I am in the middle of finishing in that other chatroom where you appeared, so I have to finish there, then read your question, then I can come back here. So you will need to wait a few minutes for me...
To improve the question, you would need to show how it is not an XY-problem i.e. explain the application, explain why you need the shielding, explain why you need that amount of reduction (40 dB in the title, 30 dB in the text). It is a very specialist area, and those few people who might be able to help, will likely not want to spend time on it unless they are sure that their time is "well spent" on the correct solution.
You would likely do better if you started by explaining the problem instead of asking about your solution, as you did. That will always ring alarm bells as a potential XY-problem, and those can be huge wastes of time (I'm not saying that yours is, I'm just pointing out that many of us have experienced it and want to avoid solving the wrong problem).
@galmeida No, I don't know specific users who have (a) the skills, (b) the time, and (c) the desire, to help clarify the question :-(
I see. The problem is that nobody would believe if I pointed the problem I'm trying to solve. Peope are in denial that Electromagnetic hypersensitivy and microwave syndrome exists, and I cannot proof here it does (but it does), and I'm not sure about all possible bands that could have some effects - I'm pretty sure microwave does, but people are talking about ELF on the internet
I understand your situation. Unfortunately starting with a solution and asking specifically for that as you did, is often likely to get a poor reception, due to people wanting to avoid the XY-problem time-sinks :-(
And if the problem itself is not likely to get a good reception either, as you kindly explained, then I don't know how to proceed - for free.
The only option which comes to mind, is to get people's time and expertise, even if they think it could be a waste of their time, by paying them i.e. engage a consultant.
Unfortunately I cannot do the research for you to choose a suitable consultant. You could try asking in the main chatroom.
@galmeida - I wish you good luck, however I have given as much advice on this as I can. So, unless you have any final points, I'll close this chatroom shortly. Thanks.