A Comparison of Modal Parameter Extraction Methods When Applied to Measurements of Stringed Instruments
M. Rau, Julius O. Smith, Jonathan S. Abel · 2024
Modal testing is a commonly used method to measure the transfer function or frequency response function of musical instruments or their components.Various excitation and measurement tools are used, and the recorded signals are analyzed to estimate the modal frequencies, damping ratios, and mode shapes of the object.These modal parameters are used to compare musical instruments, study changes to their geometry and materials, create synthesis models, and verify finite element and other simulation models.An object is typically excited with an impact hammer or shaker, while the resulting vibrations are measured with a microphone, accelerometer, or laser Doppler vibrometer.However, musical instrument builders don't typically have access to expensive measurement equipment, so more ad-hoc methods may be used.Multiple methods exist to extract modal parameters from the measured transfer function, each with its own strengths and weaknesses.This study compares commonly used modal extraction methods when applied to measurements of stringed instruments made with a wide spectrum of excitation and measurement sensors.The methods are evaluated based on generated modal data, and then tested with measurements of musical instruments and other objects.