Peak-picking method for identifying natural frequencies and damping ratios from free vibration measurements

This paper introduces a method for identifying natural frequencies and damping ratios from a free vibration response induced by an impact, without requiring measurement of the excitation force. The approach combines the conceptual simplicity of peak-picking with the robustness of a multi-component time-domain model of the signal. Modal components are identified iteratively, based on spectral peaks selected by the user. The method is deliberately supervised, yet designed to remain accessible to non-expert users. A graphical interface provides intuitive control over the identification process and immediate feedback on the quality of the reconstructed signal, both in the time and frequency domains. The method is illustrated through experimental applications, demonstrating that natural frequencies and damping ratios can be extracted from simple, non-invasive measurements of the sound radiated by structures following an impact excitation. The robustness of the method to measurement noise and modal overlap is evaluated, and the identified parameters are shown to be consistent with those obtained from conventional FRF-based modal identification.