I just moved to an older mansion, where the core stairwell connects each apartment. Overall it’s fairly soundproof except for the hollow steel door. I can basically hear everything in the stairwell, even in front of the building crystal clear. [pictured here](https://i.imgur.com/nDPTN2v.jpeg). It seems like a fairly typical door so I wondered if anyone else has advice for soundproofing it. I have added weather tape to the cracks but it made basically no difference, I feel that maybe most of the sound echoes straight through the hollow door.
by Telemachuss