The interior noise levels in the Saab 2000 turboprop aircraft were found to be dominated by the starboard propeller. Extensive in-flight measurements of the exterior pressure field were carried out in order to better understand this phenomena and to find means to reduce the noise. The exterior pressure field on the port side of the fuselage behaved as expected. How-ever, on the starboard side the measured pressure field was very different from what was predicted. At some positions unexpected low levels of BPF were noticed. At starboard positions under the fuselage in the plane of the propellers very high levels with a pronounced content of higher harmonics were found. A theoretical study was undertaken to explain the unusual pattern found on the starboard side. The different character of the time histories on the starboard and port side of the propeller could be qualitatively predicted by including the effect of the inhomogenous inflow to the propeller disk in the noise calculations. The non-uniform inflow is created by the enginer air inlet being very close to the propeller disc in combination with the high speed of Mach 0.62 of the Saab 2000. A less disturbed flow for the starboard propeller was created by extending the propeller shaft i.e. moving the propeller further away from the air inlet. The interior noise levels were hereby considerably reduced for all of the propeller harmonics in the entire cabin.
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