A rig for measuring violin sound radiation

A now-standard way of measuring violin sound radiation is to tap the bridge with a miniature impact hammer while a microphone samples the resulting sound field. At least three factors complicate the process: (1) the strings exert three-dimensional forces at the bridge; (2) radiation becomes increasingly directional above 1 kHz; and (3) unless measurements are done under anechoic conditions, the acoustics of the measurement space must be considered. This video describes a rig that uses a solenoid-driven hammer, two driving directions (one horizontal at the bass corner of the bridge; the other vertical at the top-center), and twelve equatorial microphone positions 20 cm from the central axis of the violin. The resulting 24 FRFs can be used to estimate total sound output per-unit-force at the bridge. Alternatively, impulse responses from individual measurements can be convolved with recordings made on an electric violin to create realistic emulations of a normally played violin for use in psycho-acoustic testing.