The velocity of a transverse wave depends on the tension force FT and the mass per unit length .
Sound waves in a fluid such as water or air are examples of compression or longitudinal waves. In these waves the particles (molecules) of water or air move back and forth along the direction of the wave, causing compression and rarefaction.
The velocity of a compression wave depends on the Bulk Modulus B of the fluid and the mass per unit volume .
Note that in both formulas for wave velocity, the numerator represents a quantity which tells how "stiff" the material is, and the denominator represents a quantity which tells how massive it is.