Hierarchical Neural Network Architecture In Keyword Spotting

Keyword Spotting (KWS) provides the start signal of ASR problem, and thus it is essential to ensure a high recall rate. However, its real-time property requires low computation complexity. This contradiction inspires people to find a suitable model which is small enough to perform well in multi environments. To deal with this contradiction, we implement the Hierarchical Neural Network(HNN), which is proved to be effective in many speech recognition problems. HNN outperforms traditional DNN and CNN even though its model size and computation complexity are slightly less. Also, its simple topology structure makes easy to deploy on any device.Comment: To be submitted in part to IEEE ICASSP 201

Improving bottleneck features for Vietnamese large vocabulary continuous speech recognition system using deep neural networks

In this paper, the pre-training method based on denoising auto-encoder is investigated and proved to be good models for initializing bottleneck networks of Vietnamese speech recognition system that result in better recognition performance compared to base bottleneck features reported previously. The experiments are carried out on the dataset containing speeches on Voice of Vietnam channel (VOV). The results show that the DBNF extraction for Vietnamese recognition decreases relative word error rate by 14 % and 39 % compared to the base bottleneck features and MFCC baseline, respectively

The RWTH Aachen German and English LVCSR systems for IWSLT-2013

Abstract In this paper, German and English large vocabulary continuous speech recognition (LVCSR) systems developed by the RWTH Aachen University for the IWSLT-2013 evaluation campaign are presented. Good improvements are obtained with state-of-the-art monolingual and multilingual bottleneck features. In addition, an open vocabulary approach using morphemic sub-lexical units is investigated along with the language model adaptation for the German LVCSR. For both the languages, competitive WERs are achieved using system combination

Multilingual representations for low resource speech recognition and keyword search

© 2015 IEEE. This paper examines the impact of multilingual (ML) acoustic representations on Automatic Speech Recognition (ASR) and keyword search (KWS) for low resource languages in the context of the OpenKWS15 evaluation of the IARPA Babel program. The task is to develop Swahili ASR and KWS systems within two weeks using as little as 3 hours of transcribed data. Multilingual acoustic representations proved to be crucial for building these systems under strict time constraints. The paper discusses several key insights on how these representations are derived and used. First, we present a data sampling strategy that can speed up the training of multilingual representations without appreciable loss in ASR performance. Second, we show that fusion of diverse multilingual representations developed at different LORELEI sites yields substantial ASR and KWS gains. Speaker adaptation and data augmentation of these representations improves both ASR and KWS performance (up to 8.7% relative). Third, incorporating un-transcribed data through semi-supervised learning, improves WER and KWS performance. Finally, we show that these multilingual representations significantly improve ASR and KWS performance (relative 9% for WER and 5% for MTWV) even when forty hours of transcribed audio in the target language is available. Multilingual representations significantly contributed to the LORELEI KWS systems winning the OpenKWS15 evaluation

Áp dụng Bottle Neck Feature cho nhận dạng tiếng nói tiếng Việt

In the paper, the basic idea of Bottle Neck Feature (BNF) and the process how to extract BNF are presented. We apply BNF for Vietnamese speech recognition with five layers MLP network of different sizes for the first hidden layer. Input features to extract BNF feature are Perceptual Linear Prediction (PLP) and Mel Frequency Cepstral Coefficient (MFCC). The experiments are carried out on a data set of VOV (Voice of Vietnam). The results show that using BNF for Vietnamese speech recognition, a WER (Word Error Rate) is improved up to 6-7% comparing to the baseline system, and MFCC feature gives a better result than PLP feature.Bài báo trình bày việc áp dụng Bottle Neck Feature (BNF) - một dạng đặc trưng của tín hiệu tiếng nói được trích chọn thông qua mạng neural (Neural Network) - cho nhận dạng tiếng nói tiếng Việt. Nghiên cứu sử dụng mạng Multilayer Perceptron (MLP) năm lớp với kích thước của lớp ẩn thứ nhất khác nhau để trích chọn đặc trưng BNF từ hai loại dữ liệu đầu vào là Perceptual Linear Prediction (PLP) và Mel Frequency Cepstral Coefficient (MFCC), nhằm đánh giá hiệu quả của mỗi loại đặc trưng sau khi được áp dụng BNF. Kết quả thử nghiệm chứng tỏ BNF hiệu quả với tiếng nói tiếng Việt, kết quả nhận dạng trên đặc trưng BNF tốt hơn so với hệ thống cơ sở (baseline system) trong khoảng từ 6% đến 7%, và đặc trưng MFCC cho kết quả tốt hơn PLP.

Automatic Speech Recognition for Low-resource Languages and Accents Using Multilingual and Crosslingual Information

This thesis explores methods to rapidly bootstrap automatic speech recognition systems for languages, which lack resources for speech and language processing. We focus on finding approaches which allow using data from multiple languages to improve the performance for those languages on different levels, such as feature extraction, acoustic modeling and language modeling. Under application aspects, this thesis also includes research work on non-native and Code-Switching speech