German Standard DIN 18041 “Acoustical quality in small to medium-sized rooms” includes a table called “Guideline values for the free ceiling and wall surface areas to be covered with sound absorbers as a multiple of the room basic area (…)”. The table Download file presents for different room types the amount of sound absorbers to be used depending on their sound absorption performance (expressed as αw).
I asked two questions to Bernd Kunzmann, Chairman of the DIN Technical Committee responsible for the writing of DIN 18041.
The answers confirm that reduction of sound pressure level is at least as important as reverberation time as a room acoustic descriptor.
What were the assumptions made regarding the recommended reverberation time in the mentioned rooms?
Since they represent rather different situations (size, furnishing, etc), one could assume that each room type has an optimal reverberation time. This optimal reverberation time can then be reached if the recommended amount of absorption is used.
Was the amount then calculated from EN 12354-6:2003 “Building acoustics – Estimation of acoustic performance of buildings from the performance of elements. Sound absorption in enclosed spaces”?
Your question concerns from our point of view exclusively rooms relevant for speech communication at short distances (rooms of category B). The specification of measures taking mostly reverberation time into account would be inadequate. The main goal is the increase of the sound absorption, needed for the reduction of the background noise level and for the reduction of the reverberation time. No assumptions have been made regarding values of reverberation time.
The reverberation time seems to be of secondary importance for the field of application. Main objective is the insertion of the required equivalent sound absorption area. Corresponding knowledge has been gathered based on measurements and calculations (approx. 3 dB). EN 12354-6 specifies a calculation model for determining the entire equivalent sound absorption area for the determination of the reverberation time. The calculation procedure is applicable to rooms of category A in sense of DIN 18041.
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