If you could take a look at the insides of your wall, you would notice that there are two solid layers with an empty space in between.
Insulation materials are usually installed to keep the house warm in winter or cold during summer. The fibrous component of the insulation material traps the hot air that passes through.
Soundwaves usually travel by air though they could also travel through solid objects like in the case of impact sound. So the same component that keeps a house warm or cold also traps the soundwaves that travel through the air.
Basically, there are 3 types of insulation materials:
- Batt insulation – they are rectangular panels or rolls usually made of fiberglass, cotton, or mineral wool used in insulating walls
- Foam spray insulation – these are liquid polyurethane sprays that expand to fill the space on the wall
- Blown insulation – similar to batt insulation used in insulating attics but the materials are blown to pieces to fill the space
Out of the three, batt insulation is the most effective when it comes to soundproofing. Blown insulation clearly can’t do much soundproofing.