3 - Cello acoustics

Summary

There is a huge diversity of bowed stringed instruments throughout the world. Their acoustical principles, however, are common. A bow is drawn across a taut string. Friction between the bow and the string excites the string into vibration. The string has particular vibrational properties which make it an ‘ideal’ musical signal source, but unfortunately its small size renders it practically inaudible. The string is therefore connected to some form of resonator, which is traditionally a wooden box (as in the case of the cello), a stretched animal skin or a gourd. The function of the resonator box is to vibrate in sympathy with the strings. The larger surface area of the box interacts readily with the surrounding air, creating sizeable pressure fluctuations which we hear as sounds.

This chapter aims to provide a brief introduction to cello acoustics and to add sufficient detail to the above simple model to explain various features of practical importance to players. The last thirty years have witnessed intense activity in the study of the acoustics of stringed musical instruments. In the case of bowed stringed instruments, work has concentrated almost exclusively on the violin, and readers interested in pursuing the subject further are directed to several standard works on the subject. In many respects, the differences between violins and cellos are simply a matter of scale, the acoustical principles being the same in both cases. However, the increased body size and heavier strings and structure bring particular problems associated with starting transients and wolf-notes, both of which will be discussed later.