When something vibrates, the vibrations can travel as waves through solids, liquids, and gases. Even animals that have no ears can often feel these vibrations. But in order to understand language and hear music, the brain has to be given more information than just "there's a vibration". It needs to know the frequency and amplitude of all the waves that the ear is collecting. Interestingly, the ear sends this information to the brain very accurately by turning the sound waves in the air (vibrations in a gas) into vibrations in bones (solid), and then into waves in a fluid in the inner ear (a liquid), before they become (electrical) nerve signals. This might seem like a lot of unnecessary translation, but it allows the sense of hearing to be both sturdy and very sensitive, as explained below.