I have a home built circa 1960 (US). The original subfloor on the first floor is 5" tongue-and-groove planks that are at approximately a 45 degree angle to the joists (is there a name for that type of subfloor?). I don't know if they were originally installed wrong or have simply dried out and contracted over the years but the tongue-and-grooves no longer fit together in many places leaving a fairly weak floor with lots of gaps. On top of that is a classic red oak hardwood floor. It is in great shape but likewise does not quite fit seamlessly, particularly in colder, drier times.
At some point in the home's history, the basement was finished. The ceiling in the basement is a drop ceiling with 2'x4' tiles that I suspect are pretty much the cheapest that could be found at the time.
The floor has so many gaps that sound transfers between the first floor and basement as if there is almost no floor there at all. Someone talking or watching TV at a normal level in the basement transfers up to the first floor without much dampening at all. On top of this, I'm in a band and we practice in the basement so you can imagine how bad that gets for people in the rest of the house.
Tearing up the floors and replacing with a better subfloor like plywood isn't really an option due to the cost, disruption of life, and the fact that the oak layer is in great shape and looks great.
I am aware of things like sound reduction rated drop ceiling tiles, insulation, etc. but not sure what will actually be effective or if there are better approaches.
What's my best approach for damping the sound as much as possible without major renovations?