From my prior comment: "Even a small nick in the insulation is supposed to change the impedance enough to create a detectable reflection." This is what I was t

From my prior comment: "Even a small nick in the insulation is supposed to change the impedance enough to create a detectable reflection." This is what I was told by the person who saw the demo. I believe them, because it'd just be a matter of sending an impulse (or sweeping a tone) and looking at all of the spikes in the impulse response.