Parameter Selection for Using Parametric Array Loudspeakers as Excitation Source at Selected Points

Background Experimental Modal Analysis (EMA) of thin and lightweight rotating structures is challenging due to the difficulty of applying controlled non-contact excitation. Existing non-contact excitation methods often suffer from limited spatial precision. Objective Seek a set of design and measurement parameters of an acoustic non-contact excitation device for thin and lightweight structures, such that the effective excitation area is comparable to that of impact hammers. Methods Parametric Array Loudspeaker (PAL) is utilized to generate amplitude-modulated ultrasonic waves, producing a highly-directive acoustic field. An exponential horn is placed in front of the PAL to enhance acoustic focus. Directivity is evaluated by an area scan through the area. The validated system is duplicated and two-point excitation EMA of real artefact is carried out. Results The proposed system, consisting of a PAL and an exponential horn, achieves an effective excitation area of around 216~mm² 216 m m 2 . The system has demonstrated its ability in supressing the responses of selected modes. Conclusion The proposed non-contact excitation system enables the excitation location with precision comparable to impact hammers. Its feasibility as an effective excitation approach for multiple-point excitation of thin and lightweight structures is demonstrated.