HVAC Control in the New Millennium.pdf - HVAC.Amickracing

Artificial Intelligence, Fuzzy Logic and Controlman. A word spoken by a human has a complex waveform that is asunique as a fingerprint. The electronic recordings of human words arecalled voice prints. A speaker-dependent system is less costly than aspeaker-independent system, but it must be trained by having the intendeduser speak the command words while the system records them.These voice prints are later used by the system for matching the presentinput.Most systems digitize the voice print and break it down into itsdifferent frequency components. The more information saved about thevoice, the more secure the system is from unauthorized use. If the personis talking under stress or in a noisy environment, the system maynot recognize the commands given. Most speaker-dependent systemshave a limited number of words in their vocabulary. A speaker-dependentsystem must also be retrained when you switch users.Speaker-independent SystemsA speaker-independent system is a voice recognition system designedto recognize commands given to it no matter who does thespeaking. Since different persons say words at different speeds, frequencies,and inflections, a speaker-independent system must analyze thespeech in several steps and then base its identification on the results.First, it breaks the sounds down into phonemes so it must be ableto find the pauses in the words. Then, it looks up the phonemes in itsmemory and tries to find the words they represent, which can requirestoring several pronunciations of the words. Then, it compares thesewords against known commands and selects a command. If a commandis not understood, the speech recognition system must request that thecommand be given again.For short vocabularies, the voice print technique can be used by aspeaker-dependent system. For large vocabularies, the phonic techniquetakes less memory space and is more efficient.Isolated-word Recognition SystemsIsolated-word recognition refers to a speech recognition systemthat only hears one word at a time (Figure 6-1). It processes the word it©2001 by The Fairmont Press, Inc. All rights reserved.