Magnetic door gaskets only work on doors which are built into metal frames so they aren t a suitable method of soundproofing for most doors.
Soundproof door panel.
To soundproof a door make it structurally strong enough to block noise by replacing it with a solid core door or by adding mass loaded vinyl soundproof blankets and panels to the existing door.
They have a cut out for the door handle slits to fit around the hinges and velcro sewn onto the back for quick and easy installation.
If you are willing to change your doorframe to a metal one then this is a very effective door sealing method which will make a huge difference to the sound resistance of your door.
If adding many soundproofing elements to your door seems like too much work try adding an acoustic door panel.
You can also coat the door with sound absorbing paint which can reduce external noise by nearly 30.
Acoustic door blanket panels overlap the door and extend beyond the frame to prevent acoustical leaks.
Soundproofing doors is easier when you understand the acoustics involved.
While closed doors do a decent job shutting out the noise outside the room cracks between a door and its casing or threshold offer just enough space for some sound to filter in.