Abstract
In dynamic environments, fast-moving interferers can quickly traverse resolution cells, posing a challenge for the minimum variance distortionless response (MVDR) beamformer to accurately place notches in the direction of the interferers. One common solution is to create a wider notch at the interferer's location. The hybrid MVDR (HMVDR) beamformer offers a novel approach for creating implicit wide notches within the beampattern. The HMVDR beamformer generates serendipitous wide notches by factoring the beampattern into adaptive and fixed components. The adaptive component places the notches in the interferer direction for suppression and attenuates some of the background noise, while the fixed component attenuates the background white noise more. The HMVDR product beampattern allows us to allocate degrees of freedom (DoFs) separately between the adaptive part and the fixed components. However, the challenge for the HMVDR beamformer lies in determining the optimal allocation of the DoFs for the adaptive component to ensure adequate notches for the interferers in a dynamic environment. In practical scenarios, the number of moving interferers in a given environment is often unknown and can change over time. To address this issue, a universal beamformer is designed to dynamically adapt the distribution of DoFs between the adaptive and fixed components within the product beampattern. Our universal beamformer implements a performance-weighted blend across a competing set of beamformers. This ensures that the universal beamformer's per snapshot regret asymptotically approaches zero for any bounded energy input signal. In this work, the regret is the difference between the universal beamformer's loss and the loss of the best beamformer in the competing set. Here, the loss quantifies the performance of each beamformer in the set based on their array output powers for each received snapshot. The proposed universal beamformer, UHMVDR, rivals the performance of the best beamformer in a competing set by blending their array weights without any prior knowledge about the number of interferers in an environment. This paper evaluates the performance of the UHMVDR beamformer through simulations and microphone array experiments involving multiple interferers. Simulations and microphone array experiment results demonstrate that the UHMVDR beamformer significantly outperforms competing beamformers in terms of array output power and white noise gain.