Some include "staggering" hallway doors so they don't line up directly across from each other. That way the sound doesn't transfer across and through opposite open doors. It's also a good idea that at least 25% of a room have some absorbent material to reduce reverberation. Carpet, furniture, curtains all work. Soundproofing mat on walls and ceilings can also help.

Ceiling noise from squeaking flooring above can be halted by tearing down the ceiling and woodscrewing triangular wood strips to the flooring above and to the joists. Liquid adhesive also helps to keep the flooring from moving and to stop the squeaking.

Using two sets of disconnected wall studs when framing back to back walls and using fiberglass insulation bats as sound absorbers is another solution.

In a traditional house the wall framing and drywall covering transmit sound from the noisy side through the wall to the other side. This is because the wall studs transfer the sound bouncing off the drywall in one room through the stud to the drywall mounted on the back of the same stud in an adjoining room. This is why simply inserting fiberglass insulation bats will dampen the sound transmission somewhat but not eliminate it. By having separate studs for each wall this transfer is stopped thus limiting the sound transfer and the noise. Double paned glass and vinyl frames are another solution. They are a bit more expensive, but over the life of the house, well worth it. Add shutters on the inside and if you have trouble with a noisy neighbor, a party or traffic and really need to get to sleep, just stuff a layer of soundproofing mat in the window.

-- Tips courtesy of HomeAdvisor.com