Signal Scattering

The digital waveguide was introduced in §1.4. A basic fact from acoustics is that traveling waves only happen in a uniform medium. For a medium to be uniform, its wave impedance^2.14must be constant. When a traveling wave encounters a change in the wave impedance, it will reflect, at least partially. If the reflection is not total, it will also partially transmit into the new impedance. This is called scattering of the traveling wave.

Let denote the constant impedance in some waveguide, such as a stretched steel string or acoustic bore. Then signal scattering is caused by a change in wave impedance from to . We can depict the partial reflection and transmission as shown in Fig.1.27.

Figure 1.27: Signal scattering at a junction of different wave impedances & .

The computation of reflection and transmission in both directions, as shown in Fig.1.27 is called a scattering junction.

As derived in Appendix H, for