Automated hammer-impact modal analysis with a scanning laser vibrometer : Working example - a violin

Typically hammer-impact modal analysis uses hand-held roving hammer excitation with fixed response transducers, although automated hammer striking units are available. Careful measurements with hammer impact can lead to fairly reliable results. Unfortunately the hand-held hammer cannot really provide reproducible - same direction, same point, same magnitude -- excitation, so that coherence suffers. Placing the hammer in a pendulum mount is a better way to control striking parameters, but adds additional positioning time. An alternative method using fixed hammer excitation and a scanning laser vibrometer for response has been developed for automated modal analysis on a system where zero-mass loading for excitation and response is a fundamental requirement - violins. Fixed auto-hammer excitation with SLDV response measurements demonstrates significantly increased data collection rates, improved coherence (attaining levels observed with other excitation techniques), and enhanced reliability and reproducibility (of note for updating finite element models).