Improving the acoustic working conditions for musicians in small spaces

In the acoustic consulting, testing, design and engineering work of the Fraunhofer-Institute of Building Physics (IBP) the low-frequency end of the noise spectra and the room acoustic conditioning has gained tremendous importance over the years. For solving the long-ranging noise pollution from e.g. exhaust stacks and chimneys, a series of low- frequency sound attenuators with minimum flow resistance were developed. Its first representative was a novel membrane absorber [Ackermann U., et al., Sound absorbers of a novel membrane construction. Applied Acoustics 1998;25:197-215]. Thanks to its slenderness and ruggedness it could also be employed for noise control and reverberation adjustment purposes in relatively narrow enclosures and harsh environments [Ver IL. Enclosures and wrappings. In: Harris C.M., editor. Handbook of acoustical measurements and noise control. New York: McGraw-Hill, 1991; Fuchs H.V., Hunecke J.] The room plays its part at low frequencies. Das Musikinstrument 1993;42:40-6 (in German). Meanwhile a new type of panel absorber has been optimized for both kinds of application. Its absorption efficiency at frequencies far below 100 Hz could be demonstrated and quantified by a special measuring procedure based on the reverberation of a small rectangular room at its eigenfrequencies (Zha X, et al. Measurements of an effective absorption coefficient below 100 Hz. Acoustics Bulletin 1999;24:5-10). With the aid of this novel tool it is now possible to qualify reverberation rooms and anechoic chambers for frequencies down to 63 and 31 Hz, respectively (Fuchs HV, et al. Qualifying freefield and reverberation rooms for frequencies below 100 Hz. Applied Acoustics 2000;59:303-22). In a companion paper in this same journal [4] [Fuchs H.V., et al.: Creating low-noise environments in communication rooms. Applied Acoustics (in print)] appropriate experience is reported in creating low-noise environments in multi-purpose rooms like offices, restaurants, foyers and seminars. A number of representative case studies (Drotleff H., et al.: Attractive acoustic design of multi-purpose halls. 1. Chinese-German Platform Innovative Acoustics 2000 (October, 21-25. 2000)) show ample evidence that the low-frequency performance of the rooms has a strong influence on both the amplification of intruding external noise and the development of internally generated noise emanating from communication processes provoked by the users themselves. At work places where producing sound (by voices or/and instruments) is the main or only purpose for their existence, the acoustic qualification of the room at low frequencies turns out to be of the utmost importance, especially when musicians are forced to work in extremely narrow spaces like orchestra pits and rehearsal halls for many hours a day and often under extreme physical and mental pressure. The measures taken and described herein have proven to mitigate if not remove some of the acoustic burden put on musicians employed in states theatres