Ecophon Acoustic Bulletin

During the Baltic-Nordic Acoustics Meeting in Gothenburg this November a workshop on classroom acoustics took place which I had the pleasure to organise. The workshop started with a presentation of four prepared papers. Among the papers, Nils-Åke Andersson presented the planning of an extensive study of the acoustics in classrooms initiated by Ecophon. In this project several classrooms are investigated both in Sweden, Norway, Denmark and Germany. A large amount of data will be collected. Different types of ceiling treatments are tested and subjective and objective evaluations of the classrooms are carried out. At the workshop I presented preliminary results from a listening test on speech recorded in some of the classrooms.
The last part of the workshop was devoted an open discussion. Acoustical conditions in open-plan premises for education were an item that many of the participants took an active interest in.
The presentations will be soon be presented here

Posted by Erling Nilsson at 12:44 PM | Permalink

In the beginning of November Ecophon sponsored and participated in BNAM at Chalmers Institute of Technology in Gothenburg on the west coast of Sweden. This was a 2-days event organized by the Swedish Acoustical Society (SAS) and the Scandinavian Vibration Society SVIB). About 250 persons participated, mainly from the Nordic countries. Presentations will soon be available at http://www.svib.se.
Ecophon presented 4 papers
- A reverberation time formula for rooms with ceiling treatment, by Erling Nilsson :Download file
- Speech privacy descriptors for offices - Do they work in Europe, by Pierre Chigot.
- Classroom acoustics. Systematic measurements, Nils-Åke Andersson. Download file
- Classroom acoustics. A listening test, by Erling Nilsson. Download file
One of the most interesting presentations was the key note speech from prof. Stig Arlinger from Linköping University in Sweden, with the title "Speech recognition in noise".
The day before BNAM an interesting symposium took place, "Man and Noise", organized by the Swedish noise network. Abstracts and powerpoint presentations from this symposium can be downloaded from the following link http://www.noisenetwork.org/bnam2006.htm
Next BNAM will take place 2008 in Reykjavik at Iceland.

Posted by Nils-Åke Andersson at 10:30 AM | Permalink

As a complement to an acoustic ceiling it is sometimes useful to attach absorbing panels to the walls. This could be the case when a disturbing flutter echo is present or expected and gives an unpleasant coloration to the sound. Another situation is when the amount of sound diffusing objects is small, resulting in long reverberation times. A sometimes ignored fact is that the main complaint in many public premises for education and child-minding is the high noise levels. In these cases it is not enough to only consider that a certain reverberation time is achieved. Different acoustical treatment can give similar reverberation time but significant differences concerning the ability of reducing the disturbing noise. Concerning noise levels in rooms and it's relation to the absorption it is mainly the amount of absorption that is of importance. This relation is not true for the reverberation time. Thus, wall absorbers are an excellent tool to create good and pleasant acoustical environments. Attaching the wall absorbers in a non-regular pattern could also be a benefit since this will increase the sound diffusion in the rooms which is desirable and good for the acoustics.

More information about wall absorbers? Continue here

Posted by Erling Nilsson at 1:31 PM | Permalink

In the latest issue of Acta Acoustica united with Acustica, Eddy Gerritsen (TNO) discusses engineering methods for the prediction of reverberation time and sound pressure levels in spaces with non-diffuse conditions. The assumptions and theoretical considerations behind the formulas in EN 12354-6 annex D are clarified.

There is definitely a need for engineering models to estimate reverberation time and sound levels in this large group of rooms where the acoustical treatment consist of an absorbent ceiling. The discrepancy between Sabine calculations and measurements in e.g. classrooms, offices, day-care centres among others, are well documented. So, if you are interested in this matter I recommend you to read the article.
The abstract is available here.

Posted by Erling Nilsson at 2:24 PM | Permalink