Sound is a mechanical wave that needs a material medium like air, water, steel, etc. for its propagation. We can describe a sound wave by its frequency, wavelength and velocity. The sound wave is a longitudinal wave, i.e., the particles of the medium vibrate in a direction parallel to the direction of the propagation of the wave. Sound always originates from some vibrating body. The bell jar experiment is a common experiment used to demonstrate that sound needs a medium to travel.
This video demonstrate that sound needs a material medium for its propagation.