I have a bit of a weird situation. I'm a hinge in an N-shape. One of my partners has a SEVERE phobia concerning overhearing other people have sex due to a childhood trauma situation in which he was severely abused for accidentally walking in on a parent partner. Simply overhearing what could possibly be sex or anything rhythmic etc is enough to make him literally suicidal (he has borderline personality disorder; anyone with BPD or with a partner with BPD can understand that a severe trigger can be incredibly dangerous and lead to days of chaos). This is NOT a poly/relationship problem, my partner is in EMDR and related therapies and everyone has good boundaries etc., but for the foreseeable future this trigger is not going to go away so the soundproofing needs to work VERY well. It is imperative that if we are to combine our households we need A soundproofing for all bedrooms, so that sound does not leak into common areas and so that his room can be a safe space in case he gets paranoid that he IS hearing sound leaking into a common area. Has anyone figured anything cheap out for this? We have heard that egg cartons can be used as wall-lining, but it seems like it would require a ridiculous number of them. We have also heard about foam, but I have not found a cheap enough source. I have looked things up on musician-related sites and forums, but this doesn't need to be such good soundproofing that you could host a rock concert in a room, just good enough that loud rough sex wouldn't get through (probably would have different frequencies as well). We currently have the highest-NMR-rated noise blocking headphones on the market and that is not good enough.