Laplace’s correction:
Laplace suggested that the compression or rarefaction takes place too rapidly. Heat produced during compression and lost during rarefaction does not get sufficient time for dissipation. Due to this, the whole heat content remains same.
Thus, it is an adiabatic process.
According to Laplace, E is the adiabatic modulus of elasticity of air medium which is given by,
E = γP ….(1)
where P = pressure of the air medium γ = ratio of specific heat of air at constant pressure (cP) and specific heat of air at constant volume (cv). i.e., γ = cp/cv.
iii. Using equation, v = \(\sqrt{\frac{E}{ρ}}\), we have velocity of sound in air,
v = \(\sqrt{\frac{γP}{ρ}}\), …. [From equation (1)]
For air, γ = 1.41
At NTP, P = 0.76 × 13600 × 9.8 N/m2
ρ = 1.293 kg/m3.
This value is in close agreement with the experimental value.
