An exact one-dimensional analysis of the acoustic sensitivity of the antiturbulence probe tube in a duct

Abstract

The antiturbulence probe tube used in the in-duct method for the measurement of acoustic power of ducted fans and in active noise control systems is analyzed for its acoustic sensitivity or frequency response by means of the distributed parameter approach wherein mutual interaction of the acoustic pressure fields in the probe tube and the annular duct are considered. This enables one, incidentally, to check the correctness of the one-way interaction implied in the available analytical methods. The analysis takes into account both the locations of the microphone, the mean flow convection, and the normal radiation condtions as well as anechoic termination used in the literature. Arising from the computed plots, some general criteria for the design of the windscreen probe tubes have been offered.