How do I turn up the sound on my camera?

If you’re playing back through the camera and the camera has no speakers, then the response to your question is self-evident: no capability to reproduce sound.

This is what I’d expect from a replay through most cameras offered to the consumer market. You may get better results from a playback through the computer – if the computer has internal or external speakers hooked up to a graphics card or motherboard that can support them.

Yes, the video feature must be strictly for video. You bought the camera to take pictures, right?

On my Lumix there is a volume setting under menu/setup. I don’t know of a way to change the level during playback.