These noises are a frustrating problem that some home owners are sensitive to and others are not. They are hard to repair because they move around with changes in temperature and humidity. They can sometimes be fixed (at least for a while) by crawling under the home with a wrench and tightening the lag bolts that hold the house to it’s metal frame. If the squeak is under a carpeted area you can try driving screws through the carpet and into the floor joists.
I have seen various kinds of metal supports that are designed to be placed between the floor joists under the home and then tightened against the floor boards. Putting them into place required LARGE holes in the belly of the home and I could never convince myself it would be worth it. Of course, if I had sensitive ears and the noise was driving me crazy… It might be a different story. In any case, I would try the simple things first.
Floorboard movement can be sensitive to where weight is located on the floor. You may be able to reduce the amount of noise by moving furniture around. This takes experimentation and may not be 100% effective. See if you can tell where the separate plywood panels are located, then try walking around on them to cause the noise. Notice where the feet of furniture are located in relation to the squeaky floors. Having a second person available to stand in different locations can be helpful too.
Locating the noisy boards is very useful for installing something like Squeak-Ender, carried by Magic Mobile Home Supply. The linked page has a large picture of the product which shows installation steps.