2. Propagation of diverging spherical waves

2.1 The three-dimensional wave equation

Generalizing the equations established for plane waves to three-dimensional media leads us to consider the three components ρ ₀ dx dy dzf _x , ρ ₀ dx dy dzf _y and ρ ₀ dx dy dzf _z of the resultant of external forces.

The equation of state remains unchanged: p = c ² ρ.

The Euler equation, which for one-dimensional media could have been written as : $$