The didjeridu: Relating acoustical properties to players' reports of performance qualities

Abstract

Relating objective acoustical measurements of an instrument, without a player, to the qualities reported by players is often a difficult goal in music acoustics. The didjeridu offers advantages in such a study because it is inherently ‘blind’—neither player nor researcher knows what is inside—and because there are wide variations in objective parameters. Here, seven experienced players reported several qualities and overall quality of 38 traditionally made didjeridus whose acoustic impedance spectra and overall geometry were measured. The rankings for ‘overtones’, ‘vocals’, ‘resonance’, ‘loudness’ and overall quality were all negatively correlated with the characteristic impedance of the instrument, defined as the geometric mean of the first impedance maximum and minimum. ‘Speed’ was correlated positively with the frequency of the lowest frequency impedance peak, near which the instrument plays. Assessments of geometrically simple PVC pipes yielded similar results. The overall ranking was highest for instruments with a low magnitude impedance, particularly in the 1-2 kHz range. This is the range in which players produce a strong formant in the radiated sound by varying vocal tract resonances with comparable ranges of impedance. This study and the researchers were inspired by the pioneering research in music acoustics by Neville Fletcher.