The audio port of the NVRx-7000, NVRx-7090, NVRx-7095, NVRx-7200 and NVRx-7250
NVR4-7000, NVR8-7090, NVR16-7090, NVR8-7095, NVR16-7095, NVR4-7200, NVR8-7200, NVR16-7200, NVR16-7250
The Audio Port of the NVR only provides intercom functionality. You can connect a microphone to it and you will be able to hear what is happening live on both the PC software and the phone app.
However, the NVR does not have any audio recording capability and it is not scheduled to be an added feature.