Source Separation from Multiple Microphone Measurements in the Far Field of a Full Scale Aero Engine

Noise-Source Separation Using Internal and Far-Field Sensors for a Full-Scale Turbofan Engine

“…The results in Fig. 6 are in general agreement with the ones presented by Mendoza et al 25 in their Fig. 12(b).…”

“…21,25 As long as the spatial (polar angle) separation of the microphones is large enough, the jet noise at each location can be assumed to be mutually uncorrelated and Eq. (2) would apply.…”

“…Ref. 25 analyzed data from a Honeywell TECH977 static test 26 using a three-signal far-field method, among other multiple-microphone signal-processing techniques. 27 They found that the method worked well in frequency regions where a single engine-internal source was dominant.…”

A Comparison of Combustor-Noise Models

“…Figure 7 also shows that the spectral peaks of the mid-and high-frequency components in the Stone et al method predictions fall above 1 kHz, with levels at least comparable to that of the low-frequency component. The implication from the Stone et al method prediction shown in this figure, i.e., that there would be a significant amount of combustor noise present for frequencies higher than log f 1/3-octave SPL, dB 1 kHz, is in direct contradiction with prior analyses 22,23,29,46 of EVNERT TECH977 acoustic data. Even though there are some uncertainties in the actual values used for the geometry parameters in Eqs.…”

“…Since flight effects reduce jet noise more than combustor noise, combustor noise can be a significant contributor to aircraft in-flight noise but may be masked by jet noise under the corresponding static-engine test conditions. To overcome this obstacle, researchers [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] developed coherence techniques utilizing engine-internal, as well as far-field, measurements to identify the far-field combustor-noise component. Modal analyses [24][25][26][27][28][29] were also carried out to determine the source and propagation characteristics of combustor noise.…”