Ravi:
There is much than can be done, but not within practical limits for most.
"Floating floors", additional walls/sheetrock with dead air between, sealing all openings and applying lead sheeting will all do the trick when applied together. But unless you want to get involved in $10,000 worth of materials and labor, think "heavy" carpeting, drapes, furniture, etc. They won't make much of a real-world difference, but the next steps are
so much more involved that the simpler solutions are worth a try if you're desperate.
Keep in mind you're looking for isolation or barrier products, NOT diffusion materials:
http://www.soundproofing.org/infopages/channel.htm
http://www.extremesoundproofing.com/
http://www.acoustics101.com/
http://www.allnoisecontrol.com/NoiseAbsorption.cfm
http://www.sonex-online.com/ 
