An automated directory listing retrieval system based on recognition of connected letter strings
Cory S. Myers, L. R. Rabiner · The Journal of the Acoustical Society of America · 1982
In this paper we describe a system which is capable of recognizing spoken spelled names from a directory of names. These names are spelled in a connected fashion, i.e., without any pause between letters, over a dialed-up telephone line. This system uses a level building dynamic time warping algorithm to perform a time registration between the input speech and a sequence of letters drawn from isolated word templates. The initial result of the matching procedure is a string of letter classes. Letter classes are formed by breaking the alphabet up into groups of acoustically similar letters. The directory of names is also sorted by letter classes. After the input string is classified into letter classes, a second pass is performed to determine the optimally matching name. This system was tested on four talkers each of whom spoke a given set of 50 names. The names were spoken at both a deliberate and at a normal talking rate. Recognition was performed in both a speaker-trained and a speaker-independent manner. The directory consisted of about 18 000 names drawn from the Bell Laboratories directory. Recognition accuracies of 99% and 91% were achieved for speaker-dependent recognition using the deliberate talking rate and the normal talking rate, respectively. Recognition accuracies of 94% and 88% were achieved for speaker-independent recognition for the two talking rates.