Hafte Abera


2020

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Large Vocabulary Read Speech Corpora for Four Ethiopian Languages: Amharic, Tigrigna, Oromo and Wolaytta
Solomon Teferra Abate | Martha Yifiru Tachbelie | Michael Melese | Hafte Abera | Tewodros Abebe | Wondwossen Mulugeta | Yaregal Assabie | Million Meshesha | Solomon Afnafu | Binyam Ephrem Seyoum
Proceedings of the 12th Language Resources and Evaluation Conference

Automatic Speech Recognition (ASR) is one of the most important technologies to support spoken communication in modern life. However, its development benefits from large speech corpus. The development of such a corpus is expensive and most of the human languages, including the Ethiopian languages, do not have such resources. To address this problem, we have developed four large (about 22 hours) speech corpora for four Ethiopian languages: Amharic, Tigrigna, Oromo and Wolaytta. To assess usability of the corpora for (the purpose of) speech processing, we have developed ASR systems for each language. In this paper, we present the corpora and the baseline ASR systems we have developed. We have achieved word error rates (WERs) of 37.65%, 31.03%, 38.02%, 33.89% for Amharic, Tigrigna, Oromo and Wolaytta, respectively. This results show that the corpora are suitable for further investigation towards the development of ASR systems. Thus, the research community can use the corpora to further improve speech processing systems. From our results, it is clear that the collection of text corpora to train strong language models for all of the languages is still required, especially for Oromo and Wolaytta.

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Large Vocabulary Read Speech Corpora for Four Ethiopian Languages: Amharic, Tigrigna, Oromo, and Wolaytta
Solomon Teferra Abate | Martha Yifiru Tachbelie | Michael Melese | Hafte Abera | Tewodros Gebreselassie | Wondwossen Mulugeta | Yaregal Assabie | Million Meshesha Beyene | Solomon Atinafu | Binyam Ephrem Seyoum
Proceedings of the The Fourth Widening Natural Language Processing Workshop

Automatic Speech Recognition (ASR) is one of the most important technologies to help people live a better life in the 21st century. However, its development requires a big speech corpus for a language. The development of such a corpus is expensive especially for under-resourced Ethiopian languages. To address this problem we have developed four medium-sized (longer than 22 hours each) speech corpora for four Ethiopian languages: Amharic, Tigrigna, Oromo, and Wolaytta. In a way of checking the usability of the corpora and deliver a baseline ASR for each language. In this paper, we present the corpora and the baseline ASR systems for each language. The word error rates (WERs) we achieved show that the corpora are usable for further investigation and we recommend the collection of text corpora to train strong language models for Oromo and Wolaytta compared to others.

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Tigrinya Automatic Speech recognition with Morpheme based recognition units
Hafte Abera | Sebsibe Hailemariam
Proceedings of the The Fourth Widening Natural Language Processing Workshop

The Tigrinya language is agglutinative and has a large number of inflected and derived forms of words. Therefore a Tigrinya large vocabulary continuous speech recognition system often has a large number of different units and a high out-of-vocabulary (OOV) rate if a word is used as a recognition unit of a language model (LM) and lexicon. Therefore a morpheme-based approach has often been used and a morpheme is used as the recognition unit to reduce the high OOV rate. This paper presents an automatic speech recognition experiment conducted to see the effect of OOV words on the performance speech recognition system for Tigrinya. We tried to solve the OOV problem by using morphemes as lexicon and language model units. It has been found that the morpheme-based recognition system is better lexical and language modeling units than words. An absolute improvement (in word recognition accuracy) of 3.45 token and 8.36 types has been obtained as a result of using a morph-based vocabulary.

2019

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Speech Recognition for Tigrinya language Using Deep Neural Network Approach
Hafte Abera | Sebsibe H/mariam
Proceedings of the 2019 Workshop on Widening NLP

This work presents a speech recognition model for Tigrinya language .The Deep Neural Network is used to make the recognition model. The Long Short-Term Memory Network (LSTM), which is a special kind of Recurrent Neural Network composed of Long Short-Term Memory blocks, is the primary layer of our neural network model. The 40-dimensional features are MFCC-LDA-MLLT-fMLLR with CMN were used. The acoustic models are trained on features that are obtained by projecting down to 40 dimensions using linear discriminant analysis (LDA). Moreover, speaker adaptive training (SAT) is done using a single feature-space maximum likelihood linear regression (FMLLR) transform estimated per speaker. We train and compare LSTM and DNN models at various numbers of parameters and configurations. We show that LSTM models converge quickly and give state of the art speech recognition performance for relatively small sized models. Finally, the accuracy of the model is evaluated based on the recognition rate.

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English-Ethiopian Languages Statistical Machine Translation
Solomon Teferra Abate | Michael Melese | Martha Yifiru Tachbelie | Million Meshesha | Solomon Atinafu | Wondwossen Mulugeta | Yaregal Assabie | Hafte Abera | Biniyam Ephrem | Tewodros Gebreselassie | Wondimagegnhue Tsegaye Tufa | Amanuel Lemma | Tsegaye Andargie | Seifedin Shifaw
Proceedings of the 2019 Workshop on Widening NLP

In this paper, we describe an attempt towards the development of parallel corpora for English and Ethiopian Languages, such as Amharic, Tigrigna, Afan-Oromo, Wolaytta and Ge’ez. The corpora are used for conducting bi-directional SMT experiments. The BLEU scores of the bi-directional SMT systems show a promising result. The morphological richness of the Ethiopian languages has a great impact on the performance of SMT especially when the targets are Ethiopian languages.

2018

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Parallel Corpora for bi-lingual English-Ethiopian Languages Statistical Machine Translation
Solomon Teferra Abate | Michael Melese | Martha Yifiru Tachbelie | Million Meshesha | Solomon Atinafu | Wondwossen Mulugeta | Yaregal Assabie | Hafte Abera | Binyam Ephrem | Tewodros Abebe | Wondimagegnhue Tsegaye | Amanuel Lemma | Tsegaye Andargie | Seifedin Shifaw
Proceedings of the 27th International Conference on Computational Linguistics

In this paper, we describe an attempt towards the development of parallel corpora for English and Ethiopian Languages, such as Amharic, Tigrigna, Afan-Oromo, Wolaytta and Ge’ez. The corpora are used for conducting a bi-directional statistical machine translation experiments. The BLEU scores of the bi-directional Statistical Machine Translation (SMT) systems show a promising result. The morphological richness of the Ethiopian languages has a great impact on the performance of SMT specially when the targets are Ethiopian languages. Now we are working towards an optimal alignment for a bi-directional English-Ethiopian languages SMT.

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Design of a Tigrinya Language Speech Corpus for Speech Recognition
Hafte Abera | Sebsibe H/Mariam
Proceedings of the First Workshop on Linguistic Resources for Natural Language Processing

In this paper, we describe the first Tigrinya Languages speech corpora designed and development for speech recognition purposes. Tigrinya, often written as Tigrigna (ትግርኛ) /tɪˈɡrinjə/ belongs to the Semitic branch of the Afro-Asiatic languages where it shows the characteristic features of a Semitic language. It is spoken by ethnic Tigray-Tigrigna people in the Horn of Africa. The paper outlines different corpus designing process analysis of related work on speech corpora creation for different languages. The authors provide also procedures that were used for the creation of Tigrinya speech recognition corpus which is the under-resourced language. One hundred and thirty speakers, native to Tigrinya language, were recorded for training and test dataset set. Each speaker read 100 texts, which consisted of syllabically rich and balanced sentences. Ten thousand sets of sentences were used to prompt sheets. These sentences contained all of the contextual syllables and phones.

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Parallel Corpora for bi-Directional Statistical Machine Translation for Seven Ethiopian Language Pairs
Solomon Teferra Abate | Michael Melese | Martha Yifiru Tachbelie | Million Meshesha | Solomon Atinafu | Wondwossen Mulugeta | Yaregal Assabie | Hafte Abera | Binyam Ephrem | Tewodros Abebe | Wondimagegnhue Tsegaye | Amanuel Lemma | Tsegaye Andargie | Seifedin Shifaw
Proceedings of the First Workshop on Linguistic Resources for Natural Language Processing

In this paper, we describe the development of parallel corpora for Ethiopian Languages: Amharic, Tigrigna, Afan-Oromo, Wolaytta and Geez. To check the usability of all the corpora we conducted baseline bi-directional statistical machine translation (SMT) experiments for seven language pairs. The performance of the bi-directional SMT systems shows that all the corpora can be used for further investigations. We have also shown that the morphological complexity of the Ethio-Semitic languages has a negative impact on the performance of the SMT especially when they are target languages. Based on the results we obtained, we are currently working towards handling the morphological complexities to improve the performance of statistical machine translation among the Ethiopian languages.