External audio can be sourced from your Audio Equipped Axis camera.
In addition if your cam does not support audio capabilities and you wish to capture Live Audio there exists 3 options.
1-Via an Axis I/O audio module:
The C8033 Audio Bridge and the P8221 Audio Module.
The P8221 audio module is not supported at this time.
If you require standalone microphones to plug into these units please see the axis Product link:
Please note that the Axis T6112 audio I/O interface can only be used via plugin into an Axis cam that has the audio input option. The audio source would then be derived from the cam the T6112 unit is plugged into. But this unit is not compatible with all Axis cams.
Here is the list of compatible cams for Axis T6112audio module:
3- Deskcamera - create audio only stream and transmit Mic to RTSP