Passive noise-canceling refers to the ability of certain materials or designs to block out external sounds without using electronic components. This is typically achieved through the use of thick padding or sound-absorbing materials in products like headphones or earplugs. By creating a physical barrier, passive noise-canceling helps reduce unwanted noise from the environment. Unlike active noise-canceling, which uses microphones and speakers to counteract sound waves, passive noise-canceling relies solely on the structure of the device. Many headphones and earplugs utilize this method to provide a quieter listening experience, making them popular for travel or noisy environments.