Unit Selection Synthesis: A technique for improving speech synthesis quality by leveraging accurate alignments and data augmentation.
Unit selection synthesis is a method used in speech synthesis systems to enhance the quality of synthesized speech. It involves the accurate segmentation and labeling of speech signals, which is crucial for the concatenative nature of these systems. With the advent of end-to-end (E2E) speech synthesis systems, researchers have found that accurate alignments and prosody representation are essential for high-quality synthesis. In particular, the durations of sub-word units play a significant role in achieving good synthesis quality.
One of the challenges in unit selection synthesis is obtaining accurate phone durations during training. Researchers have proposed using signal processing cues in tandem with forced alignment to produce accurate phone durations. Data augmentation techniques have also been employed to improve the performance of speaker verification systems, particularly in limited-resource scenarios. By breaking up text-independent speeches into speech segments containing individual phone units, researchers can synthesize speech with target transcripts by concatenating the selected segments.
Recent studies have compared statistical speech waveform synthesis (SSWS) systems with hybrid unit selection synthesis to identify their strengths and weaknesses. SSWS has shown improvements in synthesis quality across various domains, but further research is needed to enhance this technology. Long-Short Term Memory (LSTM) Deep Neural Networks have been used as a postfiltering step in HMM-based speech synthesis to obtain spectral characteristics closer to natural speech, resulting in improved synthesis quality.
Practical applications of unit selection synthesis include:
1. Text-to-speech systems: Enhancing the quality of synthesized speech for applications like virtual assistants, audiobooks, and language learning tools.
2. Speaker verification: Improving the performance of speaker verification systems by leveraging data augmentation techniques based on unit selection synthesis.
3. Customized voice synthesis: Creating personalized synthetic voices for users with speech impairments or for generating unique voices in entertainment and gaming.
A company case study in this field is Amazon, which has conducted an in-depth evaluation of its SSWS system across multiple domains to better understand the consistency in quality and identify areas for future improvement.
In conclusion, unit selection synthesis is a promising technique for improving the quality of synthesized speech in various applications. By focusing on accurate alignments, data augmentation, and leveraging advanced machine learning techniques, researchers can continue to enhance the performance of speech synthesis systems and expand their practical applications.

Unit Selection Synthesis
Unit Selection Synthesis Further Reading
1.The Importance of Accurate Alignments in End-to-End Speech Synthesis http://arxiv.org/abs/2210.17153v1 Anusha Prakash, Hema A Murthy2.Modernist Materials Synthesis: Finding Thermodynamic Shortcuts with Hyperdimensional Chemistry http://arxiv.org/abs/2303.11915v1 James R Neilson, Matthew J McDermott, Kristin A Persson3.Balancing, Regression, Difference-In-Differences and Synthetic Control Methods: A Synthesis http://arxiv.org/abs/1610.07748v2 Nikolay Doudchenko, Guido W. Imbens4.Unit selection synthesis based data augmentation for fixed phrase speaker verification http://arxiv.org/abs/2102.09817v1 Houjun Huang, Xu Xiang, Fei Zhao, Shuai Wang, Yanmin Qian5.Comprehensive evaluation of statistical speech waveform synthesis http://arxiv.org/abs/1811.06296v2 Thomas Merritt, Bartosz Putrycz, Adam Nadolski, Tianjun Ye, Daniel Korzekwa, Wiktor Dolecki, Thomas Drugman, Viacheslav Klimkov, Alexis Moinet, Andrew Breen, Rafal Kuklinski, Nikko Strom, Roberto Barra-Chicote6.Plausible deniability for privacy-preserving data synthesis http://arxiv.org/abs/2212.06604v1 Song Mei, Zhiqiang Ye7.In-Network View Synthesis for Interactive Multiview Video Systems http://arxiv.org/abs/1509.00464v1 Laura Toni, Gene Cheung, Pascal Frossard8.LSTM Deep Neural Networks Postfiltering for Improving the Quality of Synthetic Voices http://arxiv.org/abs/1602.02656v1 Marvin Coto-Jiménez, John Goddard-Close9.The Dynamic Replicon: adapting to a changing cellular environment http://arxiv.org/abs/0812.4238v1 John Herrick10.Selecting Boron Fullerenes by Cage-Doping Mechanisms http://arxiv.org/abs/1302.4003v1 Paul Boulanger, Maxime Moriniere, Luigi Genovese, Pascal PochetUnit Selection Synthesis Frequently Asked Questions
What is Unit Selection Synthesis?
Unit Selection Synthesis is a technique used in speech synthesis systems to improve the quality of synthesized speech. It involves accurately segmenting and labeling speech signals, which is crucial for the concatenative nature of these systems. By focusing on accurate alignments, data augmentation, and leveraging advanced machine learning techniques, researchers can enhance the performance of speech synthesis systems and expand their practical applications.
How does Unit Selection Synthesis work?
Unit Selection Synthesis works by breaking up text-independent speeches into speech segments containing individual phone units. These segments are then accurately aligned and labeled. When synthesizing speech with target transcripts, the system concatenates the selected segments to produce high-quality synthesized speech.
What is the role of data augmentation in Unit Selection Synthesis?
Data augmentation techniques are employed in Unit Selection Synthesis to improve the performance of speaker verification systems, particularly in limited-resource scenarios. By creating more diverse and representative training data, data augmentation helps enhance the quality of synthesized speech and the overall performance of the system.
What is the difference between Statistical Speech Waveform Synthesis (SSWS) and Unit Selection Synthesis?
Statistical Speech Waveform Synthesis (SSWS) is a method that uses statistical models to generate speech waveforms, while Unit Selection Synthesis relies on accurate segmentation and labeling of speech signals for concatenation. SSWS has shown improvements in synthesis quality across various domains, but further research is needed to enhance this technology. On the other hand, Unit Selection Synthesis focuses on accurate alignments and prosody representation, which are essential for high-quality synthesis.
How do Long-Short Term Memory (LSTM) Deep Neural Networks contribute to speech synthesis?
Long-Short Term Memory (LSTM) Deep Neural Networks have been used as a postfiltering step in HMM-based speech synthesis to obtain spectral characteristics closer to natural speech. By capturing long-term dependencies in the speech signal, LSTM networks can model the complex dynamics of speech, resulting in improved synthesis quality.
What are some practical applications of Unit Selection Synthesis?
Some practical applications of Unit Selection Synthesis include: 1. Text-to-speech systems: Enhancing the quality of synthesized speech for applications like virtual assistants, audiobooks, and language learning tools. 2. Speaker verification: Improving the performance of speaker verification systems by leveraging data augmentation techniques based on unit selection synthesis. 3. Customized voice synthesis: Creating personalized synthetic voices for users with speech impairments or for generating unique voices in entertainment and gaming.
How has Amazon utilized Unit Selection Synthesis in their research?
Amazon has conducted an in-depth evaluation of its Statistical Speech Waveform Synthesis (SSWS) system across multiple domains to better understand the consistency in quality and identify areas for future improvement. This research helps the company enhance the performance of its speech synthesis systems and expand their practical applications.
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