Akustische Aufwertung von Räumen durch Breitband-Absorption - Ein Beitrag zur Überarbeitung von DIN 18041

Acoustical revalorization of spaces by broadband absorption - A contribution to the revision of DIN 18041.

In a preceding contribution to this topic [1] the relevance of the low frequencies in room acoustics was discussed on the basis given by v. Békésy, Beranek, Skudrzyk, Reichardt, Fasold, Kuttruff, Lazarus, Genuit and others. In conjunction with an up-to-date opinion of a linguistics expert [2] the corresponding DIN working group has also come to the conclusion that "towards the lower frequencies a linear characteristic or even a decrease of the reverberation is advantageous". An increase of up to 50 % over the mid frequencies would, however, remain tolerable when the frequency-dependent tolerance according to Fig. 2 in DIN 18041:2004 were retained. A very remarkable investigation recently performed by the British Association of Teachers of the Deaf BATOD [3] confirms "the need to control the RT at low frequencies, at which many absorbers are less efficient", by extensive measurements and questioning of teachers and pupils in 9 differently conditioned classrooms of equal size and construction. In a press release [4], however, the inclusion of the 63 Hz octave is posted as an unnecessary extension of the frequency range. As the low frequencies are particularly devastating for the noise exposure in schools, the main points in [1], [2] are here discussed with reference to the fundamentals in [5]. Three current restoration examples will demonstrate how one may raise the value of spaces, acoustically 'unfit for purpose', by simple refit measures by means of novel broadband absorbers covering the entire relevant frequency range.