Approximate model for sound generation due to unsteady flows in pipes

An approximate model for the generation of sound due to unsteady vortical flow in pipes of varying cross‐sectional area is described. This model, which is being used in speech synthesis research, is based upon Howe's acoustic analogy. This formulation allows the sound generation to be specified in terms of properties of the unsteady behavior of a vortical flow and the potential flow solution for the pipe that would exist in the absence of vortical inhomogeneities. An approximate model for vorticity formation and evolution is presented, and the potential flow solution is obtained from the axial duct shape. Computed estimates of the time evolution of the sound generated by a confined jet passing through a pipe constriction are presented. These results are compared to experimental data.