Microphone Array Feedback Suppression for Indoor Room Acoustics

The objective of this project was to use a standoff microphone array to suppress feedback for a microphone-loudspeaker system in an indoor environment. When the gain on the amplifying loudspeaker is too high, the sounds from the loudspeaker that are picked by the microphone keep being re-amplified until there is a loud squeal in a process called feedback. This limits the amount of gain that can be put on the microphone-loudspeaker system. In this project, minimum variance distortionless response (MVDR) beamforming was used to focus a microphone array on only the source and attenuate the sound from the loudspeaker, thereby suppressing the feedback loop. The maximum gain that could be applied to the loudspeaker without inducing feedback was measured experimentally for MVDR and compared to that of conventional beamforming and no beamforming. The experiments were performed on a system that processed the output of 4 microphones from an NIST MK3 array online in Java and output the processed signal to the loudspeaker. The results showed that MVDR allowed for a greater gain than both conventional beamforming and no beamforming.