Very common concern that sometimes causes people to sell and move. The problem can be divided up into two considerations:
#1 There is predominantly
airborne noise. TV, stereo, etc.
#2 There is predominantly
footfall (impact) noise.
These two scenarios require different solutions.
In situation #1 you would not prefer to introduce an underlayment. Doing so will create a compressible layer, which will have a resonance. Any compressible layer between two layers of mass will have a resonance. This resonance will hurt our sound isolation efforts at some frequency range. so for airborne noise, we avoid this.
In situation #2, however, there is such a large amount of energy in such a small area (heel of a foot) that we have to look at the compressible layer despite the fact that it introduces a resonance. Generally 1/4" to 3/8" thick underlayment.
If you are using an engineered floor (no nail-down) this can float atop a suitable underlayment.
If you are using true 3/4" nail-down hardwood, you cannot nail through the underlayment. You would need to float a layer of subflooring on top of the underlayment to give the nail-down Hardwood something to nail into.
More info here:
How to Soundproof a Ceiling | Soundproofing Ceilings Solutions | Soundproofing Company