The sound of fly-over aircraft is measured with the use of an acoustic camera to gain more information on aircraft noise. This camera can be optimised to gain data of a higher quality. Within the ANCE section this optimisation was required mainly to diminish the influence of the ground effect in the data and to increase the resolution of the eventual source plots. The increase in resolution was required to be able to separate engine and airframe noise also for the smaller aircraft. The research started with a quantification of the previous fly-over camera of the ANCE section. It appeared that the fringes from Lloyds’s mirror pattern were present, but different for each microphone. This was due to the edge diffraction and should be solved by placing the microphones at least 30 cm from the edge. The increase in resolution should be solved by doubling the array aperture to 3.4 m. These and many other findings were implemented in a new design. This design consists out of a de-attachable rigid structure of 4x4m placed on adjustable legs to which 64 microphones could be clipped in an Underbrink spiral array configuration. The design was built and tested for fly-over aircraft at Schiphol Airport. The measured data was analysed and it appeared that the fringes from the ground effect were gone. Furthermore, the resolution was improved and the engines and main landing could be separated for smaller aircraft as the B737 and A321.

This work aims to determine the optimal microphone placement on an acoustic array of TU Delft’s ‘V-tunnel’ which is used for beamforming in aero-acoustic studies. The beamforming performance is driven by two parameters; the Maximum Side lobe Level (MSL) and the Main Lobe Width (MLW). The array design should give a good trade-off between these parameters. The proposed optimization method has two optimization loops. First, the main loop consists of design variables used to collectively describe the distribution of microphones. Then the nested loop generates arrays which satisfy the geometry descriptions from the main loop. Finally, the main loop searches for the optimal design variables. The optimized array is able to achieve the MSL below -15 dB up to the distance approximately four times the MLW around the main lobe. Experimental validation was also carried out to compare the optimized array’s performance with a benchmark array and an array from the beginning of the optimization.