Passive noise cancellation refers to the ability of certain materials to block or reduce unwanted sounds. This is achieved through physical barriers, such as padded ear cups in headphones or soundproofing materials in buildings. These barriers absorb or reflect sound waves, preventing them from reaching the ears or the interior space. Unlike active noise cancellation, which uses electronic methods to counteract sound, passive noise cancellation relies solely on the design and materials used. It is effective in reducing ambient noise, making it popular in various applications, including audiophile headphones and quiet rooms in offices or homes.