Many computer devices use automatic speech recognition (recognition of the words and the definition of the words being spoken) and speaker recognition (recognition of the speaker) such as on smartphones, tablets, automobile audio systems, smart houses and so forth. Thus, receiving a clear audio signal on these systems is very important. One or more microphones may be used on a device with an audio system to receive the acoustic waves from a person speaking. The microphone(s) then receive both direct sound waves and reverberated sound waves that reflect off of nearby walls and objects in an area with both the sound source and the receiving microphone(s). When the speaker is holding a phone to his/her ear to speak on the phone and so that the microphone(s) on the phone are within a mere couple of inches of the person's mouth, the interference from reverberation is usually insignificant. When a person, however, holds the phone relatively far away from his/her mouth such as when placed down on a counter or on no hands-mode within an automobile, the signal to noise ratio (SNR) and direct to reverberant ratio (DRR) can be very low such that operation of the applications that use the signal may provide low quality results.
Many systems perform dereverberation to remove the reverberations and make the speech signal clearer. The conventional dereverberation which treats reverberation as an independent interference, however, is often inadequate due to a failure to effectively consider the actual acoustic environment. The acoustic environment is affected by the objects forming the acoustic space, such as walls, and by spatial shading which is the position of objects in the acoustic environment that block an acoustic transmission path from source to microphone. The acoustic environment also may be considered to include physical (such as position) and frequency response variations of the microphone and non-uniform reverberation fields.