Acoustic changes produced by hydration and burnishing of violin plates.
Frank Denaro, M. Roman Serbyn · The Journal of the Acoustical Society of America · 2010
To achieve the proper balance of tone and loudness throughout the frequency range of a fine violin, various methods of plate tuning have been proposed. Unfortunately, their effectiveness can be judged only a posteriori, for even if a violin plate response is well characterized, where to work the wood is poorly known. What is needed is a process that does not remove wood until the desired acoustical characteristics are produced regardless of the method used. The technique proposed by us consists of systematic hydrations and/or compressional burnishing of focal areas of the violin plates or corpus. Hydration is acoustically equivalent to a decrease in stiffness, while burnishing increases stiffness. Both are reversible without marked changes to the wood. In order to establish how these treatments affect the material constants of the plates, strips of maple and pine were tested in both treated and untreated states and the changes noted. Results suggest temporary changes to plate stiffness. The magnitude of these changes is sufficient to affect acoustic signatures and holographic patterns and hence can be detected. The accumulative effects of such changes to violin tone are noted in our companion paper.