Automatic Speech Recognition

AUTOMATIC SPEECH RECOGNITION (ASR).   The concept of a machine than can recognize the human voice has long been an accepted feature in Science Fiction.   From ‘Star Trek’ to George Orwell’s ‘1984’ - “Actually he was not used to writing by hand.   Apart from very short notes, it was usual to dictate everything into the speakwriter.” - it has been commonly assumed that one day it will be possible to converse naturally with an advanced computer-based system.   Indeed in his book ‘The Road Ahead’, Bill Gates (co-founder of Microsoft Corp.) hails ASR as one of the most important innovations for future computer operating systems.
          From a technological perspective it is possible to distinguish between two broad types of ASR: ‘direct voice input’ (DVI) and ‘large vocabulary continuous speech recognition’ (LVCSR).   DVI devices are primarily aimed at voice command-and-control, whereas LVCSR systems are used for form filling or voice-based document creation.   In both cases the underlying technology is more or less the same.   DVI systems are typically configured for small to medium sized vocabularies (up to several thousand words) and might employ word or phrase spotting techniques.   Also, DVI systems are usually required to respond immediately to a voice command.   LVCSR systems involve vocabularies of perhaps hundreds of thousands of words, and are typically configured to transcribe continuous speech.   Also, LVCSR need not be performed in real-time - for example, at least one vendor has offered a telephone-based dictation service in which the transcribed document is e-mailed back to the user.
          From an application viewpoint, the benefits of using ASR derive from providing an extra communication channel in hands-busy eyes-busy human-machine interaction (HMI), or simply from the fact that talking can be faster than typing.   Also, whilst speaking to a machine cannot be described as natural, it can nevertheless be considered intuitive; as one ASR advertisement...