ESDU 75020:2003

ESDU 75020 provides both a graphical procedure and a computer program for estimating far-field sound pressure levels due to buzz-saw noise of a supersonic fan or compressor for a stationary engine. For a graphical procedure a set of curves is provided for components of the sound pressure level. The components evaluated are those depending on intake duct length/radius ratio, the Mach number of the flow incident to the blades, the observer's angular position and distance from the intake plane, and the shock-wave characteristics (for which guidance on appropriate values is also provided). Finally a set of curves defines the cut-off frequency below which tones do not propagate along the intake duct.
A computer program, known as ESDUpac A7520, which uses the same equations as the graphical procedure is provided. A second program, known as ESDUpac B7520 and also provided, can help the user create files containing input data.

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