It's clear some disturbances must be measurable because as I walk around the room, the magnetic field measured by my smartphone constantly changes and since the

It's clear some disturbances must be measurable because as I walk around the room, the magnetic field measured by my smartphone constantly changes and since the magnetic field of the Earth is practically uniform over small distances, this must mean the disturbances come from my surroundings. However, when toggling some apparatuses in my room, nothing happened. My laptop doesn't have a hard drive though, but even only centimetres from it, no change was measurable. Neither did anything happen near my lamps or the AC/DC transformator. The only place I measured a difference (<10%) was on the stove (why yes I'll put my smartphone worth hundreds of euros on a hot stove). However, this faded into the background at a distance of about 10 cm.