3.1 Background 

 

The resonances of the violin body produce a filter for the radiated sound, emphasizing some frequencies and reducing others. The pattern of resonances thus gives an ‘acoustic fingerprint’ of each particular violin. The names of many of the parts of the violin were labelled in figure 14. The box, or corpus, is made up of a top plate (usually made of spruce) and a back plate (usually made of maple), separated by the garland of ribs, thin strips of maple held together by corner blocks and end blocks.

 

The structural vibration of the violin body in response to the dynamic force applied by the vibrating strings has certain pattern and strength of sound radiation. Provided linear theory is an adequate approximation, each mode has a natural frequency, a damping factor, a mode shape and a radiation pattern and strength. A violin, in common with most other vibrating structures, shows qualitatively different behaviour at high and low frequency. The first few modes are well separated from each other, but as frequency rises the damping bandwidth goes up while the typical modal spacing stays roughly constant.

 

First, the low-frequency modes of a typical violin are discussed. There are a small number of modes, often called the ‘signature modes’, with frequencies that fall in the range where all three of the dimensionless numbers are small. However, a satisfying explanation of how and why these particular mode shapes arise is only now beginning to appear. Hybrid modelling of high-frequency structural vibration has been applied in a wide range of engineering areas in recent years

 

Makers usually have a pragmatic perspective, wanting to use measurement technology and theoretical understanding to help them make better instruments—although of course the word ‘better’ covers many aspects of behaviour and has no simple definition.

 

One specific concern of makers is the choice of materials: this question includes detailed choice between specimens of the same wood species, comparison of different species, treatment of wood by various means to improve the properties, and also possible alternative materials such as carbon-fibre composites.