Introduction To Sound

Medium for Sound to Travel
Does the sound need a material medium to travel around? Most of the sounds that we hear reach us by travelling through air. Air is a medium through which sound can travel. However, the sound can also travel through liquids and solids. We can understand this by the following activities.
Sound cannot Travel through vacuum

           Figure 8.4 Loud sound of jet plane
High sounds produced in the core of the Sun are not heard on the Earth. The reason is that sound cannot pass through vacuum in space. If a jet plane passes over at low height, a loud sound is heard. But when the same jet plane is flying at very great height, we hear less sound due to thin air and long distance (Figure 8.4).