Download presentation

Presentation is loading. Please wait.

Published byPrincess Dabb Modified over 2 years ago

1
Robust Speech recognition V. Barreaud LORIA

2
Mismatch Between Training and Testing n mismatch influences scores n causes of mismatch u Speech Variation u Inter-Speaker Variation

3
Robust Approaches n three categories u noise resistant features (Speech var.) u speech enhancement (Speech var. + Inter-speaker var.) u model adaptation for noise (Speech var. + Inter-speaker var.) Recognition system testing training Models Features encoding Word sequence Spk. A Spk. B

4
Contents n Overview u Noise resistant features u Speach enhancement u Model adaptation n Stochastic Matching n Our current work

5
Noise resistant features n Acoustic representation u Emphasis on less affected evidences n Auditory systems inspired models u Filter banks, Loudness curve, Lateral inhibition n Slow variation removal u Cepstrum Mean Normalization, Time derivatives n Linear Discriminative Analysis u Searches for the best parameterization

6
Speech enhancement n Parameter mapping u stereo data u observation subspace n Bayesian estimation u stochastic modelization of speech and noise n Template based estimation u restriction to a subspace u output is noise free u various templates and combination methods n Spectral Subtraction u noise and speech uncorrelated u slowly varying noise

7
Model Adaptation for noise n Decomposition of HMM or PMC u Viterbi algorithm searches in a NxM state HMM u Noise and speech simultaneously recognized u complex noises recognized n State dependant Wiener filtering u Wiener filtering in spectral domain faces non-stationary u Hmms divide speech in quasi-stationary segments u wiener filters specific to the state n Discriminative training u Classical technique trains models independently u error corrective training u minimum classification error training n Training data contamination u training set corrupted with noisy speech u depends on the test environment u lower discriminative scores Training

8
Stochastic Matching : Introduction n General framework n in feature space n in model space

9
Stochastic Matching : General framework n HMM Models X, X training space n Y ={y 1, …, y t } observation in testing space n and Y W

10
Stochastic Matching : In Feature Space n Estimation step : Auxiliary function n Maximization step

11
Stochastic Matching : In Feature Space (2) n Simple distorsion function n Computation of the simple bias

12
Stochastic Matching : In Model Space n random additive bias sequence B={b 1,…,b t } independent of speech stochastic process of mean b and diagonal covariance b

13
On-Line Frame-Synchronous Noise Compensation n Lies on stochastic matching method n Transformation parameter estimated along with optimal path. n Uses forward probabilities b1b1 b2b2 b3b3 b4b4 Sequence of observations Bias computation y2y2 y3y3 y4y4 z2z2 z3z3 z4z4 z5z5 reco Transformed observations

14
Theoretical framework and issue n On line frame synchronous n cascade of errors 1. Initiate bias of first frame b 0 =0 2. Compute and then b 3. Transform next frame with b 4. Goto next frame n Classical Stochastic Matching

15
Viterbi Hypothesis vs Linear Combination n Viterbi Hypothesis take into account only the « most probable » state and gaussian component. n Linear combination t t+1 states

16
Experiments n Phone numbers in a running car n Forced Align u transcription + optimum path n Free Align u optimum path n Wild Align u no data

17
Perspectives n Error recovery problem u a forgetting process u a model of distorsion function u environmental clues n More elaborated transform

Similar presentations

OK

A Study on Speaker Adaptation of Continuous Density HMM Parameters By Chin-Hui Lee, Chih-Heng Lin, and Biing-Hwang Juang Presented by: 陳亮宇 1990 ICASSP/IEEE.

A Study on Speaker Adaptation of Continuous Density HMM Parameters By Chin-Hui Lee, Chih-Heng Lin, and Biing-Hwang Juang Presented by: 陳亮宇 1990 ICASSP/IEEE.

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on intel core i7 processor Ppt on various services provided by internet Download ppt on medical tourism in india Ppt on different types of farming in india Presentations ppt online shopping Ppt on different solid figures with flat Ppt on travelling salesman problem branch and bound Download ppt on pulse code modulation Ppt on holographic technology games Ppt on any one mathematician turing