DBLSTM based multilingual articulatory feature extraction for language documentation

With more than 7,000 living languages in the world and many of them facing extinction, the need for language documentation is now more pressing than ever. This process is time-consuming, requiring linguists as each language features peculiarities that need to be addressed. While automating the whole process is difficult, we aim at providing methods to support linguists during documentation. One important step in the workflow is the discovery of the phonetic inventory. In the past, we proposed a first approach of first automatically segmenting recordings into phone-line units and second clustering these segments based on acoustic similarity, determined by articulatory features (AFs). We now propose a refined method using Deep Bi-directional LSTMs (DBLSTMs) over DNNs. Additionally, we use Language Feature Vectors (LFVs) which encode language specific peculiarities in a low dimensional representation. In contrast to adding LFVs to the acoustic input features, we modulated the output of the last hidden LSTM layer, forcing groups of LSTM cells to adapt to language related features. We evaluated our approach multilingually, using data from multiple languages. Results show an improvement in recognition accuracy across AF types: While LFVs improved the performance of DNNs, the gain is even bigger when using DBLSTMs.