Fail to separate sound signals by FastICA on real-world recording I have written a program to perform FastICA on a stereo WAV file using the code on Python MDP FastICA Example

With the audio examples I get very good results.

Then I try to do real world recording using two computer mono microphones connected to the stereo mic in of my pc by connecting mic 1 to L channel and mic 2 to R channel. I test by playing some music at the background while I am talking in a quiet room.

However, running FastICA does not separate the signals at all. Is it possible that the quality of microphones is too poor? Do I need to do anything to the recorded WAV file (16 bits, signed PCM, 44100Hz) before running FastICA?

You can download the recording here.
ICA in raw form is only suitable for use with phase synchronised observation mixtures. Using microphones as you have described will introduce a phase delay as pointed out by other posters. However this phase delay can be used to great avail. The best known algorithm that deals with stereo separation in the presence of delays is DUET. The links are broken but the references you are looking for are here >http://eleceng.ucd.ie/~srickard/bss.html. 

This is the paper you should look for > 
A. Jourjine, S. Rickard, and O. Yilmaz, Blind Separation of Disjoint Orthogonal Signals: Demixing N Sources from 2 Mixtures, IEEE Conference on Acoustics, Speech, and Signal Processing (ICASSP2000), Volume 5, Pages 2985-2988, Istanbul, Turkey, June 2000