Small enclosures show a bumpy transmission for sound at low frequencies regardless of their geometry. If the eigenfrequencies of the room are excited without damping the result is a change of timbre and rumbling of the room. The Fraunhofer IBP has tackled this problem and developed the compound baffel absorber (CBA) as an easy-to-handle bass absorber  for various applications in representative building projects [2,3].
In studios, conference rooms, offices, music rehearsal chambers etc. the acoustic problems of small rooms lead to distortions of music as well as poor intelligibility of speech. The CBA-modules are easy to install in a do-it-yourself manner and yield a clear improvement of the acoustic conditions at low frequencies; resonances of the room are smoothed, the booming is eliminated and communication is eased. The modules will help to bring modern, state-of-the-art acoustic technology into practice. They supply the experienced practitioner with an effective tool at a reasonable prize for improving the acoustic response of a room.
 Performance and layout of compound-baffle-resonators. Zeitschrift für Lärmbekämpfung 43 (1996), H. 1, S. 1-8.
 On the acoustics of office and conference rooms. Bauphysik 19 (1997), H. 4, S. 105-112.
 Room and building acoustic design of a multi-channel listening room. Rundfunktech. Mitt. 40(1996), H. 2, S. 49-57.
 Measurement of an effective absorption coefficient in small rooms. Rundfunktech. Mitt. 40 (1996), H. 3, S. 77- 83.
Our industrial partners:
Renz GmbH, Aidlingen - http://www.renz-akustik.de
M. FAIST Anlagenbau GmbH, Krumbach - http://www.faist.de