One of the oldest, most sustainable and effective sound and thermal insulations comes from harvested cork oak tree bark. Generally, if a tree is allowed 9 years to recuperate from a previous harvest, the tree is not harmed. In fact, the bark improves with each harvest.

The harvest is then considered a sustainable source. Mostly produced in Portugal and around the Mediterranean, although India and California both have cork oak tree forests and production facilities.
Cork is naturally fire-retardant, resistant to rot and mold and in its natural state, it is non-toxic and safe. For home use, cork composition is most commonly used as floorcovering underlayment under hardwood and ceramic floors for its good resilience and acoustical characteristics. Cork insulating materials are also used under wallcoverings, in ceilings and as tape around pipes. More often used in commercial and industrial projects. See appropriate sections for cork wallcovering, floorcovering or accessories.
Some products are treated with chemicals and synthetic backing materials, or are processed into sheets by adding a resin. Others are just steam baked into molds. Most people are not affected by these processes.
The source of production will determine shipping costs and related transportation issues which may make this excellent choice more costly and detract from its otherwise high level of sustainability.