Using a spherical microphone array for stage acoustics: A preliminary case for a new spatial parameter

The acoustic conditions on stage for musicians are traditionally assessed with an omnidirectional receiver; however, with the use of a spherical microphone array the directionality of on-stage sound fields can be examined. This paper explores the issues around using such a microphone for stage acoustic measurements. As part of this study the 32-channel spherical microphone array Eigenmike has been used for acoustic measurements on-stage in six Australian auditoria; additionally, in four of these venues a traditional omnidirectional receiver was also used. This paper compares the results of standard omnidirectional parameters with the Eigenmike and omnidirectional receiver to assess the 189 validity of the omnidirectional parameters derived from measurements with the Eigenmike. For example, the stage acoustic parameters the ‘support measures’ deviate between the microphones by no more than 0.5 dB. Additionally, the paper explores redefining the standard acoustic parameters to consider directionality, and presents these results in comparison to subjective musician assessments. A new parameter is proposed that corresponds well with the preferences of musician playing in ensemble. This work is being completed as part of larger study examining stage acoustics for chamber orchestras, which has also included subjective musician surveys with the Australian Chamber Orchestra regarding the venues included in the objective acoustic study.