How You Can Hear Through Your Bones
Your skull is constantly vibrating to conduct sound to your inner ear. You can actually hear audio even if your ear canals are completely blocked because your bones act as natural sound transmitters.
While we typically think of sound traveling through the air, your bones provide a secret pathway to your inner ear. This process happens all the time, but it is usually drowned out by air-conducted sounds. Modern technology now uses this phenomenon to let people listen to music without covering their ears. It is also a life-changing solution for those with hearing impairments, as it bypasses damaged parts of the ear entirely.
Source: Bone conduction