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.
Soundproof door panel.
Then seal the gaps with a door gasket door sweep or spray foam to prevent air leaks.
To soundproof a door install a curtain rod over the back of the door and get a heavy fabric drape to hang from the rod.
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.
You can also coat the door with sound absorbing paint which can reduce external noise by nearly 30.
These panels offer a step up from gluing a sheet of plywood to your door but they re not generally as expensive as high end solutions like fiberglass soundproofing blankets.
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.
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.
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.