How to Soundproof a Door Easily : howto

Hi fellas

Here’s the problem:

I live in a studio where sound insulation is pretty good. However, the entrance door that leads to the hallway, for some reason, has a very poor sound insulation. When someone is speaking in front of my studio, I can hear them just as if the door was open. I don’t know why is that so, maybe because when the door is closed it doesn’t make a good seal. I’m looking for a way to insulate the door but I cannot do heavy work, like drilling holes inside of it or something because it’s university housing. I was thinking about putting some kind of foam around the frame so that the seal is better when the door is closed, but I don’t know what material to use.

Thanks!

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