Laplace pointed out that the changes in pressure of air layers caused by passage of sound take place under adiabatic condition owing to the following reasons:
Under adiabatic conditions
Where γ = Cp/Cv
Hence, v = √(γP/ρ)
For air, γ = 1.4. Therefore, at STP, speed of sound is
v = 333 ms–1
This value is very close to the experimentally observed value.