News & Events

Clicks Beyond the Midsagittal Plane: 3D/4D Ultrasound Evidence from Hadza

Jeremy Coburn

University of Rochester

Dewey Hall 1-101 Auditorium

Click consonants are typologically rare and articulatorily complex speech sounds that require tightly coordinated lingual gestures and dual oral closures. While a large body of descriptive and instrumental work has examined click articulation, almost all prior imaging has been limited to the midsagittal plane. This restriction obscures tongue shape and movement in the coronal dimension and prevents us from observing lateral asymmetries—an especially crucial limitation for understanding lateral clicks.

This talk introduces new multidimensional articulatory data from Hadza, an endangered language isolate of Tanzania, based on 3D/4D volumetric ultrasound tongue imaging. Using this technique, we simultaneously visualize sagittal, coronal, and transverse cross-sections of the tongue surface, allowing us to reconstruct full 3D tongue postures over time. I present data from dental, post-alveolar, and lateral clicks produced in a controlled elicitation task, supplemented with synchronized acoustics and a digitally scanned palate model.

The results reveal systematic articulatory differences across click types that are not observable in midsagittal imaging alone. In particular, lateral clicks show robust lateral asymmetry, with one side of the tongue forming sustained contact while the other lowers to create the lateral release channel—confirming patterns previously suggested by electropalatography, but here demonstrated directly in full tongue-surface reconstructions. The 3D data also show that the machine’s default midsagittal alignment consistently misses the tongue's true midline, raising methodological concerns for prior 2D studies of click articulation.

More broadly, this work contributes:

• Novel empirical evidence about the articulatory basis of click typology,

• A demonstration of the analytical value of 3D/4D ultrasound for complex speech gestures, and

• Documentation of a key component of the sound system of Hadza, an endangered isolate with a typologically rich consonant inventory.

The talk will include a brief introduction to 3D/4D ultrasound methodology, accessible walkthroughs of the reconstructed articulatory data, and implications for phonological features, biomechanical modeling, and field-based phonetic research.