Which factor directly influences the speed of sound in a medium?

The speed of sound in a medium is primarily determined by the medium's density and elasticity. Density refers to the mass per unit volume of the material, while elasticity indicates how well a material can return to its original shape after deformation.

In general, sound waves travel faster in materials that are more elastic because they can transmit energy more quickly. Conversely, in denser mediums, where particles are closely packed, sound can also travel faster due to the efficient transfer of sound wave energy among particles.

Frequency, amplitude, and wavelength do relate to sound waves but do not directly affect the speed of sound in a given medium. Frequency and amplitude are characteristics of the sound wave itself, while wavelength is a result of the speed of sound divided by frequency. Thus, they are not the fundamental factors determining how quickly sound can travel through different materials.