Mud Acoustics in Modern Drilling - Wave Propagation in Drilling, Well Logging and Reservoir Applications - page 297

Figure 5.14. Very long “acoustic” wind tunnel in Shandong, China.
Computational methods and analysis played strong roles in defining and
understanding system architecture. The large-scale propagation of acoustic
waves in the drilling channel can be modeled accurately using the wave equation
for Lagrangian displacements, as we have shown, as this formulation also
naturally captures the “delta-p” character of the siren signal source. In Figure
5.15, we show a typical six-section waveguide describing the downhole drilling
channel. The input siren p depends on flow rate, rotation speed and valve
geometry and is measured in the short wind tunnel.