ASA 125th Meeting Ottawa 1993 May

4pMU1. Dynamic mechanical properties of violin wood and the tone qualities of violins. I: Audiofrequency complex shear compliance, modulus, and shear sound velocity and attenuation measurements.

Edwin R. Fitzgerald

Johns Hopkins Univ., 3400 N. Charles St., Baltimore, MD 21218

Carleen M. Hutchins

Morton A. Hutchins

Catgut Acoust. Soc., Montclair, NJ 07042

Values of complex shear compliance (J*=J'-iJ''), modulus, (G*=1/J*), and shear sound velocity and attenuation have been measured over a continuous frequency range from 10 to 10 000 Hz for samples of spruce and maple wood used in the construction of six violins. Measurements were made with an automated electromagnetic transducer system in which samples are sheared while clamped between stainless steel blocks. [E. R. Fitzgerald, Proc. Am. Chem. Soc. Div. Polymeric Mater. Sci. 60, 573--578 (1989); E. R. Fitzgerald, U.S. Patent 5,081,870 (1992)]. Four wood samples were measured for each finished violin, viz., samples of spruce and maple with and cross grain. As reported earlier, values of the shear parameters vary with frequency and grain orientation, but also with moisture content and the clamping force on the sample faces while they are vibrated in shear [E. R. Fitzgerald, J. Acoust. Soc. Am. 89, 1927(A) (1991)]. The details of the mechanical spectra of the six sets of samples vary, but, in general, several sharp, microstructural compliance modes are superimposed on broad retardation spectra [E. R. Fitzgerald, J. Acoust. Soc. Am. 33, 1305--1314 (1961)]. Comparisons among the six sample sets are made for the same clamping force at 20 (degrees)C and 52% R.H.