Microphone array designs
At NLR microphone arrays were designed for several applications:
- wind tunnel measurements (for open jet & closed test section),
- measurements on wind turbines,
- circular mode detection (in intake and exhaust ducts of engines),
- radial mode detection (with a slowly rotating rake).
Wind tunnel acoustic processing tools
Software was made for:
- cross-spectral matrix calculations,
- several methods for phased array beamforming, including the widely-used deconvolution method CLEAN-SC ,
- acoustic transmission from a source in an open jet to a microphone outside the flow,
- the calculation of “real life” fly-over data from measurements on scale model in a wind tunnel.
Beamforming on moving sources
Software was made for:
- moving sources (applied to flying aircraft),
- rotating sources (applied to wind turbines).
Acoustic field modelling
Acoustic field modelling software was made for the following applications:
- propagation of sound through a lined flow duct (extensions to existing software, with bulk-absorbers and multiple lined segments),
- propagation of sound through a C-shaped duct,
- Green’s functions in non-uniform parallel flow,
- rotor-stator interaction (extension to existing software).
