Favorable reverberation time in concert halls revisited for piano and violin solos

A favorable reverberation time in concert halls is a fundamental issue for room acoustic design, and various recommendations have been suggested so far. Nevertheless, one must track back more than half a century when it comes to systematic subjective experiments on this topic. In this study, binaural room impulse responses (RIRs) measured with a dodecahedral loudspeaker in concert halls, where orchestra concerts are regularly held, are used. First, signal processing is applied to RIR to equalize the dodecahedral loudspeaker response as flat and broad as possible within the audible frequency range. Then, anechoic recordings of music by piano and violin, excerpts from cadenzas, are convoluted with the equalized RIR. Next, subjective experiments are conducted to seek favorable reverberation times. Reverberance and clarity were judged by 16 music experts. From this research, the favorable reverberation times RT_M (octave band average for 500 and 1000 Hz) for piano and violin solos are from 1.2 to 2.0 s and 1.8 to 2.4 s, respectively. However, the clarity index C_80,3 (octave band average for 500, 1000, and 2000 Hz) needs to range from 0 to 2.4 dB and -1.6 to 0.7 dB, respectively, to meet the optimum reverberance for piano and violin.