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Analysis of the Behaviour between Measuring Distance and Image Resolution for Air Coupled Beamforming Microphone Array

: Daudré, Julie
: Summa, Jannik; Rabe, Ute; John, Thomas

Saarbrücken, 2020, 73 S.
Saarbrücken, Univ., Bachelor Thesis, 2020
Bachelor Thesis
Fraunhofer IZFP ()
air-coupled ultrasound; Acoustic Camera; beamforming

Nowadays, modern materials such as polymers reinforced with different type of fibres, made out of carbon or glass for example, are used in the framework of lightweight constructions. These materials are not to be immerged in a fluid. This is why an appropriate investigation technique to detect quality defects is air-coupled ultrasonic measurements. However, this way of measuring with ultrasound is not as widespread as ultrasonic measurement in contact direct with the sample or measurement in immersion in a fluid. Indeed, the air coupled technique presents some disadvantages and difficulties which are covered later in this work. Furthermore, in order to achieve a satisfying resolution of the picture to detect different kinds of defects and to reduce the measurement duration, signal processing techniques such as beamforming are to be used. However, there is very few studies based on air-coupled ultrasound and beamforming. Moreover, the lack of these studies got interested in using these two methods on reality-like samples. This is what is going to be done here, understand the influencing factors to improve the resolution of a reconstructed (using delay-and-sum beamforming) air-coupled ultrasonic measurement of a sample presenting reality-like defects. The relation between the resolution, the array configuration and the measuring distance will be here of interest.