When an object vibrates, it also vibrates the particles of the medium around it. These particles do not reach our ears by moving from the vibrating object themselves, but the particles of the medium closest to the vibrating object get displaced from their balanced state, which displaces then by applying force on their nearest particle and the initial particle returns to it’s original state. This process continues in the medium until the sound reaches our ears. In this way the disturbance produced by sound in the medium (not the particles of the medium) is propagated through the medium.