A note on the reverberance in unroofed spaces

The reverberation time in an enclosed space is denoted by the parameter of the sound energy decay rate in the time domain.It can be well represented the reverberance in a diffused sound field.But it is questionable for reverberance evaluation of an unroofed space such as a courtyard,with the absence of reflections from the top.Series of subjective comparison tests in our laboratory showed that the perceived reverberation might be also affected by the spatial situation,especially noticeable and unneglectable in an unroofed space.Therefore the conventional reverberation time based on monaural receiver is not adequate for describing the reverberance in a courtyard space.