You heard that right.
Or, if you're reading this by pointing a surveillance camera at a monitor, you didn't hear that at all. Most surveillance cameras don't record sound. They're video only.
The conventional wisdom is that you don't need sound for surveillance, because you're really trying just to capture an image of someone stealing your stuff. In the past, most security systems only recorded a few frames per second of video so sound didn't make a lot of sense. Today's systems are a lot more powerful, often recording full motion video from multiple feeds. So why no sound?
I'm not saying you couldn't have sound if you wanted it, but it would take a security DVR that recorded sound feeds as well as a set of microphones. That means more wiring and that's a more expensive proposition. Security companies will probably come around to the idea that putting a five-cent microphone into their cameras will probably let them charge more, so personally I do expect this to change eventually. I just wouldn't wait around for it, because in the world of business, this isn't a priority. If you're looking for a way to spy on your kids or your coworkers in real time, a baby monitor
(also referred to as a nanny cam) is probably a better choice. We're being told that the next generation will probably include motion activated DVRs as well, although the recording capacity will probably be somewhat smaller.