If you do a search, you'll find that there have been several threads on this topic recently. In terms of what it is called, you want to provide sound attenuation. You would never "sound proof" your house. It would be ridiculously expensive (if you could even manage it), and it would be very uncomfortable. I am an audiologist (although I no longer practice), and I find that being in a "real" sound proof room is a very weird feeling. Almost suffocating... So, what you would be looking for is a product that would help to decrease the transmission of sound between rooms. You need to determine what dB level of noise transmission would be acceptable to you and from there you can begin to plan the products and strategies to make it happen. You can work with an acoustical engineer to come up with the correct formulas, but you will need to take into account multiple factors, including but not limited to flooring materials, ceiling heights, room sizes, etc. Most homeowners never go into that level of detail...it certainly does not sound from your posting that you would very much attenuation. One very easy fix is to use carpet upstairs rather than a hardwood...much quieter.

Pb Scot is correct Soundproofing is difficult esp in your situation. That said there are products that certainly can do a very good job - If you are re-flooring or have new construction I would rec looking into Mass loaded vinyl 1/8" heavy -goes on like rolled flooring under your finish floor. Below is a website that I used when I was looking into soundproofing during our renovation 3 yrs ago. We have a 1930 home that is plaster & lost quite a bit of plaster, which has an excellent sound proofing quality. The folks here are helpful & knowledgeable - I took my time to understand the science of soundproofing as much as I could before purchasing anything. I also have a bro in law that is a master carpenter and built many of the Sony studios in Manhattan - He used multiple layers of sheetrock (differing widths, and staggering joints) Good luck - quietness is something I'm willing to go an extra mile for ! Here is a link that might be useful: SOundproofing.org

I hear or notice the noise way less now, but still hear it from time to time when walking over an area for the first time. We have a couple of seams that have a small gap forming. As others have pointed out and i have come to learn, the problems that we have with the floors are caused by the unevern (not flat) subfloor. So, from that perspective, i cant blame flooret. However, most people that are buying these vinyl floors are doing so for the advertised ”value” and installing them in extisting homes. When you consider the time and expense to make old subfloors PERFECTLY flat, they are no longer a good value. That is my biggest complaint at this point; they drastically under communicate the amount of time and money required to achieve the desired outcome. To those of you who installed these Flooret floors, im sorry and hang in there. The noise and /or your attention to it will improve greatly over time.

Cork underlay with 3mm or 6mm = awesome sound deadening properties. It can be used with a glue down install or a floating wood floor install. Do NOT nail through. QuietWalk has the ability to be NAILED down. This is SUPER important if you are looking at a nail-in-place hardwood. Yes acoustic underlayments are 'expensive'. The acoustic value is HARD to achieve. It takes TONS of engineering to get it right. Quietwalk, once pierced should become a vapour retarder = acceptable over wood. I know it 'feels' expensive ($1/sf = $1400 more) but NEVER go cheap on flooring. Ever. The biggest complaints people have with wood floors on a second floor = noise transfer from up-to-down. And the second biggest complain = noise transfer down hallways and underneath doors. If I told you, for a mere $1400, you could get rid of BOTH issues would you think it a great insurance plan? Probably. I counsel my clients to think of their floors as if they were a roof. How much did you spend on the roof? Did you go cheap with the insulation or the water protection (eaves, downspouts, etc)? Probably not. A floor INSIDE takes the SAME ABUSE as a roof on the outside. It is the SINGLE MOST abused 'finish' in your home. Everything touches the floors. Gravity means anything that goes up must come down...and when it comes down it makes noise. A good acoustic insulation will make you happier than a floor without. Go ahead and get people to turn on a stereo upstairs on the wooden subfloor. Now get them to talk on their phones or talk to one another in the same room (as the stereo). Stand down stairs and see how much you can hear. Now move to a room on the same LEVEL as the stereo and close the door. How much do you hear? A wooden subfloor has roughly the same acoustic value as wooden floors. What you hear today is what you can expect to hear TOMORROW. How happy will you be with that level of noise transfer? Roughly 90% of people can't stand it. The other 10% couldn't care less. The question becomes are you part of the 90% (I know I am) or are you in the 10% camp?