Thanks dude, well aware they’re looking for an AC signal. The added magnet isn’t going to influence that, is my point.

Besides limited magnetic permeability of the magnet itself (the thing the loop is looking for), it’s physically not big enough. What you really need is an amplified field distortion, e.g. a field coil which reads the sinusoidal signal being emanated by the sense coil, and loudly plays the inverse back so the sense coil thinks a giant block of steel slid over it.