Acoustics: Sound Fields, Transducers and Vibration, 2nd Edition

13.3. The Kirchhoff–Helmholtz boundary integral

In the previous section we introduced the Green's function

g ( r | r 0 ) = e − j k ( r − r 0 ) 4 π ( r − r 0 ) ,

(13.16)

which turns out to be a solution of the following inhomogeneous wave equation:

( ∇ 2 + k 2 ) g ( r | r 0 ) = − δ ( r − r 0 ) .

(13.17)

An important principle in acoustics is that of reciprocity whereby the locations of the sound source r ₀ and its observation point r are interchangeable. It can be seen ...