ESDU 76020 gives a method based on the Gutin theory for the first harmonic sound pressure level@ together with corrections that enable estimates of higher harmonic levels to be derived. The method predicts the first harmonic to 3 dB for 75 per cent of experimental data compared with it@ and higher harmonics to 10 dB for 93 per cent of the data; it is applicable to static rotors and propellers or to forward speeds up 40 knots (20 m/s). The input parameters for the method are thrust and thrust coefficient@ engine power@ number of blades and diameter@ tip Mach number and distance to observer. Both a graphical method and a computer program are included in this Item.
ESDU 76020 A-2011 history
2011ESDU 76020 A-2011 Estimation of the maximum discrete frequency noise from isolated rotors and propellers
2008ESDU 76020 A-2008 Estimation of the maximum discrete frequency noise from isolated rotors and propellers.