multi-factor authentication Speech to text (transcription of speech into text, real time video captioning, Court reporting ) Telematics (e.g. vehicle Navigation Systems) Transcription (digital speech-to-text) Video games, with Tom Clancy's EndWar and Lifeline as working examples Virtual assistant (e.g. Apple's Siri) Performance The performance of speech recognition systems is usually evaluated in terms of accuracy and speed. Accuracy is usually rated with word error rate (WER), whereas speed is measured with the real time factor. Other measures of accuracy include Single Word Error Rate (SWER) and Command Success Rate (CSR). Speech recognition by machine is a very complex problem, however. Vocalizations vary in terms of accent, pronunciation, articulation, roughness, nasality, pitch, volume, and speed. Speech is distorted by a background noise and echoes, electrical characteristics. Accuracy of speech recognition may vary with the following: Vocabulary size and confusability Speaker dependence versus independence Isolated, discontinuous or continuous speech Task and language constraints Read versus spontaneous speech Adverse conditions Accuracy As mentioned earlier in this article, the accuracy of speech recognition may vary depending on the following factors: Error rates increase as the vocabulary size grows: e.g. the 10 digits "zero" to "nine" can be recognized essentially perfectly, but vocabulary sizes of 200, 5000 or 100000 may have error rates of 3%, 7%, or 45% respectively. Vocabulary is hard to recognize if it contains confusing words: e.g. the 26 letters of the English alphabet are difficult to discriminate because they are confusing words (most notoriously, the E-set: "B, C, D, E, G, P, T, V, Z — when "Z" is pronounced "zee" rather than "zed" depending on the English region); an 8% error rate is considered good for this vocabulary. Speaker dependence vs. independence: A speaker-dependent system is intended for use by a single speaker. A speaker-independent system is intended for use by any speaker (more difficult). Isolated, Discontinuous or continuous speech With isolated speech, single words are used, therefore it becomes easier to recognize the speech. With discontinuous speech full sentences separated by silence are used, therefore it becomes easier to recognize the speech as well as with isolated speech. With continuous speech naturally spoken sentences are used, therefore it becomes harder to recognize the speech, different from both isolated and discontinuous speech. Task and language constraints e.g. Querying application may dismiss the hypothesis "The apple is red." e.g. Constraints may be semantic; rejecting "The apple is angry." e.g. Syntactic; rejecting