Answer:
1: v = √E/ρ where E is the elasticity and ρ is the density. Newton's assumed that sound wave travel in air under isothermal condition
2: He corrected Newton's formula by assuming that, there is no heat exchange takes place as the compression and rarefaction takes place very fast. Thus, the temperature does not remain constant and the propagation of the sound wave in air is an adiabatic process.