De invloed van het orkest op de akoestiek van de podiumomgeving The influence of the orchestra on stage acoustics

Abstract

Abstract The available stage acoustic parameters measure the energy ratio between certain time intervals derived from an impulse response. The parameter time intervals may be based on typical sound paths on a stage. A study of typical sound paths and their time intervals indicates that a transition time point may exist between early reflected sound and late reflected sound at approximately 100 ms and that this transition time point is measured relative to the 'departure' of the sound from the sound source. However, the current choices for the time intervals in the available parameter formulas do not agree. There are two types of transition time points that reflect certain stage acoustical aspects related to a stage for a symphonic orchestra. The first is the transition time point between direct sound and reflected sound 'x' and the second is the transition time point between the early reflected sound and late reflected sound 'y'. The effect of the choice of transition time points is investigated for G x-y , G y-inf and LQ x-y from measured impulse responses. It is shown that the direct sound should be omitted to measure differences between halls and that different choices of time intervals do not result in large differences in the ranking of 7 concert hall stages. All parameters are commonly determined on an unoccupied (empty) stage, preferably with chairs and stands. In this paper, results of measurements on an occupied stage are presented which show large differences between empty and occupied stages. These measurements also indicate that a fixed time interval relative to the time of departure of the sound seems most appropriate