I am trying to do speech recognition on an audio file which has 1 channel (mono). My problem is that the channel is comprised of the signal of 3 microphones which have captured the audio at different distances of a person speaking and the signals have been mixed into mono, which I suspect has added reverberation and noise into the audio, making it impossible for the ASR (automatic speech recognition) to recognize speech.
I am unable to obtain the original signals from each microphone so I need to know in which way I can clean the audio or revert the effect of the downmix.
I have already tried applying the Weighted Prediction Error (Nakatani et al, 2012) filter under the hypothesis that 2 of the 3 microphones would account for reverberation in the audio as the signal has its phase shifted (due to reverberation time) but had no improvements.
I do not have the transcriptions of the audios.
What can I do? I have no more ideas on how to continue.
EDIT: This is an example utterance of the audio file (WAV file, it is in spanish and intelligible for a person)
Yoshioka, Takuya, and Tomohiro Nakatani. "Generalization of multi-channel linear prediction methods for blind MIMO impulse response shortening." IEEE Transactions on Audio, Speech, and Language Processing 20.10 (2012): 2707-2720.