used as a home recording studio, it is highly recommended that the insulation will be done on floor, walls, ceiling, windows and doors. To avoid sound and vibration transmission to adjacent rooms (for example on the other side of a wall), it is necessary to block not only the direct transmission through the partition, but also the flanking paths through the connected structures (the other three walls, the floor and the ceiling). Regarding the walls, products from the Trywall and Rewall Line provide and excellent increase in insulation in reduced thickness. For the floor, a floating floor on Megamat and Fybro bearings with an additional floating flooring using Sylwood and Sylcer provide a good attenuation of vibration from the most demanding instruments (double bass, drums, …). A well done ceiling made of a double gypsumboard and a filler of 10 cm Fybro will limit the transmission through the upper floor. A good design of these solutions allows people to live musical passion in the building’s spaces.

Having a lot of space to dedicate to the insulation is for sure an advantage, because more efficient techniques and solutions can be adopted, especially for the low frequency range. When space is a limit, some excellent results can be achieved with products from the Rewall Line. Depending on the chosen product and base wall, the sound insulation can be increased of 16 dB with only 5 cm cladding, installing the panels directly on the base wall, without additional structures.

Isolgomma Trywall is an insulation panel made of polyesther fiber and recycled rubber, used in the cavity of light structures (walls and claddings) Compared to a traditional panel made of mineral wool, it provides a better structural stability, an easier and healthier lay and a higher attenuation.

To soundproof an existing traditional brick wall, a cladding with metal structure with Isolgomma Trywall in the cavity and closed with a double gypsumboard can provide an increment in airborne sound insulation of about 20 dB. This solution takes approximately 8 cm of space (metal structure 50 mm thickness, double gypsumboard 2 x 12.5 mm, separation of the structure from the base wall approximately half centimeter). In the case of lack of space for the insulation layers, excellent results can be achieved with products for direct cladding in adherence, in particular with Rewall and Mustwall B lines.

Modern industrial technology uses powerful and sofisticated machinery wich can transmit forces in the surrounding environment when installed in the factory. These vibrations are generated by moving mechanisms of the machines or by the impacts of big masses (presses, power hammers, …); when no control is designed for these installations, the vibrations can cause damages to the buildings and disturbance to the people, especially to the exposed workers. Isolgomma offers a wide range of products for vibration control, the Megamat Line, made of recycled selected rubber granules glued with polyurethanic binder; Megamat products are produced in panels and they can be used to separate plinths and foundations from the ground. It is very important to choose the correct insulating system in the designing phase, before building the plinth, to get a sensible decrease of the transmitted vibration.

HVACs are very light machines, that can be installed both at ground level, but also on top of roofs in multy-story buildings. In the first case a floating slab with a Megamat layer can be used (or a system made of Megamat bearings and Fybro, to focus the load in single spots); the advantage of using the floating slab is a better stability, together with a better insulation. When it is suggested or necessary to limitate the weight, for example in the case of rooftop application with thin base floors, the product can be installed directly under the machine’s feet or under a lighter base made of steel beams.

To insulate the airborne noise emitted directly from a machine, it is necessary to build a soundproofing cabin. Megamat will be used at the base of the machine (under a floating slab or under the feet in bearings) to block the vibration transmission from the machine to the base floor, limitating also the propagation of vibration and noise to the adjacent rooms in the building.

For a correct installation of Megasafe safety flooring, it is necessary to cure the substrate according to the installation manual. Most common substrates can be made of asphalt, cement or gravel on compacted ground. In any case, the substrate must be clean and without bumps. In the case the product has to be installed on gravel (stones dimension 7 mm), the application has to be done without glue, while on a rigid substrate glu can be adopted.

Safety flooring mats are chosen primarily for their HIC value: the playground equipments have different geometry and height, for this reason the choice of the most suitable safety mat allows to fit each equipment, avoiding and limiting eventual damage from falls. The thicker the tile, the safer is the application (higher critical fall height). The safety flooring mats are produced in different colours (red, green grey) and dimensions and a lot of accessories can be chosen, to make the installation nicer and safer.

Sound insulation in buildings is a very important requirement, to obtain the fitness for use for a dwelling. Differently from the thermal insulation, acoustic insulation does not provide saving in the mantainance costs of a building, but increases quality of life and work and the privacy inside buildings, reducing the fights between neighbours. A good acoustic insulation allows to use domestic rooms with a different purpose than the primary design (for example a living room with a Home Cinema, or a cellar used as music studio).

Installation & support.

A floating screed has to be completely separated from the walls and side structures, to work properly. For this reason, at the edges of the room the special perimetral bands Isolgomma Profyle are installed and the mat is laid on the whole floor. The mats should be installed without overlappings (to avoid thickness variations in the screed), positioning the mats adjacently without leaving any gaps and sealing the junctions with the built-in adhesive overlapping band. As alternative to the application of the perimetral bands, the mat can be folded vertically, to match the design height of the final floor. The screed can be a traditional sand and cement, or either a self-levelling screed (for example anhydrate), with a density of approximately 2000 kg/m³. The perimetral band should be left uncut until the final application of the ceramic tiles or parquet, and the exceeding parts should be cut only before the application of the skirting, carefully avoiding to connect it rigidly to the floor: the application of a siliconic sealant in the gap between skirting and floor is suggested.

The products for the direct covering of walls, for example Isolgomma Line Rewall and Mustwall B, can be installed to an existing wall with a gypsum based glue (see the installation manual anfd the technical data sheets for more details) and long exapnsion bolts. Glue is applied in dots and curing time is reasonably fast. If applied on a ceiling, it is strongly suggested the use of a steel structure, with hangers correctly chosen (type and quantity).

Technical specifications can be found in the technical data sheets, that can be downloaded from the website without registration. Detailed laying procedures are reported briefly in the same technical data sheets, while the complete installation procedures are reported in the installation manual, with lot of pictures and practical suggestions.

Isolgomma is respresented locally by a net of distributors, that give an everyday support regarding technical and commercial requests. You can find our local distributor on the website at this link. For areas not covered by our network, contact Isolgomma directly at tecservice@isolgomma.com

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