This presentation slide contains, Introduction to Gaussian mixture model and its application in identifying speaker.

1. GMMGaussian mixture models
8/15/2014 1
Saurab Dulal
IOE, pulchowk Campus

2. Introduction to GMM
• Gaussian
“Gaussian is a
characteristic symmetric
"bell curve" shape that
quickly falls off towards 0
(practically)”
• Mixture Model
“mixture model is a
probabilistic model which
assumes the underlying
data to belong to a
mixture distribution”
2

3. Introduction to GMM
• Mathematical Description of GMM
p(x) = w1 p1 (x) + w2p2 (x) + w3 p3 (x) ……… +wn pn (x)
where p(x) = mixture component
w1, w2 ….. wn = mixture weight or mixture coefficient
pi (x) = Density functions
Fig :- Image
showing
Best fit
Gaussian
Curve
3

4. Introduction to GMM
“The most common mixture distribution is the Gaussian
(Normal) density function, in which each of the mixture
components are Gaussian distributions, each with their
own mean and variance parameters.”
p(x) = w1N( x | µ1∑1 )+ w1N( x | µ2∑2 )… +w1N( x | µn∑n )
µi ‘s are means and ∑i ‘s are covariance-matrix of
individual components(probability density function)
4
G1,w1 G2,w2
G3,w3
G4,w4
G5,w5

5. -5 0 5 10
0
0.1
0.2
0.3
0.4
0.5
Component 1 Component 2
p(x)
-5 0 5 10
0
0.1
0.2
0.3
0.4
0.5
Mixture Model
x
p(x)

6. -5 0 5 10
0
0.1
0.2
0.3
0.4
0.5
Component 1 Component 2
p(x)
-5 0 5 10
0
0.1
0.2
0.3
0.4
0.5
Mixture Model
x
p(x)

7. -5 0 5 10
0
0.5
1
1.5
2
Component Models
p(x)
-5 0 5 10
0
0.1
0.2
0.3
0.4
0.5
Mixture Model
x
p(x)

8. GMM for Speaker Recognition
Motivation
• Interpretation that Gaussian component
represent some general speaker –dependent
spectral shapes
• Capabilities of Gaussian mixture to model
arbitrary densities
8

9. Description of SR-using GMM
• Speech Analysis
• Model Description
• Model Interpretations
• Maximum Likelihood Parameters Estimation
• Speaker Identification
9

10. Speech Analysis
10
• Linear predictive coding(LPC)
•Mel-scale filter-bank(to reduce
noise)
Analysis is ended with the
generation of
Cepstrum coefficients x1
’, x2
’
x3’….xn
’
A cepstrum is the result of taking the Inverse Fourier transform (IFT)
of the logarithm of the estimated spectrum of a signal.
Cosine transform

11. 2000/05/03 11
Model Description
Gaussian Mixture Density
)()|(
1
xbpxp
M
i
ii



Where x
 D-dimensional random vector
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
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
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2
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exp
)2(
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212 iii
i
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
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 iiip  ,,
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Mi ,,1 
Nodal, Grand,Global
Nodal, diagonal (this)
Covariance matrix
Mean
Component Density
Speaker Model

12. Choice of Covariance Matrix
12
• Nodal Covariance
One co-variance matrix per Gaussian component
• Grand Covariance
One co-variance matrix for all Gaussian component
• Global Covariance
single co-variance matrix shared by all speaker
component

13. Model Interpretation
• Intuitive notion
Acoustic classes(vowels, nasals, fricatives) reflects
some general speaker-dependent vocal tract
configuration that are useful for characterizing speaker-
identity
• GMM have ability to form smooth approximation to
arbitrary shaped density
• It doesn’t only have smooth approx but also
multimodal nature of densities
13

14. 2000/05/03 14
ML-Parameters Estimation
Step:
1. Beginning with an initial model
2. Estimate a new model such that
Mixture density
3. Repeated 2. until certain threshold is
reached.
…Maximum Likelihood
)|()|(  XpXp 
 

15. 2000/05/03 15
(Mixture Weights)
(Means)
(Variances)

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and refers to arbitrary elements of vectors ii 
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16. 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4
3.7
3.8
3.9
4
4.1
4.2
4.3
4.4
ANEMIA PATIENTS AND CONTROLS
Red Blood Cell Volume
RedBloodCellHemoglobinConcentration

17. 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4
3.7
3.8
3.9
4
4.1
4.2
4.3
4.4
Red Blood Cell Volume
RedBloodCellHemoglobinConcentration
EM ITERATION 1

18. 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4
3.7
3.8
3.9
4
4.1
4.2
4.3
4.4
Red Blood Cell Volume
RedBloodCellHemoglobinConcentration
EM ITERATION 3

19. 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4
3.7
3.8
3.9
4
4.1
4.2
4.3
4.4
Red Blood Cell Volume
RedBloodCellHemoglobinConcentration
EM ITERATION 5

20. 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4
3.7
3.8
3.9
4
4.1
4.2
4.3
4.4
Red Blood Cell Volume
RedBloodCellHemoglobinConcentration
EM ITERATION 10

21. 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4
3.7
3.8
3.9
4
4.1
4.2
4.3
4.4
Red Blood Cell Volume
RedBloodCellHemoglobinConcentration
EM ITERATION 15

22. 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4
3.7
3.8
3.9
4
4.1
4.2
4.3
4.4
Red Blood Cell Volume
RedBloodCellHemoglobinConcentration
EM ITERATION 25

23. 0 5 10 15 20 25
400
410
420
430
440
450
460
470
480
490
LOG-LIKELIHOOD AS A FUNCTION OF EM ITERATIONS
EM Iteration
Log-Likelihood

24. 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4
3.7
3.8
3.9
4
4.1
4.2
4.3
4.4
Red Blood Cell Volume
RedBloodCellHemoglobinConcentration
ANEMIA DATA WITH LABELS
Anemia Group
Control Group

25. 2000/05/03 25
Speaker Identification
A group of speakers S = {1,2,…,S} is represented by GMM’s
λ1, λ2, …, λs, the obective is to find the speaker model which
has the maximum a posteriori probability for a given observation
sequence
)(
)Pr()|(
maxarg)|Pr(maxargˆ
11 Xp
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Sk
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26. References
D. A. Reynolds and R. C. Rose, “Robust Text- Independent
Speaker Identification Using Gaussian Mixture Speaker
Models”, IEEE Trans. on Speech and Audio Processing, vol.3,
No.1, pp.72-83,January 1995.
• http://en.wikipedia.org/wiki/Probability_density_function
• http://crsouza.blogspot.com/2010/10/gaussian-mixture-
models-and-expectation.html
• https://www.ll.mit.edu/mission/communications/ist/publications
/0802_Reynolds_Biometrics-GMM.pdf
• http://statweb.stanford.edu/~tibs/stat315a/LECTURES/em.pdf
• http://eprints.pascal
network.org/archive/00008291/01/SoftAssignReconstr_ICIP20
11.pdf
• http://home.deib.polimi.it/matteucc/Clustering/tutorial_html/km
eans.html
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