Room Acoustics Optimisation Using Virtual Microphone Arrays

Room acoustics optimisation in live sound environments using signal processing techniques has captivated the minds of audio enthusiasts and researchers alike for over half a century. From analogue filters in the 1950s, to modern research efforts such as room impulse response equalisation and adaptive sound field control, this subject has exploded to life. Controlling the sound field in a static acoustic space is complex due to the high number of system variables, such as reflections, speaker crosstalk, equipment-induced colouration, room modes, reverberation, diffraction and listener positioning. These challenges are further amplified by dynamic variables such as audience presence, environmental conditions and room occupancy changes, which continuously and unpredictably reshape the sound field. A primary objective of live sound reinforcement is to deliver uniform sound quality across the audience area. This is most critical at audience ear level, where tonal balance, clarity, and spatial imaging are most affected by variations in the sound field. While placing microphones at audience ear level positions could enable real-time monitoring, large-scale deployment is impractical due to audience interference. This study investigates the feasibility of using virtual microphones, derived from elevated microphone arrays, to monitor the sound field at listener head height and apply FIR-based room correction. Simulations show that a spherical array of 20 microphones provided the best signal reconstruction, in terms of virtual microphone array configuration. Three FIR design strategies were tested, including a single-point, a multi-point and a hybrid approach. For the hybrid approach, a spatial average of five virtual microphone signals was used to design the stereo pair of corrective FIR filters, which provided stable performance across multiple listener positions. While the single-point approach achieved the lowest error at a single location, the spatial average method performed better than the multi-point method in managing acoustic correction across a two-dimensional listening plane.