Doc tweaked the field strength. Pretty much eliminated the hand/finger twitch.
45+ minutes is a long time to sit still and do nothing, waiting for the woodpecker's return. 10 Hz, in 4 sec bursts, then 35-40 sec of nothing.
The repeated tapping sensation feels like the kind of thing which could give one a headache. Fortunately, no headaches have been forthcoming, nor bruising or scalp sensitivity.