Diffusers in small practice rooms; the effect of adding semi-cylinder diffusers in small practice rooms intended for music rehearsal

Abstract

This master’s thesis investigates the acoustical effects on the sound field of a small practice room when adding semi-cylinder diffusers. The study mainly seeks to deter mine whether general principles and applications for diffusers, proven to be effective in larger spaces, can be applied with satisfactory results to smaller rooms such as small practice rooms. A combination of subjective and objective investigations was performed to in vestigate this topic. The subjective investigations involved on-site evaluations by musicians, as well as a blind test where participants listened to binaural recordings of different combinations of diffuser setups. The objective investigations involved measurements of room acoustical parameters, as well as a binaural impulse response measurement to study early reflections. The findings suggest that semi-cylinder diffusers were not effective in removing coloration due to comb-filtering effects in a small practice room. While strong reflec tions were attenuated, and the number of reflections increased, the attenuation may not have been enough, and the introduced reflections might have been too strong, as a consequence of the small area of the practice room. This may have caused the fre quency response to exhibit an even more distinct comb-filtering pattern, indicating more coloration. However, the increase in coloration may be seen as minor as there were no indications that any coloration was heard by the participants. The findings suggest on the contrary that participants preferred the setups with more diffusers. However, this improvement may have been attributed to a lowering of the rever beration time, where the semi-cylinder diffusers were found to provide membrane absorption in the lower frequency region, and absorption in the higher frequency region from a lowering of the mean-free-path.