gabor presentation

8/3/2019 Gabor presentation

http://slidepdf.com/reader/full/gabor-presentation 1/28

Easy Does It:Robust Spectro-Temporal Many-

Stream ASR without Fine Tuning

Streams

Ravuri, Morgan, UC Berkeley

Presented by JJ



Motivation

• Physiological experiments indifferent mammal species : alarge percentage of neurons inthe primary auditory cortex (A1)respond differently to upward-versus downward-moving ripplesin the spectrogram of the input(Depireux et al., 2001).

• Spectro-temporal receptivefields (STRFs) : individual neurons

are sensitive to specific spectro-temporal modulation frequenciesin the incoming sound signal



Introduction

• Cortically-inspired TF features, which capture

spectral and temporal modulations speech

recognition and discrimination.

• Basically, spectro-temporal features are

derived from filtering spectrograms with

particular filters.

• In this case, the GABOR filter is applied to the

auditory spectrogram.



Example



Example Gabor Filters




Gaussian envelope

complex sinusoid s(n, k)



1D Gabor

Gaussian envelope complex sinusoid s(n, k)



2D GaborGaussian envelope complex sinusoid s(n, k)




Gaussian envelope

complex sinusoid s(n, k)



Their Gabor Filters



Their Gabor Filters

parametersDummy

indices



Tons of Combinations!



System

Stream

…….

…….

…….

Stream

Merge MLP outputs

PCA

MFCC Output



System

Stream

…….

…….

…….

Stream

Merge MLP outputs

PCA

MFCC Output

• MLP (Multilayer Perceptron)

• The structure of the MLP

depends on the type of feature

and corpus.

Number of Spectral Cepstral

input units 567 351

frames of context 9 9

hidden units 160 for Aurora2

500 for Number95

160 for Aurora2

500 for Number95

output units 56 56

56D

32D

56D

45D



System

Stream

…….

…….

…….

Stream

Merge MLP outputs

PCA

MFCC Output

• The outputs of the MLP stream

provide an estimate of the

posterior probability distribution

for phones.

• Then, combine each of these

phone probability estimates

across streams by inverse

entropy.56D

32D

56D

71D



System

Stream

…….

…….

…….

Stream

Merge MLP outputs

PCA

MFCC Output

• then apply the KL

Transform to the log

probabilities of the

merged MLPs

Principal Components Analysis

56D

32D

56D

71D



System

Stream

…….

…….

…….

Stream

Merge MLP outputs

PCA

MFCC Output

• then apply the KLTransform to the logprobabilities of themerged MLPs

• reduced to 32D

• orthogonalized

• the features are meanand variance normalized

by utterance• finally appended to the

MFCC feature

56D

32D

56D

71D



System

Stream

…….

…….

…….

Stream

Merge MLP outputs

PCA

MFCC Output

• Features HMM

56D

32D

56D

71D39D 32D



Experiments

Database

• Aurora 2 (0 – 20 dB)

• Numbers95

• consists of various numeric portionsextracted from telephone dialogues .

• vocabulary size of 32 words

• training set contains 3590 utterancesof clean data, totaling roughly 3 hrs

• 2 test sets contains 1227 utterances.

• The first contains only clean data

• The second contains the sameutterances with noise added at five

SNR (20dB, 15dB, 10dB, 5dB, and0dB).

• Additive noise

Baseline

• 39 MFCC

• 4-stream system

• 28-stream system

Uni-modulation system

• 150 stream

• spectral only and spectral/cepstral

Metric: Word Error Rate (WER)



ResultsAurora 2

Numbers 95



ResultsAurora 2

Numbers 95

Discussion 1



ResultsAurora 2

Numbers 95

Discussion 2



ResultsAurora 2

Numbers 95

Discussion 3



ResultsAurora 2

Numbers 95



Stream

…….

…….

…….

Stream

Merge MLP outputs

PCA

MFCC Output

• Not just additive noise

• Another TF feature

might not work

• Log-mel filterbank? Orpower like PNCC?

• How to combine MLP?

Inverse Entropy?

56D

32D

56D

71D39D 32D

Future Work

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