Acoustical improvements in Kulturhuset Oceanen using slitted low frequency absorbers

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The task was to improve the acoustic properties in the concert hall at Kulturhuset Oceanen. Measurements showed that the main problem was related to resonance frequencies around 70 and 110 Hz. There was also a peak at 40 Hz, but since the P.A. system does not excite such low frequencies, it was left without any consideration. The other two strong peaks were treated with slitted Helmholtz absorbers. The actual project did not include mounting of the full-scale absorbers; instead a prototype was constructed and built for experimentation and measurements in a reverberation chamber at Chalmers.The measurements showed that the absorber worked very well within the targeted frequency range, that is around 70 to 110 Hz. Since the absorber is mainly consisting of wood, it will also have higher absorption coefficients in the high frequency region, compared to the concrete walls that now are exposed in the concert hall. This implies that there will be a reduction of the reverberation times in the upper frequencies as well. Measurements on the prototype, together with simulations in...