The inbuilt stereo microphones at the bottom of the Eee 901's screen are supposed to allow directional recording and noise cancellation. However, some setting somewhere, perhaps in the sound driver, appears to be inverted, such that the mic picks up sound very clearly on either side of the Eee, and nothing at all from directly in front. The two internal mics seem to be combined in such a way as to cancel sound from the middle, which is the opposite behaviour to that expected (cancelling surrounding sound, and picking up only the user's voice from the centre).
E.g. if I sit and talk to the Eee facing it directly, my voice is not captured (or rather, it is cancelled out by the stereo mic). As I move left and right, to about 45 degrees either side of straight-ahead, my voice becomes clear and is recorded perfectly well. Alternatively, placing a finger or blue-tac over one of the microphones will also cause the sound to be picked up correctly, as the noise cancellation cannot be performed.
Using Ubuntu 8.10 with the Array kernel (http://www.array.org).
Expected results: sounds occurring directly in front of the Eee's internal microphones should be captured, with surrounding sounds cancelled through the noise cancellation feature of the dual microphones.
Actual results: sounds occurring directly in front of the Eee are cancelled, with surrounding sounds at 45+ degrees from centre picked up instead.
Just speculating, as I don't know the mechanics of dual-mic noise cancellation, but is it possible that in some Eee PCs the physical location of the microphones is swapped, causing the inverted noise cancellation pattern? If so, could a basic kernel / ALSA update swap the microphones back in software?