Sounds are all around us. We do not want to hear many of the sounds outside when we are inside our homes, for example: traffic noise.
Some materials are good at allowing sound to travel through them. They are DENSE MATERIALS.
Some materials are good at absorbing sound - they do not vibrate as well. These materials are called SOUND INSULATORS and are SOFT materials. In our homes we are surrounded by soft materials - curtains, carpets, duvets, soft furniture.
Sometimes we want to block-out sound because it can DAMAGE our ears!