Speed of sound depends on the bulk modulus and density of the medium

Speed of sound depends on the bulk modulus and density of the medium.

The mechanical properties of the medium for sound determine the speed of sound through the medium. Repeat that again. It is the mechanical properties of the medium that determine the speed of a sound wave, specifically the bulk modulus of the medium and its density.

For undergraduate physics, one of the most important aspects of the topic of Elasticity is how important it is to undestanding sound. In Elasticity, we learn that bulk modulus is the ratio of volume stress to volume strain. Bulk modulus tells you how hard something is to compress. For sound waves, the speed of sound in a particular medium is determined by the square root of the ratio of the bulk modulus and density of the medium. For equally dense media, the more incompressible the material, the faster sound waves will travel through it.