For the use of hearing aids in noisy environments, noise reduction or speech enhancement techniques are being investigated by many researchers. In this report, array signal-processing techniques and systems applicable to hearing aids, which are being developed by the authors, are introduced. A delay-and-sum beamformer, in which the microphone-array outputs are summed with appropriate delays and weights, can focus on a signal coming from a certain direction and can reduce environmental noise. Moreover, by scanning the beam by controlling the delays and the weights, the directions of the sound sources can also be known. By combining these techniques, a noise reduction system, which tracks the movement of a talker and suppresses the environmental noise, can be constructed. In this report, hardware equipped with two DSPs (TMS320C40), which realizes the above method, is introduced. Moreover, by extending the beamformer to stereo outputs, a listener can perceive the direction from which the sound is coming. In this report, simulation results of the stereo beamformer are also briefly described.