A note on meaningful acoustical parameters for open-air theatres

The acoustics of performance spaces are usually characterized by the reverberation time and a handful other acoustical parameters defined in ISO 3382-1. However, these have been derived with closed mind, it is not obvious that same meaningful an open-air theatre. lack late reflections means decay curve often far from straight line, turn out to be unreliable. Also, use balance between early problematic when more or less absent. It necessary rethink need for instead sticking well-established meant concert halls. most important features theatre speech sufficiently loud clear, which can described strength clarity. In addition, avoid echoes, likely appear outdoor environment than room. Thus, there objective echo parameter. Acoustical vary strongly receiver position well suited global characterization space. For this purpose, parameter efficiency suggested; as ten times logarithm total sound energy impulse response relative direct sound. spatial average used comparison different theatres.