1. In the camera web interface, go to Configuration - Video/Audio and set the video type to Video&Audio, and then go to Audio tab to set audio input to LineIn.
2. Go to Live View tab, enable the audio output by clicking the icon and adjust its volume.
3. Connect the camera with a NVR, and make sure its footages have been stored into the NVR.4. In the NVR web interface, go to Playback tab, enable the audio output by clicking sound icon and adjust its volume.
Audio should now have been activated.