We have tested the first AXIS camera P3235-LVE with a digital microphone and the result is simply amazing. Noise is virtually non-existent. To achieve this, you'll also need a T8355 Axis digital microphone and set your input to “Ring-powered digital input 12V”.
Other cameras with digital audio: P3235-LV, P1375, P1375-E, P3245-LV/-LVE
For cameras without digital audio input, we have had a very good experience with the Behringer MIC800, which removes all unwanted noise.
With any camera you can connect audio via RTSP link from network audio bridge C8033 / C8110. Format of RTSP link is rtsp://root:password@IPaddress/axis-media/media.amp?audio=1&video=0.