The speed of sound, c, is given by the Newton-Laplace formula

where
K = bulk modulus
ρ = density
Because the density is constant, the speed of sound is proportional to the square root of the bulk modulus.
Therefore when the bulk modulus increases, the speed of sound increases by the square root of the bulk modulus.
For example, if K is doubled, then

Answer:
If the bulk modulus increases by a factor of n, then c increases by a factor of √n.