Beamforming techniques combine signals from two or more hearing aid microphones with the aim of capturing sounds from a specific direction in space while suppressing unwanted signals coming from other directions. They are therefore most effective in combatting directional noise sources. Unlike classical fixed beamforming approaches, adaptive beamforming techniques build a model of the acoustic environment the hearing aid user is currently in. In this way, the location of unwanted background noise sources can automatically be found and be tracked, giving rise to an increased performance with respect to classical fixed solutions. The noise reduction schemes used in the most advanced state-of-the-art multi-microphone hearing aid and cochlear implant devices are based on adaptive beamforming.