Validation of the Source Localization Method SODIX for Coherent Sound Sources

A new validation of the source localization method SODIX for coherent sound sources is presented. The DLR fan noise prediction tool PropNoise is used to model the tonal noise of a low-speed fan stage that is generated by the interaction of the rotor wakes with the stator vanes. The simulated data is used to evaluate the capabilities of the source localization method SODIX to determine the coherent sound radiation from the intake and the nozzle exit. The analysis technique includes a parameterization of the source directivities using cubic B-splines. A parametric study on the number of base elements is carried out for the simulated tones with different radiation patterns. The results show that SODIX is able to accurately reproduce the coherent sound radiation of the simulated tones from the intake and the nozzle exit. The results also indicate that a number of base elements from 20 to 100 is a reasonable choice for a large frequency range

Validation of the Source Localization Method SODIX for Coherent Sound Sources

A new validation of the source localization method SODIX for coherent sound sources is presented. The DLR fan noise prediction tool PropNoise is used to model the tonal noise of a low-speed fan stage that is generated by the interaction of the rotor wakes with the stator vanes. The simulated data is used to evaluate the capabilities of the source localization method SODIX to determine the coherent sound radiation from the intake and the nozzle exit. The analysis technique includes a parameterization of the source directivities using cubic B-splines. A parametric study on the number of base elements is carried out for the simulated tones with different radiation patterns. The results show that SODIX is able to accurately reproduce the coherent sound radiation of the simulated tones from the intake and the nozzle exit. The results also indicate that a number of base elements from 20 to 100 is a reasonable choice for a large frequency range

SODIX for fully and partially coherent sound sources

The source localisation method SODIX is capable of determining the amplitudes and the directivity of sound sources based on measurements with a microphone array. The source model of the method has recently been extended with fully coherent sound sources which improves the application of SODIX to tonal noise. This paper presents a further extension of the SODIX source model with partially coherent sources in order to overcome residual effects that cannot be correctly modelled with a fully coherent source model, e.g. due to propagation effects that decorrelate the sound field radiated by a sound source for different receiver positions. The extension relies on a parameterisation of the source directivities and a compressed-sensing based algorithm in combination with an eigenvalue decomposition of the measured cross-spectral matrix to determine the unknown source directivities. The extended localization method with the partially coherent source model is validated using simulated sound sources that have different source directivities and mutual coherence. The results show that only the new source model with partially coherent sound sources is able to resolve the simulated source directivities accurately, when the sources are partially coherent or both coherent and incoherent sources are present

Source localization and far-field extrapolation for wind tunnel measurements of jet installation noise

Experimental data from the AWB aeroacoustic wind tunnel of DLR in Braunschweig measured with linear microphone arrays is analyzed using the SODIX method. The data from the European project DJINN for isolated and installed jets is processed in order to achieve a far-field projection of the source directivity based on the near field data using the capability of SODIX to reconstruct a set of equivalent sources with directive radiation on the engine axis that matches the data measured in the near field

Improving source localization with SODIX for far-field measurements in static engine noise tests

The source localization method SODIX is able to determine the individual contributions of the engine components to the overall radiated noise. The method is now applied to new far-field measurements of a short-cowl engine. SODIX is used to evaluate the effect of an intake liner on the sound field radiated from the engine intake by comparing different engine configurations with and without the intake liner. The source localization results show that SODIX is able to quantify the effect of the intake liner even when the overall sound pressure levels are dominated by other sound sources like jet noise