Speech processing is the study of speech signals and the processing methods of these signals. The signals are usually processed in a digital representation, so speech processing can be regarded as a special case of digital signal processing, applied to speech signals. Aspects of speech processing includes the acquisition, manipulation, storage, transfer and output of speech signals. The input is called speech recognition and the output is called speech synthesis.
Early attempts at speech processing and recognition were primarily focused on understanding a handful of simple phonetic elements such as vowels. In 1952, three researchers at Bell Labs, Stephen. Balashek, R. Biddulph, and K. H. Davis, developed a system that could recognize digits spoken by a single speaker. 
One of the first commercially available speech recognition products was Dragon Dictate, released in 1990. In 1992, technology developed by Lawrence Rabiner and others at Bell Labs was used by AT&T in their Voice Recognition Call Processing service to route calls without a human operator. By this point, the vocabulary of these systems was larger than the average human vocabulary.
Dynamic Time Warping
Hidden Markov Models
- Interactive Voice Systems
- Virtual Assistants
- Voice Identification
- Emotion Recognition
- Call Center Automation
- Juang, B.-H.; Rabiner, L.R. (2006), "Speech Recognition, Automatic: History", Encyclopedia of Language & Linguistics, Elsevier, pp. 806–819, ISBN 9780080448541, retrieved 2018-10-26
- Huang, Xuedong; Baker, James; Reddy, Raj (2014-01-01). "A historical perspective of speech recognition". Communications of the ACM. 57 (1): 94–103. doi:10.1145/2500887. ISSN 0001-0782.