Comparative evaluation of violins through sound quality analyses

The paper illustrates a methodical comparison of violins oriented to the identification of their peculiar sound characteristics. Acoustic experiments are applied to a representative group of violins, having quantitative differences, ranging greatly in price and sound quality. For each violin, spherical mapping, time histories, frequency response functions and corresponding spectrograms are detected playing open strings and sequences of notes, determining the percent of sound in each harmonic. High quality instruments are compared in detail, in order to identify the peculiar acoustic response of each instrument and to define their "sound signature". Sound waves must be examined to achieve an understanding of violin tone, amplitude and characteristic frequencies. High quality violins tested have higher relative strengths of the fourth harmonic: most of the other harmonics have relatively low strengths. In the lower quality violins, no significant correlation could be made between the strengths of the various harmonics. The "randomness" of the distribution of the strength of the harmonics in the lower quality violins probably contributes to their poor tone. In addition, experiments oriented to detect the noise generated by the friction during slipping of a bowed string are developed and described, correlating noise to generated sound.