An experimental study of changes in the impulse response of a wood plate that is subject to vibrational stimulus

Abstract

It is a well-known dictum among players of stringed instruments that the tone of a new instrument improves with playing and that a fine instrument needs to be played if it is to maintain its optimum sound quality. This process is sometimes referred to as ‘‘playing in’’ an instrument. There is scant mention in the scientific literature, however, of a quantitative analysis of this phenomenon. As a first step in rigorously testing this hypothesis, measurements were made of tap tones of rectangular pieces of thin spruce before and after they were subjected to vibrational stimulus. Four spruce rectangles (20x28 cm) were cut from a single sheet obtained from a luthier supplier; three of these were stimulated at different amplitudes, while the fourth was a control plate. The stimulus (provided by a harmonically driven guitar string connected to the plate via a bridge) lasted approximately 10 weeks, during which time tap tones of all four plates were periodically recorded. Spectrograms of the tap tones are compared among the plates and over time. A preliminary analysis of the data does not reveal any significant changes in the acoustic response of the plates.