Soundbox behavior in environments with varying sound speed

The radiation produced by the wooden soundbox of a string instrument is largely the result of the coupling of oscillations in the wood and those of the enclosed air. The traditional way of studying this interaction is to make modifications to the instrument such as adding masses to the soundboard and chimneys to the soundhole. Presented here is an alternative approach that changes the sound speed of the environment using a tent filled with different gases. The resulting admittance data, expressed as contour plots, show clearly the relationship between air and wood modes. The effect of these modes on the radiation of the instrument is demonstrated by measurements of monopole radiativity for a guitar (with and without the hole blocked) and these data are compared to the output of a simple model. Other instruments studied with the gas tent include violins (regular and balsa), viola, setar, and sound.