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We think a lot. We have opinions. About architecture. About acoustics. And why a really good album hasn’t been released since December 1, 1973 – in other words, Black Sabbath’s fifth studio album. Sometimes it happens. The magic. Protests, songs of praise? Speak now or forever hold your peace.

Inflated NRC

12 March 2012 | Category: How does it really work, The incomparable Fellert humor, Interesting facts

A while ago our American colleagues went ballistic about the latest absorption data published by one of our competitors.

Why? -simply because the competitor had managed to manipulate the test specimen in a way that gave them approximately 0,2 extra NRC. A product with an NRC of 0,7 would then suddenly, like magic, have an NRC of 0,9.

How? – look at this flyer, made by our US colleagues (in fury):





















This is marketing at its best. There is nothing wrong in saying that they can achieve an NRC of 0,9 but what they forget to mention is that you can’t apply the product on larger surfaces than 72 sq ft which is approximately 7 m2.

A little bit like the tv – commercials about the latest detergents, isn’t it??

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Acoustics made easy-phase inverted anti noise

10 March 2012 | Category: How does it really work, Interesting facts

Have you heard that there are aircrafts that have microphones installed in the cabin recording the cabin noise and speakers playing this noise back in the cabin and that all this is done to reduce the noise in the cabin.

This technique is also used in more trivial things like earphones. I know that Sennheiser’s got a nice pair using this technique for instance.

You add noise to actually reduce noise – how is this possible?

Sound are often illustrated as a wave, we are talking about sound waves.

These waves have their tops and bottoms.In reality sound as well as noise for that matter, are not waves lurking around in the air surrounding us. Instead sound/noise are variations in the air pressure where a top of a sound wave actually is an increase of air pressure and a bottom of a sound wave is a decrease of air pressure.


This is then picked up my a membrane in the human which is moving back when it is hit by the higher air pressure and forth when it is exposed to the lower air pressure. The human brain then interpreters this as sound or noise.

For the brain to understand complete silence it must not get any signals at all from the membrane in the ear. This in turn means that the membrane must be completely still. No movements back and forth at all.

In order to get the membrane in the ear to stop moving there must be no variations at all in the air pressure. Zero variations in air pressure is actually equal to complete silence.

What we need to do then is to fill up the gaps, the bottom of the waves so they will have the same pressure as the tops.

This is what the microphones and speakers in the cabin are doing. They record the pattern of tops and bottoms of the cabin noise. Then they transmit an exact copy of this but they turn it upside down. Every time the cabin noise is at a top, the upside down copy is at a bottom and opposite.

This is not so far from what is going on, at a micro-level in sound absorbing materials such as Fellert. Of course there are no microphones and speakers installed inside the Fellert systems, but if you would look at the surface through a microscope you would see that there would be millions of pores where the differences in sound pressure can be leveled out.

More on how that actually works later.


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the State Mosque in Doha, Qatar

9 March 2012 | Category: Good Looks, Great Sound, Spiritual places, churches & temples

Everytime i see pictures from the State Mosque i keep getting amazed by the beautiful architecture and the attention to every detail. It is for sure a privilege to have been selected as a supplier to such a project.

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Summertime in Sweden

8 March 2012 | Category: Things happens

Just got an email from Fellert North America displaying the current standings of the sales competition Summertime in Sweden 2013. That made me think back on the previous competition Summertime in Sweden 2011.

We had one week of perfect weather and a lot of fun. Just look at this:

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Church Fátima Portugal

8 March 2012 | Category: Good Looks, Great Sound, Spiritual places, churches & temples

Not the biggest Fellert project, but nice design, especially the combinations of using both Fellert Ultra and Fellert Alpha on different sections of the ceiling.

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Bullet proof vest technology

8 March 2012 | Category: How does it really work, Interesting facts

Buildings tend to move a little bit as gravity and pressure does its work.Sometimes temperature variations and variations in humidity adds up to this as well. The solution to this is normally called expansion joint.

An expansion joint however is nothing you’d like to have in your design because of its fabulous look – on the contrary it’s often quite ugly.

The expansion joints needed to take care of the movements in the construction of the building are difficult to do anything about, but the expansion joints needed to take care of the internal stress in for example ceilings and walls are something completely different. They can be eliminated by the selection of which type of material to use.

Let’s use seamless acoustical ceilings as an example. Convenient as we happen to know quite a lot about them.

Most types of seamless acoustical ceilings have limitations due to the internal stress in the material. Normally these limitations are set to 150 – 200 m2 single sheet without having to start over with an expansion joint in between.

Fellert acoustical ceilings however, can be installed in single sheets 1000 m2 in size (sometimes even larger) without any need of expansion joints.

This is because of the extreme flexibility of the Fellert plaster, where the cotton fibers used in the plaster will act as reinforcement taking up a the shifitings and movements internally. We call it Bullet proof vest technology.

Follow the link below and watch this simple but yet revealing Youtube video clip. The sample is actually bent almost 45 degrees before it cracks!

Extremely flexible Fellert

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The Bloody Mary quality index

12 February 2012 | Category: The incomparable Fellert humor, Interesting facts

We would like to launch the unofficial “Bloody Mary quality index”. We use it to rate hotels all over the world.

The best Bloody Mary we have even been served, was served to us by the bartender at the Knickerbocker Hotel in Chicago, USA.
In addition to the traditional ingredients as tomato juice, Worchester sauce, lemon and Tabasco, he also added a slice of orange and a couple of olives.
We would like rate that with no less than 10 bald heads. Top score that is.


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The princess Noura Abdulraham university for women

3 February 2012 | Category: Offices, schools & libraries, Great Sound, Good Looks

The princess Noura Abdulraham university for women is the largest Fellert project so far with almost 40,000 m2 of Fellert Ultra installed. It was installed by Sinar for trading & contracting during 2010 – 2011.
here are some pictures from that project.

Please enjoy…








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Fellert University

30 January 2012 | Category: Things happens

Last week we had this years first Fellert training session with new Fellert contractors from Sweden and Denmark.


Nine new Fellert contractors graduated after three days of practical training.


Practical training is mandatory for anyone working with installing Fellert ceilings. This doesn’t automatically mean that it is especially difficult to do Fellert installations but there a few things one need to know and it helps us to keep good quality all through the process.

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The birth of Fellert

17 January 2012 | Category: History (if we were allowed to write it)

cotton is the base material of FellertEveryone who has been in an empty room knows about the hard, unfriendly atmosphere there. It is not just the fact that there is no furniture, but just as much that every sound made in that room sounds hard, unfriendly and uncomfortable.

Everyone who has experienced that has also been amazed by the difference once the room is filled with furniture, curtains, pillows, paintings and whatever you can think of. Is it still the same room you wonder?

What once was hostile and unfriendly is now warm and cosy. It has become a room where one can live and be comfortable.

Maybe it was this difference in atmosphere in combination with living in the heart of the Swedish textile industry that drew John Fellert to start experimenting with cotton-based plaster as a sound absorber 15 years ago. To make a long story short, cotton turned out to be the perfect material to use in more or less every aspect. It was organic, recycled and therefore environmentally friendly, stretchable and therefore strong and binding.

Regardless of how much we would like to be able to tell a story on how years of advance research and development performed by the most skilled scientists gave us the product we see today, we just can’t. The product of today is nothing but a coincidence, however an extremely fortunate one.

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