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Engine 3D modelShip 3d modelBus 3d modelHVAC 3d modelConstruction vehicle 3dnoise barrier 3d modelAir plane 3d modelTrain 3d modelTram 3d model

Acustimet ECER118 approved!

Fire retardent sound absorber #1

We would like to show you why!


Like foam

But better!

Acustimet is easy!

No need for foams

Acustimet® is our innovative microperforated panel in all-metal and no fibres. Since we first developed the product in our labs 20 years ago, we have made continuous improvements to the material as well as its applications. Acustimet® is especially well-suited for high temperatures and fire resistant applications.


Acustimet fire retardant sound absorber sample
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“We changed from using rockwool to Acustimet and the result was amazing. The best part is no more dust and itchy fibers in our products.”

“Acustimet is a really easy sound absorber to use and design with. Applications where we could not use traditional foams because of high heat and liquids we used Acustimer sound absorber. It does not burn and does not absorb liquids! ”


sustainable alternative used by many.

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Acustimet fire retardant sound absorber


Check out costumers that use Acustimet sound absorber. Buses, trains and much more coming soon.

More info

See data sheet for Acustimet sound absorber and charts. Click button below and read more about Acustimet.


Noise problems are often hard and very complex to solve. Contact us and let our experts in sound proofing help you out.

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Microperforated panels as fire retardant sound absorber

Micro perforated panels are becoming a vital tool in the acoustician’s battle to reduce noise emissions. The basic concept has now been expanded to cover more applications.

The world of micro perforated panels (MPP) for sound absorption has started to occupy the thoughts of acousticians over the past 10 years. For a while, perforated metal panels with holes in the 1-10 mm range have been used as a cage for sound-absorbing glass- fiber bats where large holes let the sound waves reach into the absorbent fiber.

Acustimet a fire retardant sound absorber.
Acustimet mounted on the hinged part of the engine hood.

Another use has been the creation of narrowband Helmholtz absorbers which can be tuned by hole size and the dimensions of hole distance and air gap behind the panel.

However, when the hole dimensions are in the region of 0.05-0.5mm, it proves that narrow absorption peaks become much wider,making the additional fiber absorber more or less unnecessary, while still maintaining a very high absorption factor. By varying geometrical and material parameters, the acoustical performance can be tailored to meet a multitude of specifications in various applications.
In general, the three acoustical/material interaction phenomena’s of reflection, absorption and transmission can be optimized in relation to the acoustical field near the sound source and further away in the far field. Put simply, the holes in the walls are utilized to dissipate the vibration energy into friction heat.

Applications for engine compartments

Acustimet fire retardant sound absorber, is an all-metal sound-absorbing panel for lining the interiors of engine enclosures and hoods in tractors, construction equipment, trucks, buses, gen sets, boats and robot systems.

The level of absorption can be calculated using the theory for resistive sheet absorbers. Therefore, the most important parameters are:
• Flow resistance of the resistive sheet.
• Distance of resistive sheet from back wall, i.e. size of air-gap.
• Sound field and reaction characteristics.
• Mass of the resistive sheet.

Acustimet fire retardant soudn absorber close up
Acustimet fire retardant sound absorber zoomed in.

The Acustimet material, a fire retardant sound absorber, is normally mounted at 30-50mm distance from the engine compartment walls, as can be seen in Figures 1 & 2. The absorption factor calculated for a 50mm air-gap application is shown in Figure 3(?) The first step is to adjust and optimize the resistive sheet flow resistance for each
application. The effect of too much flow resistance, which gives rather poor dissipative effects can be seen in the graph. The next step is to optimize the distance – if the air gap between the resistive sheet and the wall is increased, then the curves are shifted towards lower frequencies and vice versa.
The decrease of absorption factor for higher frequencies is an effect of the distance from the wall
being similar to multiples of λ /2, giving air particle velocity equal to zero for the corresponding frequencies. Optimization of the air-gap is therefore required for each specific application or sound
spectrum. The λ /2 problem can be eliminated by using two sheets of Acustimet fire retardant sound absorber.

The final step involves non-local reaction treatment. As can be seen, the low- and mid-frequency region is also affected by the type of reaction. Non-local reaction can be avoided by increasing the
absorption inside the air cavity between the resistive sheet and the back wall as well as by forming the resistive sheet surface. The effect of increased absorption in the air-cavity is shown in DIAGRAM pic.
Since 1997, Volvo and Scania have been pioneers in using these panels for lining engine compartments. EU directives on the flammability of materials used near engines for many years demands that these materials do not act as wicks to absorb fuels and oils.

The whole text with figures and images “Microperforated panels as fire retardant sound absorber” can be read here in pdf.

Acustimet sound absorber compared to foam and rockwool

Good sound absorptionYESYESYES
Fire retardantYES Only special foams YES
Recycable 100% YES NONO
Oil resistant YES Only special foams NO
UV resistant YES Only special foams NO
ECE r118 annex 8 approved YES Only special foamsYES

How to mount fire retardant sound absorber Acustimet

Acustimet, a fire retardant sound absorber is mounted mechanical with screws. It works just like a foam so you can always substitute your foam sound absorber with Acustimet fire retardant sound absorber . There are several advantages why you should use our fire retardant sound absorber Acustimet. See our compression table for different sound absorbers compared to our ECE R118 approved f fire retardant sound absorber.

Scania bus with acustimet panels for sound absorbing noise
Fire retardant sound absorber for Scania engine hood.

Fire retardant sound absorber Acustimet mounted on a bus engine compartment. Advantages is to have a fire retardant sound absorber which is oil/petrol resistant. Acustimet fire retardant sound absorber is ECE r118 annex 8 & 9 approved. Acustimet is also 100% recyclable and fiber free.

Volvo bus with acustimet close up
Fire retardant sound absorber inside engine compartment, Volvo bus.

Fire retardant sound absorber Acustimet mounted in a Volvo bus. The fire retardant sound absorber is placed inside the hood instead of foam absorber. Acustimet absorbs noise and helps to create a cool climate by letting air pass through sealing.

Acustimet fire retardant sound absorber on walls in production factory.
Fire retardant sound absorber wall mounted with different colors in production factory.

Fire retardant sound absorber Acustimet mounted on the wall inside factory. Acustimet can be produced with any color of choice. The wall mounted panels are also placed on the factory sealing. Acustimet fire retardant sound absorber is easy to clean and withstands liquid and chemicals.