- Change in density: If the density of the medium changes, the wave velocity changes. For example, sound waves travel faster in denser media like solids and slower in less dense media like gases.

- Change in elasticity: The elasticity of the medium affects the wave velocity. Elastic materials, such as stretched strings or rubber bands, transmit waves faster than non-elastic materials like plastic or foam.

- Change in temperature: Temperature changes can affect the wave velocity in some media. For instance, sound waves travel faster in warmer air and slower in colder air.

- Change in medium: When a wave passes from one medium to another, its velocity changes. For instance, when a light wave travels from air to glass, its speed decreases because the glass has a higher refractive index.

- Change in frequency: For some waves, like electromagnetic waves, the velocity can change with frequency due to phenomena such as dispersion.