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The myths of room acoustics


Foam under tables and chairs?

This myth has lasted for decades. In conventional rooms, unpleasant room acoustics arise from the first wall and ceiling reflections. In the floor area, the sound is mostly already partially absorbed and scattered by furniture and people. Attaching sound absorbers below tables and chairs has only minimal effects and is more likely to be described as pseudo-acoustics.


Clean the carpet and everything is fine?

Here it is similar to the sound absorbers under chairs and tables. the     disturbing wall and ceiling reflections are preserved. In addition, carpets (depending on the carpet thickness) absorb in a frequency range above 800Hz, with the unpleasant reverberation mostly occurring in the middle range. Pure treble absorption also sounds rather unnatural and not balanced. Carpets can be used as a support - professional room acoustics optimization is not conceivable with carpets alone.


Are A-absorbers always the best choice?

Unfortunately, in many cases the wrong sound absorber is used according to the motto "absorber is absorber". In order to be able to choose the right absorber, one has to understand which frequency ranges in the room are disturbing or in which   Frequency ranges the human voice behaves like. Porous high frequency absorbers (mostly class A absorbers) in lecture or conference rooms are rather counterproductive as they minimize the frequencies of speech intelligibility. On the other hand, the unpleasant reverberation in public rooms is usually between 150-800Hz and not> 1kHz. The correct choice of absorber should always be made with a view to the benefit, and the equally important position of the absorber in the room should be chosen.


Convoluted foam in recording rooms?

In many recording rooms or speaker booths, too many surfaces on the walls and ceiling are clad with convoluted foam. Foams have a very absorptive effect, especially in the high frequency range. As a result, rooms with too much foam sound rather dull in the upper frequency range and take away from the speaker the lack of presence and thus speech intelligibility of the voice.


Plants: acoustically effective or Feng Shui?

Basically, every material is acoustically effective. The only question is in what way? Each material has an absorption and a reflection factor in the different frequency ranges. With classic porous absorbers such as foams, curtains, etc., the sound energy is converted into heat through friction. How well a porous absorber works depends on the thickness, the length-related flow resistance and the structure of the absorber. Plants indicate by the very open       Arrangement of leaves, branches and styles or due to the coarse structure only minimal absorption.

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