Investigating the Impact of Speech Compression on the Acoustics of Dysarthric Speech

Acoustic analysis plays an important role in the assessment of dysarthria. Out of a public health necessity, telepractice has become increasingly adopted as the modality in which clinical care is given. While there are differences in software among telepractice platforms, they all use some form of speech compression to preserve bandwidth, with the most common algorithm being the Opus codec. Opus has been optimized for compression of speech from the general (mostly healthy) population. As a result, for speech-language pathologists, this begs the question: is the remotely transmitted speech signal a faithful representation of dysarthric speech? Existing high-fidelity audio recordings from 20 speakers of various dysarthria types were encoded at three different bit rates defined within Opus to simulate different internet bandwidth conditions. Acoustic measures of articulation, voice, and prosody were extracted, and mixed-effect models were used to evaluate the impact of bandwidth conditions on the measures. Significant differences in cepstral peak prominence, degree of voice breaks, jitter, vowel space area, pitch, and vowel space area were observed after Opus processing, providing insight into the types of acoustic measures that are susceptible to speech compression algorithms.