Mechanical Characterisation of Materials for String Instrument

Abstract

A large variety of materials are used traditionally for constructing string musical instruments in the Western cultural tradition. Since the last decades of the XIX th century it has been recognised that mechanical and acoustical properties of materials are the most relevant for these instruments. Wood is the predominant material. Other materials such as metals, or natural materials—bone, ivory mother of pearl, etc. are also used. The elastic constants of these materials can be determined experimentally with acoustic non-destructive methods such as resonance methods and ultrasonic methods. These constants are required for modal analysis, which allows the study of the vibration of plates or of instruments. In all materials internal friction is produced during the propagation of acoustic waves, reflecting the viscoelastic characteristics of these materials. Some of these materials are highly hygroscopic, such as wood. The properties of wood are dependent on moisture content. Modal analysis can be used to illustrate the influence of very low variations of moisture content on the vibration of plates of string musical instruments.