Resolution and Robustness of a Three-Microphone DOA System

Built a direction-of-arrival (DOA) system using three omnidirectional CMA-4544PF-W microphones arranged in an equilateral triangle. Each microphone is filtered, sampled by an MCP3201 12-bit ADC over SPI, and read by a Raspberry Pi using DMA before SFTP upload for offline analysis.

Direction estimates come from pairwise cross-correlation between channels: the lag that maximises each correlation gives the inter-microphone delay, and the three delays are combined into an angle of incidence. Systematic testing covered 0°, 90°, 110°, and 270°, with additional sweeps over microphone spacing, source distance, and background-noise conditions.

Average angular deviation was under 2° at most directions, with low standard deviation. The notable failure mode appeared at 270° and 300°, where both bias and variance jumped sharply, most likely from room reflections, finite angular resolution at small inter-mic spacing, and per-microphone gain or phase variation.