Unsupervised Word Segmentation from Discrete Speech Units in Low-Resource Settings
This work addresses the problem of documenting endangered oral languages for linguists and communities, but it is incremental as it compares existing discretization models rather than introducing a new method.
The paper tackled unsupervised word segmentation from discrete speech units in low-resource settings, comparing five discretization models (three Bayesian and two neural) and finding that Bayesian models produced the best results, with specific performance metrics reported for languages like Mboshi, Finnish, Hungarian, Romanian, and Russian using only 4 hours of speech.
Documenting languages helps to prevent the extinction of endangered dialects, many of which are otherwise expected to disappear by the end of the century. When documenting oral languages, unsupervised word segmentation (UWS) from speech is a useful, yet challenging, task. It consists in producing time-stamps for slicing utterances into smaller segments corresponding to words, being performed from phonetic transcriptions, or in the absence of these, from the output of unsupervised speech discretization models. These discretization models are trained using raw speech only, producing discrete speech units that can be applied for downstream (text-based) tasks. In this paper we compare five of these models: three Bayesian and two neural approaches, with regards to the exploitability of the produced units for UWS. For the UWS task, we experiment with two models, using as our target language the Mboshi (Bantu C25), an unwritten language from Congo-Brazzaville. Additionally, we report results for Finnish, Hungarian, Romanian and Russian in equally low-resource settings, using only 4 hours of speech. Our results suggest that neural models for speech discretization are difficult to exploit in our setting, and that it might be necessary to adapt them to limit sequence length. We obtain our best UWS results by using Bayesian models that produce high quality, yet compressed, discrete representations of the input speech signal.