  Complex plasmas consist of microparticles embedded in a low-temperature
plasma and allow investigating various effects by tracing the motion of these
microparticles. Dust density waves appear in complex plasmas as self-excited
acoustic waves in the microparticle fluid at low neutral gas pressures. Here we
show that various properties of these waves depend on the position of the
microparticle cloud with respect to the plasma sheath and explain this finding
in terms of the underlying ion-drift instability. These results may be helpful
in better understanding the propagation of dust density waves in complex
plasmas and beyond, for instance, in astrophysical dusty plasmas.
