Acoustic properties of sheep's wool felts
Properly processed sheep's wool knows Extremely good properties in acoustic room optimisation on.
- Sound waves of different frequencies are refracted in the 'felt layers and are therefore not reflected into the room but absorbed by the felt
- Sheep's wool felt is particularly effective at dampening low or particularly high-pitched sounds.
In addition to its acoustic properties, sheep's wool also has other outstanding characteristics
- Indoor air improver: Sheep's wool improves the indoor air as it filters sustainable pollutants. For example, the formaldehyde found in MDF boards
- Climate regulator: Sheep's wool regulates the room climate: the wool absorbs excess moisture in the room air and releases it again when the air is dry.
- Fire protection helpers: Sheep's wool has a very high flash point. The acoustic felts are therefore flame-retardant and hardly any smoke is produced in the event of a fire.
- Dirt repellent: Sheep's wool is naturally dirt-repellent and therefore a very grateful product in everyday life.
Building sound absorber panels
As the felt is wallpapered onto wooden panels to construct the acoustic absorbers, we recommend that you hire a specialist with the necessary expertise and tools to manufacture the absorbers.
Alternatively, the motivated and well-equipped DIY enthusiast can, of course, build their own acoustic panels with a few adjustments to the work process.
Our end result is acoustic panels with a Sound absorption coefficient of αw=0.85 (H).
Tools
- Circular saw or panels cut to size from the DIY store or carpenter
- Cutter knife and cutting bar
(for precise felt cutting) - Glue roller or large brush
(for applying the adhesive) - Tacker (compressed air or electric tacker at best)
- possibly scissors
- For the professional: Veneer press
Materials
- Blockboard or three-layer board, 18 mm
- Soft fibreboard 15mm
- White glue (PVAc glue)
- Acoustic sheep's wool felt
The quantity and dimensions depend on how many absorber panels you want to produce and in what size.
When producing larger acoustic panels, at least one other person should assist you when laying the acoustic felt (step 4) and when lifting and turning the panels.
Step 1: Prepare the wooden panels
As a basis for a stable construction, we recommend a Blockboard or three-layer board with a thickness of 18mm. For the top layer, use a Soft fibreboard in a thickness of 15mm. Together with the sheep's wool felt, this panel ensures that your end product achieves a sound absorption coefficient of αw=0.85 (H).
Join the two boards together by applying glue to the wooden board with a glue roller or brush. Low formaldehyde white glue (PVAc glue) and then place the soft fibreboard on top and press both boards together.
Without a press, you should wait about an hour before continuing to work so that the adhesive dries, takes effect and the two panels are well bonded.
Attention: When working with wood, make sure that no shavings get onto the felt surface, as these can adhere very stubbornly to the wool.
Step 2: Cut the felt to size
The rolls of felt supplied are 1-10 metres long, depending on the order. Before further processing, cut the acoustic felt to your desired size. Make sure that you fold the felt over once onto the back of the panel for fastening (step 6).
In our example, this is 33mm for the panel thickness and a further 7-10mm to fix the felt on the back with the stapler. In total, this is an increase of 40-45mm on the target dimension.
You can easily cut the felt using a good cutter with a sharp, sturdy blade and a cutting strip.
Step 3: Apply adhesive
Now prepare the surface with glue: To do this, apply white glue to the softwood panel again using a glue roller.
Make sure to spread the adhesive evenly so that the entire surface is covered with adhesive right up to the edges.
Step 4: Apply acoustic felt
Carefully place the acoustic felt on the side of the wooden panel that has been treated with glue. Smooth the felt by hand and make sure that there are no uneven areas.
White glue does not normally allow corrections. You can therefore still get rid of any unsightly creases or waves. It is best to pay attention to the open time indicated on the glue. This way you know exactly how much time you have until the glue becomes active.
Step 5: Pressing the felt and panels
For professionals: To achieve an optimum bond and continue working quickly, you must now place the panels with the felt in the press for approx. 5 minutes and press at 80 bar at approx. 62-70°.
For the do-it-yourselfer If you don't have a professional press to hand, you need to wait a little. Give the glue another hour or so to work optimally.
Step 6: Stapling the acoustic felt
Carefully turn the panel over and fold back the protruding acoustic felt. Secure the felt with the stapler and place the staples close together.
It's easy with a pneumatic or electric tacker. This saves both energy and time. If you are not afraid of using more muscle power, you can also use a hand tacker.
Make sure that the staples are high enough to penetrate the 9mm felt and sit firmly in the panel. Narrow back staples or fine wire staples with a depth of approx. 10-14mm are best.
Step 7: Cut off the excess
Last but not least, cut off the double-layered, protruding felt at the corners with scissors or a cutter knife. This prevents unevenness and makes assembly easier.
Mounting the acoustic absorbers
Mounted on feet:
If you want to use your sound absorbers free-standing, we recommend using feet. This means you can also use the modules as room dividers, for example, and remain flexible in terms of placement
Ceiling mounting with chain suspension:
The use as a ceiling canopy with wire holder allows an airy design and also enables you to regulate the room height. It also allows you to plan ceiling lights.
Installation with wall or ceiling mouldings: With our prefabricated Silentum acoustic panels, we work with wooden mounting strips. This allows the various modules to be positioned quite flexibly in some cases.
Depending on where you want to install your acoustic panels, you can choose from a variety of installation options. Make sure you always take the weight of the panels into account when choosing the installation method.
The Mounting directly on the wall is possible: recesses are milled into the back of the modules for this purpose. You can now hang your modules directly on the wall using normal wall plugs and screws, without the distance between the mounting strips.
Wall mounting, as we know it from hanging picture frames, is not ideal. Weight is also a major factor here. Even if you want to combine several modules to form an acoustic wall, alignment will be difficult with a wire suspension.
Conclusion
Acoustic absorbers made of sheep's wool felt are a stylish element in acoustic interior design. They serve as sound insulation and at the same time provide living space design. Pure new sheep's wool is also a Sustainable, high-quality natural product with many positive properties.
Sheep's wool felt is easy to work with and the acoustic panels are simple to install.
It is not without reason that acoustic felts and sound absorbers made of wool felt are often used in offices, healthcare facilities or public buildings such as nurseries and schools.
