Questions about decoding by single microphone or double microphone

We use the ADAU1761 evelopment toolkit for a decoding project, but we find some questions. We need your help.

Questionsdescription is as follows:

Background: we use the ADAu761 development toolkit for a decoding project, and now a single microphone access left sound channel, and the DSP program (see the attachment, is provided by the ADI).

Phenomenon: we use DSP on-line simulation, open left and right channels, found around a track has the sound, but a single microphone input to the left channel.

Question: A single microphone input to the left channel, why the right track has the sound? If double microphone, then open the left and right channel at the same time, both sides have sound, this problem is that single microphone and double microphone decoding is the same,what is the difference between single microphone and double microphone on decoding?

Ask for your help. I am anticipating your reply,thanks.

Audio Signal Processors

SigmaDSP Audio Processors

adau1761