Sound waves superimpose linearly because their energy flow is preserved.

Evidence

This is because although the total pressure, or velocity component, may lie anywhere between zero and the sum of the individual pressures or velocities, the energy flow of the sound waves is still preserved and so the waves continue to propagate. Thus the pressure or velocity at a given point in space is simply the sum, or superposition, of the individual waves that are propagating through that point, as shown in Figure 1.18. This characteristic of sound waves is called linear superposition and is very useful as it allows us to describe, and there­ fore analyze, the sound wave at a given point in space as the linear sum of individual components. — David Howard, Jamie Angus, coustics and Psychoacoustics, 322

Categorization

• DEFINE: Defines linear superposition as the founding principle that lets analysts decompose any complex sound wave into simple component waves.