Speech and Audio Signal Processing: Processing and Perception of Speech and Music, Second Edition

CHAPTER 5

SPEECH-RECOGNITION OVERVIEW

5.1 WHY STUDY AUTOMATIC SPEECH RECOGNITION?

Why do we study automatic speech recognition (ASR)? For one thing, there is a lot of money at stake: speech recognition is potentially a multi-billion-dollar industry in the near future. As of 2011, earnings (and savings) from simple telephone applications are reputed to be billions of dollars per year.

There are many aspects of speech recognition that are already well understood. However, it is also clear that there is much that we still don't know. We don't have human-quality speech recognition; performance degrades rapidly when small changes are made to the speech signal, such as those that can be caused from switching microphones.

Speech recognition is potentially very useful. Sample applications include the following.

Telephone applications: For many current voice-mail systems, one has to follow a series of touch-tone button presses to navigate through a hierarchical menu. Speech recognition has the potential to cut through the menu hierarchy, although simple “press or say one” speech applications do not do this. Many “smart phones” now also incorporate speech recognition, for instance to simplify dialing a number in the phone's contact list.

Hands-free operation: There are many situations in which hands are not available to issue commands to a device. Using a car phone and controlling the microscope ...