All earphones/headphones have small permanent magnets that creates SOUND.
It generates STATIC magnetic fields that goes upto 100 µT
For reference, Earth’s geomagnetic field varies from 25-65 µT
In-Ear monitors (IEMs) often have slightly stronger fields due to their packed design (small but strong magnets)
Large over-the-ear headphones with powerful drivers & bigger magnets have even higher localized static magnetic fields
BUT these fields drop off quickly with distance.
And that’s where Physics steps in.
Magnetic fields don’t spread like light, They fade much faster.
Instead of the Inverse Square Law you hear about with radiation, magnetic dipole (like a bar magnet or headphone driver) obey the inverse cube law (1/r³)
That means
2x the gap → field drops to 1/8th
3x the gap → fields drop to 1/27th of the intensity
So while over-ear headphones might have beefier magnets inside, their distance from your skull makes all the difference
This makes over-the-ear headphones better than in-ear
