Acoustic characterisation of string instruments by internal cavity measurements.

Abstract

The use of internal cavity sound measurements to characterise the acoustic properties of any hollow-bodied string instrument is described using the violin family as an example. Measurements are described using inexpensive sub-miniature electret microphones as sensors for the impact hammer, both internal and radiated sound, and bridge admittance. The excited vibrations of the body shell are shown to excite a rich spectrum of internal cavity resonances, which are strongly correlated with the radiated sound, particularly in the signature and transitional frequency ranges below around 1.5 kHz for the violin. Examples of how such measurements can be used as a working tool in the luthier's workshop and for research on the acoustics of string instruments of any kind or size are illustrated by measurements on the violin, viola, cello, and double bass.