First of all make sure your Hikvision IP camera supports audio function: either by have a built-in mic (such as these cameras) or you can install an external one (read this article for more info). This article assumes that your microphone is functional and set up properly.
Step 1. Access the Hikvision IP cameras via your web browser (Internet Explorer or Mozilla Firefox). Go to Configuration > Video/Audio and set the video type to Video&Audio, and then go to the Audio tab to set audio input to LineIn. If needed, you may enable environmental noise filter. This feature will help you get a clearer audio feedback from the surroundings. It’s recommended to try it out before deploying, in some cases it gives a humming noise.
By default the audio is disabled on all IP cameras. Make sure you’re allowed to record audio, many state legislations won’t allow to record audio on public and sometimes even private properties. Talk to a lawyer just to make sure. You’ll be ok if you’re planning to record audio on your own house/dwelling.
Step 2. Go to Live View tab, enable the audio output by clicking the icon and adjust its volume.
Step 3. Connect the camera with a Hikvision NVR, and make sure its footages have been stored into the NVR.
Step 4. In the NVR’s web interface, go to Playback tab, enable the audio output by clicking the icon and adjust its volume.
Note: You may have audio live view and playback in iVMS client software as well (phone app or computer program). In all cases, make sure the volume on your monitor, computer or phone is not muted. This link shows a few Hikvsion IP cameras that come with the “audio-in” function.