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Measurement of the Impulse Response of the Guitar to Extract Timbre Features

Title Measurement of the Impulse Response of the Guitar to Extract Timbre Features
Publication Type Master Thesis
Year of Publication 2019
Authors Nieves, S.
Abstract Record Description: Nowadays, the guitar is one of the most popular musical instruments all over the world. We can find a great number of models with a wide range of acoustic quality, depending on the way the guitar has been built. The guitar luthiers need to know how to control certain acoustic attributes depending on the type of instrument they want to make. Currently, most luthiers check these acoustic features by analysing the vibration modes and trying to tune them to certain frequencies. To analyse these modes, one of the most used techniques is to analyse the spectrum of the impulsive response by recording a guitar tapped just below its bridge. Although the vibration modes are very important for the final sound of the guitar, there are many more elements that affect the different characteristics that compose the timbre. In this master thesis, developed in the context of the company MIIL–Musical Instruments Innovation Lab, we have created a computing tool named GIRAS-Guitar Impulse Response Analysis Software. This software allows us to record impulsive responses of guitars, using the technique explained above, and analyse them to obtain new acoustic parameters in addition to the vibration modes, with the aim that these can be used to define the timbre of the instrument. The acoustic parameters we have extracted from the impulsive response have been: the vibration modes, attack time, decay time, vibration sensitivity, centroid, low-to-high frequency ratio and MFCC. To verify if all these computations are related to any timbre feature of the guitar, a small experiment has been made using 5 classical guitars and 4 guitarists, where each of the guitarists had to evaluate the timbre of the guitars according to certain characteristics such as attack, sustain, intelligibility, warmness, balance, volume and dynamic range. After measuring these 5 guitars with our programme, the results are that there are some parameters such as the vibration modes, the attack time, the decay time and the low-to-high frequency ratio, which are clear about their influence on the timbre, and others in which a deeper research and an improvement of the methodology followed is needed to know if they can help to describe the timbre. The most important conclusion of this project is that we have created a software that makes much easier the research on the guitar timber.
Final publication