There are multiple perturbations that can occur that will prevent a beamforming algorithm from reaching its theoretical performance. Synchronization issues in the audio codec and microphone ordering mismatches in audio driver firmware should not be one of them. During board bring up there are two tests that need be performed to verify microphone arrays performance before evaluating the beamforming algorithm.

The first test is a phase alignment test. The purpose of this test is to verify the audio codec(s) and the audio serial interface has properly synchronized all microphones. A tonal sound source should be played out of a loudspeaker perpendicular to the array, such that the sound source arrives at all microphones simultaneously. In software prior to the beamformer, capture the raw digital audio samples of each microphone. In audio editor program like Audacity, the samples can be reviewed to verify that microphone signals are indeed aligned.

phase alignment test verify microphone arraysmic order test verify microphone arrays

A second test is a microphone ordering test. The audio codec configuration registers can be configured to have the left or right audio channel to appear first. The purpose of this test is to verify the expected microphone order matches the observed order. Sound source should be placed in the endfire orientation to array, such that the sound source arrives at the microphones at different times. In software prior to the beamforming software, capture the raw digital audio samples of each microphone, and verify sample ordering in an audio editor.

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