Please refer to the attached simple Workbench example of a tube with an excitation applied on one end (radiation b.c. applied on both ends to simulate anechoic termination on both ends). Here, a mass source is used such that Q=2p\/c. C=1480, so if we want a pressure of 1 Pa, Q=0.00135. The results show pressure at outlet of 1 Pa through the frequency range. If one used this type of excitation where, in the middle of the pipe, they had additional geometry, the pressures at the inlet\/outlet would vary from 1 Pa, but the excitation would be equivalent to an incident wave of 1 Pa. This is typically how such interior wave propagation systems are modeled. <\/p>\n