Which characteristic has a greater influence on the speed of sound?

The speed of sound in a medium is influenced significantly by the stiffness of that medium. Stiffness, or the bulk modulus, refers to how incompressible a material is. When a material is stiffer, it can transmit sound waves more quickly because the molecules are more tightly packed and can transfer energy more efficiently.

In simpler terms, a medium that is stiffer will have particles that resist deformation, allowing sound waves to move through it rapidly. For example, sound travels much faster in solids compared to liquids and gases because the particles in solids are held together more tightly, providing higher stiffness.

While density and temperature also play roles in the speed of sound, stiffness has a more dominant effect. An increase in temperature generally increases the speed of sound in gases because it makes them less dense, but stiffness remains the overriding factor. Similarly, density, while it does affect sound speed, is inversely related to speed in the context of stiffness: an increase in density typically leads to a decrease in sound speed unless accompanied by an increase in stiffness.

Overall, the characteristic that has the greatest influence on the speed of sound is stiffness, making it the correct answer.