Colloquia

Summary

This thesis investigates the uncertainty in Conventional Acoustic Phased Array Beamforming  using the Monte Carlo method. An analytical line source CBF model is made and an experimental CBF case is conducted in the wind tunnel at the University of Twente. Both models focus on uncertainties arising from the microphone phased array, as well as from environmental factors such as background noise, which affects the Cross Spectral Matrix and the temperature during the beamforming process. The experimental case measures the sound power output of the turbulent boundary layer trailing edge noise generated by an airfoil, while the analytical model simulates it. The uncertainties are evaluated by perturbing variables within the beamforming algorithm. The perturbed variables that are related to the microphone array include the microphone phases, microphone sensitivities, microphone coordinates, and the array broadband distance. In addition to the microphone parameters, the environmental factors such as the temperature and the cross correlated spectral signals received from the microphones are also perturbed. The error bounds are then defined around the frequency range, allowing the uncertainty in the beamforming method to be quantified both analytically and experimentally.

Results show that the microphone sensitivity is the dominant perturbation mechanism in the analytical model. Despite this, the uncertainty in the CBF output remained sufficiently small. Additionally, the results show that, in the experimental model, the dominant perturbation mechanisms were the cross spectral matrix and the array’s broadband distance perturbations, where both significantly impacted the CBF output.

This work primarily develops an uncertainty quantification method and tool which will enhance the reliability of acoustic far field phased array beamforming results. Additionally, this work will serve as a valuable resource for guiding the design and planning of future experimental campaigns in Aeroacoustics.