Some IP cameras allow you to play audio through them. Recent ones might be ONVIF compliant, but with old ones, you need to do it following their proprietary methods. Here are a few resources for that.
- “Sample code to decode and play audio on Windows,”
- “Interfacing FI8910W to Windows 8,” and
- Manual of the low level protocol in Chinese and its English translation.
These may be pertinent only to Foscam cameras, but many are their clones.