They can be made of metal and rubber or just rubber or soft foam and fabric the kind you choose will depend on the type of door you re dealing with.
Soundproofing tape door.
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.
Door insulation and soundproofing tape 2 rolls 3 4 inch wide x 3 8 inch thick foam draft gasket tape 10mm thick and black total 13 feet long 2 x 6 5 ft each 4 4 out of 5 stars 3 403 15 98 15.
Adhesive foam tape weather stripiping 50 1 2 inch wide x 1 16 inch thick black seal gasket for speaker door insulation soundproofing rattle 33 ft length 4 6 out of 5 stars 521 12 99 12.
Generally you should stick with the pillowy kind if you re soundproofing interior doors and rubber sweeps for exterior ones.
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.