The acoustic and psychoacoustic characteristics of barbershop singing

For a cappella singing groups to produce a memorable listener experience they need to be able to generate a broad palette of sounds. This capability requires an understanding of the key factors which affect their acoustic output. The advent of computers capable of rapid real time analysis has enabled the development of objective metrics for identifying and classifying sounds. In parallel, perceptual descriptions of sounds have evolved so practitioners can communicate their intent to performers and listeners can describe their experiences. Having these two ways of delineating sounds raises the question of whether the acoustic metrics and the perceptual descriptions correlate and what are the key variables affecting their values.

This thesis describes investigations into the objective acoustic metrics and the perceived acoustic features of Barbershop singing. A research programme comprising an analysis of published quartet recordings, the development of a computer model to simulate a Barbershop quartet, live testing with a Barbershop quartet in an audio laboratory and perception tests with a panel of Barbershop judges identified the primary influences of compositional choices (chord structure, chord pitch and vowel sung) and singing characteristics which affected the acoustic metrics and the perceptual features. The distinctive qualitative properties of Barbershop have been described as Lock, Ring and Expanded Sound. From the research it is concluded Lock correlates with intonation accuracy. Ring correlates with a high spectral centroid in the frequency domain and Expanded Sound does not correlate with spectral spread, nor is it a result of combination tones, but is more likely to correlate with increasing spectral amplitude as a result of vocal efficiency. The effects can be enhanced in sustained chords as the singers make real time adjustments to their vocal techniques. Practical applications of the research which could help practitioners achieve these performance goals are presented.