Originally Posted by TallMinnesota
Unfortunately this product does not read the sound through a sheet of sheetrock.
Stud detectors are actually a kind of metal detector. While they work best with ferrous metals, their inductive operating principle can work with metal wires that are not even hooked up.
Devices like the one I mentioned can sometimes pick up the signal injected into the wire by means of capacitance to their probe tip.
Unless you know that wires were orphaned in the walls, it is highly probable that both ends are exposed someplace.
The telephone and cable guys use tools like the one I pointed out.