Vocal drum sounds in human beatboxing: An acoustic and articulatory exploration using electromagnetic articulography

Acoustic characteristics, lingual and labial articulatory dynamics, and ventilatory behaviors were studied on a beatboxer producing twelve drum sounds belonging to five main categories of his repertoire (kick, snare, hi-hat, rimshot, cymbal). Various types of experimental data were collected synchronously (respiratory inductance plethysmography, electroglottography, electromagnetic articulography, and acoustic recording). Automatic unsupervised classification was successfully applied on acoustic data with t-SNE spectral clustering technique. A cluster purity value of 94% was achieved, showing that each sound has a specific acoustic signature. Acoustical intensity of sounds produced with the humming technique was found to be significantly lower than their non-humming counterparts. For these sounds, a dissociation between articulation and breathing was observed. Overall, a wide range of articulatory gestures was observed, some of which were non-linguistic. The tongue was systematically involved in the articulation of the explored beatboxing sounds, either as the main articulator or as accompanying the lip dynamics. Two pulmonic and three non-pulmonic airstream mechanisms were identified. Ejectives were found in the production of all the sounds with bilabial occlusion or alveolar occlusion with egressive airstream. A phonetic annotation using the IPA alphabet was performed, highlighting the complexity of such sound production and the limits of speech-based annotation.