1. A hearing assistance system for processing speech from a sound source, comprising: a microphone configured to receive an input sound and produce a microphone signal representative of the input sound, the input sound including the speech from the sound source; a processing circuit configured to process the microphone signal to produce an output signal, the processing circuit including a multichannel Wiener filter (MWF) and configured to approximately optimize the MWF for noise reduction and speech quality in the output sound using a priori spatial information about the sound source; and a receiver configured to produce an output sound including the speech using the output signal.