DOAs
Estimating the directions of arrival of a direct source signal, and enhancing the signal components coming from the source direction by controlling the directivity of the microphone array.
For satisfactory dereverberation results, this technique requires a relatively large number of microphones in order to obtain sufficient directivity gain.
inverse filtering
Find the inverse filter of the room that caused the reverberation and deconvolve the captured signal with the estimated inverse filter to recover the original signal.
This approach will work when the room transfer functions from the source to the microphones are given. The number of microphones is more than the number of active source signals.
New approach in paper 2008 (Blind Dereverberation)
The approach in which the concept of inverse filtering is relaxed to dereverberation filtering and no prior knowledge of RTFs is mathematically required.
p.s. Inverse filter is replaced by a filter that effectively reduces the energy of the reverberant components so as to make signal more like nonreverberant speech in a probabilistic sense.
