Measurement and analysis of acoustic flight test data for two advanced design high speed propeller models

Advanced turboprop noise prediction based on recent theoretical results

“…A similar trend is also seen in the spectra. Prediction based on Hanson's method for one harmonic from reference [13] agrees well with prediction from the present code. No information on assumed blade loads is given in reference [13].…”

“…Prediction based on Hanson's method for one harmonic from reference [13] agrees well with prediction from the present code. No information on assumed blade loads is given in reference [13]. It is known that in Hanson's method the thickness and loading sources are located on a helicoidal surface which is infinitely thin.…”

“…When the fuselage reflection and boom effects are considered, the agreement between the two spectra is good. Prediction of the first harmonic based on Hanson's method [13] agrees slightly better than that by the present method, perhaps due to differences in the geometric and aerodynamic input data. Figure 17 shows the measured and predicted acoustic pressure signature and spectra for boom microphone 4.…”

“…Similarly, predicted acoustic pressure signatures were multiplied by the factor 1-58. This was the correction suggested and used by Brooks and Mackall [13]. It is known that this correction is a function of frequency [ 12].…”

“…It is known that in Hanson's method the thickness and loading sources are located on a helicoidal surface which is infinitely thin. Quadrupole sources were also used in acoustic calculations of reference [13] but they make only a small contribution. It is interesting to note that this boom microphone is significantly influenced by the presence of the fuselage.…”