Answer:
increasing the temperature of the rod
Step-by-step explanation:
Sound wave is a longitudinal wave and its speed in a solid rod is given by the formula
![v = \sqrt{(Y)/(\rho)}](https://img.qammunity.org/2020/formulas/physics/middle-school/kw7gzaahsk283vgjg54a2z4tkqm5vkfi76.png)
here we know that
Y = young's modulus
= density of the medium
so as we increase the temperature of rod the density of the rod will decrease while the elasticity will remain same
So on increasing the temperature we can say that speed will increase due to decrease in the density