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”.
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. Format of RTSP link is rtsp://root:password@IPaddress/axis-media/media.amp?audio=1&video=0.