Are sound waves transverse or longitudinal?

A wave propagates and oscillates. The wavenumber , or k, or momentum vector determines the propagation direction. If the oscillation direction is the same as the k vector, then its longitudinal wave, if its transverse to it, then its a transverse wave. read more

Sound can propagate through a medium such as air, water and solids as longitudinal waves and also as a transverse wave in solids (see Longitudinal and transverse waves, below). The sound waves are generated by a sound source, such as the vibrating diaphragm of a stereo speaker. read more

Longitudinal waves, like sound and unlike transverse waves, have vibrations parallel to the direction of motion that the wave is traveling. The different parts of a longitudinal wave are shown below. Sound wave also travel at different speeds depending on the state of matter in which they are traveling through. read more

In longitudinal waves the displacement of the medium is parallel to the propagation of the wave. A wave in a "slinky" is a good visualization. Sound waves in air: are longitudinal waves. read more