Evolution of the Modal Behaviour of Nominally Identical Electric Guitars During the Making Process

Abstract

Recent studies have shown that the sound of the solid-body electric guitar depends not only on the extended electronic chain running from the pickup to the loudspeaker, but also on the vibratory behaviour of its structure. Indeed, the strings couple with the structure of the instrument, so the vibratory behaviour of the structure alters the sound. However, nominally ``identical'' electric guitars can show different vibratory behaviours. Measurements during the making process might help finding the origin of these differences. The aim of the article is to understand how the modal behaviour of electric guitars changes during the making process. In this paper, the making process is split in 6 stages: raw neck, shaped neck, equipped neck, body, raw guitar and equipped guitar. Vibratory measurements are performed on 11 nominally ``identical'' guitars at each of the 6 stages, in order to track the evolution of modal frequencies during the making process. Simple analytical models predict quite well the evolution of modal frequencies experimentally observed. The study also provides information about the evolution of modal damping ratios and about the variability of the modal parameters among the 11 guitars. Knowledge of the evolution of modal parameters can be of great help for luthiers, for example to make a selection of suitable separated parts at the beginning of the making process. Knowledge of the modal parameter variability at each stage can help separating the respective influence of raw material properties and making process.