How a sound insulator works?

Answer 1

drop a pebble in a glass of water. Notice the same effect, where the water ripples and spreads out in a circle. But notice that when the ripples reach the sides of the glass, they can travel no further. To a certain extent, this is how sound-proofing works.

Sound-proof insulation

• Sound-proof insulation is often made from vinyl/nitrile-blended foams that come in thick padding or an egg-crate shape. The foam is laden with minute air cells. When sound waves hit these air cells, friction occurs and the waves are quickly dissipated, thus significantly reducing decibel levels. The leftover energy created from when the sound waves hit the foam is released as heat (though not something you will particularly notice).

  Thus, sound-proof insulation acts as a trap for sound by absorbing the energy (remember the waves in your pool of water) created by noise. When properly installed in the walls of your home and around your heat and water pipes, sound-proof materials will help to reduce the drama of the outside world going on around you.

• (source ehow) (hope it helped :) )