Isolated word recognition over the DDD telephone network. Results of two extensive field studies

In a continuing effort to ascertain the viability of deploying speaker independent word recognition systems that could function reliably in normal telephone environments, two large scale field trials were carried out in AT&T central offices in Reno, Nevada, and in Hayward, California. The trials used live customer traffic to test the call handling procedures being developed for a new generation of telephone switching equipment. These procedures would use automatic speech recognition (ASR) to give users of `O⁺´ calls the option of verbally identifying the type of call they wish to make. The goal of these studies were of a particular training set to assess the performance of current ASR algorithms, both template-based and hidden Markov model based, on speech data collected over the DDD network. Over the course of the trial, upwards of 75000 caller responses were recorded on Sony PCM-F1 recording equipment. ASR performance (speaker independent) using algorithms currently under research yielded a word recognition accuracy of 99.7% on the 5-word target vocabulary. Discussion of these and other experiments are given