# Methodology for Obtaining High-Quality Speech Corpora
## 2 Background
### Criteria Applied for Describing Speech Corpora  
Speech corpora are created for various purposes, e.g., ASR, speaker identification, linguistics, and speech synthesis. Therefore, data in the corpus are collected according to predefined assumptions, the corpus structure, and data description [10; 13; 47; 48].  
The following parameters describe the contents of the speech corpora:  
* Speaker specification:
* Age and sex (correlated with pitch);
* The speech of children and teenagers can be included in the corpus;
* Voice quality;
* Disordered speech data are also collected for medical research and to create personalized ASR models for users with speech disorders, etc., [49; 50; 51];
* Text specification:
* For read text: novels, dramas, poetry, handbooks, guides, children's literature, crime fiction, adventure books, fantasy, biographies, scientific books and papers, government and parliament documents, laws, academic and commercial booklets, newspaper and magazine texts, and correspondence;
* For spoken text: scenarios;
* Style: scientific, legal, or journalistic text or blogs;
* Words or nonwords (which may constitute up to approximately 30% of the tokens in the transcripts [52; 53]);
* Domain or domains:
* Art, architecture, fashion, music, literature, economy, management, finance, environment, nature, education, pedagogy, politics, social issues, family, philosophy,
religion, culture, sports, tourism, army, security, technology, biology, chemistry, medicine, pharmacy, engineering, law, mathematics, physics, information technology, electronics, psychology, sociology, humanities, everyday life and recreation, humor, news (radio, television, or newspapers), international affairs, interviews, everyday conversations and gossip, the Internet (including Wikipedia), fables, and children's books;
* Speech type:
* Read speech [54], spontaneous, expressive/emotional [55], or monotonous.
* Number of speakers:
* Monologs, dialogs, more speakers, along with the number of men, women, and children and the percentage of overlapping utterances;
* Recording parameters:
* The recording environment (including the following: studio, live conversations outside of the recording studio, phone conversations, voice calls via apps, and video calls providing audiovisual data), the software and equipment applied for recording, the sampling rate, bit depth, number of channels, microphones used and their setup, background noise, etc.;
* Specification of annotation:
* The levels of annotation, guidelines for annotation, tags used (tagsets, e.g., POS tags), segmentation, phonetic annotation, prosodic annotation, time alignment, semantic annotation, and discourse annotation [56; 57; 58];
* Corpus size (in hours);
* Number of utterances, sentences, or words and the speaking rate;
* Criteria that should be met for the corpus:
* Selection criteria, corpus structure, and validation criteria;
* Storage;
* Access for users. These parameters can be described in the corpus metadata. The corpus contents can be prepared according to the needs of the target users. The corpus size and annotation are the most important factors influencing corpus quality. Additionally, the corpus should be up to date.