Egan, you are absolutely right. The first thing one notices upon entering my music room is the quality of the silence. Not only are there no distracting noises, but the room has a positive quality of its own - sorry, but that’s the best description I can write. Could be as Tomic says, "the baseline noise floor of the room."
I would add that books and articles on acoustics often discuss H x W x D in terms of opinion and rumour instead of science. The only way, IMO, is to do very many computer simulations. Cox and D'Antonio at Salford have done all this - all the heavy lifting. I am just the beneficiary.
@tomic601 , I had the same experience at Quietrock. After talking with them I bit the bullet and paid the bucks. May your project prosper!