Developing acoustic field distribution analysis tools for noninvasive assessment of laterality and nasality in disordered and typical pronunciation.

Abstract

This research note presents an acoustic field distribution analyser with sample visualisations, applied to the study of typical and disordered laterality and nasality in speech - an area lacking fully non-invasive diagnostic tools. A portable system was developed by combining a custom circular microphone array with software for temporal, spectral and spatial speech analysis in both horizontal and vertical planes. The array comprises 16 micro-electro-mechanical microphones equipped with pulse-density modulators, along with a laser distance sensor that focuses the acoustic beam on the facial contours and compensates for the speaker's head movements - thereby increasing the array's focusing precision. Two case studies visualise disordered speech in patients with (1) occlusal development disorders and compensatory articulation, and (2) bilateral cleft lip and palate with resonance issues, compared to typical speech patterns. Spatial analysis of the acoustic field distribution enabled a non-invasive comparison of articulation symmetry and air pressure distribution in both the horizontal and vertical planes, facilitating the investigation of (undesired) lateral and (hyper)nasalised pronunciations. The system allows for the investigation of the acoustic field distribution around the speaker's face, offering potential for research, diagnostic and therapeutic uses. Further validation involving a larger group of patients is underway.