Lecture 3: Acoustics; wave equations linear and nonlinear.

Review of the wave equation in one space dimension. Fundamental and Kirchoff solutions
in 3D. Weakly nonlinear theory and Burgers' equation, viscous and nonviscous. Begin discussion of characteristic methods.

Suggested reading:

• Any PDE text on the wave equation, e.g. Zachmanoglou and Thoe,  Intro. to PDE with Applications , Dover.
  
• Landau & Lifshitz: 353-354.
• Courant and Friedrichs 12-23.