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SOFSCI Sounds Of Science Päike conference room with sound absorbers

Image taken at the Skype office in Tallinn, showing nine Zpeech panels with a total area of 167*167 cm, with a very typical "Skype design", in a conference room. These nine panels on one wall alone proved enough to lower the reverberation time with 40% on reverberations from 260 Hertz and upwards. In other words: Excellent improvement when it comes to dealing with reverberations coming from a meeting and thus creating a much nicer acoustic environment for both face to face meetings and Skype calls.
(Päike means sun in Estonian)

 

Sounds Of Science - SOFSCI - Voice Energy

A conference room is designed for two acoustic purposes

 

•  Confine sound within the walls so people on the outside cannot hear what is said inside.
•  Create a good environment for conversations, both those made within and those made through a speakerphone or similar.


This means that the walls are thick and rigid – not letting much sound through and thus the sound is trapped inside in the form of echoes or reverberations. These echoes pollute the acoustic environment on the inside and must therefore be eliminated – something which is best done by sound absorption. Since the conversation that created these echoes consists of both high and low frequencies then the echoes also consists of both high and low frequencies. Because of this both high and low frequencies alike need to be removed, or absorbed, and preferably equally much of each.


Aim for having at least 15% of the wall surface covered with panels for the best result (if there are no other acoustic improvements). The best way is to either have them on all walls or on two walls out of four - this way there is no room for echoes to bounce back and forth.
  
The human voice has a range of between 300 and 3000 Hz, therefore we need sound absorbers that are effective within these ranges. And especially in the lower range for this is where the most energy is.
As you can see in this graph (click on it for larger image) the most energy in the human voice is actually around 300 Hz, which is quite low.
Most products aimed for conference rooms, open offices and similar are fairly ineffective on the lower part of the voice bandwidth and thus they only manage to absorb the higher parts: leaving the user with a bad acoustic environment.  The absorbers should be placed in such a way that the primary echoes are the first points of attack. That is, they should be placed on the walls and in the ceiling.