SUMMARYThis paper aims to improve the domain robustness of language modeling for automatic speech recognition (ASR). To this end, we focus on applying the latent words language model (LWLM) to ASR. LWLMs are generative models whose structure is based on Bayesian soft class-based modeling with vast latent variable space. Their flexible attributes help us to efficiently realize the effects of smoothing and dimensionality reduction and so address the data sparseness problem; LWLMs constructed from limited domain data are expected to robustly cover unknown multiple domains in ASR. However, the attribute flexibility seriously increases computation complexity. If we rigorously compute the generative probability for an observed word sequence, we must consider the huge quantities of all possible latent word assignments. Since this is computationally impractical, some approximation is inevitable for ASR implementation. To solve the problem and apply this approach to ASR, this paper presents an n-gram approximation of LWLM. The n-gram approximation is a method that approximates LWLM as a simple back-off n-gram structure, and offers LWLM-based robust one-pass ASR decoding. Our experiments verify the effectiveness of our approach by evaluating perplexity and ASR performance in not only in-domain data sets but also out-of-domain data sets.
Background and study aims
We developed a new reporting system based on structured data entry, which selectively extracts only endoscopic findings from endoscopists’ oral statements and automatically inputs them into appropriate columns in real time during endoscopic procedures.
Methods
We compared the time for endoscopic procedures and report preparation (ER time) by using an esophagogastroduodenoscopy simulator in three groups: one preparing reports using a mouse after endoscopic procedures (CE group); a second group preparing reports by using voice alone during endoscopic procedures (SR group); and the final group preparing reports by operating the system with a foot switch and inputting findings using voice during endoscopic procedures (SR + FS group). For the SR and SR + FS groups, we identified the recognition rates of the speech recognition system.
Results
Mean ER times for cases with three findings each were 162, 130 and 119 seconds in the CE, SR and SR + FS groups, respectively. The mean ER times for cases with six findings each were 220, 144 and 128 seconds, respectively. The times in the SR and SR + FS groups were significantly shorter than that in the CE group (
P
< 0.017). The recognition rate of the SR group for cases with three findings each was 98.4 %, and 97.6 % in the same group for cases with six findings each. The rates in the SR + FS group were 95.2 % and 98.4 %, respectively.
Conclusion
Our reporting system was demonstrated to allow an endoscopist to efficiently complete the report in real time during endoscopic procedures.
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