A unified general solution for the acoustic field of circular chamber which has arbitrary inlet/outlet ports ; side port/side port volume velocity, side port/end port volume velocity, end port/end port volume velocity is obtained. The three dimensional acoustic solution is derived by Green's function approach as well as modal expansion technique. The mathematical expressions are derived for the prediction of the transmission losses of the circular chamber which has side-in side-out ports, side-in end-out ports. These results are compared with experimental results, and found to be in good agreements in terms of the transmission losses of silencers.
The transmission loss of silencer system was measured by using two-microphone method. The method itself is also investigated in terms of various experimental parameters ; duct length, microphone spacing, the location of microphone, signal acquisition method, and coherence of two microphones. Error associated with these measurement parameters are studied and the experimental configuration which minimize those errors are suggested.