Noninvasive methods for quantifying sound post placement in a cello

The position and orientation of the sound post in violin family instruments has long been known to color the sound of the instrument. Small changes in the position of the sound post relative to the top and back plates of the instrument can result in audible changes in the instrument’s tone. Quantifying the effect of the sound post’s placement on tone requires precise localization of the sound post. Luthiers have developed simple techniques to localize the post relative to the top of the instrument. Precisely localizing the post relative to the back, however, typically requires disassembly of the endpin. In this study, a noninvasive technique was developed using a force hammer to localize the sound post relative to the back of the instrument. This method was verified on a wooden box model and subsequently applied to two cellos, one with a laminate construction and the other carved. The sound post was localized well in the wooden box and laminate cello, but not as well in the carved cello.