After applying Soundproofing Sealant to the corners and top, inside the room, The 3x3 room becomes echoing and ringy and when i close the DIY thick door the sound leakage is much greater then before.
Seems to me that until now the sound had a place where to run in the corners and top to the Roxul Insulation, and be absorbed.
However now the sound can't run so it leaks through the door' WeatherProofing foam seal.
SomethIng to consider is that In my expirence the quieter the space the more distinctive the remaining sounds become. A noisey room can be just so much white noise, in a quiet room the air rushing through a duct can be irritating. just like me blowing an answer out my $ss.
Don't confuse soundproofing with acoustic treatment. You ahould put absorbers and diffusers and bass traps to deal with ringing, reverberation, bass moding, etc. First, get the room as quiet as you possibly can with soundproofing.
That foam is a draft stopping product if you are really serious you will want to get adjustable rubber seals like the zero mentioned, see soundproofingcompany.com Turn out the lights in the booth and shine a bright light around outside perimeter of the door to see if you have any gaps in your current setup. A Two person job.